Cutis

The XXXIII Olympic Summer Games will take place in Paris, France, from July 26 to August 11, 2024, and a variety of outdoor sporting events (eg, surfing, cycling, beach volleyball) will be included. Participation in the Olympic Games is a distinct honor for athletes selected to compete at the highest level in their sports.

Because of their training regimens and lifestyles, Olympic athletes face unique health risks. One such risk appears to be skin cancer, a substantial contributor to the global burden of disease. Taken together, basal cell carcinoma, squamous cell carcinoma, and melanoma account for 6.7 million cases of skin cancer worldwide. Squamous cell carcinoma and malignant skin melanoma were attributed to 1.2 million and 1.7 million life-years lost to disability, respectively.¹

Olympic athletes are at increased risk for sunburn from UVA and UVB radiation, placing them at higher risk for both melanoma and nonmelanoma skin cancers.^2,3 Sweating increases skin photosensitivity, sportswear often offers inadequate sun protection, and sustained high-intensity exercise itself has an immunosuppressive effect. Athletes competing in skiing and snowboarding events also receive radiation reflected off snow and ice at high altitudes.³ In fact, skiing without sunscreen at 11,000-feet above sea level can induce sunburn after only 6 minutes of exposure.⁴ Moreover, sweat, water immersion, and friction can decrease the effectiveness of topical sunscreens.⁵

World-class athletes appear to be exposed to UV radiation to a substantially higher degree than the general public. In an analysis of 144 events at the 2020 XXXII Olympic Summer Games in Tokyo, Japan, the highest exposure assessments were for women’s tennis, men’s golf, and men’s road cycling.⁶ In a 2020 study (N=240), the rates of sunburn were as high as 76.7% among Olympic sailors, elite surfers, and windsurfers, with more than one-quarter of athletes reporting sunburn that lasted longer than 24 hours.⁷ An earlier study reported that professional cyclists were exposed to UV radiation during a single race that exceeded the personal exposure limit by 30 times.⁸

Regrettably, the high level of sun exposure experienced by elite athletes is compounded by their low rate of sunscreen use. In a 2020 survey of 95 Olympians and super sprint triathletes, approximately half rarely used sunscreen, with 1 in 5 athletes never using sunscreen during training.⁹ In another study of 246 elite athletes in surfing, windsurfing, and sailing, nearly half used inadequate sun protection and nearly one-quarter reported never using sunscreen.¹⁰ Surprisingly, as many as 90% of Olympic athletes and super sprint competitors understood the importance of using sunscreen.⁹

What can we learn from these findings?

First, elite athletes remain at high risk for skin cancer because of training regimens, occupational environmental hazards, and other requirements of their sport. Second, despite awareness of the risks of UV radiation exposure, Olympic athletes utilize inadequate photoprotection. Athletes with darker skin are still at risk for skin cancer, photoaging, and pigmentation disorders—indicating a need for photoprotective behaviors in athletes of all skin types.¹¹

Therefore, efforts to promote adequate sunscreen use and understanding of the consequences of UV radiation may need to be prioritized earlier in athletes’ careers and implemented according to evidence-based guidelines. For example, the Stanford University Network for Sun Protection, Outreach, Research and Teamwork (Sunsport) provided information about skin cancer risk and prevention by educating student-athletes, coaches, and trainers in the National Collegiate Athletic Association in the United States. The Sunsport initiative led to a dramatic increase in sunscreen use by student-athletes as well as increased knowledge and discussion of skin cancer risk.¹²

The XXXIII Olympic Summer Games will take place in Paris, France, from July 26 to August 11, 2024, and a variety of outdoor sporting events (eg, surfing, cycling, beach volleyball) will be included. Participation in the Olympic Games is a distinct honor for athletes selected to compete at the highest level in their sports.

Because of their training regimens and lifestyles, Olympic athletes face unique health risks. One such risk appears to be skin cancer, a substantial contributor to the global burden of disease. Taken together, basal cell carcinoma, squamous cell carcinoma, and melanoma account for 6.7 million cases of skin cancer worldwide. Squamous cell carcinoma and malignant skin melanoma were attributed to 1.2 million and 1.7 million life-years lost to disability, respectively.¹

Olympic athletes are at increased risk for sunburn from UVA and UVB radiation, placing them at higher risk for both melanoma and nonmelanoma skin cancers.^2,3 Sweating increases skin photosensitivity, sportswear often offers inadequate sun protection, and sustained high-intensity exercise itself has an immunosuppressive effect. Athletes competing in skiing and snowboarding events also receive radiation reflected off snow and ice at high altitudes.³ In fact, skiing without sunscreen at 11,000-feet above sea level can induce sunburn after only 6 minutes of exposure.⁴ Moreover, sweat, water immersion, and friction can decrease the effectiveness of topical sunscreens.⁵

World-class athletes appear to be exposed to UV radiation to a substantially higher degree than the general public. In an analysis of 144 events at the 2020 XXXII Olympic Summer Games in Tokyo, Japan, the highest exposure assessments were for women’s tennis, men’s golf, and men’s road cycling.⁶ In a 2020 study (N=240), the rates of sunburn were as high as 76.7% among Olympic sailors, elite surfers, and windsurfers, with more than one-quarter of athletes reporting sunburn that lasted longer than 24 hours.⁷ An earlier study reported that professional cyclists were exposed to UV radiation during a single race that exceeded the personal exposure limit by 30 times.⁸

Regrettably, the high level of sun exposure experienced by elite athletes is compounded by their low rate of sunscreen use. In a 2020 survey of 95 Olympians and super sprint triathletes, approximately half rarely used sunscreen, with 1 in 5 athletes never using sunscreen during training.⁹ In another study of 246 elite athletes in surfing, windsurfing, and sailing, nearly half used inadequate sun protection and nearly one-quarter reported never using sunscreen.¹⁰ Surprisingly, as many as 90% of Olympic athletes and super sprint competitors understood the importance of using sunscreen.⁹

What can we learn from these findings?

First, elite athletes remain at high risk for skin cancer because of training regimens, occupational environmental hazards, and other requirements of their sport. Second, despite awareness of the risks of UV radiation exposure, Olympic athletes utilize inadequate photoprotection. Athletes with darker skin are still at risk for skin cancer, photoaging, and pigmentation disorders—indicating a need for photoprotective behaviors in athletes of all skin types.¹¹

Therefore, efforts to promote adequate sunscreen use and understanding of the consequences of UV radiation may need to be prioritized earlier in athletes’ careers and implemented according to evidence-based guidelines. For example, the Stanford University Network for Sun Protection, Outreach, Research and Teamwork (Sunsport) provided information about skin cancer risk and prevention by educating student-athletes, coaches, and trainers in the National Collegiate Athletic Association in the United States. The Sunsport initiative led to a dramatic increase in sunscreen use by student-athletes as well as increased knowledge and discussion of skin cancer risk.¹²

The XXXIII Olympic Summer Games will take place in Paris, France, from July 26 to August 11, 2024, and a variety of outdoor sporting events (eg, surfing, cycling, beach volleyball) will be included. Participation in the Olympic Games is a distinct honor for athletes selected to compete at the highest level in their sports.

Because of their training regimens and lifestyles, Olympic athletes face unique health risks. One such risk appears to be skin cancer, a substantial contributor to the global burden of disease. Taken together, basal cell carcinoma, squamous cell carcinoma, and melanoma account for 6.7 million cases of skin cancer worldwide. Squamous cell carcinoma and malignant skin melanoma were attributed to 1.2 million and 1.7 million life-years lost to disability, respectively.¹

Olympic athletes are at increased risk for sunburn from UVA and UVB radiation, placing them at higher risk for both melanoma and nonmelanoma skin cancers.^2,3 Sweating increases skin photosensitivity, sportswear often offers inadequate sun protection, and sustained high-intensity exercise itself has an immunosuppressive effect. Athletes competing in skiing and snowboarding events also receive radiation reflected off snow and ice at high altitudes.³ In fact, skiing without sunscreen at 11,000-feet above sea level can induce sunburn after only 6 minutes of exposure.⁴ Moreover, sweat, water immersion, and friction can decrease the effectiveness of topical sunscreens.⁵

World-class athletes appear to be exposed to UV radiation to a substantially higher degree than the general public. In an analysis of 144 events at the 2020 XXXII Olympic Summer Games in Tokyo, Japan, the highest exposure assessments were for women’s tennis, men’s golf, and men’s road cycling.⁶ In a 2020 study (N=240), the rates of sunburn were as high as 76.7% among Olympic sailors, elite surfers, and windsurfers, with more than one-quarter of athletes reporting sunburn that lasted longer than 24 hours.⁷ An earlier study reported that professional cyclists were exposed to UV radiation during a single race that exceeded the personal exposure limit by 30 times.⁸

Regrettably, the high level of sun exposure experienced by elite athletes is compounded by their low rate of sunscreen use. In a 2020 survey of 95 Olympians and super sprint triathletes, approximately half rarely used sunscreen, with 1 in 5 athletes never using sunscreen during training.⁹ In another study of 246 elite athletes in surfing, windsurfing, and sailing, nearly half used inadequate sun protection and nearly one-quarter reported never using sunscreen.¹⁰ Surprisingly, as many as 90% of Olympic athletes and super sprint competitors understood the importance of using sunscreen.⁹

What can we learn from these findings?

First, elite athletes remain at high risk for skin cancer because of training regimens, occupational environmental hazards, and other requirements of their sport. Second, despite awareness of the risks of UV radiation exposure, Olympic athletes utilize inadequate photoprotection. Athletes with darker skin are still at risk for skin cancer, photoaging, and pigmentation disorders—indicating a need for photoprotective behaviors in athletes of all skin types.¹¹

Therefore, efforts to promote adequate sunscreen use and understanding of the consequences of UV radiation may need to be prioritized earlier in athletes’ careers and implemented according to evidence-based guidelines. For example, the Stanford University Network for Sun Protection, Outreach, Research and Teamwork (Sunsport) provided information about skin cancer risk and prevention by educating student-athletes, coaches, and trainers in the National Collegiate Athletic Association in the United States. The Sunsport initiative led to a dramatic increase in sunscreen use by student-athletes as well as increased knowledge and discussion of skin cancer risk.¹²

Atopic dermatitis (AD) is a chronic inflammatory disorder that affects individuals worldwide.¹ Although AD previously was commonly described as a skin-limited disease of childhood characterized by eczema in the flexural folds and pruritus, our current understanding supports a more heterogeneous condition.² We review the wide range of cutaneous presentations of AD with a focus on clinical and morphological presentations across diverse skin types—commonly referred to as skin of color (SOC).

Defining SOC in Relation to AD

The terms SOC, race, and ethnicity are used interchangeably, but their true meanings are distinct. Traditionally, race has been defined as a biological concept, grouping cohorts of individuals with a large degree of shared ancestry and genetic similarities,³ and ethnicity as a social construct, grouping individuals with common racial, national, tribal, religious, linguistic, or cultural backgrounds.⁴ In practice, both concepts can broadly be envisioned as mixed social, political, and economic constructs, as no one gene or biologic characteristic distinguishes one racial or ethnic group from another.⁵

The US Census Bureau recognizes 5 racial groupings: White, Black or African American, American Indian or Alaska Native, Asian, and Native Hawaiian or other Pacific Islander.⁶ Hispanic or Latinx origin is considered an ethnicity. It is important to note the limitations of these labels, as they do not completely encapsulate the heterogeneity of the US population. Overgeneralization of racial and ethnic categories may dull or obscure true differences among populations.⁷

From an evolutionary perspective, skin pigmentation represents the product of 2 opposing clines produced by natural selection in response to both need for and protection from UV radiation across lattitudes.⁸ Defining SOC is not quite as simple. Skin of color often is equated with certain racial/ethnic groups, or even binary categories of Black vs non-Black or White vs non-White. Others may use the Fitzpatrick scale to discuss SOC, though this scale was originally created to measure the response of skin to UVA radiation exposure.⁹ The reality is that SOC is a complex term that cannot simply be defined by a certain group of skin tones, races, ethnicities, and/or Fitzpatrick skin types. With this in mind, SOC in the context of this article will often refer to non-White individuals based on the investigators’ terminology, but this definition is not all-encompassing.

Historically in medicine, racial/ethnic differences in outcomes have been equated to differences in biology/genetics without consideration of many external factors.¹⁰ The effects of racism, economic stability, health care access, environment, and education quality rarely are discussed, though they have a major impact on health and may better define associations with race or an SOC population. A discussion of the structural and social determinants of health contributing to disease outcomes should accompany any race-based guidelines to prevent inaccurately pathologizing race or SOC.¹⁰

Within the scope of AD, social determinants of health play an important role in contributing to disease morbidity. Environmental factors, including tobacco smoke, climate, pollutants, water hardness, und urban living, are related to AD prevalence and severity.¹¹ Higher socioeconomic status is associated with increased AD rates,¹² yet lower socioeconomic status is associated with more severe disease.¹³ Barriers to health care access and suboptimal care drive worse AD outcomes.¹⁴ Underrepresentation in clinical trials prevents the generalizability and safety of AD treatments.¹⁵ Disparities in these health determinants associated with AD likely are among the most important drivers of observed differences in disease presentation, severity, burden, and even prevalence—more so than genetics or ancestry alone¹⁶—yet this relationship is poorly understood and often presented as a consequence of race. It is critical to redefine the narrative when considering the heterogeneous presentations of AD in patients with SOC and acknowledge the limitations of current terminology when attempting to capture clinical diversity in AD, including in this review, where published findings often are limited by race-based analysis.

Epidemiology

The prevalence of AD has been increasing over the last few decades, and rates vary by region. In the United States, the prevalence of childhood and adult AD is 13% and 7%, respectively.^17,18 Globally, higher rates of pediatric AD are seen in Africa, Oceania, Southeast Asia (SEA), and Latin America compared to South Asia, Northern Europe, and Eastern Europe.¹⁹ The prevalence of AD varies widely within the same continent and country; for example, throughout Africa, prevalence was found to be anywhere between 4.7% and 23.3%.²⁰

Although AD lesions often are described as pruritic erythematous papules and plaques, other common morphologies in SOC populations include prurigo nodules, lichenoid papules, perifollicular papules, nummular lesions, and psoriasiform lesions (Table). Instead of applying normative terms such as classic vs atypical to AD morphology, we urge clinicians to be familiar with the full spectrum of AD skin signs.

Prurigo Nodules—Prurigo nodules are hyperkeratotic or erosive nodules with severe pruritus, often grouped symmetrically on the extensor surfaces of the arms, legs, and trunk (Figure 1).^14,21 The skin between lesions usually is unaffected but can be dry or lichenified or display postinflammatory pigmentary changes.¹⁴ Prurigo nodules are common. In a study of a cohort of patients with prurigo nodularis (N=108), nearly half (46.3%) were determined to have either an atopic predisposition or underlying AD as a contributing cause of the lesions.²¹

Prurigo nodules as a phenotype of AD may be more common in certain SOC populations. Studies from SEA have reported a higher prevalence of prurigo nodules among patients with AD.²⁸ Although there are limited formal studies assessing the true prevalence of this lesion type in African American AD patients in the United States, clinical evidence supports more frequent appearance of prurigo nodules in non-White patients.²⁹ Contributing factors include suboptimal care for AD in SOC populations and/or barriers to health care access, resulting in more severe disease that increases the risk for this lesion type.¹⁴

Lichenoid Papules—Papular lichenoid lesions often present on the extensor surfaces of the arms and legs in AD (Figure 2).²² In a study of Nigerian patients with AD (N=1019), 54.1% had lichenoid papules.²⁴ A systematic review of AD characteristics by region similarly reported an increased prevalence of this lesion type in African studies.²⁸ Lichenoid variants of AD have been well described in SOC patients in the United States.²³ In contrast to the lesions of lichen planus, the lichenoid papules of AD usually are round, rarely display koebnerization, do not have Wickham striae, and predominantly are located on extensor surfaces.

Perifollicular Papules—Perifollicular accentuation—dermatitis enhanced around hair follicles—is a well-described lesional morphology of AD that is noted in all racial/ethnic groups (Figure 3).²² In fact, perifollicular accentuation is included as one of the Hanifin and Rajka minor criteria for AD.³⁰ Studies performed in Nigeria and India showed perifollicular accentuation in up to 70% of AD patients.^24,31 In a study of adult Thai patients (N=56), follicular lesions were found more frequently in intrinsic AD (29%) compared with extrinsic AD (12%).³²

Nummular and Psoriasiform Lesions—Nummular lesions may be red, oozing, excoriated, studded with pustules and/or present on the extensor extremities (Figure 4). In SOC patients, these lesions often occur in areas where hyperpigmentation is noted.²² Studies in the United States and Mexico demonstrated that 15% to 17% of AD patients displayed nummular lesions.^23,33 Similar to follicular papules, nummular lesions were linked to intrinsic AD in a study of adult Thai patients.³²

Psoriasiform lesions show prominent scaling, lichenification, and clear demarcation.²⁵ It has been reported that the psoriasiform phenotype of AD is more common in Asian patients,²⁵ though this is likely an oversimplification. The participants in these studies were of Japanese and Korean ancestry, which covers a broad geographic region, and the grouping of individuals under a heterogeneous Asian category is unlikely to convey generalizable biologic or clinical information. Unsurprisingly, a systematic review of AD characteristics by region noted considerable phenotypical differences among patients in SEA, East Asia, Iran, and India.²⁸

Disease Severity

Several factors contribute to AD disease severity,³⁴ including objective assessments of inflammation, such as erythema and lichenification (Table), as well as subjective measures of symptoms, such as itch. The severity of AD is exacerbated by the social determinants of health, and a lower socioeconomic status, lower household income, lower parental education level and health, dilapidated housing, and presence of garbage on the street are among factors linked to worse AD disease severity.^13,17 Although non-White individuals with AD often are reported to have more severe disease than their White counterparts,³⁵ these types of health determinants may be the most relevant causes of observed differences.

Erythema—Erythema is a feature of inflammation used in the AD severity assessment. Erythema may appear in shades beyond red, including maroon, violaceous, or brown, in patients with darker pigmented skin, which may contribute to diagnosis of AD at a later disease stage.²⁶ Multiple AD severity scoring tools, such as the SCORing Atopic Dermatitis and Eczema Area and Severity Index, include erythema as a measure, which can lead to underestimation of AD severity in SOC populations. After adjusting for erythema score, one study found that Black children with AD had a risk for severe disease that was 6-times higher than White children.³⁶ Dermatological training must adequately teach physicians to recognize erythema across all skin tones.³⁷

Erythroderma (also known as exfoliative dermatitis) is rapidly spreading erythema on at least 90% of the total body surface area, often sparing the palms and soles.³² Erythroderma is a potentially life-threatening manifestation of severe AD. Although erythroderma may have many underlying causes, AD has been reported to be the cause in 5% to 24% of cases,³⁸ and compared to studies in Europe, the prevalence of erythroderma was higher in East Asian studies of AD.²⁸

Excoriation and Pruritus—Pruritus is a defining characteristic of AD, and the resulting excoriations often are predominant on physical examination, which is a key part of severity scores. Itch is the most prevalent symptom among patients with AD, and a greater itch severity has been linked to decreased health-related quality of life, increased mental health symptoms, impaired sleep, and decreased daily function.^39,40 The burden of itch may be greater in SOC populations. The impact of itch on quality of life among US military veterans was significantly higher in those who identified as non-White (P=.05).⁴¹ In another study of US military veterans, African American individuals reported a significantly higher emotional impact from itch (P<.05).⁴²

Lichenification—Lichenification is thickening of the skin due to chronic rubbing and scratching that causes a leathery elevated appearance with exaggerated skin lines.²⁷ Lichenification is included as a factor in common clinical scoring tools, with greater lichenification indicating greater disease severity. Studies from SEA and Africa suggested a higher prevalence of lichenification in AD patients.²⁸ A greater itch burden and thus increased rubbing/scratching in these populations may contribute to some of these findings.^42,43

Xerosis—Xerosis (or dry skin) is a common finding in AD that results from increased transepidermal water loss due to a dysfunctional epidermal barrier.⁴⁴ In a systematic review of AD characteristics by region, xerosis was among the top 5 most reported AD features globally in all regions except SEA.²⁸ Xerosis may be more stigmatizing in SOC populations because of the greater visibility of scaling and dryness on darker skin tones.¹

Postinflammatory Dyspigmentation—Postinflammatory pigment alteration may be a consequence of AD lesions, resulting in hyperpigmented and hypopigmented macules and patches. Patients with AD with darker skin tones are more likely to develop postinflammatory dyspigmentation.²⁶ A study of AD patients in Nigeria found that 63% displayed postinflammatory dyspigmentation.⁴⁵ Dyschromia, including postinflammatory hyperpigmentation, is one of the most common reasons for SOC patients to seek dermatologic care.⁴⁶ Postinflammatory pigment alteration can cause severe distress in patients, even more so than the cutaneous findings of AD. Although altered skin pigmentation usually returns to normal over weeks to months, skin depigmentation from chronic excoriation may be permanent.²⁶ Appropriately treating hyperpigmentation and hypopigmentation in SOC populations can greatly improve quality of life.⁴⁷

Conclusion

Atopic dermatitis is a cutaneous inflammatory disease that presents with many clinical phenotypes. Dermatologists should be trained to recognize the heterogeneous signs of AD present across the diverse skin types in SOC patients. Future research should move away from race-based analyses and focus on the complex interplay of environmental factors, social determinants of health, and skin pigmentation, as well as how these factors drive variations in AD lesional morphology and inflammation.

Atopic dermatitis (AD) is a chronic inflammatory disorder that affects individuals worldwide.¹ Although AD previously was commonly described as a skin-limited disease of childhood characterized by eczema in the flexural folds and pruritus, our current understanding supports a more heterogeneous condition.² We review the wide range of cutaneous presentations of AD with a focus on clinical and morphological presentations across diverse skin types—commonly referred to as skin of color (SOC).

Defining SOC in Relation to AD

The terms SOC, race, and ethnicity are used interchangeably, but their true meanings are distinct. Traditionally, race has been defined as a biological concept, grouping cohorts of individuals with a large degree of shared ancestry and genetic similarities,³ and ethnicity as a social construct, grouping individuals with common racial, national, tribal, religious, linguistic, or cultural backgrounds.⁴ In practice, both concepts can broadly be envisioned as mixed social, political, and economic constructs, as no one gene or biologic characteristic distinguishes one racial or ethnic group from another.⁵

The US Census Bureau recognizes 5 racial groupings: White, Black or African American, American Indian or Alaska Native, Asian, and Native Hawaiian or other Pacific Islander.⁶ Hispanic or Latinx origin is considered an ethnicity. It is important to note the limitations of these labels, as they do not completely encapsulate the heterogeneity of the US population. Overgeneralization of racial and ethnic categories may dull or obscure true differences among populations.⁷

From an evolutionary perspective, skin pigmentation represents the product of 2 opposing clines produced by natural selection in response to both need for and protection from UV radiation across lattitudes.⁸ Defining SOC is not quite as simple. Skin of color often is equated with certain racial/ethnic groups, or even binary categories of Black vs non-Black or White vs non-White. Others may use the Fitzpatrick scale to discuss SOC, though this scale was originally created to measure the response of skin to UVA radiation exposure.⁹ The reality is that SOC is a complex term that cannot simply be defined by a certain group of skin tones, races, ethnicities, and/or Fitzpatrick skin types. With this in mind, SOC in the context of this article will often refer to non-White individuals based on the investigators’ terminology, but this definition is not all-encompassing.

Historically in medicine, racial/ethnic differences in outcomes have been equated to differences in biology/genetics without consideration of many external factors.¹⁰ The effects of racism, economic stability, health care access, environment, and education quality rarely are discussed, though they have a major impact on health and may better define associations with race or an SOC population. A discussion of the structural and social determinants of health contributing to disease outcomes should accompany any race-based guidelines to prevent inaccurately pathologizing race or SOC.¹⁰

Within the scope of AD, social determinants of health play an important role in contributing to disease morbidity. Environmental factors, including tobacco smoke, climate, pollutants, water hardness, und urban living, are related to AD prevalence and severity.¹¹ Higher socioeconomic status is associated with increased AD rates,¹² yet lower socioeconomic status is associated with more severe disease.¹³ Barriers to health care access and suboptimal care drive worse AD outcomes.¹⁴ Underrepresentation in clinical trials prevents the generalizability and safety of AD treatments.¹⁵ Disparities in these health determinants associated with AD likely are among the most important drivers of observed differences in disease presentation, severity, burden, and even prevalence—more so than genetics or ancestry alone¹⁶—yet this relationship is poorly understood and often presented as a consequence of race. It is critical to redefine the narrative when considering the heterogeneous presentations of AD in patients with SOC and acknowledge the limitations of current terminology when attempting to capture clinical diversity in AD, including in this review, where published findings often are limited by race-based analysis.

Epidemiology

The prevalence of AD has been increasing over the last few decades, and rates vary by region. In the United States, the prevalence of childhood and adult AD is 13% and 7%, respectively.^17,18 Globally, higher rates of pediatric AD are seen in Africa, Oceania, Southeast Asia (SEA), and Latin America compared to South Asia, Northern Europe, and Eastern Europe.¹⁹ The prevalence of AD varies widely within the same continent and country; for example, throughout Africa, prevalence was found to be anywhere between 4.7% and 23.3%.²⁰

Although AD lesions often are described as pruritic erythematous papules and plaques, other common morphologies in SOC populations include prurigo nodules, lichenoid papules, perifollicular papules, nummular lesions, and psoriasiform lesions (Table). Instead of applying normative terms such as classic vs atypical to AD morphology, we urge clinicians to be familiar with the full spectrum of AD skin signs.

Prurigo Nodules—Prurigo nodules are hyperkeratotic or erosive nodules with severe pruritus, often grouped symmetrically on the extensor surfaces of the arms, legs, and trunk (Figure 1).^14,21 The skin between lesions usually is unaffected but can be dry or lichenified or display postinflammatory pigmentary changes.¹⁴ Prurigo nodules are common. In a study of a cohort of patients with prurigo nodularis (N=108), nearly half (46.3%) were determined to have either an atopic predisposition or underlying AD as a contributing cause of the lesions.²¹

Prurigo nodules as a phenotype of AD may be more common in certain SOC populations. Studies from SEA have reported a higher prevalence of prurigo nodules among patients with AD.²⁸ Although there are limited formal studies assessing the true prevalence of this lesion type in African American AD patients in the United States, clinical evidence supports more frequent appearance of prurigo nodules in non-White patients.²⁹ Contributing factors include suboptimal care for AD in SOC populations and/or barriers to health care access, resulting in more severe disease that increases the risk for this lesion type.¹⁴

Lichenoid Papules—Papular lichenoid lesions often present on the extensor surfaces of the arms and legs in AD (Figure 2).²² In a study of Nigerian patients with AD (N=1019), 54.1% had lichenoid papules.²⁴ A systematic review of AD characteristics by region similarly reported an increased prevalence of this lesion type in African studies.²⁸ Lichenoid variants of AD have been well described in SOC patients in the United States.²³ In contrast to the lesions of lichen planus, the lichenoid papules of AD usually are round, rarely display koebnerization, do not have Wickham striae, and predominantly are located on extensor surfaces.

Perifollicular Papules—Perifollicular accentuation—dermatitis enhanced around hair follicles—is a well-described lesional morphology of AD that is noted in all racial/ethnic groups (Figure 3).²² In fact, perifollicular accentuation is included as one of the Hanifin and Rajka minor criteria for AD.³⁰ Studies performed in Nigeria and India showed perifollicular accentuation in up to 70% of AD patients.^24,31 In a study of adult Thai patients (N=56), follicular lesions were found more frequently in intrinsic AD (29%) compared with extrinsic AD (12%).³²

Nummular and Psoriasiform Lesions—Nummular lesions may be red, oozing, excoriated, studded with pustules and/or present on the extensor extremities (Figure 4). In SOC patients, these lesions often occur in areas where hyperpigmentation is noted.²² Studies in the United States and Mexico demonstrated that 15% to 17% of AD patients displayed nummular lesions.^23,33 Similar to follicular papules, nummular lesions were linked to intrinsic AD in a study of adult Thai patients.³²

Psoriasiform lesions show prominent scaling, lichenification, and clear demarcation.²⁵ It has been reported that the psoriasiform phenotype of AD is more common in Asian patients,²⁵ though this is likely an oversimplification. The participants in these studies were of Japanese and Korean ancestry, which covers a broad geographic region, and the grouping of individuals under a heterogeneous Asian category is unlikely to convey generalizable biologic or clinical information. Unsurprisingly, a systematic review of AD characteristics by region noted considerable phenotypical differences among patients in SEA, East Asia, Iran, and India.²⁸

Disease Severity

Several factors contribute to AD disease severity,³⁴ including objective assessments of inflammation, such as erythema and lichenification (Table), as well as subjective measures of symptoms, such as itch. The severity of AD is exacerbated by the social determinants of health, and a lower socioeconomic status, lower household income, lower parental education level and health, dilapidated housing, and presence of garbage on the street are among factors linked to worse AD disease severity.^13,17 Although non-White individuals with AD often are reported to have more severe disease than their White counterparts,³⁵ these types of health determinants may be the most relevant causes of observed differences.

Erythema—Erythema is a feature of inflammation used in the AD severity assessment. Erythema may appear in shades beyond red, including maroon, violaceous, or brown, in patients with darker pigmented skin, which may contribute to diagnosis of AD at a later disease stage.²⁶ Multiple AD severity scoring tools, such as the SCORing Atopic Dermatitis and Eczema Area and Severity Index, include erythema as a measure, which can lead to underestimation of AD severity in SOC populations. After adjusting for erythema score, one study found that Black children with AD had a risk for severe disease that was 6-times higher than White children.³⁶ Dermatological training must adequately teach physicians to recognize erythema across all skin tones.³⁷

Erythroderma (also known as exfoliative dermatitis) is rapidly spreading erythema on at least 90% of the total body surface area, often sparing the palms and soles.³² Erythroderma is a potentially life-threatening manifestation of severe AD. Although erythroderma may have many underlying causes, AD has been reported to be the cause in 5% to 24% of cases,³⁸ and compared to studies in Europe, the prevalence of erythroderma was higher in East Asian studies of AD.²⁸

Excoriation and Pruritus—Pruritus is a defining characteristic of AD, and the resulting excoriations often are predominant on physical examination, which is a key part of severity scores. Itch is the most prevalent symptom among patients with AD, and a greater itch severity has been linked to decreased health-related quality of life, increased mental health symptoms, impaired sleep, and decreased daily function.^39,40 The burden of itch may be greater in SOC populations. The impact of itch on quality of life among US military veterans was significantly higher in those who identified as non-White (P=.05).⁴¹ In another study of US military veterans, African American individuals reported a significantly higher emotional impact from itch (P<.05).⁴²

Lichenification—Lichenification is thickening of the skin due to chronic rubbing and scratching that causes a leathery elevated appearance with exaggerated skin lines.²⁷ Lichenification is included as a factor in common clinical scoring tools, with greater lichenification indicating greater disease severity. Studies from SEA and Africa suggested a higher prevalence of lichenification in AD patients.²⁸ A greater itch burden and thus increased rubbing/scratching in these populations may contribute to some of these findings.^42,43

Xerosis—Xerosis (or dry skin) is a common finding in AD that results from increased transepidermal water loss due to a dysfunctional epidermal barrier.⁴⁴ In a systematic review of AD characteristics by region, xerosis was among the top 5 most reported AD features globally in all regions except SEA.²⁸ Xerosis may be more stigmatizing in SOC populations because of the greater visibility of scaling and dryness on darker skin tones.¹

Postinflammatory Dyspigmentation—Postinflammatory pigment alteration may be a consequence of AD lesions, resulting in hyperpigmented and hypopigmented macules and patches. Patients with AD with darker skin tones are more likely to develop postinflammatory dyspigmentation.²⁶ A study of AD patients in Nigeria found that 63% displayed postinflammatory dyspigmentation.⁴⁵ Dyschromia, including postinflammatory hyperpigmentation, is one of the most common reasons for SOC patients to seek dermatologic care.⁴⁶ Postinflammatory pigment alteration can cause severe distress in patients, even more so than the cutaneous findings of AD. Although altered skin pigmentation usually returns to normal over weeks to months, skin depigmentation from chronic excoriation may be permanent.²⁶ Appropriately treating hyperpigmentation and hypopigmentation in SOC populations can greatly improve quality of life.⁴⁷

Conclusion

Atopic dermatitis is a cutaneous inflammatory disease that presents with many clinical phenotypes. Dermatologists should be trained to recognize the heterogeneous signs of AD present across the diverse skin types in SOC patients. Future research should move away from race-based analyses and focus on the complex interplay of environmental factors, social determinants of health, and skin pigmentation, as well as how these factors drive variations in AD lesional morphology and inflammation.

Atopic dermatitis (AD) is a chronic inflammatory disorder that affects individuals worldwide.¹ Although AD previously was commonly described as a skin-limited disease of childhood characterized by eczema in the flexural folds and pruritus, our current understanding supports a more heterogeneous condition.² We review the wide range of cutaneous presentations of AD with a focus on clinical and morphological presentations across diverse skin types—commonly referred to as skin of color (SOC).

Defining SOC in Relation to AD

The terms SOC, race, and ethnicity are used interchangeably, but their true meanings are distinct. Traditionally, race has been defined as a biological concept, grouping cohorts of individuals with a large degree of shared ancestry and genetic similarities,³ and ethnicity as a social construct, grouping individuals with common racial, national, tribal, religious, linguistic, or cultural backgrounds.⁴ In practice, both concepts can broadly be envisioned as mixed social, political, and economic constructs, as no one gene or biologic characteristic distinguishes one racial or ethnic group from another.⁵

The US Census Bureau recognizes 5 racial groupings: White, Black or African American, American Indian or Alaska Native, Asian, and Native Hawaiian or other Pacific Islander.⁶ Hispanic or Latinx origin is considered an ethnicity. It is important to note the limitations of these labels, as they do not completely encapsulate the heterogeneity of the US population. Overgeneralization of racial and ethnic categories may dull or obscure true differences among populations.⁷

From an evolutionary perspective, skin pigmentation represents the product of 2 opposing clines produced by natural selection in response to both need for and protection from UV radiation across lattitudes.⁸ Defining SOC is not quite as simple. Skin of color often is equated with certain racial/ethnic groups, or even binary categories of Black vs non-Black or White vs non-White. Others may use the Fitzpatrick scale to discuss SOC, though this scale was originally created to measure the response of skin to UVA radiation exposure.⁹ The reality is that SOC is a complex term that cannot simply be defined by a certain group of skin tones, races, ethnicities, and/or Fitzpatrick skin types. With this in mind, SOC in the context of this article will often refer to non-White individuals based on the investigators’ terminology, but this definition is not all-encompassing.

Historically in medicine, racial/ethnic differences in outcomes have been equated to differences in biology/genetics without consideration of many external factors.¹⁰ The effects of racism, economic stability, health care access, environment, and education quality rarely are discussed, though they have a major impact on health and may better define associations with race or an SOC population. A discussion of the structural and social determinants of health contributing to disease outcomes should accompany any race-based guidelines to prevent inaccurately pathologizing race or SOC.¹⁰

Within the scope of AD, social determinants of health play an important role in contributing to disease morbidity. Environmental factors, including tobacco smoke, climate, pollutants, water hardness, und urban living, are related to AD prevalence and severity.¹¹ Higher socioeconomic status is associated with increased AD rates,¹² yet lower socioeconomic status is associated with more severe disease.¹³ Barriers to health care access and suboptimal care drive worse AD outcomes.¹⁴ Underrepresentation in clinical trials prevents the generalizability and safety of AD treatments.¹⁵ Disparities in these health determinants associated with AD likely are among the most important drivers of observed differences in disease presentation, severity, burden, and even prevalence—more so than genetics or ancestry alone¹⁶—yet this relationship is poorly understood and often presented as a consequence of race. It is critical to redefine the narrative when considering the heterogeneous presentations of AD in patients with SOC and acknowledge the limitations of current terminology when attempting to capture clinical diversity in AD, including in this review, where published findings often are limited by race-based analysis.

Epidemiology

The prevalence of AD has been increasing over the last few decades, and rates vary by region. In the United States, the prevalence of childhood and adult AD is 13% and 7%, respectively.^17,18 Globally, higher rates of pediatric AD are seen in Africa, Oceania, Southeast Asia (SEA), and Latin America compared to South Asia, Northern Europe, and Eastern Europe.¹⁹ The prevalence of AD varies widely within the same continent and country; for example, throughout Africa, prevalence was found to be anywhere between 4.7% and 23.3%.²⁰

Although AD lesions often are described as pruritic erythematous papules and plaques, other common morphologies in SOC populations include prurigo nodules, lichenoid papules, perifollicular papules, nummular lesions, and psoriasiform lesions (Table). Instead of applying normative terms such as classic vs atypical to AD morphology, we urge clinicians to be familiar with the full spectrum of AD skin signs.

Prurigo Nodules—Prurigo nodules are hyperkeratotic or erosive nodules with severe pruritus, often grouped symmetrically on the extensor surfaces of the arms, legs, and trunk (Figure 1).^14,21 The skin between lesions usually is unaffected but can be dry or lichenified or display postinflammatory pigmentary changes.¹⁴ Prurigo nodules are common. In a study of a cohort of patients with prurigo nodularis (N=108), nearly half (46.3%) were determined to have either an atopic predisposition or underlying AD as a contributing cause of the lesions.²¹

Prurigo nodules as a phenotype of AD may be more common in certain SOC populations. Studies from SEA have reported a higher prevalence of prurigo nodules among patients with AD.²⁸ Although there are limited formal studies assessing the true prevalence of this lesion type in African American AD patients in the United States, clinical evidence supports more frequent appearance of prurigo nodules in non-White patients.²⁹ Contributing factors include suboptimal care for AD in SOC populations and/or barriers to health care access, resulting in more severe disease that increases the risk for this lesion type.¹⁴

Lichenoid Papules—Papular lichenoid lesions often present on the extensor surfaces of the arms and legs in AD (Figure 2).²² In a study of Nigerian patients with AD (N=1019), 54.1% had lichenoid papules.²⁴ A systematic review of AD characteristics by region similarly reported an increased prevalence of this lesion type in African studies.²⁸ Lichenoid variants of AD have been well described in SOC patients in the United States.²³ In contrast to the lesions of lichen planus, the lichenoid papules of AD usually are round, rarely display koebnerization, do not have Wickham striae, and predominantly are located on extensor surfaces.

Perifollicular Papules—Perifollicular accentuation—dermatitis enhanced around hair follicles—is a well-described lesional morphology of AD that is noted in all racial/ethnic groups (Figure 3).²² In fact, perifollicular accentuation is included as one of the Hanifin and Rajka minor criteria for AD.³⁰ Studies performed in Nigeria and India showed perifollicular accentuation in up to 70% of AD patients.^24,31 In a study of adult Thai patients (N=56), follicular lesions were found more frequently in intrinsic AD (29%) compared with extrinsic AD (12%).³²

Nummular and Psoriasiform Lesions—Nummular lesions may be red, oozing, excoriated, studded with pustules and/or present on the extensor extremities (Figure 4). In SOC patients, these lesions often occur in areas where hyperpigmentation is noted.²² Studies in the United States and Mexico demonstrated that 15% to 17% of AD patients displayed nummular lesions.^23,33 Similar to follicular papules, nummular lesions were linked to intrinsic AD in a study of adult Thai patients.³²

Psoriasiform lesions show prominent scaling, lichenification, and clear demarcation.²⁵ It has been reported that the psoriasiform phenotype of AD is more common in Asian patients,²⁵ though this is likely an oversimplification. The participants in these studies were of Japanese and Korean ancestry, which covers a broad geographic region, and the grouping of individuals under a heterogeneous Asian category is unlikely to convey generalizable biologic or clinical information. Unsurprisingly, a systematic review of AD characteristics by region noted considerable phenotypical differences among patients in SEA, East Asia, Iran, and India.²⁸

Disease Severity

Several factors contribute to AD disease severity,³⁴ including objective assessments of inflammation, such as erythema and lichenification (Table), as well as subjective measures of symptoms, such as itch. The severity of AD is exacerbated by the social determinants of health, and a lower socioeconomic status, lower household income, lower parental education level and health, dilapidated housing, and presence of garbage on the street are among factors linked to worse AD disease severity.^13,17 Although non-White individuals with AD often are reported to have more severe disease than their White counterparts,³⁵ these types of health determinants may be the most relevant causes of observed differences.

Erythema—Erythema is a feature of inflammation used in the AD severity assessment. Erythema may appear in shades beyond red, including maroon, violaceous, or brown, in patients with darker pigmented skin, which may contribute to diagnosis of AD at a later disease stage.²⁶ Multiple AD severity scoring tools, such as the SCORing Atopic Dermatitis and Eczema Area and Severity Index, include erythema as a measure, which can lead to underestimation of AD severity in SOC populations. After adjusting for erythema score, one study found that Black children with AD had a risk for severe disease that was 6-times higher than White children.³⁶ Dermatological training must adequately teach physicians to recognize erythema across all skin tones.³⁷

Erythroderma (also known as exfoliative dermatitis) is rapidly spreading erythema on at least 90% of the total body surface area, often sparing the palms and soles.³² Erythroderma is a potentially life-threatening manifestation of severe AD. Although erythroderma may have many underlying causes, AD has been reported to be the cause in 5% to 24% of cases,³⁸ and compared to studies in Europe, the prevalence of erythroderma was higher in East Asian studies of AD.²⁸

Excoriation and Pruritus—Pruritus is a defining characteristic of AD, and the resulting excoriations often are predominant on physical examination, which is a key part of severity scores. Itch is the most prevalent symptom among patients with AD, and a greater itch severity has been linked to decreased health-related quality of life, increased mental health symptoms, impaired sleep, and decreased daily function.^39,40 The burden of itch may be greater in SOC populations. The impact of itch on quality of life among US military veterans was significantly higher in those who identified as non-White (P=.05).⁴¹ In another study of US military veterans, African American individuals reported a significantly higher emotional impact from itch (P<.05).⁴²

Lichenification—Lichenification is thickening of the skin due to chronic rubbing and scratching that causes a leathery elevated appearance with exaggerated skin lines.²⁷ Lichenification is included as a factor in common clinical scoring tools, with greater lichenification indicating greater disease severity. Studies from SEA and Africa suggested a higher prevalence of lichenification in AD patients.²⁸ A greater itch burden and thus increased rubbing/scratching in these populations may contribute to some of these findings.^42,43

Xerosis—Xerosis (or dry skin) is a common finding in AD that results from increased transepidermal water loss due to a dysfunctional epidermal barrier.⁴⁴ In a systematic review of AD characteristics by region, xerosis was among the top 5 most reported AD features globally in all regions except SEA.²⁸ Xerosis may be more stigmatizing in SOC populations because of the greater visibility of scaling and dryness on darker skin tones.¹

Postinflammatory Dyspigmentation—Postinflammatory pigment alteration may be a consequence of AD lesions, resulting in hyperpigmented and hypopigmented macules and patches. Patients with AD with darker skin tones are more likely to develop postinflammatory dyspigmentation.²⁶ A study of AD patients in Nigeria found that 63% displayed postinflammatory dyspigmentation.⁴⁵ Dyschromia, including postinflammatory hyperpigmentation, is one of the most common reasons for SOC patients to seek dermatologic care.⁴⁶ Postinflammatory pigment alteration can cause severe distress in patients, even more so than the cutaneous findings of AD. Although altered skin pigmentation usually returns to normal over weeks to months, skin depigmentation from chronic excoriation may be permanent.²⁶ Appropriately treating hyperpigmentation and hypopigmentation in SOC populations can greatly improve quality of life.⁴⁷

Conclusion

Atopic dermatitis is a cutaneous inflammatory disease that presents with many clinical phenotypes. Dermatologists should be trained to recognize the heterogeneous signs of AD present across the diverse skin types in SOC patients. Future research should move away from race-based analyses and focus on the complex interplay of environmental factors, social determinants of health, and skin pigmentation, as well as how these factors drive variations in AD lesional morphology and inflammation.

To the Editor:

Plaquelike or plaque-type syringoma is a lesser-known variant of syringoma that can appear histologically indistinguishable from the superficial portion of microcystic adnexal carcinoma (MAC). The plaquelike variant of syringoma holds a benign clinical course, and no treatment is necessary. Microcystic adnexal carcinoma is distinguished from plaquelike syringoma by an aggressive growth pattern with a high risk for local invasion and recurrence if inadequately treated. Thus, treatment with Mohs micrographic surgery (MMS) has been recommended as the mainstay for MAC. If superficial biopsy specimens reveal suspicion for MAC and patients are referred for MMS, careful consideration should be made to differentiate MAC and plaquelike syringoma early to prevent unnecessary morbidity.

A 78-year-old woman was referred for MMS for a left forehead lesion that was diagnosed via shave biopsy as a desmoplastic and cystic adnexal neoplasm with suspicion for desmoplastic trichoepithelioma or MAC (Figure 1). Upon presentation for MMS, a well-healed, 1.0×0.9-cm scar at the biopsy site on the left forehead was observed (Figure 2A). One stage was obtained by standard MMS technique and sent for intraoperative processing (Figure 2B). Frozen section examination of the first stage demonstrated peripheral margin involvement with syringomatous change confined to the superficial and mid dermis (Figure 3). Before proceeding further, these findings were reviewed with an in-house dermatopathologist, and it was determined that no infiltrative tumor, perineural involvement, or other features to indicate malignancy were noted. A decision was made to refrain from obtaining any additional layers and to send excised Burow triangles for permanent section analysis. A primary linear closure was performed without complication, and the patient was discharged from the ambulatory surgery suite. Histopathologic examination of the Burow triangles later confirmed findings consistent with plaquelike syringoma with no evidence of malignancy (Figure 4).

Syringomas present as small flesh-colored papules in the periorbital areas. These benign neoplasms previously have been classified into 4 major clinical variants: localized, generalized, Down syndrome associated, and familial.¹ The lesser-known plaquelike variant of syringoma was first described by Kikuchi et al² in 1979. Aside from our report, a PubMed search of articles indexed for MEDLINE using the terms plaquelike or plaque-type syringoma yielded 16 cases in the literature.^2-14 Of these, 6 were referred to or encountered in the MMS setting.^8,9,11,12,14 Plaquelike syringoma can be solitary or multiple in presentation.⁶ It most commonly involves the head and neck but also can present on the trunk, arms, legs, and groin areas. The clinical size of plaquelike syringoma is variable, with the largest reported cases extending several centimeters in diameter.^2,6 Similar to reported associations with conventional syringoma, the plaquelike subtype of syringoma has been reported in association with Down syndrome.¹³

Histopathologically, plaquelike syringoma shares features with MAC as well as desmoplastic trichoepithelioma and desmoplastic basal cell carcinoma. Plaquelike syringoma demonstrates broad proliferations of small tubules morphologically reminiscent of tadpoles confined within the dermis. Ducts typically are lined with 2 or 3 layers of small cuboidal cells. Microcystic adnexal carcinoma typically features asymmetric ductal structures lined with single cells extending from the dermis into the subcutis and even underlying muscle, cartilage, or bone.⁸ There are no reliable immunohistochemical stains to differentiate between these 2 entities; thus, the primary distinction lies in the depth of involvement. Desmoplastic trichoepithelioma is composed of narrow cords and nests of basaloid cells of follicular origin commonly admixed with small cornifying cysts appearing in the dermis.⁸ Colonizing Merkel cells positive for cytokeratin 20 often are present in desmoplastic trichoepithelioma and not in syringoma or MAC.¹⁵ Desmoplastic basal cell carcinoma demonstrates narrow strands of basaloid cells of follicular origin appearing in the dermis. Desmoplastic trichoepithelioma and desmoplastic basal cell carcinoma are each fundamentally differentiated from plaquelike syringoma in that proliferations of cords and nests are not of eccrine or apocrine origin.

Several cases of plaquelike syringoma have been challenging to distinguish from MAC in performing MMS.^8,9,11 Underlying extension of this syringoma variant can be far-reaching, extending to several centimeters in size and involving multiple cosmetic subunits.^6,11,14 Inadvertent overtreatment with multiple MMS stages can be avoided with careful recognition of the differentiating histopathologic features. Syringomatous lesions commonly are encountered in MMS and may even be present at the edge of other tumor types. Plaquelike syringoma has been reported as a coexistent entity with nodular basal cell carcinoma.¹² Boos et al¹⁶ similarly reported the presence of deceptive ductal proliferations along the immediate peripheral margin of MAC, which prompted multiple re-excisions. Pursuit of permanent section analysis in these cases revealed the appearance of small syringomas, and a diagnosis of benign subclinical syringomatous proliferations was made, averting further intervention.¹⁶

Our case sheds light on the threat of commission bias in dermatologic surgery, which is the tendency for action rather than inaction.¹⁷ In this context, it is important to avoid the perspective that harm to the patient can only be prevented by active intervention. Cognitive bias has been increasingly recognized as a source of medical error, and methods to mitigate bias in medical practice have been well described.¹⁷ Microcystic adnexal carcinoma and plaquelike syringoma can be hard to differentiate especially initially, as demonstrated in our case, which particularly illustrates the importance of slowing down a surgical case at the appropriate time, considering and revisiting alternative diagnoses, implementing checklists, and seeking histopathologic collaboration with colleagues when necessary. Our attempted implementation of these principles, especially early collaboration with colleagues, led to intraoperative recognition of plaquelike syringoma within the first stage of MMS.

We seek to raise the index of suspicion for plaquelike syringoma among dermatologists and dermatologic surgeons, especially when syringomatous structures are limited to the superficial dermis. We encourage familiarity with the plaquelike syringoma entity as well as careful consideration of further investigation via scouting biopsies or permanent section analysis when other characteristic features of MAC are unclear or lacking. Adequate sampling as well as collaboration with a dermatopathologist in cases of suspected syringoma can help to reduce the susceptibility to commission bias and prevent histopathologic pitfalls and unwarranted surgical morbidity.

To the Editor:

Plaquelike or plaque-type syringoma is a lesser-known variant of syringoma that can appear histologically indistinguishable from the superficial portion of microcystic adnexal carcinoma (MAC). The plaquelike variant of syringoma holds a benign clinical course, and no treatment is necessary. Microcystic adnexal carcinoma is distinguished from plaquelike syringoma by an aggressive growth pattern with a high risk for local invasion and recurrence if inadequately treated. Thus, treatment with Mohs micrographic surgery (MMS) has been recommended as the mainstay for MAC. If superficial biopsy specimens reveal suspicion for MAC and patients are referred for MMS, careful consideration should be made to differentiate MAC and plaquelike syringoma early to prevent unnecessary morbidity.

A 78-year-old woman was referred for MMS for a left forehead lesion that was diagnosed via shave biopsy as a desmoplastic and cystic adnexal neoplasm with suspicion for desmoplastic trichoepithelioma or MAC (Figure 1). Upon presentation for MMS, a well-healed, 1.0×0.9-cm scar at the biopsy site on the left forehead was observed (Figure 2A). One stage was obtained by standard MMS technique and sent for intraoperative processing (Figure 2B). Frozen section examination of the first stage demonstrated peripheral margin involvement with syringomatous change confined to the superficial and mid dermis (Figure 3). Before proceeding further, these findings were reviewed with an in-house dermatopathologist, and it was determined that no infiltrative tumor, perineural involvement, or other features to indicate malignancy were noted. A decision was made to refrain from obtaining any additional layers and to send excised Burow triangles for permanent section analysis. A primary linear closure was performed without complication, and the patient was discharged from the ambulatory surgery suite. Histopathologic examination of the Burow triangles later confirmed findings consistent with plaquelike syringoma with no evidence of malignancy (Figure 4).

Syringomas present as small flesh-colored papules in the periorbital areas. These benign neoplasms previously have been classified into 4 major clinical variants: localized, generalized, Down syndrome associated, and familial.¹ The lesser-known plaquelike variant of syringoma was first described by Kikuchi et al² in 1979. Aside from our report, a PubMed search of articles indexed for MEDLINE using the terms plaquelike or plaque-type syringoma yielded 16 cases in the literature.^2-14 Of these, 6 were referred to or encountered in the MMS setting.^8,9,11,12,14 Plaquelike syringoma can be solitary or multiple in presentation.⁶ It most commonly involves the head and neck but also can present on the trunk, arms, legs, and groin areas. The clinical size of plaquelike syringoma is variable, with the largest reported cases extending several centimeters in diameter.^2,6 Similar to reported associations with conventional syringoma, the plaquelike subtype of syringoma has been reported in association with Down syndrome.¹³

Histopathologically, plaquelike syringoma shares features with MAC as well as desmoplastic trichoepithelioma and desmoplastic basal cell carcinoma. Plaquelike syringoma demonstrates broad proliferations of small tubules morphologically reminiscent of tadpoles confined within the dermis. Ducts typically are lined with 2 or 3 layers of small cuboidal cells. Microcystic adnexal carcinoma typically features asymmetric ductal structures lined with single cells extending from the dermis into the subcutis and even underlying muscle, cartilage, or bone.⁸ There are no reliable immunohistochemical stains to differentiate between these 2 entities; thus, the primary distinction lies in the depth of involvement. Desmoplastic trichoepithelioma is composed of narrow cords and nests of basaloid cells of follicular origin commonly admixed with small cornifying cysts appearing in the dermis.⁸ Colonizing Merkel cells positive for cytokeratin 20 often are present in desmoplastic trichoepithelioma and not in syringoma or MAC.¹⁵ Desmoplastic basal cell carcinoma demonstrates narrow strands of basaloid cells of follicular origin appearing in the dermis. Desmoplastic trichoepithelioma and desmoplastic basal cell carcinoma are each fundamentally differentiated from plaquelike syringoma in that proliferations of cords and nests are not of eccrine or apocrine origin.

Several cases of plaquelike syringoma have been challenging to distinguish from MAC in performing MMS.^8,9,11 Underlying extension of this syringoma variant can be far-reaching, extending to several centimeters in size and involving multiple cosmetic subunits.^6,11,14 Inadvertent overtreatment with multiple MMS stages can be avoided with careful recognition of the differentiating histopathologic features. Syringomatous lesions commonly are encountered in MMS and may even be present at the edge of other tumor types. Plaquelike syringoma has been reported as a coexistent entity with nodular basal cell carcinoma.¹² Boos et al¹⁶ similarly reported the presence of deceptive ductal proliferations along the immediate peripheral margin of MAC, which prompted multiple re-excisions. Pursuit of permanent section analysis in these cases revealed the appearance of small syringomas, and a diagnosis of benign subclinical syringomatous proliferations was made, averting further intervention.¹⁶

Our case sheds light on the threat of commission bias in dermatologic surgery, which is the tendency for action rather than inaction.¹⁷ In this context, it is important to avoid the perspective that harm to the patient can only be prevented by active intervention. Cognitive bias has been increasingly recognized as a source of medical error, and methods to mitigate bias in medical practice have been well described.¹⁷ Microcystic adnexal carcinoma and plaquelike syringoma can be hard to differentiate especially initially, as demonstrated in our case, which particularly illustrates the importance of slowing down a surgical case at the appropriate time, considering and revisiting alternative diagnoses, implementing checklists, and seeking histopathologic collaboration with colleagues when necessary. Our attempted implementation of these principles, especially early collaboration with colleagues, led to intraoperative recognition of plaquelike syringoma within the first stage of MMS.

We seek to raise the index of suspicion for plaquelike syringoma among dermatologists and dermatologic surgeons, especially when syringomatous structures are limited to the superficial dermis. We encourage familiarity with the plaquelike syringoma entity as well as careful consideration of further investigation via scouting biopsies or permanent section analysis when other characteristic features of MAC are unclear or lacking. Adequate sampling as well as collaboration with a dermatopathologist in cases of suspected syringoma can help to reduce the susceptibility to commission bias and prevent histopathologic pitfalls and unwarranted surgical morbidity.

To the Editor:

Plaquelike or plaque-type syringoma is a lesser-known variant of syringoma that can appear histologically indistinguishable from the superficial portion of microcystic adnexal carcinoma (MAC). The plaquelike variant of syringoma holds a benign clinical course, and no treatment is necessary. Microcystic adnexal carcinoma is distinguished from plaquelike syringoma by an aggressive growth pattern with a high risk for local invasion and recurrence if inadequately treated. Thus, treatment with Mohs micrographic surgery (MMS) has been recommended as the mainstay for MAC. If superficial biopsy specimens reveal suspicion for MAC and patients are referred for MMS, careful consideration should be made to differentiate MAC and plaquelike syringoma early to prevent unnecessary morbidity.

A 78-year-old woman was referred for MMS for a left forehead lesion that was diagnosed via shave biopsy as a desmoplastic and cystic adnexal neoplasm with suspicion for desmoplastic trichoepithelioma or MAC (Figure 1). Upon presentation for MMS, a well-healed, 1.0×0.9-cm scar at the biopsy site on the left forehead was observed (Figure 2A). One stage was obtained by standard MMS technique and sent for intraoperative processing (Figure 2B). Frozen section examination of the first stage demonstrated peripheral margin involvement with syringomatous change confined to the superficial and mid dermis (Figure 3). Before proceeding further, these findings were reviewed with an in-house dermatopathologist, and it was determined that no infiltrative tumor, perineural involvement, or other features to indicate malignancy were noted. A decision was made to refrain from obtaining any additional layers and to send excised Burow triangles for permanent section analysis. A primary linear closure was performed without complication, and the patient was discharged from the ambulatory surgery suite. Histopathologic examination of the Burow triangles later confirmed findings consistent with plaquelike syringoma with no evidence of malignancy (Figure 4).

Syringomas present as small flesh-colored papules in the periorbital areas. These benign neoplasms previously have been classified into 4 major clinical variants: localized, generalized, Down syndrome associated, and familial.¹ The lesser-known plaquelike variant of syringoma was first described by Kikuchi et al² in 1979. Aside from our report, a PubMed search of articles indexed for MEDLINE using the terms plaquelike or plaque-type syringoma yielded 16 cases in the literature.^2-14 Of these, 6 were referred to or encountered in the MMS setting.^8,9,11,12,14 Plaquelike syringoma can be solitary or multiple in presentation.⁶ It most commonly involves the head and neck but also can present on the trunk, arms, legs, and groin areas. The clinical size of plaquelike syringoma is variable, with the largest reported cases extending several centimeters in diameter.^2,6 Similar to reported associations with conventional syringoma, the plaquelike subtype of syringoma has been reported in association with Down syndrome.¹³

Histopathologically, plaquelike syringoma shares features with MAC as well as desmoplastic trichoepithelioma and desmoplastic basal cell carcinoma. Plaquelike syringoma demonstrates broad proliferations of small tubules morphologically reminiscent of tadpoles confined within the dermis. Ducts typically are lined with 2 or 3 layers of small cuboidal cells. Microcystic adnexal carcinoma typically features asymmetric ductal structures lined with single cells extending from the dermis into the subcutis and even underlying muscle, cartilage, or bone.⁸ There are no reliable immunohistochemical stains to differentiate between these 2 entities; thus, the primary distinction lies in the depth of involvement. Desmoplastic trichoepithelioma is composed of narrow cords and nests of basaloid cells of follicular origin commonly admixed with small cornifying cysts appearing in the dermis.⁸ Colonizing Merkel cells positive for cytokeratin 20 often are present in desmoplastic trichoepithelioma and not in syringoma or MAC.¹⁵ Desmoplastic basal cell carcinoma demonstrates narrow strands of basaloid cells of follicular origin appearing in the dermis. Desmoplastic trichoepithelioma and desmoplastic basal cell carcinoma are each fundamentally differentiated from plaquelike syringoma in that proliferations of cords and nests are not of eccrine or apocrine origin.

Several cases of plaquelike syringoma have been challenging to distinguish from MAC in performing MMS.^8,9,11 Underlying extension of this syringoma variant can be far-reaching, extending to several centimeters in size and involving multiple cosmetic subunits.^6,11,14 Inadvertent overtreatment with multiple MMS stages can be avoided with careful recognition of the differentiating histopathologic features. Syringomatous lesions commonly are encountered in MMS and may even be present at the edge of other tumor types. Plaquelike syringoma has been reported as a coexistent entity with nodular basal cell carcinoma.¹² Boos et al¹⁶ similarly reported the presence of deceptive ductal proliferations along the immediate peripheral margin of MAC, which prompted multiple re-excisions. Pursuit of permanent section analysis in these cases revealed the appearance of small syringomas, and a diagnosis of benign subclinical syringomatous proliferations was made, averting further intervention.¹⁶

Our case sheds light on the threat of commission bias in dermatologic surgery, which is the tendency for action rather than inaction.¹⁷ In this context, it is important to avoid the perspective that harm to the patient can only be prevented by active intervention. Cognitive bias has been increasingly recognized as a source of medical error, and methods to mitigate bias in medical practice have been well described.¹⁷ Microcystic adnexal carcinoma and plaquelike syringoma can be hard to differentiate especially initially, as demonstrated in our case, which particularly illustrates the importance of slowing down a surgical case at the appropriate time, considering and revisiting alternative diagnoses, implementing checklists, and seeking histopathologic collaboration with colleagues when necessary. Our attempted implementation of these principles, especially early collaboration with colleagues, led to intraoperative recognition of plaquelike syringoma within the first stage of MMS.

We seek to raise the index of suspicion for plaquelike syringoma among dermatologists and dermatologic surgeons, especially when syringomatous structures are limited to the superficial dermis. We encourage familiarity with the plaquelike syringoma entity as well as careful consideration of further investigation via scouting biopsies or permanent section analysis when other characteristic features of MAC are unclear or lacking. Adequate sampling as well as collaboration with a dermatopathologist in cases of suspected syringoma can help to reduce the susceptibility to commission bias and prevent histopathologic pitfalls and unwarranted surgical morbidity.

The Diagnosis: Glomangiomyoma

A punch biopsy of the right forearm revealed a collection of vascular and smooth muscle components with small and spindled bland cells containing minimal eosinophilic cytoplasm (Figure 1), confirming the diagnosis of glomangiomyoma. Immunohistochemical stains also supported the diagnosis and were positive for smooth muscle actin, desmin, and CD34 (Figure 2). Magnetic resonance imaging from a prior attempt at treatment with sclerotherapy demonstrated scattered vascular malformations with no notable internal derangement. There was no improvement with sclerotherapy. Given the number and vascular nature of the lesions, a trial of pulsed dye laser (PDL) therapy was administered and tolerated by the patient. He subsequently moved to a new military duty station. On follow-up, he reported no noticeable clinical improvement in the lesions after PDL and opted not to continue with laser treatment.

Glomangiomyoma is a rare and benign glomus tumor variant that demonstrates differentiation into the smooth muscle and potentially can result in substantial complications.¹ Glomus tumors generally are benign neoplasms of the glomus apparatus, and glomus cells function as thermoregulators in the reticular dermis.² Glomus tumors comprise less than 2% of soft tissue neoplasms and generally are solitary nodules; only 10% of glomus tumors occur with multiple lesions, and among them, glomangiomyoma is the rarest subtype, presenting in only 15% of cases.^2,3 The 3 main subtypes of glomus tumors are solid, glomangioma, and glomangiomyoma.4 Clinically, the lesions may present as small blue nodules with associated pain and cold or pressure sensitivity. Although there appears to be variation of the nomenclature depending on the source in the literature, glomangiomas are characterized by their predominant vascular malformations on biopsy. Glomangiomyomas are a subset of glomus tumors with distinct smooth muscle differentiation.⁴ Given their pathologic presentation, our patient’s lesions were most consistent with the diagnosis of glomangiomyoma.

The small size of the lesions may result in difficulty establishing a clinical diagnosis, particularly if there is no hand involvement, where lesions most commonly occur.² Therefore, histopathologic evaluation is essential and is the best initial step in evaluating glomangiomyomas.⁴ Biopsy is the most reliable means of confirming a diagnosis^2,4,5; however, diagnostic imaging such as a computed tomography also should be performed if considering blue rubber bleb nevus syndrome due to the primary site of involvement. Surgical excision is the treatment of choice after confirming the diagnosis in most cases of symptomatic glomangiomyomas, particularly with painful lesions.⁶

Neurilemmomas (also known as schwannomas) are benign lesions that generally present as asymptomatic, soft, smooth nodules most often on the neck; however, they also may present on the flexor extremities or in internal organs. Although primarily asymptomatic, the tumors may be associated with pain and paresthesia as they enlarge and affect surrounding structures. Neurilemmomas may occur spontaneously or as part of a syndrome, such as neurofibromatosis type 2 or Carney complex.⁷

Hereditary hemorrhagic telangiectasia (formerly known as Osler-Weber-Rendu syndrome) is an autosomal-dominant disease that presents with arteriovenous malformations and telangiectases. Patients generally present in the third decade of life, with the main concern generally being epistaxis.⁸

Kaposi sarcoma is a viral infection secondary to human herpesvirus 8 that results in red-purple lesions commonly on mucocutaneous sites. Kaposi sarcoma can be AIDS associated and non-HIV associated. Although clinically indistinguishable, a few subtle histologic features can assist in differentiating the 2 etiologies. In addition to a potential history of immunodeficiency, evaluating for involvement of the lymphatic system, respiratory tract, or gastrointestinal tract can aid in differentiating this entity from glomus tumors.9

Leiomyomas are smooth muscle lesions divided into 3 subcategories: angioleiomyoma, piloleiomyoma, and genital leiomyoma. The clinical presentation and histopathology will vary depending on the subcategory. Although cutaneous leiomyomas are benign, further workup for piloleiomyoma may be required given the reported association with hereditary leiomyomatosis and renal cell cancer (Reed syndrome).¹⁰

Imaging can be helpful when the clinical diagnosis of a glomus tumor vs other painful neoplasms of the skin is unclear, such as in blue rubber bleb nevus syndrome, angioleiomyomas, neuromas, glomus tumors, leiomyomas, eccrine spiradenomas, congenital vascular malformations, schwannomas, or hemangiomas.⁴ Radiologic findings for glomus tumors may demonstrate cortical or cystic osseous defects. Magnetic resonance imaging and ultrasonography can help provide additional information on the lesion size and depth of involvement.¹ Additionally, deeper glomangiomyomas have been associated with malignancy,² potentially highlighting the benefit of early incorporation of imaging in the workup for this condition. Malignant transformation is rare and has been reported in less than 1% of cases.⁶

Treatment of glomus tumors predominantly is directed to the patient’s symptoms; asymptomatic lesions may be monitored.⁴ For symptomatic lesions, therapeutic options include wide local excision; sclerotherapy; and incorporation of various lasers, including Nd:YAG, CO₂, and flashlamp tunable dye laser.^4,5 One case report documented use of a PDL that successfully eliminated the pain associated with glomangiomyoma; however, the lesion in that report was not biopsy proven.¹¹

Our case highlights the need to consider glomus tumors in patients presenting with multiple small nodules given the potential for misdiagnosis, impact on quality of life with associated psychological distress, and potential utility of incorporating PDL in treatment. Although our patient did not report clinical improvement in the appearance of the lesions with PDL therapy, additional treatment sessions may have helped,¹¹ but he opted to discontinue. Follow-up for persistently symptomatic or changing lesions is necessary, given the minimal risk for malignant transformation.⁶

The Diagnosis: Glomangiomyoma

A punch biopsy of the right forearm revealed a collection of vascular and smooth muscle components with small and spindled bland cells containing minimal eosinophilic cytoplasm (Figure 1), confirming the diagnosis of glomangiomyoma. Immunohistochemical stains also supported the diagnosis and were positive for smooth muscle actin, desmin, and CD34 (Figure 2). Magnetic resonance imaging from a prior attempt at treatment with sclerotherapy demonstrated scattered vascular malformations with no notable internal derangement. There was no improvement with sclerotherapy. Given the number and vascular nature of the lesions, a trial of pulsed dye laser (PDL) therapy was administered and tolerated by the patient. He subsequently moved to a new military duty station. On follow-up, he reported no noticeable clinical improvement in the lesions after PDL and opted not to continue with laser treatment.

Glomangiomyoma is a rare and benign glomus tumor variant that demonstrates differentiation into the smooth muscle and potentially can result in substantial complications.¹ Glomus tumors generally are benign neoplasms of the glomus apparatus, and glomus cells function as thermoregulators in the reticular dermis.² Glomus tumors comprise less than 2% of soft tissue neoplasms and generally are solitary nodules; only 10% of glomus tumors occur with multiple lesions, and among them, glomangiomyoma is the rarest subtype, presenting in only 15% of cases.^2,3 The 3 main subtypes of glomus tumors are solid, glomangioma, and glomangiomyoma.4 Clinically, the lesions may present as small blue nodules with associated pain and cold or pressure sensitivity. Although there appears to be variation of the nomenclature depending on the source in the literature, glomangiomas are characterized by their predominant vascular malformations on biopsy. Glomangiomyomas are a subset of glomus tumors with distinct smooth muscle differentiation.⁴ Given their pathologic presentation, our patient’s lesions were most consistent with the diagnosis of glomangiomyoma.

The small size of the lesions may result in difficulty establishing a clinical diagnosis, particularly if there is no hand involvement, where lesions most commonly occur.² Therefore, histopathologic evaluation is essential and is the best initial step in evaluating glomangiomyomas.⁴ Biopsy is the most reliable means of confirming a diagnosis^2,4,5; however, diagnostic imaging such as a computed tomography also should be performed if considering blue rubber bleb nevus syndrome due to the primary site of involvement. Surgical excision is the treatment of choice after confirming the diagnosis in most cases of symptomatic glomangiomyomas, particularly with painful lesions.⁶

Neurilemmomas (also known as schwannomas) are benign lesions that generally present as asymptomatic, soft, smooth nodules most often on the neck; however, they also may present on the flexor extremities or in internal organs. Although primarily asymptomatic, the tumors may be associated with pain and paresthesia as they enlarge and affect surrounding structures. Neurilemmomas may occur spontaneously or as part of a syndrome, such as neurofibromatosis type 2 or Carney complex.⁷

Hereditary hemorrhagic telangiectasia (formerly known as Osler-Weber-Rendu syndrome) is an autosomal-dominant disease that presents with arteriovenous malformations and telangiectases. Patients generally present in the third decade of life, with the main concern generally being epistaxis.⁸

Kaposi sarcoma is a viral infection secondary to human herpesvirus 8 that results in red-purple lesions commonly on mucocutaneous sites. Kaposi sarcoma can be AIDS associated and non-HIV associated. Although clinically indistinguishable, a few subtle histologic features can assist in differentiating the 2 etiologies. In addition to a potential history of immunodeficiency, evaluating for involvement of the lymphatic system, respiratory tract, or gastrointestinal tract can aid in differentiating this entity from glomus tumors.9

Leiomyomas are smooth muscle lesions divided into 3 subcategories: angioleiomyoma, piloleiomyoma, and genital leiomyoma. The clinical presentation and histopathology will vary depending on the subcategory. Although cutaneous leiomyomas are benign, further workup for piloleiomyoma may be required given the reported association with hereditary leiomyomatosis and renal cell cancer (Reed syndrome).¹⁰

Imaging can be helpful when the clinical diagnosis of a glomus tumor vs other painful neoplasms of the skin is unclear, such as in blue rubber bleb nevus syndrome, angioleiomyomas, neuromas, glomus tumors, leiomyomas, eccrine spiradenomas, congenital vascular malformations, schwannomas, or hemangiomas.⁴ Radiologic findings for glomus tumors may demonstrate cortical or cystic osseous defects. Magnetic resonance imaging and ultrasonography can help provide additional information on the lesion size and depth of involvement.¹ Additionally, deeper glomangiomyomas have been associated with malignancy,² potentially highlighting the benefit of early incorporation of imaging in the workup for this condition. Malignant transformation is rare and has been reported in less than 1% of cases.⁶

Treatment of glomus tumors predominantly is directed to the patient’s symptoms; asymptomatic lesions may be monitored.⁴ For symptomatic lesions, therapeutic options include wide local excision; sclerotherapy; and incorporation of various lasers, including Nd:YAG, CO₂, and flashlamp tunable dye laser.^4,5 One case report documented use of a PDL that successfully eliminated the pain associated with glomangiomyoma; however, the lesion in that report was not biopsy proven.¹¹

Our case highlights the need to consider glomus tumors in patients presenting with multiple small nodules given the potential for misdiagnosis, impact on quality of life with associated psychological distress, and potential utility of incorporating PDL in treatment. Although our patient did not report clinical improvement in the appearance of the lesions with PDL therapy, additional treatment sessions may have helped,¹¹ but he opted to discontinue. Follow-up for persistently symptomatic or changing lesions is necessary, given the minimal risk for malignant transformation.⁶

The Diagnosis: Glomangiomyoma

A punch biopsy of the right forearm revealed a collection of vascular and smooth muscle components with small and spindled bland cells containing minimal eosinophilic cytoplasm (Figure 1), confirming the diagnosis of glomangiomyoma. Immunohistochemical stains also supported the diagnosis and were positive for smooth muscle actin, desmin, and CD34 (Figure 2). Magnetic resonance imaging from a prior attempt at treatment with sclerotherapy demonstrated scattered vascular malformations with no notable internal derangement. There was no improvement with sclerotherapy. Given the number and vascular nature of the lesions, a trial of pulsed dye laser (PDL) therapy was administered and tolerated by the patient. He subsequently moved to a new military duty station. On follow-up, he reported no noticeable clinical improvement in the lesions after PDL and opted not to continue with laser treatment.

Glomangiomyoma is a rare and benign glomus tumor variant that demonstrates differentiation into the smooth muscle and potentially can result in substantial complications.¹ Glomus tumors generally are benign neoplasms of the glomus apparatus, and glomus cells function as thermoregulators in the reticular dermis.² Glomus tumors comprise less than 2% of soft tissue neoplasms and generally are solitary nodules; only 10% of glomus tumors occur with multiple lesions, and among them, glomangiomyoma is the rarest subtype, presenting in only 15% of cases.^2,3 The 3 main subtypes of glomus tumors are solid, glomangioma, and glomangiomyoma.4 Clinically, the lesions may present as small blue nodules with associated pain and cold or pressure sensitivity. Although there appears to be variation of the nomenclature depending on the source in the literature, glomangiomas are characterized by their predominant vascular malformations on biopsy. Glomangiomyomas are a subset of glomus tumors with distinct smooth muscle differentiation.⁴ Given their pathologic presentation, our patient’s lesions were most consistent with the diagnosis of glomangiomyoma.

The small size of the lesions may result in difficulty establishing a clinical diagnosis, particularly if there is no hand involvement, where lesions most commonly occur.² Therefore, histopathologic evaluation is essential and is the best initial step in evaluating glomangiomyomas.⁴ Biopsy is the most reliable means of confirming a diagnosis^2,4,5; however, diagnostic imaging such as a computed tomography also should be performed if considering blue rubber bleb nevus syndrome due to the primary site of involvement. Surgical excision is the treatment of choice after confirming the diagnosis in most cases of symptomatic glomangiomyomas, particularly with painful lesions.⁶

Neurilemmomas (also known as schwannomas) are benign lesions that generally present as asymptomatic, soft, smooth nodules most often on the neck; however, they also may present on the flexor extremities or in internal organs. Although primarily asymptomatic, the tumors may be associated with pain and paresthesia as they enlarge and affect surrounding structures. Neurilemmomas may occur spontaneously or as part of a syndrome, such as neurofibromatosis type 2 or Carney complex.⁷

Hereditary hemorrhagic telangiectasia (formerly known as Osler-Weber-Rendu syndrome) is an autosomal-dominant disease that presents with arteriovenous malformations and telangiectases. Patients generally present in the third decade of life, with the main concern generally being epistaxis.⁸

Kaposi sarcoma is a viral infection secondary to human herpesvirus 8 that results in red-purple lesions commonly on mucocutaneous sites. Kaposi sarcoma can be AIDS associated and non-HIV associated. Although clinically indistinguishable, a few subtle histologic features can assist in differentiating the 2 etiologies. In addition to a potential history of immunodeficiency, evaluating for involvement of the lymphatic system, respiratory tract, or gastrointestinal tract can aid in differentiating this entity from glomus tumors.9

Leiomyomas are smooth muscle lesions divided into 3 subcategories: angioleiomyoma, piloleiomyoma, and genital leiomyoma. The clinical presentation and histopathology will vary depending on the subcategory. Although cutaneous leiomyomas are benign, further workup for piloleiomyoma may be required given the reported association with hereditary leiomyomatosis and renal cell cancer (Reed syndrome).¹⁰

Imaging can be helpful when the clinical diagnosis of a glomus tumor vs other painful neoplasms of the skin is unclear, such as in blue rubber bleb nevus syndrome, angioleiomyomas, neuromas, glomus tumors, leiomyomas, eccrine spiradenomas, congenital vascular malformations, schwannomas, or hemangiomas.⁴ Radiologic findings for glomus tumors may demonstrate cortical or cystic osseous defects. Magnetic resonance imaging and ultrasonography can help provide additional information on the lesion size and depth of involvement.¹ Additionally, deeper glomangiomyomas have been associated with malignancy,² potentially highlighting the benefit of early incorporation of imaging in the workup for this condition. Malignant transformation is rare and has been reported in less than 1% of cases.⁶

Treatment of glomus tumors predominantly is directed to the patient’s symptoms; asymptomatic lesions may be monitored.⁴ For symptomatic lesions, therapeutic options include wide local excision; sclerotherapy; and incorporation of various lasers, including Nd:YAG, CO₂, and flashlamp tunable dye laser.^4,5 One case report documented use of a PDL that successfully eliminated the pain associated with glomangiomyoma; however, the lesion in that report was not biopsy proven.¹¹

Our case highlights the need to consider glomus tumors in patients presenting with multiple small nodules given the potential for misdiagnosis, impact on quality of life with associated psychological distress, and potential utility of incorporating PDL in treatment. Although our patient did not report clinical improvement in the appearance of the lesions with PDL therapy, additional treatment sessions may have helped,¹¹ but he opted to discontinue. Follow-up for persistently symptomatic or changing lesions is necessary, given the minimal risk for malignant transformation.⁶

The genus Leishmania comprises protozoan parasites that cause approximately 2 million new cases of leishmaniasis each year across 98 countries.¹ These protozoa are obligate intracellular parasites of phlebotomine sandfly species that transmit leishmaniasis and result in a considerable parasitic cause of fatalities globally, second only to malaria.^2,3

Phlebotomine sandflies primarily live in tropical and subtropical regions and function as vectors for many pathogens in addition to Leishmania species, such as Bartonella species and arboviruses.³ In 2004, it was noted that the majority of leishmaniasis cases affected developing countries: 90% of visceral leishmaniasis cases occurred in Bangladesh, India, Nepal, Sudan, and Brazil, and 90% of cutaneous leishmaniasis cases occurred in Afghanistan, Algeria, Brazil, Iran, Peru, Saudi Arabia, and Syria.⁴ Of note, with recent environmental changes, phlebotomine sandflies have gradually migrated to more northerly latitudes, extending into Europe.⁵

Twenty Leishmania species and 30 sandfly species have been identified as causes of leishmaniasis.⁴Leishmania infection occurs when an infected sandfly bites a mammalian host and transmits the parasite’s flagellated form, known as a promastigote. Host inflammatory cells, such as monocytes and dendritic cells, phagocytize parasites that enter the skin. The interaction between parasites and dendritic cells become an important factor in the outcome of Leishmania infection in the host because dendritic cells promote development of CD4 and CD8 T lymphocytes with specificity to target Leishmania parasites and protect the host.¹

The number of cases of leishmaniasis has increased worldwide, most likely due to changes in the environment and human behaviors such as urbanization, the creation of new settlements, and migration from rural to urban areas.^3,5 Important risk factors in individual patients include malnutrition; low-quality housing and sanitation; a history of migration or travel; and immunosuppression, such as that caused by HIV co-infection.^2,5

Case Report

An otherwise healthy 25-year-old Bangladeshi man presented to our community hospital for evaluation of a painful leg ulcer of 1 month’s duration. The patient had migrated from Bangladesh to Panama, then to Costa Rica, followed by Guatemala, Honduras, Mexico, and, last, Texas. In Texas, he was identified by the US Immigration and Customs Enforcement, transported to a detention facility, and transferred to this hospital shortly afterward.

The patient reported that, during his extensive migration, he had lived in the jungle and reported what he described as mosquito bites on the legs. He subsequently developed a 3-cm ulcerated and crusted plaque with rolled borders on the right medial ankle (Figure 1). In addition, he had a palpable nodular cord on the medial leg from the ankle lesion to the mid thigh that was consistent with lymphocutaneous spread. Ultrasonography was negative for deep-vein thrombosis.

Because the patient’s recent migration from Central America was highly concerning for microbial infection, vancomycin and piperacillin-tazobactam were started empirically on admission. A punch biopsy from the right medial ankle was nondiagnostic, showing acute and chronic necrotizing inflammation along with numerous epithelioid histiocytes with a vaguely granulomatous appearance (Figure 2). A specimen from the right medial ankle that had already been taken by an astute border patrol medical provider was sent to the Centers for Disease Control and Prevention (CDC) for polymerase chain reaction analysis following admission and was found to be positive for Leishmania panamensis.

Given the concern for mucocutaneous leishmaniasis with this particular species, otolaryngology was consulted; however, the patient did not demonstrate mucocutaneous disease. Because of the elevated risk for persistent disease with L panamensis, systemic therapy was indicated and administered: IV amphotericin B 200 mg on days 1 through 5 and again on day 10. Improvement in the ulcer was seen after the 10-day regimen was completed.

Comment

Leishmaniasis can be broadly classified by geographic region or clinical presentation. Under the geographic region system, leishmaniasis can be categorized as Old World or New World. Old World leishmaniasis primarily is transmitted by Phlebotomus sandflies and carries the parasites Leishmania major and Leishmania tropica, among others. New World leishmaniasis is caused by Lutzomyia sandflies, which carry Leishmania mexicana, Leishmania braziliensis, Leishmania amazonensis, and others.⁶

Our patient presented with cutaneous leishmaniasis, one of 4 primary clinical disease forms of leishmaniasis; the other 3 forms under this classification system are diffuse cutaneous, mucocutaneous, and visceral leishmaniasis, also known as kala-azar.^3,6 Cutaneous leishmaniasis is limited to the skin, particularly the face and extremities. This form is more common with Old World vectors, with most cases occurring in Peru, Brazil, and the Middle East. In Old World cutaneous leishmaniasis, the disease begins with a solitary nodule at the site of the bite that ulcerates and can continue to spread in a sporotrichoid pattern. This cutaneous form tends to heal slowly over months to years with residual scarring. New World cutaneous leishmaniasis can present with a variety of clinical manifestations, including ulcerative, sarcoidlike, miliary, and nodular lesions.^6,7

The diffuse form of cutaneous leishmaniasis begins in a similar manner to the Old World cutaneous form: a single nodule spreads widely over the body, especially the nose, and covers the patient’s skin with keloidal or verrucous lesions that do not ulcerate. These nodules contain large groupings of Leishmania-filled foamy macrophages. Often, patients with diffuse cutaneous leishmaniasis are immunosuppressed and are unable to develop an immune response to leishmanin and other skin antigens.^6,7

Mucocutaneous leishmaniasis predominantly is caused by the New World species L braziliensis but also has been attributed to L amazonensis, L panamensis, and L guyanensis. This form manifests as mucosal lesions that can develop simultaneously with cutaneous lesions but more commonly appear months to years after resolution of the skin infection. Patients often present with ulceration of the lip, nose, and oropharynx, and destruction of the nasopharynx can result in severe consequences such as obstruction of the airway and perforation of the nasal septum (also known as espundia).^6,7

The most severe presentation of leishmaniasis is the visceral form (kala-azar), which presents with parasitic infection of the liver, spleen, and bone marrow. Most commonly caused by Leishmania donovani, Leishmania infantum, and Leishmania chagasi, this form has a long incubation period spanning months to years before presenting with diarrhea, hepatomegaly, splenomegaly, darkening of the skin (in Hindi, kala-azar means “black fever”), pancytopenia, lymphadenopathy, nephritis, and intestinal hemorrhage, among other severe manifestations. Visceral leishmaniasis has a poor prognosis: patients succumb to disease within 2 years if not treated.^6,7

Diagnosis—Diagnosing leishmaniasis starts with a complete personal and medical history, paying close attention to travel and exposures. Diagnosis is most successfully performed by polymerase chain reaction analysis, which is both highly sensitive and specific but also can be determined by culture using Novy-McNeal-Nicolle medium or by light microscopy. Histologic findings include the marquee sign, which describes an array of amastigotes (promastigotes that have developed into the intracellular tissue-stage form) with kinetoplasts surrounding the periphery of parasitized histiocytes. Giemsa staining can be helpful in identifying organisms.^2,6,7

The diagnosis in our case was challenging, as none of the above findings were seen in our patient. The specimen taken by the border patrol medical provider was negative on Gram, Giemsa, and Grocott-Gömöri methenamine silver staining; no amastigotes were identified. Another diagnostic modality (not performed in our patient) is the Montenegro delayed skin-reaction test, which often is positive in patients with cutaneous leishmaniasis but also yields a positive result in patients who have been cured of Leishmania infection.⁶

An important consideration in the diagnostic workup of leishmaniasis is that collaboration with the CDC can be helpful, such as in our case, as they provide clear guidance for specimen collection and processing.²

Treatment—Treating leishmaniasis is challenging and complex. Even the initial decision to treat depends on several factors, including the form of infection. Most visceral and mucocutaneous infections should be treated due to both the lack of self-resolution of these forms and the higher risk for a potentially life-threatening disease course; in contrast, cutaneous forms require further consideration before initiating treatment. Some indicators for treating cutaneous leishmaniasis include widespread infection, intention to decrease scarring, and lesions with the potential to cause further complications (eg, on the face or ears or close to joints).^6-8

The treatment of choice for cutaneous and mucocutaneous leishmaniasis is pentavalent antimony; however, this drug can only be obtained in the United States for investigational use, requiring approval by the CDC. A 20-day intravenous or intramuscular course of 20 mg/kg per day typically is used for cutaneous cases; a 28-day course typically is used for mucosal forms.

Amphotericin B is not only the treatment of choice for visceral leishmaniasis but also is an important alternative therapy for patients with mucosal leishmaniasis or who are co-infected with HIV. Patients with visceral infection also should receive supportive care for any concomitant afflictions, such as malnutrition or other infections. Although different regimens have been described, the US Food and Drug Administration has created outlines of specific intravenous infusion schedules for liposomal amphotericin B in immunocompetent and immunosuppressed patients.⁸ Liposomal amphotericin B also has a more favorable toxicity profile than conventional amphotericin B deoxycholate, which is otherwise effective in combating visceral leishmaniasis.^6-8

Other treatments that have been attempted include pentamidine, miltefosine, thermotherapy, oral itraconazole and fluconazole, rifampicin, metronidazole and cotrimoxazole, dapsone, photodynamic therapy, thermotherapy, topical paromomycin formulations, intralesional pentavalent antimony, and laser cryotherapy. Notable among these other agents is miltefosine, a US Food and Drug Administration–approved oral medication for adults and adolescents (used off-label for patients younger than 12 years) with cutaneous leishmaniasis caused by L braziliensis, L panamensis, or L guyanensis. Other oral options mentioned include the so-called azole antifungal medications, which historically have produced variable results. From the CDC’s reports, ketoconazole was moderately effective in Guatemala and Panama,⁸ whereas itraconazole did not demonstrate efficacy in Colombia, and the efficacy of fluconazole was inconsistent in different countries.⁸ When considering one of the local (as opposed to oral and parenteral) therapies mentioned, the extent of cutaneous findings as well as the risk of mucosal spread should be factored in.^6-8

Understandably, a number of considerations can come into play in determining the appropriate treatment modality, including body region affected, clinical form, severity, and Leishmania species.^6-8 Our case is of particular interest because it demonstrates the complexities behind the diagnosis and treatment of cutaneous leishmaniasis, with careful consideration geared toward the species; for example, because our patient was infected with L panamensis, which is known to cause mucocutaneous disease, the infectious disease service decided to pursue systemic therapy with amphotericin B rather than topical treatment.

Prevention—Vector control is the primary means of preventing leishmaniasis under 2 umbrellas: environmental management and synthetic insecticides. The goal of environmental management is to eliminate the phlebotomine sandfly habitat; this was the primary method of vector control until 1940. Until that time, tree stumps were removed, indoor cracks and crevices were filled to prevent sandfly emergence, and areas around animal shelters were cleaned. These methods were highly dependent on community awareness and involvement; today, they can be combined with synthetic insecticides to offer maximum protection.

Synthetic insecticides include indoor sprays, treated nets, repellents, and impregnated dog collars, all of which control sandflies. However, the use of these insecticides in endemic areas, such as India, has driven development of insecticide resistance in many sandfly vector species.³

As of 2020, 5 vaccines against Leishmania have been created. Two are approved–one in Brazil and one in Uzbekistan–for human use as immunotherapy, while the other 3 have been developed to immunize dogs in Brazil. However, the effectiveness of these vaccines is under debate. First, one of the vaccines used as immunotherapy for cutaneous leishmaniasis must be used in combination with conventional chemotherapy; second, long-term effects of the canine vaccine are unknown.¹ A preventive vaccine for humans is under development.^1,3

Final Thoughts

Leishmaniasis remains a notable parasitic disease that is increasing in prevalence worldwide. Clinicians should be aware of this disease because early detection and treatment are essential to control infection.³ Health care providers in the United States should be especially aware of this condition among patients who have a history of travel or migration; those in Texas should recognize the current endemic status of leishmaniasis there.^4,6

The genus Leishmania comprises protozoan parasites that cause approximately 2 million new cases of leishmaniasis each year across 98 countries.¹ These protozoa are obligate intracellular parasites of phlebotomine sandfly species that transmit leishmaniasis and result in a considerable parasitic cause of fatalities globally, second only to malaria.^2,3

Phlebotomine sandflies primarily live in tropical and subtropical regions and function as vectors for many pathogens in addition to Leishmania species, such as Bartonella species and arboviruses.³ In 2004, it was noted that the majority of leishmaniasis cases affected developing countries: 90% of visceral leishmaniasis cases occurred in Bangladesh, India, Nepal, Sudan, and Brazil, and 90% of cutaneous leishmaniasis cases occurred in Afghanistan, Algeria, Brazil, Iran, Peru, Saudi Arabia, and Syria.⁴ Of note, with recent environmental changes, phlebotomine sandflies have gradually migrated to more northerly latitudes, extending into Europe.⁵

Twenty Leishmania species and 30 sandfly species have been identified as causes of leishmaniasis.⁴Leishmania infection occurs when an infected sandfly bites a mammalian host and transmits the parasite’s flagellated form, known as a promastigote. Host inflammatory cells, such as monocytes and dendritic cells, phagocytize parasites that enter the skin. The interaction between parasites and dendritic cells become an important factor in the outcome of Leishmania infection in the host because dendritic cells promote development of CD4 and CD8 T lymphocytes with specificity to target Leishmania parasites and protect the host.¹

The number of cases of leishmaniasis has increased worldwide, most likely due to changes in the environment and human behaviors such as urbanization, the creation of new settlements, and migration from rural to urban areas.^3,5 Important risk factors in individual patients include malnutrition; low-quality housing and sanitation; a history of migration or travel; and immunosuppression, such as that caused by HIV co-infection.^2,5

Case Report

An otherwise healthy 25-year-old Bangladeshi man presented to our community hospital for evaluation of a painful leg ulcer of 1 month’s duration. The patient had migrated from Bangladesh to Panama, then to Costa Rica, followed by Guatemala, Honduras, Mexico, and, last, Texas. In Texas, he was identified by the US Immigration and Customs Enforcement, transported to a detention facility, and transferred to this hospital shortly afterward.

The patient reported that, during his extensive migration, he had lived in the jungle and reported what he described as mosquito bites on the legs. He subsequently developed a 3-cm ulcerated and crusted plaque with rolled borders on the right medial ankle (Figure 1). In addition, he had a palpable nodular cord on the medial leg from the ankle lesion to the mid thigh that was consistent with lymphocutaneous spread. Ultrasonography was negative for deep-vein thrombosis.

Because the patient’s recent migration from Central America was highly concerning for microbial infection, vancomycin and piperacillin-tazobactam were started empirically on admission. A punch biopsy from the right medial ankle was nondiagnostic, showing acute and chronic necrotizing inflammation along with numerous epithelioid histiocytes with a vaguely granulomatous appearance (Figure 2). A specimen from the right medial ankle that had already been taken by an astute border patrol medical provider was sent to the Centers for Disease Control and Prevention (CDC) for polymerase chain reaction analysis following admission and was found to be positive for Leishmania panamensis.

Given the concern for mucocutaneous leishmaniasis with this particular species, otolaryngology was consulted; however, the patient did not demonstrate mucocutaneous disease. Because of the elevated risk for persistent disease with L panamensis, systemic therapy was indicated and administered: IV amphotericin B 200 mg on days 1 through 5 and again on day 10. Improvement in the ulcer was seen after the 10-day regimen was completed.

Comment

Leishmaniasis can be broadly classified by geographic region or clinical presentation. Under the geographic region system, leishmaniasis can be categorized as Old World or New World. Old World leishmaniasis primarily is transmitted by Phlebotomus sandflies and carries the parasites Leishmania major and Leishmania tropica, among others. New World leishmaniasis is caused by Lutzomyia sandflies, which carry Leishmania mexicana, Leishmania braziliensis, Leishmania amazonensis, and others.⁶

Our patient presented with cutaneous leishmaniasis, one of 4 primary clinical disease forms of leishmaniasis; the other 3 forms under this classification system are diffuse cutaneous, mucocutaneous, and visceral leishmaniasis, also known as kala-azar.^3,6 Cutaneous leishmaniasis is limited to the skin, particularly the face and extremities. This form is more common with Old World vectors, with most cases occurring in Peru, Brazil, and the Middle East. In Old World cutaneous leishmaniasis, the disease begins with a solitary nodule at the site of the bite that ulcerates and can continue to spread in a sporotrichoid pattern. This cutaneous form tends to heal slowly over months to years with residual scarring. New World cutaneous leishmaniasis can present with a variety of clinical manifestations, including ulcerative, sarcoidlike, miliary, and nodular lesions.^6,7

The diffuse form of cutaneous leishmaniasis begins in a similar manner to the Old World cutaneous form: a single nodule spreads widely over the body, especially the nose, and covers the patient’s skin with keloidal or verrucous lesions that do not ulcerate. These nodules contain large groupings of Leishmania-filled foamy macrophages. Often, patients with diffuse cutaneous leishmaniasis are immunosuppressed and are unable to develop an immune response to leishmanin and other skin antigens.^6,7

Mucocutaneous leishmaniasis predominantly is caused by the New World species L braziliensis but also has been attributed to L amazonensis, L panamensis, and L guyanensis. This form manifests as mucosal lesions that can develop simultaneously with cutaneous lesions but more commonly appear months to years after resolution of the skin infection. Patients often present with ulceration of the lip, nose, and oropharynx, and destruction of the nasopharynx can result in severe consequences such as obstruction of the airway and perforation of the nasal septum (also known as espundia).^6,7

The most severe presentation of leishmaniasis is the visceral form (kala-azar), which presents with parasitic infection of the liver, spleen, and bone marrow. Most commonly caused by Leishmania donovani, Leishmania infantum, and Leishmania chagasi, this form has a long incubation period spanning months to years before presenting with diarrhea, hepatomegaly, splenomegaly, darkening of the skin (in Hindi, kala-azar means “black fever”), pancytopenia, lymphadenopathy, nephritis, and intestinal hemorrhage, among other severe manifestations. Visceral leishmaniasis has a poor prognosis: patients succumb to disease within 2 years if not treated.^6,7

Diagnosis—Diagnosing leishmaniasis starts with a complete personal and medical history, paying close attention to travel and exposures. Diagnosis is most successfully performed by polymerase chain reaction analysis, which is both highly sensitive and specific but also can be determined by culture using Novy-McNeal-Nicolle medium or by light microscopy. Histologic findings include the marquee sign, which describes an array of amastigotes (promastigotes that have developed into the intracellular tissue-stage form) with kinetoplasts surrounding the periphery of parasitized histiocytes. Giemsa staining can be helpful in identifying organisms.^2,6,7

The diagnosis in our case was challenging, as none of the above findings were seen in our patient. The specimen taken by the border patrol medical provider was negative on Gram, Giemsa, and Grocott-Gömöri methenamine silver staining; no amastigotes were identified. Another diagnostic modality (not performed in our patient) is the Montenegro delayed skin-reaction test, which often is positive in patients with cutaneous leishmaniasis but also yields a positive result in patients who have been cured of Leishmania infection.⁶

An important consideration in the diagnostic workup of leishmaniasis is that collaboration with the CDC can be helpful, such as in our case, as they provide clear guidance for specimen collection and processing.²

Treatment—Treating leishmaniasis is challenging and complex. Even the initial decision to treat depends on several factors, including the form of infection. Most visceral and mucocutaneous infections should be treated due to both the lack of self-resolution of these forms and the higher risk for a potentially life-threatening disease course; in contrast, cutaneous forms require further consideration before initiating treatment. Some indicators for treating cutaneous leishmaniasis include widespread infection, intention to decrease scarring, and lesions with the potential to cause further complications (eg, on the face or ears or close to joints).^6-8

The treatment of choice for cutaneous and mucocutaneous leishmaniasis is pentavalent antimony; however, this drug can only be obtained in the United States for investigational use, requiring approval by the CDC. A 20-day intravenous or intramuscular course of 20 mg/kg per day typically is used for cutaneous cases; a 28-day course typically is used for mucosal forms.

Amphotericin B is not only the treatment of choice for visceral leishmaniasis but also is an important alternative therapy for patients with mucosal leishmaniasis or who are co-infected with HIV. Patients with visceral infection also should receive supportive care for any concomitant afflictions, such as malnutrition or other infections. Although different regimens have been described, the US Food and Drug Administration has created outlines of specific intravenous infusion schedules for liposomal amphotericin B in immunocompetent and immunosuppressed patients.⁸ Liposomal amphotericin B also has a more favorable toxicity profile than conventional amphotericin B deoxycholate, which is otherwise effective in combating visceral leishmaniasis.^6-8

Other treatments that have been attempted include pentamidine, miltefosine, thermotherapy, oral itraconazole and fluconazole, rifampicin, metronidazole and cotrimoxazole, dapsone, photodynamic therapy, thermotherapy, topical paromomycin formulations, intralesional pentavalent antimony, and laser cryotherapy. Notable among these other agents is miltefosine, a US Food and Drug Administration–approved oral medication for adults and adolescents (used off-label for patients younger than 12 years) with cutaneous leishmaniasis caused by L braziliensis, L panamensis, or L guyanensis. Other oral options mentioned include the so-called azole antifungal medications, which historically have produced variable results. From the CDC’s reports, ketoconazole was moderately effective in Guatemala and Panama,⁸ whereas itraconazole did not demonstrate efficacy in Colombia, and the efficacy of fluconazole was inconsistent in different countries.⁸ When considering one of the local (as opposed to oral and parenteral) therapies mentioned, the extent of cutaneous findings as well as the risk of mucosal spread should be factored in.^6-8

Understandably, a number of considerations can come into play in determining the appropriate treatment modality, including body region affected, clinical form, severity, and Leishmania species.^6-8 Our case is of particular interest because it demonstrates the complexities behind the diagnosis and treatment of cutaneous leishmaniasis, with careful consideration geared toward the species; for example, because our patient was infected with L panamensis, which is known to cause mucocutaneous disease, the infectious disease service decided to pursue systemic therapy with amphotericin B rather than topical treatment.

Prevention—Vector control is the primary means of preventing leishmaniasis under 2 umbrellas: environmental management and synthetic insecticides. The goal of environmental management is to eliminate the phlebotomine sandfly habitat; this was the primary method of vector control until 1940. Until that time, tree stumps were removed, indoor cracks and crevices were filled to prevent sandfly emergence, and areas around animal shelters were cleaned. These methods were highly dependent on community awareness and involvement; today, they can be combined with synthetic insecticides to offer maximum protection.

Synthetic insecticides include indoor sprays, treated nets, repellents, and impregnated dog collars, all of which control sandflies. However, the use of these insecticides in endemic areas, such as India, has driven development of insecticide resistance in many sandfly vector species.³

As of 2020, 5 vaccines against Leishmania have been created. Two are approved–one in Brazil and one in Uzbekistan–for human use as immunotherapy, while the other 3 have been developed to immunize dogs in Brazil. However, the effectiveness of these vaccines is under debate. First, one of the vaccines used as immunotherapy for cutaneous leishmaniasis must be used in combination with conventional chemotherapy; second, long-term effects of the canine vaccine are unknown.¹ A preventive vaccine for humans is under development.^1,3

Final Thoughts

Leishmaniasis remains a notable parasitic disease that is increasing in prevalence worldwide. Clinicians should be aware of this disease because early detection and treatment are essential to control infection.³ Health care providers in the United States should be especially aware of this condition among patients who have a history of travel or migration; those in Texas should recognize the current endemic status of leishmaniasis there.^4,6

The genus Leishmania comprises protozoan parasites that cause approximately 2 million new cases of leishmaniasis each year across 98 countries.¹ These protozoa are obligate intracellular parasites of phlebotomine sandfly species that transmit leishmaniasis and result in a considerable parasitic cause of fatalities globally, second only to malaria.^2,3

Phlebotomine sandflies primarily live in tropical and subtropical regions and function as vectors for many pathogens in addition to Leishmania species, such as Bartonella species and arboviruses.³ In 2004, it was noted that the majority of leishmaniasis cases affected developing countries: 90% of visceral leishmaniasis cases occurred in Bangladesh, India, Nepal, Sudan, and Brazil, and 90% of cutaneous leishmaniasis cases occurred in Afghanistan, Algeria, Brazil, Iran, Peru, Saudi Arabia, and Syria.⁴ Of note, with recent environmental changes, phlebotomine sandflies have gradually migrated to more northerly latitudes, extending into Europe.⁵

Twenty Leishmania species and 30 sandfly species have been identified as causes of leishmaniasis.⁴Leishmania infection occurs when an infected sandfly bites a mammalian host and transmits the parasite’s flagellated form, known as a promastigote. Host inflammatory cells, such as monocytes and dendritic cells, phagocytize parasites that enter the skin. The interaction between parasites and dendritic cells become an important factor in the outcome of Leishmania infection in the host because dendritic cells promote development of CD4 and CD8 T lymphocytes with specificity to target Leishmania parasites and protect the host.¹

The number of cases of leishmaniasis has increased worldwide, most likely due to changes in the environment and human behaviors such as urbanization, the creation of new settlements, and migration from rural to urban areas.^3,5 Important risk factors in individual patients include malnutrition; low-quality housing and sanitation; a history of migration or travel; and immunosuppression, such as that caused by HIV co-infection.^2,5

Case Report

An otherwise healthy 25-year-old Bangladeshi man presented to our community hospital for evaluation of a painful leg ulcer of 1 month’s duration. The patient had migrated from Bangladesh to Panama, then to Costa Rica, followed by Guatemala, Honduras, Mexico, and, last, Texas. In Texas, he was identified by the US Immigration and Customs Enforcement, transported to a detention facility, and transferred to this hospital shortly afterward.

The patient reported that, during his extensive migration, he had lived in the jungle and reported what he described as mosquito bites on the legs. He subsequently developed a 3-cm ulcerated and crusted plaque with rolled borders on the right medial ankle (Figure 1). In addition, he had a palpable nodular cord on the medial leg from the ankle lesion to the mid thigh that was consistent with lymphocutaneous spread. Ultrasonography was negative for deep-vein thrombosis.

Because the patient’s recent migration from Central America was highly concerning for microbial infection, vancomycin and piperacillin-tazobactam were started empirically on admission. A punch biopsy from the right medial ankle was nondiagnostic, showing acute and chronic necrotizing inflammation along with numerous epithelioid histiocytes with a vaguely granulomatous appearance (Figure 2). A specimen from the right medial ankle that had already been taken by an astute border patrol medical provider was sent to the Centers for Disease Control and Prevention (CDC) for polymerase chain reaction analysis following admission and was found to be positive for Leishmania panamensis.

Given the concern for mucocutaneous leishmaniasis with this particular species, otolaryngology was consulted; however, the patient did not demonstrate mucocutaneous disease. Because of the elevated risk for persistent disease with L panamensis, systemic therapy was indicated and administered: IV amphotericin B 200 mg on days 1 through 5 and again on day 10. Improvement in the ulcer was seen after the 10-day regimen was completed.

Comment

Leishmaniasis can be broadly classified by geographic region or clinical presentation. Under the geographic region system, leishmaniasis can be categorized as Old World or New World. Old World leishmaniasis primarily is transmitted by Phlebotomus sandflies and carries the parasites Leishmania major and Leishmania tropica, among others. New World leishmaniasis is caused by Lutzomyia sandflies, which carry Leishmania mexicana, Leishmania braziliensis, Leishmania amazonensis, and others.⁶

Our patient presented with cutaneous leishmaniasis, one of 4 primary clinical disease forms of leishmaniasis; the other 3 forms under this classification system are diffuse cutaneous, mucocutaneous, and visceral leishmaniasis, also known as kala-azar.^3,6 Cutaneous leishmaniasis is limited to the skin, particularly the face and extremities. This form is more common with Old World vectors, with most cases occurring in Peru, Brazil, and the Middle East. In Old World cutaneous leishmaniasis, the disease begins with a solitary nodule at the site of the bite that ulcerates and can continue to spread in a sporotrichoid pattern. This cutaneous form tends to heal slowly over months to years with residual scarring. New World cutaneous leishmaniasis can present with a variety of clinical manifestations, including ulcerative, sarcoidlike, miliary, and nodular lesions.^6,7

The diffuse form of cutaneous leishmaniasis begins in a similar manner to the Old World cutaneous form: a single nodule spreads widely over the body, especially the nose, and covers the patient’s skin with keloidal or verrucous lesions that do not ulcerate. These nodules contain large groupings of Leishmania-filled foamy macrophages. Often, patients with diffuse cutaneous leishmaniasis are immunosuppressed and are unable to develop an immune response to leishmanin and other skin antigens.^6,7

Mucocutaneous leishmaniasis predominantly is caused by the New World species L braziliensis but also has been attributed to L amazonensis, L panamensis, and L guyanensis. This form manifests as mucosal lesions that can develop simultaneously with cutaneous lesions but more commonly appear months to years after resolution of the skin infection. Patients often present with ulceration of the lip, nose, and oropharynx, and destruction of the nasopharynx can result in severe consequences such as obstruction of the airway and perforation of the nasal septum (also known as espundia).^6,7

The most severe presentation of leishmaniasis is the visceral form (kala-azar), which presents with parasitic infection of the liver, spleen, and bone marrow. Most commonly caused by Leishmania donovani, Leishmania infantum, and Leishmania chagasi, this form has a long incubation period spanning months to years before presenting with diarrhea, hepatomegaly, splenomegaly, darkening of the skin (in Hindi, kala-azar means “black fever”), pancytopenia, lymphadenopathy, nephritis, and intestinal hemorrhage, among other severe manifestations. Visceral leishmaniasis has a poor prognosis: patients succumb to disease within 2 years if not treated.^6,7

Diagnosis—Diagnosing leishmaniasis starts with a complete personal and medical history, paying close attention to travel and exposures. Diagnosis is most successfully performed by polymerase chain reaction analysis, which is both highly sensitive and specific but also can be determined by culture using Novy-McNeal-Nicolle medium or by light microscopy. Histologic findings include the marquee sign, which describes an array of amastigotes (promastigotes that have developed into the intracellular tissue-stage form) with kinetoplasts surrounding the periphery of parasitized histiocytes. Giemsa staining can be helpful in identifying organisms.^2,6,7

The diagnosis in our case was challenging, as none of the above findings were seen in our patient. The specimen taken by the border patrol medical provider was negative on Gram, Giemsa, and Grocott-Gömöri methenamine silver staining; no amastigotes were identified. Another diagnostic modality (not performed in our patient) is the Montenegro delayed skin-reaction test, which often is positive in patients with cutaneous leishmaniasis but also yields a positive result in patients who have been cured of Leishmania infection.⁶

An important consideration in the diagnostic workup of leishmaniasis is that collaboration with the CDC can be helpful, such as in our case, as they provide clear guidance for specimen collection and processing.²

Treatment—Treating leishmaniasis is challenging and complex. Even the initial decision to treat depends on several factors, including the form of infection. Most visceral and mucocutaneous infections should be treated due to both the lack of self-resolution of these forms and the higher risk for a potentially life-threatening disease course; in contrast, cutaneous forms require further consideration before initiating treatment. Some indicators for treating cutaneous leishmaniasis include widespread infection, intention to decrease scarring, and lesions with the potential to cause further complications (eg, on the face or ears or close to joints).^6-8

The treatment of choice for cutaneous and mucocutaneous leishmaniasis is pentavalent antimony; however, this drug can only be obtained in the United States for investigational use, requiring approval by the CDC. A 20-day intravenous or intramuscular course of 20 mg/kg per day typically is used for cutaneous cases; a 28-day course typically is used for mucosal forms.

Amphotericin B is not only the treatment of choice for visceral leishmaniasis but also is an important alternative therapy for patients with mucosal leishmaniasis or who are co-infected with HIV. Patients with visceral infection also should receive supportive care for any concomitant afflictions, such as malnutrition or other infections. Although different regimens have been described, the US Food and Drug Administration has created outlines of specific intravenous infusion schedules for liposomal amphotericin B in immunocompetent and immunosuppressed patients.⁸ Liposomal amphotericin B also has a more favorable toxicity profile than conventional amphotericin B deoxycholate, which is otherwise effective in combating visceral leishmaniasis.^6-8

Other treatments that have been attempted include pentamidine, miltefosine, thermotherapy, oral itraconazole and fluconazole, rifampicin, metronidazole and cotrimoxazole, dapsone, photodynamic therapy, thermotherapy, topical paromomycin formulations, intralesional pentavalent antimony, and laser cryotherapy. Notable among these other agents is miltefosine, a US Food and Drug Administration–approved oral medication for adults and adolescents (used off-label for patients younger than 12 years) with cutaneous leishmaniasis caused by L braziliensis, L panamensis, or L guyanensis. Other oral options mentioned include the so-called azole antifungal medications, which historically have produced variable results. From the CDC’s reports, ketoconazole was moderately effective in Guatemala and Panama,⁸ whereas itraconazole did not demonstrate efficacy in Colombia, and the efficacy of fluconazole was inconsistent in different countries.⁸ When considering one of the local (as opposed to oral and parenteral) therapies mentioned, the extent of cutaneous findings as well as the risk of mucosal spread should be factored in.^6-8

Understandably, a number of considerations can come into play in determining the appropriate treatment modality, including body region affected, clinical form, severity, and Leishmania species.^6-8 Our case is of particular interest because it demonstrates the complexities behind the diagnosis and treatment of cutaneous leishmaniasis, with careful consideration geared toward the species; for example, because our patient was infected with L panamensis, which is known to cause mucocutaneous disease, the infectious disease service decided to pursue systemic therapy with amphotericin B rather than topical treatment.

Prevention—Vector control is the primary means of preventing leishmaniasis under 2 umbrellas: environmental management and synthetic insecticides. The goal of environmental management is to eliminate the phlebotomine sandfly habitat; this was the primary method of vector control until 1940. Until that time, tree stumps were removed, indoor cracks and crevices were filled to prevent sandfly emergence, and areas around animal shelters were cleaned. These methods were highly dependent on community awareness and involvement; today, they can be combined with synthetic insecticides to offer maximum protection.

Synthetic insecticides include indoor sprays, treated nets, repellents, and impregnated dog collars, all of which control sandflies. However, the use of these insecticides in endemic areas, such as India, has driven development of insecticide resistance in many sandfly vector species.³

As of 2020, 5 vaccines against Leishmania have been created. Two are approved–one in Brazil and one in Uzbekistan–for human use as immunotherapy, while the other 3 have been developed to immunize dogs in Brazil. However, the effectiveness of these vaccines is under debate. First, one of the vaccines used as immunotherapy for cutaneous leishmaniasis must be used in combination with conventional chemotherapy; second, long-term effects of the canine vaccine are unknown.¹ A preventive vaccine for humans is under development.^1,3

Final Thoughts

Leishmaniasis remains a notable parasitic disease that is increasing in prevalence worldwide. Clinicians should be aware of this disease because early detection and treatment are essential to control infection.³ Health care providers in the United States should be especially aware of this condition among patients who have a history of travel or migration; those in Texas should recognize the current endemic status of leishmaniasis there.^4,6

To the Editor:

A 16-year-old adolescent boy presented to our pediatric dermatology clinic for evaluation of long-standing mild atopic dermatitis (AD) that had become severe over the last year after omalizumab was initiated for severe asthma. The patient had a history of multiple hospitalizations for severe asthma. Despite excellent control of asthma with omalizumab given every 2 weeks, he developed widespread eczematous plaques on the neck, trunk, and extremities over the course of a year. The AD often was complicated by superimposed folliculitis due to scratching from severe pruritus. Treatment with topical corticosteroids including triamcinolone ointment 0.1% to AD on the body, plus clobetasol ointment 0.05% for prurigolike lesions on the legs resulted in modest improvement; however, the AD consistently recurred within a few days after the biweekly omalizumab injection (Figure 1). When the omalizumab injections were delayed, the flares temporarily improved, and when injections were decreased to once monthly, the exacerbations subsided partially but not fully.

Because omalizumab resulted in dramatic improvement in the patient’s asthma, there was hesitation to discontinue it initially; however, the patient and his parents in conjunction with the dermatology and pulmonary teams decided to transition to dupilumab. The patient reported vast improvement of AD 1 month after initiation of dupilumab (Figure 2), which remained well controlled more than 1 year later. Mid-potency topical corticosteroids for the treatment of occasional mild eczematous flares on the extremities were used. The patient’s asthma has remained well controlled on dupilumab without any exacerbations.

Omalizumab is a recombinant DNA-derived humanized monoclonal antibody that binds both circulating and membrane-bound IgE. It has been proposed as a possible treatment for severe and/or recalcitrant AD, with mixed treatment results.¹ A case series and review of 174 patients demonstrated a moderate to complete AD response to treatment with omalizumab in 74.1% of patients.² The Atopic Dermatitis Anti-IgE Pediatric Trial (ADAPT) showed a statistically significant reduction in the Scoring Atopic Dermatitis (SCORAD) index (P=.01), along with improved quality of life in children treated with omalizumab vs those treated with placebo.³ However, a prior randomized, placebo-controlled, double-blind study did not show a significant difference in clinical disease parameters in patients treated with omalizumab.⁴

The humanized monoclonal antibody dupilumab, an anti–IL-4/IL-13 agent, has demonstrated more consistent efficacy for the treatment of AD in children and adults.¹ Dupilumab is effective for both intrinsic and extrinsic AD¹ because its clinical efficacy is unrelated to circulating levels of IgE in the bloodstream. Although IgE may have a role in childhood AD, our case demonstrated a different pathophysiologic mechanism independent of IgE. Our patient’s AD flares occurred within a few days of omalizumab injection, which may have resulted in a paradoxical increase in basophil sensitivity to other cytokines such as IL-33⁵ and led to an increase in IL-4/IL-13 production within the skin. In our patient, this increase was successfully blocked by dupilumab. Furthermore, omalizumab has been shown to modulate helper T cell (T_H2) cytokine response such as thymic stromal lymphopoietin.⁶ A cytokine imbalance could have exacerbated AD in our case.

Although additional work to clarify the pathogenesis of AD is needed, it is important to recognize the potential for the occurrence of paradoxical AD flares in patients treated with omalizumab, which is analogous to the well-documented entity of tumor necrosis factor α inhibitor–induced psoriasis. It is equally important to recognize the potential benefit for patients treated with dupilumab.

To the Editor:

A 16-year-old adolescent boy presented to our pediatric dermatology clinic for evaluation of long-standing mild atopic dermatitis (AD) that had become severe over the last year after omalizumab was initiated for severe asthma. The patient had a history of multiple hospitalizations for severe asthma. Despite excellent control of asthma with omalizumab given every 2 weeks, he developed widespread eczematous plaques on the neck, trunk, and extremities over the course of a year. The AD often was complicated by superimposed folliculitis due to scratching from severe pruritus. Treatment with topical corticosteroids including triamcinolone ointment 0.1% to AD on the body, plus clobetasol ointment 0.05% for prurigolike lesions on the legs resulted in modest improvement; however, the AD consistently recurred within a few days after the biweekly omalizumab injection (Figure 1). When the omalizumab injections were delayed, the flares temporarily improved, and when injections were decreased to once monthly, the exacerbations subsided partially but not fully.

Because omalizumab resulted in dramatic improvement in the patient’s asthma, there was hesitation to discontinue it initially; however, the patient and his parents in conjunction with the dermatology and pulmonary teams decided to transition to dupilumab. The patient reported vast improvement of AD 1 month after initiation of dupilumab (Figure 2), which remained well controlled more than 1 year later. Mid-potency topical corticosteroids for the treatment of occasional mild eczematous flares on the extremities were used. The patient’s asthma has remained well controlled on dupilumab without any exacerbations.

Omalizumab is a recombinant DNA-derived humanized monoclonal antibody that binds both circulating and membrane-bound IgE. It has been proposed as a possible treatment for severe and/or recalcitrant AD, with mixed treatment results.¹ A case series and review of 174 patients demonstrated a moderate to complete AD response to treatment with omalizumab in 74.1% of patients.² The Atopic Dermatitis Anti-IgE Pediatric Trial (ADAPT) showed a statistically significant reduction in the Scoring Atopic Dermatitis (SCORAD) index (P=.01), along with improved quality of life in children treated with omalizumab vs those treated with placebo.³ However, a prior randomized, placebo-controlled, double-blind study did not show a significant difference in clinical disease parameters in patients treated with omalizumab.⁴

The humanized monoclonal antibody dupilumab, an anti–IL-4/IL-13 agent, has demonstrated more consistent efficacy for the treatment of AD in children and adults.¹ Dupilumab is effective for both intrinsic and extrinsic AD¹ because its clinical efficacy is unrelated to circulating levels of IgE in the bloodstream. Although IgE may have a role in childhood AD, our case demonstrated a different pathophysiologic mechanism independent of IgE. Our patient’s AD flares occurred within a few days of omalizumab injection, which may have resulted in a paradoxical increase in basophil sensitivity to other cytokines such as IL-33⁵ and led to an increase in IL-4/IL-13 production within the skin. In our patient, this increase was successfully blocked by dupilumab. Furthermore, omalizumab has been shown to modulate helper T cell (T_H2) cytokine response such as thymic stromal lymphopoietin.⁶ A cytokine imbalance could have exacerbated AD in our case.

Although additional work to clarify the pathogenesis of AD is needed, it is important to recognize the potential for the occurrence of paradoxical AD flares in patients treated with omalizumab, which is analogous to the well-documented entity of tumor necrosis factor α inhibitor–induced psoriasis. It is equally important to recognize the potential benefit for patients treated with dupilumab.

To the Editor:

A 16-year-old adolescent boy presented to our pediatric dermatology clinic for evaluation of long-standing mild atopic dermatitis (AD) that had become severe over the last year after omalizumab was initiated for severe asthma. The patient had a history of multiple hospitalizations for severe asthma. Despite excellent control of asthma with omalizumab given every 2 weeks, he developed widespread eczematous plaques on the neck, trunk, and extremities over the course of a year. The AD often was complicated by superimposed folliculitis due to scratching from severe pruritus. Treatment with topical corticosteroids including triamcinolone ointment 0.1% to AD on the body, plus clobetasol ointment 0.05% for prurigolike lesions on the legs resulted in modest improvement; however, the AD consistently recurred within a few days after the biweekly omalizumab injection (Figure 1). When the omalizumab injections were delayed, the flares temporarily improved, and when injections were decreased to once monthly, the exacerbations subsided partially but not fully.

Because omalizumab resulted in dramatic improvement in the patient’s asthma, there was hesitation to discontinue it initially; however, the patient and his parents in conjunction with the dermatology and pulmonary teams decided to transition to dupilumab. The patient reported vast improvement of AD 1 month after initiation of dupilumab (Figure 2), which remained well controlled more than 1 year later. Mid-potency topical corticosteroids for the treatment of occasional mild eczematous flares on the extremities were used. The patient’s asthma has remained well controlled on dupilumab without any exacerbations.

Omalizumab is a recombinant DNA-derived humanized monoclonal antibody that binds both circulating and membrane-bound IgE. It has been proposed as a possible treatment for severe and/or recalcitrant AD, with mixed treatment results.¹ A case series and review of 174 patients demonstrated a moderate to complete AD response to treatment with omalizumab in 74.1% of patients.² The Atopic Dermatitis Anti-IgE Pediatric Trial (ADAPT) showed a statistically significant reduction in the Scoring Atopic Dermatitis (SCORAD) index (P=.01), along with improved quality of life in children treated with omalizumab vs those treated with placebo.³ However, a prior randomized, placebo-controlled, double-blind study did not show a significant difference in clinical disease parameters in patients treated with omalizumab.⁴

The humanized monoclonal antibody dupilumab, an anti–IL-4/IL-13 agent, has demonstrated more consistent efficacy for the treatment of AD in children and adults.¹ Dupilumab is effective for both intrinsic and extrinsic AD¹ because its clinical efficacy is unrelated to circulating levels of IgE in the bloodstream. Although IgE may have a role in childhood AD, our case demonstrated a different pathophysiologic mechanism independent of IgE. Our patient’s AD flares occurred within a few days of omalizumab injection, which may have resulted in a paradoxical increase in basophil sensitivity to other cytokines such as IL-33⁵ and led to an increase in IL-4/IL-13 production within the skin. In our patient, this increase was successfully blocked by dupilumab. Furthermore, omalizumab has been shown to modulate helper T cell (T_H2) cytokine response such as thymic stromal lymphopoietin.⁶ A cytokine imbalance could have exacerbated AD in our case.

Although additional work to clarify the pathogenesis of AD is needed, it is important to recognize the potential for the occurrence of paradoxical AD flares in patients treated with omalizumab, which is analogous to the well-documented entity of tumor necrosis factor α inhibitor–induced psoriasis. It is equally important to recognize the potential benefit for patients treated with dupilumab.

The Diagnosis: Cutaneous Langerhans Cell Histiocytosis

Histopathologic findings of the left axillary lesion included a diffuse infiltrate of irregular hematolymphoid cells with reniform nuclei that strongly and diffusely stained positively with CD1a and S-100 but were negative for CD138 and CD163 (Figure). Numerous eosinophils also were present. The surrounding lymphocytic infiltrate stained positively with CD45. Polymerase chain reaction of the vaginal lesion was negative for herpes simplex virus types 1 and 2. Biopsy of the vaginal lesion revealed a mildly acanthotic epidermis and an aggregation of epithelioid cells with reniform nuclei in the papillary dermis. Positron emission tomography revealed widely disseminated disease. Sequencing of the mitogen-activated protein kinase/extracellular signalregulated kinase pathway showed amplified expression of these genes but found no mutations. These results led to a diagnosis of cutaneous Langerhans cell histiocytosis (LCH) with a background of hidradenitis suppurativa (HS). Our patient has since initiated therapy with trametinib leading to disease improvement without known recurrence.

Langerhans cell histiocytosis is a rare disease of clonal dendritic cells (Langerhans cells) that can present in any organ.¹ Most LCH diagnoses are made in pediatric patients, most often presenting in the bones, with other presentations in the skin, hypophysis, liver, lymph nodes, lungs, and spleen occurring less commonly.² Proto-oncogene BRAF V600E mutations are a common determinant of LCH, with half of cases linked with this mutation that leads to enhanced activation of the mitogen-activated protein kinase pathway, though other mutations have been reported.^3,4 These genetic alterations suggest LCH is neoplastic in nature; however, this is controversial, as spontaneous regression among pulmonary LCH has been observed, pointing to a reactive inflammatory process.⁵ Cutaneous LCH can present as a distinct papular or nodular lesion or multiple lesions with possible ulceration, but it is rare that LCH first presents on the skin.^2,6 There is a substantial association of cutaneous LCH with the development of systemically disseminated LCH as well as other blood tumors, such as myelomonocytic leukemia, histiocytic sarcoma, and multiple lymphomas; this association is thought to be due to the common origin of LCH and other blood diseases in the bone marrow.⁶

Histopathology of LCH shows a diffuse papillary dermal infiltrate of clonal proliferation of reniform or cleaved histiocytes.⁵ Epidermal ulceration and epidermotropism also are common. Neoplastic cells are found admixed with variable levels of eosinophils, lymphocytes, plasma cells, and neutrophils, though eosinophils typically are elevated. Immunohistochemistry characteristically shows the expression of CD1a, S-100, and/or CD207, and the absence of CD163 expression.

Treatment of LCH is primarily dependent on disease dissemination status, with splenic and hepatic involvement, genetic panel results, and central nervous system risk considered in the treatment plan.⁵ Langerhans cell histiocytosis localized to the skin may require follow-up and monitoring, as spontaneous regression of cutaneous LCH is common. However, topical steroids or psoralen and long-wave UV radiation are potential treatments. Physicians who diagnose unifocal cutaneous LCH should have high clinical suspicion of disseminated LCH, and laboratory and radiographic evaluation may be necessary to rule out systemic disease, as more than 40% of patients with cutaneous LCH have systemic disease upon full evaluation.⁷ With systemic involvement, systemic chemotherapy may reduce morbidity and mortality, but clinical response should be monitored after 6 weeks of treatment, as results are variably effective. Vinblastine is the most common chemotherapy regimen, with an 84% survival rate and 51.5% event-free survival rate after 8 years.⁸ Targeted therapy for common genetic mutations also is possible, as vemurafenib has been used to treat patients with the BRAF V600E mutation.

Due to the variable clinical presentation of cutaneous LCH, the lesions can mimic other common skin diseases such as eczema or seborrheic dermatitis.⁷ However, there are limited data on LCH presenting in infiltrative skin disease. Langerhans cell histiocytosis that was misdiagnosed as HS has been reported,^9-11 but LCH presenting alongside long-standing HS is rare. Although LCH often mimics infiltrative skin diseases, its simultaneous presentation with a previously confirmed diagnosis of HS was notable in our patient.

In our patient, the differential diagnosis included HS, Actinomyces infection, lymphomatoid papulosis, and dermatofibrosarcoma protuberans. Cutaneous findings in HS include chronic acneform nodules with follicular plugging, ruptured ducts leading to epithelized sinuses, inflammation, and abscesses in the axillae or inguinal and perineal areas.¹¹ Histopathology reveals follicular occlusion and hyperkeratinization, which cause destruction of the pilosebaceous glands. Hidradenitis suppurativa features on immunohistochemistry often are conflicting, but there consistently is co-localization of keratinocyte hyperplasia with CD3-, CD4-, CD8-, and CD68-positive staining of cells that produce tumor necrosis factor α, IL-12, IL-23, and IL-32, with CD1a staining variable.¹² An infection with Actinomyces, a slow-progressing anaerobic or microaerophilic bacteria, may present in the skin with chronic suppurative inflammation on the neck, trunk, and abdomen. The classic presentation is subcutaneous nodules with localized infiltration of abscesses, fistulas, and draining sinuses.¹³ Morphologically, Actinomyces causes chronic granulomatous infection with 0.1- to 1-mm sulfur granules, which are seen as basophilic masses with eosinophilic terminal clubs on hematoxylin and eosin staining.¹⁴ Histopathology reveals grampositive filamentous Actinomyces bacteria that branch at the edge of the granules. Lymphomatoid papulosis, a nonaggressive T-cell lymphoma, presents as papulonodular and sometimes necrotic disseminated lesions that spontaneously can regress or can cause a higher risk for the development of more aggressive lymphomas.¹⁵ Histopathology shows consistently dense, dermal, lymphocytic infiltration. Immunohistochemistry is characterized by lymphocytes expressing CD30 of varying degrees: type A with many CD30 staining cells, type B presenting similar to mycosis fungoides with little CD30 staining, and type C with lymphocytic CD30-staining plaques. Dermatofibrosarcoma protuberans is a low-grade soft-tissue malignant tumor with extensive local infiltration characterized by asymptomatic plaques on the trunk and proximal extremities that are indurated and adhered to the skin.¹⁶ Histopathology shows extensive invasion into the adjacent tissue far from the original focus of the tumor.

The Diagnosis: Cutaneous Langerhans Cell Histiocytosis

Histopathologic findings of the left axillary lesion included a diffuse infiltrate of irregular hematolymphoid cells with reniform nuclei that strongly and diffusely stained positively with CD1a and S-100 but were negative for CD138 and CD163 (Figure). Numerous eosinophils also were present. The surrounding lymphocytic infiltrate stained positively with CD45. Polymerase chain reaction of the vaginal lesion was negative for herpes simplex virus types 1 and 2. Biopsy of the vaginal lesion revealed a mildly acanthotic epidermis and an aggregation of epithelioid cells with reniform nuclei in the papillary dermis. Positron emission tomography revealed widely disseminated disease. Sequencing of the mitogen-activated protein kinase/extracellular signalregulated kinase pathway showed amplified expression of these genes but found no mutations. These results led to a diagnosis of cutaneous Langerhans cell histiocytosis (LCH) with a background of hidradenitis suppurativa (HS). Our patient has since initiated therapy with trametinib leading to disease improvement without known recurrence.

Langerhans cell histiocytosis is a rare disease of clonal dendritic cells (Langerhans cells) that can present in any organ.¹ Most LCH diagnoses are made in pediatric patients, most often presenting in the bones, with other presentations in the skin, hypophysis, liver, lymph nodes, lungs, and spleen occurring less commonly.² Proto-oncogene BRAF V600E mutations are a common determinant of LCH, with half of cases linked with this mutation that leads to enhanced activation of the mitogen-activated protein kinase pathway, though other mutations have been reported.^3,4 These genetic alterations suggest LCH is neoplastic in nature; however, this is controversial, as spontaneous regression among pulmonary LCH has been observed, pointing to a reactive inflammatory process.⁵ Cutaneous LCH can present as a distinct papular or nodular lesion or multiple lesions with possible ulceration, but it is rare that LCH first presents on the skin.^2,6 There is a substantial association of cutaneous LCH with the development of systemically disseminated LCH as well as other blood tumors, such as myelomonocytic leukemia, histiocytic sarcoma, and multiple lymphomas; this association is thought to be due to the common origin of LCH and other blood diseases in the bone marrow.⁶

Histopathology of LCH shows a diffuse papillary dermal infiltrate of clonal proliferation of reniform or cleaved histiocytes.⁵ Epidermal ulceration and epidermotropism also are common. Neoplastic cells are found admixed with variable levels of eosinophils, lymphocytes, plasma cells, and neutrophils, though eosinophils typically are elevated. Immunohistochemistry characteristically shows the expression of CD1a, S-100, and/or CD207, and the absence of CD163 expression.

Treatment of LCH is primarily dependent on disease dissemination status, with splenic and hepatic involvement, genetic panel results, and central nervous system risk considered in the treatment plan.⁵ Langerhans cell histiocytosis localized to the skin may require follow-up and monitoring, as spontaneous regression of cutaneous LCH is common. However, topical steroids or psoralen and long-wave UV radiation are potential treatments. Physicians who diagnose unifocal cutaneous LCH should have high clinical suspicion of disseminated LCH, and laboratory and radiographic evaluation may be necessary to rule out systemic disease, as more than 40% of patients with cutaneous LCH have systemic disease upon full evaluation.⁷ With systemic involvement, systemic chemotherapy may reduce morbidity and mortality, but clinical response should be monitored after 6 weeks of treatment, as results are variably effective. Vinblastine is the most common chemotherapy regimen, with an 84% survival rate and 51.5% event-free survival rate after 8 years.⁸ Targeted therapy for common genetic mutations also is possible, as vemurafenib has been used to treat patients with the BRAF V600E mutation.

Due to the variable clinical presentation of cutaneous LCH, the lesions can mimic other common skin diseases such as eczema or seborrheic dermatitis.⁷ However, there are limited data on LCH presenting in infiltrative skin disease. Langerhans cell histiocytosis that was misdiagnosed as HS has been reported,^9-11 but LCH presenting alongside long-standing HS is rare. Although LCH often mimics infiltrative skin diseases, its simultaneous presentation with a previously confirmed diagnosis of HS was notable in our patient.

In our patient, the differential diagnosis included HS, Actinomyces infection, lymphomatoid papulosis, and dermatofibrosarcoma protuberans. Cutaneous findings in HS include chronic acneform nodules with follicular plugging, ruptured ducts leading to epithelized sinuses, inflammation, and abscesses in the axillae or inguinal and perineal areas.¹¹ Histopathology reveals follicular occlusion and hyperkeratinization, which cause destruction of the pilosebaceous glands. Hidradenitis suppurativa features on immunohistochemistry often are conflicting, but there consistently is co-localization of keratinocyte hyperplasia with CD3-, CD4-, CD8-, and CD68-positive staining of cells that produce tumor necrosis factor α, IL-12, IL-23, and IL-32, with CD1a staining variable.¹² An infection with Actinomyces, a slow-progressing anaerobic or microaerophilic bacteria, may present in the skin with chronic suppurative inflammation on the neck, trunk, and abdomen. The classic presentation is subcutaneous nodules with localized infiltration of abscesses, fistulas, and draining sinuses.¹³ Morphologically, Actinomyces causes chronic granulomatous infection with 0.1- to 1-mm sulfur granules, which are seen as basophilic masses with eosinophilic terminal clubs on hematoxylin and eosin staining.¹⁴ Histopathology reveals grampositive filamentous Actinomyces bacteria that branch at the edge of the granules. Lymphomatoid papulosis, a nonaggressive T-cell lymphoma, presents as papulonodular and sometimes necrotic disseminated lesions that spontaneously can regress or can cause a higher risk for the development of more aggressive lymphomas.¹⁵ Histopathology shows consistently dense, dermal, lymphocytic infiltration. Immunohistochemistry is characterized by lymphocytes expressing CD30 of varying degrees: type A with many CD30 staining cells, type B presenting similar to mycosis fungoides with little CD30 staining, and type C with lymphocytic CD30-staining plaques. Dermatofibrosarcoma protuberans is a low-grade soft-tissue malignant tumor with extensive local infiltration characterized by asymptomatic plaques on the trunk and proximal extremities that are indurated and adhered to the skin.¹⁶ Histopathology shows extensive invasion into the adjacent tissue far from the original focus of the tumor.

The Diagnosis: Cutaneous Langerhans Cell Histiocytosis

Histopathologic findings of the left axillary lesion included a diffuse infiltrate of irregular hematolymphoid cells with reniform nuclei that strongly and diffusely stained positively with CD1a and S-100 but were negative for CD138 and CD163 (Figure). Numerous eosinophils also were present. The surrounding lymphocytic infiltrate stained positively with CD45. Polymerase chain reaction of the vaginal lesion was negative for herpes simplex virus types 1 and 2. Biopsy of the vaginal lesion revealed a mildly acanthotic epidermis and an aggregation of epithelioid cells with reniform nuclei in the papillary dermis. Positron emission tomography revealed widely disseminated disease. Sequencing of the mitogen-activated protein kinase/extracellular signalregulated kinase pathway showed amplified expression of these genes but found no mutations. These results led to a diagnosis of cutaneous Langerhans cell histiocytosis (LCH) with a background of hidradenitis suppurativa (HS). Our patient has since initiated therapy with trametinib leading to disease improvement without known recurrence.

Langerhans cell histiocytosis is a rare disease of clonal dendritic cells (Langerhans cells) that can present in any organ.¹ Most LCH diagnoses are made in pediatric patients, most often presenting in the bones, with other presentations in the skin, hypophysis, liver, lymph nodes, lungs, and spleen occurring less commonly.² Proto-oncogene BRAF V600E mutations are a common determinant of LCH, with half of cases linked with this mutation that leads to enhanced activation of the mitogen-activated protein kinase pathway, though other mutations have been reported.^3,4 These genetic alterations suggest LCH is neoplastic in nature; however, this is controversial, as spontaneous regression among pulmonary LCH has been observed, pointing to a reactive inflammatory process.⁵ Cutaneous LCH can present as a distinct papular or nodular lesion or multiple lesions with possible ulceration, but it is rare that LCH first presents on the skin.^2,6 There is a substantial association of cutaneous LCH with the development of systemically disseminated LCH as well as other blood tumors, such as myelomonocytic leukemia, histiocytic sarcoma, and multiple lymphomas; this association is thought to be due to the common origin of LCH and other blood diseases in the bone marrow.⁶

Histopathology of LCH shows a diffuse papillary dermal infiltrate of clonal proliferation of reniform or cleaved histiocytes.⁵ Epidermal ulceration and epidermotropism also are common. Neoplastic cells are found admixed with variable levels of eosinophils, lymphocytes, plasma cells, and neutrophils, though eosinophils typically are elevated. Immunohistochemistry characteristically shows the expression of CD1a, S-100, and/or CD207, and the absence of CD163 expression.

Treatment of LCH is primarily dependent on disease dissemination status, with splenic and hepatic involvement, genetic panel results, and central nervous system risk considered in the treatment plan.⁵ Langerhans cell histiocytosis localized to the skin may require follow-up and monitoring, as spontaneous regression of cutaneous LCH is common. However, topical steroids or psoralen and long-wave UV radiation are potential treatments. Physicians who diagnose unifocal cutaneous LCH should have high clinical suspicion of disseminated LCH, and laboratory and radiographic evaluation may be necessary to rule out systemic disease, as more than 40% of patients with cutaneous LCH have systemic disease upon full evaluation.⁷ With systemic involvement, systemic chemotherapy may reduce morbidity and mortality, but clinical response should be monitored after 6 weeks of treatment, as results are variably effective. Vinblastine is the most common chemotherapy regimen, with an 84% survival rate and 51.5% event-free survival rate after 8 years.⁸ Targeted therapy for common genetic mutations also is possible, as vemurafenib has been used to treat patients with the BRAF V600E mutation.

Due to the variable clinical presentation of cutaneous LCH, the lesions can mimic other common skin diseases such as eczema or seborrheic dermatitis.⁷ However, there are limited data on LCH presenting in infiltrative skin disease. Langerhans cell histiocytosis that was misdiagnosed as HS has been reported,^9-11 but LCH presenting alongside long-standing HS is rare. Although LCH often mimics infiltrative skin diseases, its simultaneous presentation with a previously confirmed diagnosis of HS was notable in our patient.

In our patient, the differential diagnosis included HS, Actinomyces infection, lymphomatoid papulosis, and dermatofibrosarcoma protuberans. Cutaneous findings in HS include chronic acneform nodules with follicular plugging, ruptured ducts leading to epithelized sinuses, inflammation, and abscesses in the axillae or inguinal and perineal areas.¹¹ Histopathology reveals follicular occlusion and hyperkeratinization, which cause destruction of the pilosebaceous glands. Hidradenitis suppurativa features on immunohistochemistry often are conflicting, but there consistently is co-localization of keratinocyte hyperplasia with CD3-, CD4-, CD8-, and CD68-positive staining of cells that produce tumor necrosis factor α, IL-12, IL-23, and IL-32, with CD1a staining variable.¹² An infection with Actinomyces, a slow-progressing anaerobic or microaerophilic bacteria, may present in the skin with chronic suppurative inflammation on the neck, trunk, and abdomen. The classic presentation is subcutaneous nodules with localized infiltration of abscesses, fistulas, and draining sinuses.¹³ Morphologically, Actinomyces causes chronic granulomatous infection with 0.1- to 1-mm sulfur granules, which are seen as basophilic masses with eosinophilic terminal clubs on hematoxylin and eosin staining.¹⁴ Histopathology reveals grampositive filamentous Actinomyces bacteria that branch at the edge of the granules. Lymphomatoid papulosis, a nonaggressive T-cell lymphoma, presents as papulonodular and sometimes necrotic disseminated lesions that spontaneously can regress or can cause a higher risk for the development of more aggressive lymphomas.¹⁵ Histopathology shows consistently dense, dermal, lymphocytic infiltration. Immunohistochemistry is characterized by lymphocytes expressing CD30 of varying degrees: type A with many CD30 staining cells, type B presenting similar to mycosis fungoides with little CD30 staining, and type C with lymphocytic CD30-staining plaques. Dermatofibrosarcoma protuberans is a low-grade soft-tissue malignant tumor with extensive local infiltration characterized by asymptomatic plaques on the trunk and proximal extremities that are indurated and adhered to the skin.¹⁶ Histopathology shows extensive invasion into the adjacent tissue far from the original focus of the tumor.

To the Editor:

Metastatic spread of salivary duct carcinoma (SDC) to the skin is rare. Diagnosing SDC can be challenging because the cutaneous manifestations of this disease are variable and include nodules, papules, and erysipelaslike inflammation (also known as shield sign) with purpuric papules and pseudovesicles. We describe a case of cutaneous metastatic SDC that originated from the parotid gland and presented with 2 distinct cutaneous findings: sharply demarcated erythematous plaques and focally hemorrhagic angiomatous papules.

A 60-year-old man presented with a persistent polymorphous pruritic eruption of several months’ duration involving the entire face, ears, neck, and upper chest. He had a history of unspecified adenocarcinoma of the parotid gland diagnosed 2 years prior and underwent multiple treatment cycles with several chemotherapeutic agents over the course of 18 months. Physical examination showed erythematous papules and nodules on the face and neck with slight overlying scale. Sharply demarcated, erythematous plaques studded with focally hemorrhagic, angiomatous papules were noted on the neck and chest (Figure 1). Two 4-mm punch biopsies were sampled from representative nodular areas. Histopathology showed multiple round solid-tumor nodules with central necrosis in the superficial and deep dermis that were not associated with the overlying epidermis (Figures 2A and 2B). The tumor cells appeared polygonal and contained ample eosinophilic cytoplasm. Tumor nuclei showed marked pleomorphism, and numerous atypical mitotic figures were readily identifiable (Figure 2C). There was diffuse cytoplasmic staining with cytokeratin 7 and nuclear staining with androgen receptor (Figure 2D). These findings were consistent with a diagnosis of SDC metastatic to the skin.

The patient underwent 8 cycles of docetaxel chemotherapy. With disease progression, the chemotherapy regimen was changed to gemcitabine and methotrexate. The patient continued to experience disease progression and died 9 months after diagnosis of skin metastases.

Salivary duct carcinoma is rare and is estimated to represent 1% to 3% of all salivary malignancies.¹ It is a highly aggressive form of salivary gland carcinoma and is associated with a poor clinical outcome. The 3-year overall survival rate for stage I disease is 42% and only 23% for stage IV disease.² Salivary duct carcinoma has a high rate of distant metastasis,³ but cases of cutaneous metastases are rare.^3-8 Previously reported cases of SDC that metastasized to the skin originated from the parotid gland (n=6) and submandibular gland (n=1).³

The diagnosis of cutaneous metastases is challenging due to the variability of the skin manifestations. Three cases described small firm nodules in patients,^3-5 while others presented with purpuric papules and pseudovesicles.^6-8 Our patient presented with sharply demarcated, erythematous plaques studded with focally hemorrhagic, angiomatous papules, which further emphasizes the capricious nature of skin findings.

The morphology of SDC is strikingly similar to ductal adenocarcinoma of the breast, which can lead to diagnostic confusion. Both carcinomas may show oncocytic cells, ductal formations, and cribriform structures with central comedo necrosis. Moreover, immunohistochemical features overlap, including positive staining for cytokeratin 7 and gross cystic disease fluid protein 15. Positive immunohistochemistry with androgen receptor is consistent with SDC but also can be expressed in some cases of breast carcinoma.^9,10 Therefore, the diagnosis of cutaneous involvement from metastatic SDC requires not just an evaluation of the pathologic features but careful attention to the clinical history and a thorough staging evaluation.

To the Editor:

Metastatic spread of salivary duct carcinoma (SDC) to the skin is rare. Diagnosing SDC can be challenging because the cutaneous manifestations of this disease are variable and include nodules, papules, and erysipelaslike inflammation (also known as shield sign) with purpuric papules and pseudovesicles. We describe a case of cutaneous metastatic SDC that originated from the parotid gland and presented with 2 distinct cutaneous findings: sharply demarcated erythematous plaques and focally hemorrhagic angiomatous papules.

A 60-year-old man presented with a persistent polymorphous pruritic eruption of several months’ duration involving the entire face, ears, neck, and upper chest. He had a history of unspecified adenocarcinoma of the parotid gland diagnosed 2 years prior and underwent multiple treatment cycles with several chemotherapeutic agents over the course of 18 months. Physical examination showed erythematous papules and nodules on the face and neck with slight overlying scale. Sharply demarcated, erythematous plaques studded with focally hemorrhagic, angiomatous papules were noted on the neck and chest (Figure 1). Two 4-mm punch biopsies were sampled from representative nodular areas. Histopathology showed multiple round solid-tumor nodules with central necrosis in the superficial and deep dermis that were not associated with the overlying epidermis (Figures 2A and 2B). The tumor cells appeared polygonal and contained ample eosinophilic cytoplasm. Tumor nuclei showed marked pleomorphism, and numerous atypical mitotic figures were readily identifiable (Figure 2C). There was diffuse cytoplasmic staining with cytokeratin 7 and nuclear staining with androgen receptor (Figure 2D). These findings were consistent with a diagnosis of SDC metastatic to the skin.

The patient underwent 8 cycles of docetaxel chemotherapy. With disease progression, the chemotherapy regimen was changed to gemcitabine and methotrexate. The patient continued to experience disease progression and died 9 months after diagnosis of skin metastases.

Salivary duct carcinoma is rare and is estimated to represent 1% to 3% of all salivary malignancies.¹ It is a highly aggressive form of salivary gland carcinoma and is associated with a poor clinical outcome. The 3-year overall survival rate for stage I disease is 42% and only 23% for stage IV disease.² Salivary duct carcinoma has a high rate of distant metastasis,³ but cases of cutaneous metastases are rare.^3-8 Previously reported cases of SDC that metastasized to the skin originated from the parotid gland (n=6) and submandibular gland (n=1).³

The diagnosis of cutaneous metastases is challenging due to the variability of the skin manifestations. Three cases described small firm nodules in patients,^3-5 while others presented with purpuric papules and pseudovesicles.^6-8 Our patient presented with sharply demarcated, erythematous plaques studded with focally hemorrhagic, angiomatous papules, which further emphasizes the capricious nature of skin findings.

The morphology of SDC is strikingly similar to ductal adenocarcinoma of the breast, which can lead to diagnostic confusion. Both carcinomas may show oncocytic cells, ductal formations, and cribriform structures with central comedo necrosis. Moreover, immunohistochemical features overlap, including positive staining for cytokeratin 7 and gross cystic disease fluid protein 15. Positive immunohistochemistry with androgen receptor is consistent with SDC but also can be expressed in some cases of breast carcinoma.^9,10 Therefore, the diagnosis of cutaneous involvement from metastatic SDC requires not just an evaluation of the pathologic features but careful attention to the clinical history and a thorough staging evaluation.

To the Editor:

Metastatic spread of salivary duct carcinoma (SDC) to the skin is rare. Diagnosing SDC can be challenging because the cutaneous manifestations of this disease are variable and include nodules, papules, and erysipelaslike inflammation (also known as shield sign) with purpuric papules and pseudovesicles. We describe a case of cutaneous metastatic SDC that originated from the parotid gland and presented with 2 distinct cutaneous findings: sharply demarcated erythematous plaques and focally hemorrhagic angiomatous papules.

A 60-year-old man presented with a persistent polymorphous pruritic eruption of several months’ duration involving the entire face, ears, neck, and upper chest. He had a history of unspecified adenocarcinoma of the parotid gland diagnosed 2 years prior and underwent multiple treatment cycles with several chemotherapeutic agents over the course of 18 months. Physical examination showed erythematous papules and nodules on the face and neck with slight overlying scale. Sharply demarcated, erythematous plaques studded with focally hemorrhagic, angiomatous papules were noted on the neck and chest (Figure 1). Two 4-mm punch biopsies were sampled from representative nodular areas. Histopathology showed multiple round solid-tumor nodules with central necrosis in the superficial and deep dermis that were not associated with the overlying epidermis (Figures 2A and 2B). The tumor cells appeared polygonal and contained ample eosinophilic cytoplasm. Tumor nuclei showed marked pleomorphism, and numerous atypical mitotic figures were readily identifiable (Figure 2C). There was diffuse cytoplasmic staining with cytokeratin 7 and nuclear staining with androgen receptor (Figure 2D). These findings were consistent with a diagnosis of SDC metastatic to the skin.

The patient underwent 8 cycles of docetaxel chemotherapy. With disease progression, the chemotherapy regimen was changed to gemcitabine and methotrexate. The patient continued to experience disease progression and died 9 months after diagnosis of skin metastases.

Salivary duct carcinoma is rare and is estimated to represent 1% to 3% of all salivary malignancies.¹ It is a highly aggressive form of salivary gland carcinoma and is associated with a poor clinical outcome. The 3-year overall survival rate for stage I disease is 42% and only 23% for stage IV disease.² Salivary duct carcinoma has a high rate of distant metastasis,³ but cases of cutaneous metastases are rare.^3-8 Previously reported cases of SDC that metastasized to the skin originated from the parotid gland (n=6) and submandibular gland (n=1).³

The diagnosis of cutaneous metastases is challenging due to the variability of the skin manifestations. Three cases described small firm nodules in patients,^3-5 while others presented with purpuric papules and pseudovesicles.^6-8 Our patient presented with sharply demarcated, erythematous plaques studded with focally hemorrhagic, angiomatous papules, which further emphasizes the capricious nature of skin findings.

The morphology of SDC is strikingly similar to ductal adenocarcinoma of the breast, which can lead to diagnostic confusion. Both carcinomas may show oncocytic cells, ductal formations, and cribriform structures with central comedo necrosis. Moreover, immunohistochemical features overlap, including positive staining for cytokeratin 7 and gross cystic disease fluid protein 15. Positive immunohistochemistry with androgen receptor is consistent with SDC but also can be expressed in some cases of breast carcinoma.^9,10 Therefore, the diagnosis of cutaneous involvement from metastatic SDC requires not just an evaluation of the pathologic features but careful attention to the clinical history and a thorough staging evaluation.

To the Editor:

A woman in her 40s presented with acute onset of rapidly spreading lesions on the face, trunk, and extremities. She reported high fever and endorsed malaise. She had a history of end-stage renal disease and was on renal dialysis. She recently underwent revision of an arteriovenous fistula.

Physical examination revealed diffuse, erythematous, firm papules and plaques with central hemorrhage and umbilication on the dorsal aspect of the nose, forehead, temples, and cheeks. There also were purpuric papules and plaques with a peripheral rim of vesiculation (Figure 1) on the medial and posterior thighs and buttocks. Histopathology of a biopsy specimen revealed an interstitial neutrophilic infiltrate in the superficial dermis and mid dermis with scattered, haloed, acellular structures simulating cryptococcal organisms (Figure 2). Periodic acid–Schiff (PAS), Grocott methenamine-silver, and mucicarmine staining was negative. Repeat biopsy showed similar findings. A (1-3)-β-d glucan assay for invasive fungal infection and tests for serum cryptococcal antigen, serum Coccidioides antibody, serum Blastomyces antigen, and urine and serum Histoplasma antigen were negative. A fungal complement fixation battery was negative. Blood and tissue cultures for bacteria, anaerobes, fungi, and acid-fast bacilli remained sterile. Swabs were negative for varicella-zoster virus and herpes simplex virus. Urine and blood iodine levels were 344,998 μg/L (reference range, 34–523 μg/L) and 47,459 μg/L (reference range, 52–109 μg/L), respectively. The elevated iodine levels were presumed to be secondary to iodinated contrast media that the patient received for revision of the arteriovenous fistula.

The findings compatible with a diagnosis of iododerma included umbilicated hemorrhagic papules and plaques, cryptococcal-like structures with negative staining on histopathology, and elevated iodine levels with a negative infectious workup. The patient was treated with topical corticosteroids. At 1-month follow-up, the lesions had resolved.

Iododerma is a halogenoderma, a skin eruption that occurs after ingestion of or exposure to a halogen-containing substance (eg, iodine, bromine, fluorine) or medication (eg, lithium).¹ Common sources of iodine include iodinated contrast media, potassium iodide ingestion, topical application of povidone–iodine, radioactive iodine administration, and the antiarrhythmic amiodarone. Excess exposure to iodine-containing compounds typically occurs in the setting of kidney disease or failure as well as due to reduced iodine clearance.¹ Although the pathogenesis of iododerma is unknown, the most common hypothesis is that lesions are delayed hypersensitivity reactions secondary to formation of a protein-halogen complex.²

The presentation of iododerma is polymorphous and includes acneform, vegetative, or pustular eruptions; umbilicated papules and plaques can be present.^2,3 Lesions can be either asymptomatic or painful and pruritic. Timing between iodine exposure and onset of lesions varies from hours to days to years.^2,4

Systemic symptoms of iododerma can occur, including salivary gland swelling, hypotension and bradycardia, kidney injury, or thyroid and liver abnormalities. Histopathologic analysis demonstrates a dense neutrophilic dermatitis with negative staining for infectious causes.^4,5 Cryptococcal-like structures have been described in iododerma³; neutrophilic dermatoses of various causes that mimic cryptococcal infection have been reported.⁶ Ultimately, iododerma remains a diagnosis of exclusion.

Withdrawal of an offending compound is remedial. Dialysis is beneficial in end-stage renal disease. Topical, intralesional, and systemic corticosteroids, as well as antibiotics, provide variable benefit.^4,7 Lesions can take 4 to 6 weeks to clear after withdrawal of the offending agent. It is unclear whether recurrences happen; iodine-containing compounds need to be avoided after a patient has been affected.

Iododerma has a broad differential diagnosis due to the polymorphous presentation of the disorder, including acute febrile neutrophilic dermatosis (also known as Sweet syndrome), cutaneous cryptococcosis, and cutaneous histoplasmosis. Sweet syndrome presents as abrupt onset of edematous erythematous plaques with fever and leukocytosis. It is associated with infection, inflammatory disorders, medication, and malignancy.⁸ Histopathologic analysis reveals papillary dermal edema and a neutrophilic dermatosis. Cytoplasmic vacuolization resembling C neoformans has been reported.⁹ The diagnosis is less favored in the presence of renal disease, temporal association of the eruption with iodine exposure, and elevated blood and urine iodine levels, as in our patient.

Cutaneous cryptococcosis, an infection caused by C neoformans, typically occurs secondary to dissemination from the lungs; rarely, the disease is primary. Acneform plaques, vegetative plaques, and umbilicated lesions are seen.¹⁰ Histopathologic analysis shows characteristic yeast forms of cryptococcosis surrounded by gelatinous edema, which create a haloed effect, typically throughout the dermis. Capsules are positive for PAS or mucicarmine staining. Although C neoformans can closely mimic iododerma both clinically and histopathologically, negative infectious staining, localization of haloed structures to the upper dermis, a negative test for cryptococcal antigen, and elevated blood and urine iodine levels in this case all favored iododerma.

Cutaneous histoplasmosis is an infection caused by Histoplasma capsulatum, most commonly as secondary dissemination from pulmonary infection but rarely from direct inoculation of the skin.¹¹ Presentation includes erythematous to hemorrhagic, umbilicated papules and plaques. Histopathologic findings are round to oval, narrow-based, budding yeasts that stain positive for PAS or mucicarmine. Although histoplasmosis can clinically mimic iododerma, the disease is distinguished histologically by the presence of fungal microorganisms that lack the gelatinous edema and haloed effect of iododerma.

We presented a unique case of iododerma simulating cryptococcal infection both clinically and histopathologically. Prompt recognition of histologic mimickers of true infectious microorganisms is essential to prevent unnecessary delay of withdrawal of the offending substance and to initiate appropriate therapy.

To the Editor:

A woman in her 40s presented with acute onset of rapidly spreading lesions on the face, trunk, and extremities. She reported high fever and endorsed malaise. She had a history of end-stage renal disease and was on renal dialysis. She recently underwent revision of an arteriovenous fistula.

Physical examination revealed diffuse, erythematous, firm papules and plaques with central hemorrhage and umbilication on the dorsal aspect of the nose, forehead, temples, and cheeks. There also were purpuric papules and plaques with a peripheral rim of vesiculation (Figure 1) on the medial and posterior thighs and buttocks. Histopathology of a biopsy specimen revealed an interstitial neutrophilic infiltrate in the superficial dermis and mid dermis with scattered, haloed, acellular structures simulating cryptococcal organisms (Figure 2). Periodic acid–Schiff (PAS), Grocott methenamine-silver, and mucicarmine staining was negative. Repeat biopsy showed similar findings. A (1-3)-β-d glucan assay for invasive fungal infection and tests for serum cryptococcal antigen, serum Coccidioides antibody, serum Blastomyces antigen, and urine and serum Histoplasma antigen were negative. A fungal complement fixation battery was negative. Blood and tissue cultures for bacteria, anaerobes, fungi, and acid-fast bacilli remained sterile. Swabs were negative for varicella-zoster virus and herpes simplex virus. Urine and blood iodine levels were 344,998 μg/L (reference range, 34–523 μg/L) and 47,459 μg/L (reference range, 52–109 μg/L), respectively. The elevated iodine levels were presumed to be secondary to iodinated contrast media that the patient received for revision of the arteriovenous fistula.

The findings compatible with a diagnosis of iododerma included umbilicated hemorrhagic papules and plaques, cryptococcal-like structures with negative staining on histopathology, and elevated iodine levels with a negative infectious workup. The patient was treated with topical corticosteroids. At 1-month follow-up, the lesions had resolved.

Iododerma is a halogenoderma, a skin eruption that occurs after ingestion of or exposure to a halogen-containing substance (eg, iodine, bromine, fluorine) or medication (eg, lithium).¹ Common sources of iodine include iodinated contrast media, potassium iodide ingestion, topical application of povidone–iodine, radioactive iodine administration, and the antiarrhythmic amiodarone. Excess exposure to iodine-containing compounds typically occurs in the setting of kidney disease or failure as well as due to reduced iodine clearance.¹ Although the pathogenesis of iododerma is unknown, the most common hypothesis is that lesions are delayed hypersensitivity reactions secondary to formation of a protein-halogen complex.²

The presentation of iododerma is polymorphous and includes acneform, vegetative, or pustular eruptions; umbilicated papules and plaques can be present.^2,3 Lesions can be either asymptomatic or painful and pruritic. Timing between iodine exposure and onset of lesions varies from hours to days to years.^2,4

Systemic symptoms of iododerma can occur, including salivary gland swelling, hypotension and bradycardia, kidney injury, or thyroid and liver abnormalities. Histopathologic analysis demonstrates a dense neutrophilic dermatitis with negative staining for infectious causes.^4,5 Cryptococcal-like structures have been described in iododerma³; neutrophilic dermatoses of various causes that mimic cryptococcal infection have been reported.⁶ Ultimately, iododerma remains a diagnosis of exclusion.

Withdrawal of an offending compound is remedial. Dialysis is beneficial in end-stage renal disease. Topical, intralesional, and systemic corticosteroids, as well as antibiotics, provide variable benefit.^4,7 Lesions can take 4 to 6 weeks to clear after withdrawal of the offending agent. It is unclear whether recurrences happen; iodine-containing compounds need to be avoided after a patient has been affected.

Iododerma has a broad differential diagnosis due to the polymorphous presentation of the disorder, including acute febrile neutrophilic dermatosis (also known as Sweet syndrome), cutaneous cryptococcosis, and cutaneous histoplasmosis. Sweet syndrome presents as abrupt onset of edematous erythematous plaques with fever and leukocytosis. It is associated with infection, inflammatory disorders, medication, and malignancy.⁸ Histopathologic analysis reveals papillary dermal edema and a neutrophilic dermatosis. Cytoplasmic vacuolization resembling C neoformans has been reported.⁹ The diagnosis is less favored in the presence of renal disease, temporal association of the eruption with iodine exposure, and elevated blood and urine iodine levels, as in our patient.

Cutaneous cryptococcosis, an infection caused by C neoformans, typically occurs secondary to dissemination from the lungs; rarely, the disease is primary. Acneform plaques, vegetative plaques, and umbilicated lesions are seen.¹⁰ Histopathologic analysis shows characteristic yeast forms of cryptococcosis surrounded by gelatinous edema, which create a haloed effect, typically throughout the dermis. Capsules are positive for PAS or mucicarmine staining. Although C neoformans can closely mimic iododerma both clinically and histopathologically, negative infectious staining, localization of haloed structures to the upper dermis, a negative test for cryptococcal antigen, and elevated blood and urine iodine levels in this case all favored iododerma.

Cutaneous histoplasmosis is an infection caused by Histoplasma capsulatum, most commonly as secondary dissemination from pulmonary infection but rarely from direct inoculation of the skin.¹¹ Presentation includes erythematous to hemorrhagic, umbilicated papules and plaques. Histopathologic findings are round to oval, narrow-based, budding yeasts that stain positive for PAS or mucicarmine. Although histoplasmosis can clinically mimic iododerma, the disease is distinguished histologically by the presence of fungal microorganisms that lack the gelatinous edema and haloed effect of iododerma.

We presented a unique case of iododerma simulating cryptococcal infection both clinically and histopathologically. Prompt recognition of histologic mimickers of true infectious microorganisms is essential to prevent unnecessary delay of withdrawal of the offending substance and to initiate appropriate therapy.

To the Editor:

A woman in her 40s presented with acute onset of rapidly spreading lesions on the face, trunk, and extremities. She reported high fever and endorsed malaise. She had a history of end-stage renal disease and was on renal dialysis. She recently underwent revision of an arteriovenous fistula.

Physical examination revealed diffuse, erythematous, firm papules and plaques with central hemorrhage and umbilication on the dorsal aspect of the nose, forehead, temples, and cheeks. There also were purpuric papules and plaques with a peripheral rim of vesiculation (Figure 1) on the medial and posterior thighs and buttocks. Histopathology of a biopsy specimen revealed an interstitial neutrophilic infiltrate in the superficial dermis and mid dermis with scattered, haloed, acellular structures simulating cryptococcal organisms (Figure 2). Periodic acid–Schiff (PAS), Grocott methenamine-silver, and mucicarmine staining was negative. Repeat biopsy showed similar findings. A (1-3)-β-d glucan assay for invasive fungal infection and tests for serum cryptococcal antigen, serum Coccidioides antibody, serum Blastomyces antigen, and urine and serum Histoplasma antigen were negative. A fungal complement fixation battery was negative. Blood and tissue cultures for bacteria, anaerobes, fungi, and acid-fast bacilli remained sterile. Swabs were negative for varicella-zoster virus and herpes simplex virus. Urine and blood iodine levels were 344,998 μg/L (reference range, 34–523 μg/L) and 47,459 μg/L (reference range, 52–109 μg/L), respectively. The elevated iodine levels were presumed to be secondary to iodinated contrast media that the patient received for revision of the arteriovenous fistula.

The findings compatible with a diagnosis of iododerma included umbilicated hemorrhagic papules and plaques, cryptococcal-like structures with negative staining on histopathology, and elevated iodine levels with a negative infectious workup. The patient was treated with topical corticosteroids. At 1-month follow-up, the lesions had resolved.

Iododerma is a halogenoderma, a skin eruption that occurs after ingestion of or exposure to a halogen-containing substance (eg, iodine, bromine, fluorine) or medication (eg, lithium).¹ Common sources of iodine include iodinated contrast media, potassium iodide ingestion, topical application of povidone–iodine, radioactive iodine administration, and the antiarrhythmic amiodarone. Excess exposure to iodine-containing compounds typically occurs in the setting of kidney disease or failure as well as due to reduced iodine clearance.¹ Although the pathogenesis of iododerma is unknown, the most common hypothesis is that lesions are delayed hypersensitivity reactions secondary to formation of a protein-halogen complex.²

The presentation of iododerma is polymorphous and includes acneform, vegetative, or pustular eruptions; umbilicated papules and plaques can be present.^2,3 Lesions can be either asymptomatic or painful and pruritic. Timing between iodine exposure and onset of lesions varies from hours to days to years.^2,4

Systemic symptoms of iododerma can occur, including salivary gland swelling, hypotension and bradycardia, kidney injury, or thyroid and liver abnormalities. Histopathologic analysis demonstrates a dense neutrophilic dermatitis with negative staining for infectious causes.^4,5 Cryptococcal-like structures have been described in iododerma³; neutrophilic dermatoses of various causes that mimic cryptococcal infection have been reported.⁶ Ultimately, iododerma remains a diagnosis of exclusion.

Withdrawal of an offending compound is remedial. Dialysis is beneficial in end-stage renal disease. Topical, intralesional, and systemic corticosteroids, as well as antibiotics, provide variable benefit.^4,7 Lesions can take 4 to 6 weeks to clear after withdrawal of the offending agent. It is unclear whether recurrences happen; iodine-containing compounds need to be avoided after a patient has been affected.

Iododerma has a broad differential diagnosis due to the polymorphous presentation of the disorder, including acute febrile neutrophilic dermatosis (also known as Sweet syndrome), cutaneous cryptococcosis, and cutaneous histoplasmosis. Sweet syndrome presents as abrupt onset of edematous erythematous plaques with fever and leukocytosis. It is associated with infection, inflammatory disorders, medication, and malignancy.⁸ Histopathologic analysis reveals papillary dermal edema and a neutrophilic dermatosis. Cytoplasmic vacuolization resembling C neoformans has been reported.⁹ The diagnosis is less favored in the presence of renal disease, temporal association of the eruption with iodine exposure, and elevated blood and urine iodine levels, as in our patient.

Cutaneous cryptococcosis, an infection caused by C neoformans, typically occurs secondary to dissemination from the lungs; rarely, the disease is primary. Acneform plaques, vegetative plaques, and umbilicated lesions are seen.¹⁰ Histopathologic analysis shows characteristic yeast forms of cryptococcosis surrounded by gelatinous edema, which create a haloed effect, typically throughout the dermis. Capsules are positive for PAS or mucicarmine staining. Although C neoformans can closely mimic iododerma both clinically and histopathologically, negative infectious staining, localization of haloed structures to the upper dermis, a negative test for cryptococcal antigen, and elevated blood and urine iodine levels in this case all favored iododerma.

Cutaneous histoplasmosis is an infection caused by Histoplasma capsulatum, most commonly as secondary dissemination from pulmonary infection but rarely from direct inoculation of the skin.¹¹ Presentation includes erythematous to hemorrhagic, umbilicated papules and plaques. Histopathologic findings are round to oval, narrow-based, budding yeasts that stain positive for PAS or mucicarmine. Although histoplasmosis can clinically mimic iododerma, the disease is distinguished histologically by the presence of fungal microorganisms that lack the gelatinous edema and haloed effect of iododerma.

We presented a unique case of iododerma simulating cryptococcal infection both clinically and histopathologically. Prompt recognition of histologic mimickers of true infectious microorganisms is essential to prevent unnecessary delay of withdrawal of the offending substance and to initiate appropriate therapy.

The Diagnosis: Mycobacterium abscessus Infection

Upon further testing, cultures were positive for Mycobacterium abscessus. Our patient was referred to infectious disease for co-management, and his treatment plan consisted of intravenous amikacin 885 mg 3 times weekly, intravenous imipenem 1 g twice daily, azithromycin 500 mg/d, and omadacycline 150 mg/d for at least 3 months. Magnetic resonance imaging findings were consistent with a combination of cellulitis and osteomyelitis, and our patient was referred to plastic surgery for debridement. He subsequently was lost to follow-up.

Mycobacterium abscessus is classified as both a nontuberculous and rapidly growing mycobacterium. Mycobacterium abscessus recently has emerged as a pathogen of increasing public health concern, especially due to its high rate of antibiotic resistance.^1-5 It is highly prevalent in the environment, and infection has been reported from a wide variety of environmental sources.^6-8 Immunocompromised individuals, such as our patient, undergoing anti–tumor necrosis factor therapy are at increased risk for infection from all Mycobacterium species.^9-11 Recognizing these infections quickly is a priority for patient care, as M abscessus can lead to disseminated infection and high mortality rates.¹

Histopathology of M abscessus consists of granulomatous inflammation with mixed granulomas¹²; however, these findings are not always appreciable, and staining does not always reveal visible organisms. In our patient, histopathology revealed patchy plasmalymphocytic infiltrates of the dermis and subcutaneous tissue, which are signs of generalized inflammation (Figure). Therefore, cultures positive for M abscessus are the gold standard for diagnosis and established the diagnosis in this case.

The differential diagnoses for our patient’s ulceration included squamous cell carcinoma, pyoderma gangrenosum, aseptic abscess ulcer, and pyodermatitispyostomatitis vegetans. Immunosuppressive therapy is a risk factor for squamous cell carcinoma^13,14; however, ulcerated squamous cell carcinoma typically presents with prominent everted edges with a necrotic tumor base.¹⁵ Biopsy reveals cells with abundant eosinophilic cytoplasm, large nuclei, and variable keratin pearls.¹⁶ Pyoderma gangrenosum is an inflammatory skin condition associated with Crohn disease and often is a diagnosis of exclusion characterized by neutrophilic infiltrates on biopsy.^17-19 Aseptic abscess ulcers are characterized by neutrophil-filled lesions that respond to corticosteroids but not antibiotics.²⁰ Pyodermatitis-pyostomatitis vegetans is a rare skin manifestation of inflammatory bowel disease associated with a pustular eruption of the skin and/or mouth. Histopathology reveals pustules within or below the epidermis with many eosinophils or neutrophils. Granulomas do not occur as in M abscessus.²¹

Treatment of M abscessus infection requires the coadministration of several antibiotics across multiple classes to ensure complete disease resolution. High rates of antibiotic resistance are characterized by at least partial resistance to almost every antibiotic; clarithromycin has near-complete efficacy, but resistant strains have started to emerge. Amikacin and cefoxitin are other antibiotics that have reported a resistance rate of less than 50%, but they are only effective 90% and 70% of the time, respectively.^1,22 The antibiotic omadacycline, which is approved by the US Food and Drug Administration to treat acute bacterial skin and soft-tissue infections, also may have utility in treating M abscessus infections.^23,24 Finally, phage therapy may offer a potential mode of treatment for this bacterium and was used to treat pulmonary infection in a patient with cystic fibrosis.²⁵ Despite these newer innovations, the current standard of care involves clarithromycin or azithromycin in combination with a parenteral antibiotic such as cefoxitin, amikacin, or imipenem for at least 4 months.¹

The Diagnosis: Mycobacterium abscessus Infection

Upon further testing, cultures were positive for Mycobacterium abscessus. Our patient was referred to infectious disease for co-management, and his treatment plan consisted of intravenous amikacin 885 mg 3 times weekly, intravenous imipenem 1 g twice daily, azithromycin 500 mg/d, and omadacycline 150 mg/d for at least 3 months. Magnetic resonance imaging findings were consistent with a combination of cellulitis and osteomyelitis, and our patient was referred to plastic surgery for debridement. He subsequently was lost to follow-up.

Mycobacterium abscessus is classified as both a nontuberculous and rapidly growing mycobacterium. Mycobacterium abscessus recently has emerged as a pathogen of increasing public health concern, especially due to its high rate of antibiotic resistance.^1-5 It is highly prevalent in the environment, and infection has been reported from a wide variety of environmental sources.^6-8 Immunocompromised individuals, such as our patient, undergoing anti–tumor necrosis factor therapy are at increased risk for infection from all Mycobacterium species.^9-11 Recognizing these infections quickly is a priority for patient care, as M abscessus can lead to disseminated infection and high mortality rates.¹

Histopathology of M abscessus consists of granulomatous inflammation with mixed granulomas¹²; however, these findings are not always appreciable, and staining does not always reveal visible organisms. In our patient, histopathology revealed patchy plasmalymphocytic infiltrates of the dermis and subcutaneous tissue, which are signs of generalized inflammation (Figure). Therefore, cultures positive for M abscessus are the gold standard for diagnosis and established the diagnosis in this case.

The differential diagnoses for our patient’s ulceration included squamous cell carcinoma, pyoderma gangrenosum, aseptic abscess ulcer, and pyodermatitispyostomatitis vegetans. Immunosuppressive therapy is a risk factor for squamous cell carcinoma^13,14; however, ulcerated squamous cell carcinoma typically presents with prominent everted edges with a necrotic tumor base.¹⁵ Biopsy reveals cells with abundant eosinophilic cytoplasm, large nuclei, and variable keratin pearls.¹⁶ Pyoderma gangrenosum is an inflammatory skin condition associated with Crohn disease and often is a diagnosis of exclusion characterized by neutrophilic infiltrates on biopsy.^17-19 Aseptic abscess ulcers are characterized by neutrophil-filled lesions that respond to corticosteroids but not antibiotics.²⁰ Pyodermatitis-pyostomatitis vegetans is a rare skin manifestation of inflammatory bowel disease associated with a pustular eruption of the skin and/or mouth. Histopathology reveals pustules within or below the epidermis with many eosinophils or neutrophils. Granulomas do not occur as in M abscessus.²¹

Treatment of M abscessus infection requires the coadministration of several antibiotics across multiple classes to ensure complete disease resolution. High rates of antibiotic resistance are characterized by at least partial resistance to almost every antibiotic; clarithromycin has near-complete efficacy, but resistant strains have started to emerge. Amikacin and cefoxitin are other antibiotics that have reported a resistance rate of less than 50%, but they are only effective 90% and 70% of the time, respectively.^1,22 The antibiotic omadacycline, which is approved by the US Food and Drug Administration to treat acute bacterial skin and soft-tissue infections, also may have utility in treating M abscessus infections.^23,24 Finally, phage therapy may offer a potential mode of treatment for this bacterium and was used to treat pulmonary infection in a patient with cystic fibrosis.²⁵ Despite these newer innovations, the current standard of care involves clarithromycin or azithromycin in combination with a parenteral antibiotic such as cefoxitin, amikacin, or imipenem for at least 4 months.¹

The Diagnosis: Mycobacterium abscessus Infection

Upon further testing, cultures were positive for Mycobacterium abscessus. Our patient was referred to infectious disease for co-management, and his treatment plan consisted of intravenous amikacin 885 mg 3 times weekly, intravenous imipenem 1 g twice daily, azithromycin 500 mg/d, and omadacycline 150 mg/d for at least 3 months. Magnetic resonance imaging findings were consistent with a combination of cellulitis and osteomyelitis, and our patient was referred to plastic surgery for debridement. He subsequently was lost to follow-up.

Mycobacterium abscessus is classified as both a nontuberculous and rapidly growing mycobacterium. Mycobacterium abscessus recently has emerged as a pathogen of increasing public health concern, especially due to its high rate of antibiotic resistance.^1-5 It is highly prevalent in the environment, and infection has been reported from a wide variety of environmental sources.^6-8 Immunocompromised individuals, such as our patient, undergoing anti–tumor necrosis factor therapy are at increased risk for infection from all Mycobacterium species.^9-11 Recognizing these infections quickly is a priority for patient care, as M abscessus can lead to disseminated infection and high mortality rates.¹

Histopathology of M abscessus consists of granulomatous inflammation with mixed granulomas¹²; however, these findings are not always appreciable, and staining does not always reveal visible organisms. In our patient, histopathology revealed patchy plasmalymphocytic infiltrates of the dermis and subcutaneous tissue, which are signs of generalized inflammation (Figure). Therefore, cultures positive for M abscessus are the gold standard for diagnosis and established the diagnosis in this case.

The differential diagnoses for our patient’s ulceration included squamous cell carcinoma, pyoderma gangrenosum, aseptic abscess ulcer, and pyodermatitispyostomatitis vegetans. Immunosuppressive therapy is a risk factor for squamous cell carcinoma^13,14; however, ulcerated squamous cell carcinoma typically presents with prominent everted edges with a necrotic tumor base.¹⁵ Biopsy reveals cells with abundant eosinophilic cytoplasm, large nuclei, and variable keratin pearls.¹⁶ Pyoderma gangrenosum is an inflammatory skin condition associated with Crohn disease and often is a diagnosis of exclusion characterized by neutrophilic infiltrates on biopsy.^17-19 Aseptic abscess ulcers are characterized by neutrophil-filled lesions that respond to corticosteroids but not antibiotics.²⁰ Pyodermatitis-pyostomatitis vegetans is a rare skin manifestation of inflammatory bowel disease associated with a pustular eruption of the skin and/or mouth. Histopathology reveals pustules within or below the epidermis with many eosinophils or neutrophils. Granulomas do not occur as in M abscessus.²¹

Treatment of M abscessus infection requires the coadministration of several antibiotics across multiple classes to ensure complete disease resolution. High rates of antibiotic resistance are characterized by at least partial resistance to almost every antibiotic; clarithromycin has near-complete efficacy, but resistant strains have started to emerge. Amikacin and cefoxitin are other antibiotics that have reported a resistance rate of less than 50%, but they are only effective 90% and 70% of the time, respectively.^1,22 The antibiotic omadacycline, which is approved by the US Food and Drug Administration to treat acute bacterial skin and soft-tissue infections, also may have utility in treating M abscessus infections.^23,24 Finally, phage therapy may offer a potential mode of treatment for this bacterium and was used to treat pulmonary infection in a patient with cystic fibrosis.²⁵ Despite these newer innovations, the current standard of care involves clarithromycin or azithromycin in combination with a parenteral antibiotic such as cefoxitin, amikacin, or imipenem for at least 4 months.¹