Photo Challenge

The Diagnosis: Keratoderma Climactericum 

Keratoderma climactericum was first reported in 1934 by Haxthausen¹ as nonpruritic circumscribed hyperkeratosis located mainly on the palms and soles. The initial eruption was described as discrete lesions with an oval or round shape that progressed to less-defined, confluent, hyperkeratotic patches with fissures.¹ Keratoderma climactericum also may be referred to as Haxthausen disease and is considered an acquired palmoplantar keratoderma.² 

Keratoderma climactericum is a rare dermatologic disorder that presents in women of menopausal age who have no family or personal history of skin disease. Keratoderma climactericum is associated with hypertension and obesity.² Keratotic lesions usually first occur on the plantar surfaces with eventual development of fissuring and hyperkeratosis that causes painful walking. The keratotic lesions on the plantar surfaces often are nonpruritic and gradually become confluent over time. As the disease progresses, keratotic lesions appear on the central palms, which can lead to confluent hyperkeratosis on the palmar surfaces (Figure 1).² The exact mechanism of keratoderma climactericum has not been described but is believed to be due to hormonal dysregulation.²  

Treatment options for keratoderma climactericum include salicylic acid, emollients, oral retinoids, urea ointments, estriol cream, and topical steroids.^5,6 Our patient was prescribed acitretin 25 mg daily and ammonium lactate to apply topically as needed for dry skin. Five months after the initial presentation, fissures and dry skin on the bilateral soles were still present. Ammonium lactate was discontinued, and the patient was prescribed urea cream 40%. Fifteen months after the initial presentation, the patient reported substantial improvement on the hands and feet and noted that she no longer needed the urea cream. Physical examination revealed no presence of hyperkeratosis or fissuring on the palms (Figure 2), and mild hyperkeratosis was present on the plantar surfaces of the feet (Figure 3). The patient continued to use acitretin to prevent disease relapse.  

The Diagnosis: Keratoderma Climactericum 

Keratoderma climactericum was first reported in 1934 by Haxthausen¹ as nonpruritic circumscribed hyperkeratosis located mainly on the palms and soles. The initial eruption was described as discrete lesions with an oval or round shape that progressed to less-defined, confluent, hyperkeratotic patches with fissures.¹ Keratoderma climactericum also may be referred to as Haxthausen disease and is considered an acquired palmoplantar keratoderma.² 

Keratoderma climactericum is a rare dermatologic disorder that presents in women of menopausal age who have no family or personal history of skin disease. Keratoderma climactericum is associated with hypertension and obesity.² Keratotic lesions usually first occur on the plantar surfaces with eventual development of fissuring and hyperkeratosis that causes painful walking. The keratotic lesions on the plantar surfaces often are nonpruritic and gradually become confluent over time. As the disease progresses, keratotic lesions appear on the central palms, which can lead to confluent hyperkeratosis on the palmar surfaces (Figure 1).² The exact mechanism of keratoderma climactericum has not been described but is believed to be due to hormonal dysregulation.²  

Treatment options for keratoderma climactericum include salicylic acid, emollients, oral retinoids, urea ointments, estriol cream, and topical steroids.^5,6 Our patient was prescribed acitretin 25 mg daily and ammonium lactate to apply topically as needed for dry skin. Five months after the initial presentation, fissures and dry skin on the bilateral soles were still present. Ammonium lactate was discontinued, and the patient was prescribed urea cream 40%. Fifteen months after the initial presentation, the patient reported substantial improvement on the hands and feet and noted that she no longer needed the urea cream. Physical examination revealed no presence of hyperkeratosis or fissuring on the palms (Figure 2), and mild hyperkeratosis was present on the plantar surfaces of the feet (Figure 3). The patient continued to use acitretin to prevent disease relapse.  

The Diagnosis: Keratoderma Climactericum 

Keratoderma climactericum was first reported in 1934 by Haxthausen¹ as nonpruritic circumscribed hyperkeratosis located mainly on the palms and soles. The initial eruption was described as discrete lesions with an oval or round shape that progressed to less-defined, confluent, hyperkeratotic patches with fissures.¹ Keratoderma climactericum also may be referred to as Haxthausen disease and is considered an acquired palmoplantar keratoderma.² 

Keratoderma climactericum is a rare dermatologic disorder that presents in women of menopausal age who have no family or personal history of skin disease. Keratoderma climactericum is associated with hypertension and obesity.² Keratotic lesions usually first occur on the plantar surfaces with eventual development of fissuring and hyperkeratosis that causes painful walking. The keratotic lesions on the plantar surfaces often are nonpruritic and gradually become confluent over time. As the disease progresses, keratotic lesions appear on the central palms, which can lead to confluent hyperkeratosis on the palmar surfaces (Figure 1).² The exact mechanism of keratoderma climactericum has not been described but is believed to be due to hormonal dysregulation.²  

Treatment options for keratoderma climactericum include salicylic acid, emollients, oral retinoids, urea ointments, estriol cream, and topical steroids.^5,6 Our patient was prescribed acitretin 25 mg daily and ammonium lactate to apply topically as needed for dry skin. Five months after the initial presentation, fissures and dry skin on the bilateral soles were still present. Ammonium lactate was discontinued, and the patient was prescribed urea cream 40%. Fifteen months after the initial presentation, the patient reported substantial improvement on the hands and feet and noted that she no longer needed the urea cream. Physical examination revealed no presence of hyperkeratosis or fissuring on the palms (Figure 2), and mild hyperkeratosis was present on the plantar surfaces of the feet (Figure 3). The patient continued to use acitretin to prevent disease relapse.  

The Diagnosis: Extragenital Lichen Sclerosus Et Atrophicus 

Histopathologic evaluation revealed hyperkeratosis, follicular plugging, epidermal atrophy, and homogenization of papillary dermal collagen with an underlying lymphocytic infiltrate (Figure 1). Direct immunofluorescence of a plaque with a superimposed bulla was negative for deposition of C3, IgG, IgA, IgM, or fibrinogen. Accordingly, clinicopathologic correlation supported a diagnosis of extragenital lichen sclerosus et atrophicus (LSA). Of note, the patient's history of genital irritation was due to genital LSA that preceded the extragenital manifestations. 

Lichen sclerosus et atrophicus is an inflammatory dermatosis that typically presents as atrophic white papules of the anogenital area that coalesce into pruritic plaques; the exact etiology remains to be elucidated, yet various circulating autoantibodies have been identified, suggesting a role for autoimmunity.^1,2 Lichen sclerosus et atrophicus is more common in women than in men, with a bimodal peak in the age of onset affecting postmenopausal and prepubertal populations.¹ In women, affected areas include the labia minora and majora, clitoris, perineum, and perianal skin; LSA spares the mucosal surfaces of the vagina and cervix.² In men, uncircumscribed genital skin more commonly is affected. Involvement is localized to the foreskin and glans with occasional urethral involvement.²  

In contrast, extragenital LSA tends to present as asymptomatic papules and plaques that develop atrophy with time, involving the back, shoulders, neck, chest, thighs, axillae, and flexural wrists^2,3; an erythematous rim often is present,⁴ and hyperkeratosis with follicular plugging may be prominent.⁵ Our patient's case emphasizes the predilection of plaques for the chest and intermammary skin (Figure 2A). Approximately 15% of LSA cases have extragenital involvement, and extragenital-limited disease accounts for roughly 5% of cases.^6,7 Unlike genital LSA, extragenital disease has not been associated with an increased risk for squamous cell carcinoma.¹ Bullae formation within plaques of genital or extragenital LSA has been reported^3,8 and is exemplified in our patient (Figure 2B). Intralesional bullae formation likely is due to a combination of internal and external factors, mainly the inability to withstand shear forces due to an atrophic epidermis with basal vacuolar injury overlying an edematous papillary dermis with altered collagen.⁸ Dermatoscopic findings may aid in recognizing extragenital LSA9,¹⁰; our patient's plaques demonstrated the characteristic findings of comedolike openings, structureless white areas, and pink borders (Figure 3). 

The clinical differential diagnosis for well-demarcated, pink, scaly plaques is broad. Nummular eczema usually presents as coin-shaped eczematous plaques on the dorsal aspects of the hands or lower extremities, and histology shows epidermal spongiosis.¹¹ Nummular eczema may be considered due to the striking round morphology of various plaques, yet our patient's presentation was better served by a consideration of several papulosquamous disorders. 

Lichen planus (LP) presents as intensely pruritic, violaceous, polygonal, flat-topped papules with overlying reticular white lines, or Wickham striae, that favor the flexural wrists, lower back, and lower extremities. Lichen planus also may have oral and genital mucosal involvement. Similar to LSA, LP is more common in women and preferentially affects the postmenopausal population.¹² Additionally, hypertrophic LP may obscure Wickham striae and mimic extragenital LSA; distinguishing features of hypertrophic LP are intense pruritus and a predilection for the shins. Histology is defined by orthohyperkeratosis, hypergranulosis, sawtooth acanthosis, and vacuolar degeneration of the basal layer with Civatte bodies or dyskeratotic basal keratinocytes overlying a characteristic bandlike infiltrate of lymphocytes.¹² 

Lichen simplex chronicus (LSC) is characterized by intense pruritus and presents as hyperkeratotic plaques with a predilection for accessible regions such as the posterior neck and extremities.¹³ The striking annular demarcation of this case makes LSC unlikely. Comparable to LSA and LP, LSC also may present with both genital and extragenital findings. Histology of LSC is characterized by irregular acanthosis or thickening of the epidermis with vertical streaking of collagen and vascular bundles of the papillary dermis.¹³ 

Subacute cutaneous lupus erythematosus (SCLE) is important to consider for a new papulosquamous eruption with a predilection for the sun-exposed skin of a middle-aged woman. The presence of papules on the volar wrist and history of genital irritation, however, make this entity less likely. Similar to LSA, histologic examination of SCLE reveals epidermal atrophy, basal layer degeneration, and papillary dermal edema with lymphocytic inflammation. However, SCLE lacks the band of inflammation underlying pale homogenized papillary dermal collagen, the most distinguishing feature of LSA; instead, SCLE shows superficial and deep perivascular and periadnexal lymphocytes and mucin in the dermis.¹⁴ 

Lichen sclerosus et atrophicus may be chronic and progressive in nature or cycle through remissions and relapses.² Treatment is not curative, and management is directed to alleviating symptoms and preventing the progression of disease. First-line management of extragenital LSA is potent topical steroids.¹ Adjuvant topical calcineurin inhibitors may be used as steroid-sparing agents.² Phototherapy is a second-line therapy and even narrowband UVB phototherapy has demonstrated efficacy in managing extragenital LSA.^15,16 Our patient was started on mometasone ointment and calcipotriene cream with slight improvement after a 6-month trial. Ongoing management is focused on optimizing application of topical therapies.  

The Diagnosis: Extragenital Lichen Sclerosus Et Atrophicus 

Histopathologic evaluation revealed hyperkeratosis, follicular plugging, epidermal atrophy, and homogenization of papillary dermal collagen with an underlying lymphocytic infiltrate (Figure 1). Direct immunofluorescence of a plaque with a superimposed bulla was negative for deposition of C3, IgG, IgA, IgM, or fibrinogen. Accordingly, clinicopathologic correlation supported a diagnosis of extragenital lichen sclerosus et atrophicus (LSA). Of note, the patient's history of genital irritation was due to genital LSA that preceded the extragenital manifestations. 

Lichen sclerosus et atrophicus is an inflammatory dermatosis that typically presents as atrophic white papules of the anogenital area that coalesce into pruritic plaques; the exact etiology remains to be elucidated, yet various circulating autoantibodies have been identified, suggesting a role for autoimmunity.^1,2 Lichen sclerosus et atrophicus is more common in women than in men, with a bimodal peak in the age of onset affecting postmenopausal and prepubertal populations.¹ In women, affected areas include the labia minora and majora, clitoris, perineum, and perianal skin; LSA spares the mucosal surfaces of the vagina and cervix.² In men, uncircumscribed genital skin more commonly is affected. Involvement is localized to the foreskin and glans with occasional urethral involvement.²  

In contrast, extragenital LSA tends to present as asymptomatic papules and plaques that develop atrophy with time, involving the back, shoulders, neck, chest, thighs, axillae, and flexural wrists^2,3; an erythematous rim often is present,⁴ and hyperkeratosis with follicular plugging may be prominent.⁵ Our patient's case emphasizes the predilection of plaques for the chest and intermammary skin (Figure 2A). Approximately 15% of LSA cases have extragenital involvement, and extragenital-limited disease accounts for roughly 5% of cases.^6,7 Unlike genital LSA, extragenital disease has not been associated with an increased risk for squamous cell carcinoma.¹ Bullae formation within plaques of genital or extragenital LSA has been reported^3,8 and is exemplified in our patient (Figure 2B). Intralesional bullae formation likely is due to a combination of internal and external factors, mainly the inability to withstand shear forces due to an atrophic epidermis with basal vacuolar injury overlying an edematous papillary dermis with altered collagen.⁸ Dermatoscopic findings may aid in recognizing extragenital LSA9,¹⁰; our patient's plaques demonstrated the characteristic findings of comedolike openings, structureless white areas, and pink borders (Figure 3). 

The clinical differential diagnosis for well-demarcated, pink, scaly plaques is broad. Nummular eczema usually presents as coin-shaped eczematous plaques on the dorsal aspects of the hands or lower extremities, and histology shows epidermal spongiosis.¹¹ Nummular eczema may be considered due to the striking round morphology of various plaques, yet our patient's presentation was better served by a consideration of several papulosquamous disorders. 

Lichen planus (LP) presents as intensely pruritic, violaceous, polygonal, flat-topped papules with overlying reticular white lines, or Wickham striae, that favor the flexural wrists, lower back, and lower extremities. Lichen planus also may have oral and genital mucosal involvement. Similar to LSA, LP is more common in women and preferentially affects the postmenopausal population.¹² Additionally, hypertrophic LP may obscure Wickham striae and mimic extragenital LSA; distinguishing features of hypertrophic LP are intense pruritus and a predilection for the shins. Histology is defined by orthohyperkeratosis, hypergranulosis, sawtooth acanthosis, and vacuolar degeneration of the basal layer with Civatte bodies or dyskeratotic basal keratinocytes overlying a characteristic bandlike infiltrate of lymphocytes.¹² 

Lichen simplex chronicus (LSC) is characterized by intense pruritus and presents as hyperkeratotic plaques with a predilection for accessible regions such as the posterior neck and extremities.¹³ The striking annular demarcation of this case makes LSC unlikely. Comparable to LSA and LP, LSC also may present with both genital and extragenital findings. Histology of LSC is characterized by irregular acanthosis or thickening of the epidermis with vertical streaking of collagen and vascular bundles of the papillary dermis.¹³ 

Subacute cutaneous lupus erythematosus (SCLE) is important to consider for a new papulosquamous eruption with a predilection for the sun-exposed skin of a middle-aged woman. The presence of papules on the volar wrist and history of genital irritation, however, make this entity less likely. Similar to LSA, histologic examination of SCLE reveals epidermal atrophy, basal layer degeneration, and papillary dermal edema with lymphocytic inflammation. However, SCLE lacks the band of inflammation underlying pale homogenized papillary dermal collagen, the most distinguishing feature of LSA; instead, SCLE shows superficial and deep perivascular and periadnexal lymphocytes and mucin in the dermis.¹⁴ 

Lichen sclerosus et atrophicus may be chronic and progressive in nature or cycle through remissions and relapses.² Treatment is not curative, and management is directed to alleviating symptoms and preventing the progression of disease. First-line management of extragenital LSA is potent topical steroids.¹ Adjuvant topical calcineurin inhibitors may be used as steroid-sparing agents.² Phototherapy is a second-line therapy and even narrowband UVB phototherapy has demonstrated efficacy in managing extragenital LSA.^15,16 Our patient was started on mometasone ointment and calcipotriene cream with slight improvement after a 6-month trial. Ongoing management is focused on optimizing application of topical therapies.  

The Diagnosis: Extragenital Lichen Sclerosus Et Atrophicus 

Histopathologic evaluation revealed hyperkeratosis, follicular plugging, epidermal atrophy, and homogenization of papillary dermal collagen with an underlying lymphocytic infiltrate (Figure 1). Direct immunofluorescence of a plaque with a superimposed bulla was negative for deposition of C3, IgG, IgA, IgM, or fibrinogen. Accordingly, clinicopathologic correlation supported a diagnosis of extragenital lichen sclerosus et atrophicus (LSA). Of note, the patient's history of genital irritation was due to genital LSA that preceded the extragenital manifestations. 

Lichen sclerosus et atrophicus is an inflammatory dermatosis that typically presents as atrophic white papules of the anogenital area that coalesce into pruritic plaques; the exact etiology remains to be elucidated, yet various circulating autoantibodies have been identified, suggesting a role for autoimmunity.^1,2 Lichen sclerosus et atrophicus is more common in women than in men, with a bimodal peak in the age of onset affecting postmenopausal and prepubertal populations.¹ In women, affected areas include the labia minora and majora, clitoris, perineum, and perianal skin; LSA spares the mucosal surfaces of the vagina and cervix.² In men, uncircumscribed genital skin more commonly is affected. Involvement is localized to the foreskin and glans with occasional urethral involvement.²  

In contrast, extragenital LSA tends to present as asymptomatic papules and plaques that develop atrophy with time, involving the back, shoulders, neck, chest, thighs, axillae, and flexural wrists^2,3; an erythematous rim often is present,⁴ and hyperkeratosis with follicular plugging may be prominent.⁵ Our patient's case emphasizes the predilection of plaques for the chest and intermammary skin (Figure 2A). Approximately 15% of LSA cases have extragenital involvement, and extragenital-limited disease accounts for roughly 5% of cases.^6,7 Unlike genital LSA, extragenital disease has not been associated with an increased risk for squamous cell carcinoma.¹ Bullae formation within plaques of genital or extragenital LSA has been reported^3,8 and is exemplified in our patient (Figure 2B). Intralesional bullae formation likely is due to a combination of internal and external factors, mainly the inability to withstand shear forces due to an atrophic epidermis with basal vacuolar injury overlying an edematous papillary dermis with altered collagen.⁸ Dermatoscopic findings may aid in recognizing extragenital LSA9,¹⁰; our patient's plaques demonstrated the characteristic findings of comedolike openings, structureless white areas, and pink borders (Figure 3). 

The clinical differential diagnosis for well-demarcated, pink, scaly plaques is broad. Nummular eczema usually presents as coin-shaped eczematous plaques on the dorsal aspects of the hands or lower extremities, and histology shows epidermal spongiosis.¹¹ Nummular eczema may be considered due to the striking round morphology of various plaques, yet our patient's presentation was better served by a consideration of several papulosquamous disorders. 

Lichen planus (LP) presents as intensely pruritic, violaceous, polygonal, flat-topped papules with overlying reticular white lines, or Wickham striae, that favor the flexural wrists, lower back, and lower extremities. Lichen planus also may have oral and genital mucosal involvement. Similar to LSA, LP is more common in women and preferentially affects the postmenopausal population.¹² Additionally, hypertrophic LP may obscure Wickham striae and mimic extragenital LSA; distinguishing features of hypertrophic LP are intense pruritus and a predilection for the shins. Histology is defined by orthohyperkeratosis, hypergranulosis, sawtooth acanthosis, and vacuolar degeneration of the basal layer with Civatte bodies or dyskeratotic basal keratinocytes overlying a characteristic bandlike infiltrate of lymphocytes.¹² 

Lichen simplex chronicus (LSC) is characterized by intense pruritus and presents as hyperkeratotic plaques with a predilection for accessible regions such as the posterior neck and extremities.¹³ The striking annular demarcation of this case makes LSC unlikely. Comparable to LSA and LP, LSC also may present with both genital and extragenital findings. Histology of LSC is characterized by irregular acanthosis or thickening of the epidermis with vertical streaking of collagen and vascular bundles of the papillary dermis.¹³ 

Subacute cutaneous lupus erythematosus (SCLE) is important to consider for a new papulosquamous eruption with a predilection for the sun-exposed skin of a middle-aged woman. The presence of papules on the volar wrist and history of genital irritation, however, make this entity less likely. Similar to LSA, histologic examination of SCLE reveals epidermal atrophy, basal layer degeneration, and papillary dermal edema with lymphocytic inflammation. However, SCLE lacks the band of inflammation underlying pale homogenized papillary dermal collagen, the most distinguishing feature of LSA; instead, SCLE shows superficial and deep perivascular and periadnexal lymphocytes and mucin in the dermis.¹⁴ 

Lichen sclerosus et atrophicus may be chronic and progressive in nature or cycle through remissions and relapses.² Treatment is not curative, and management is directed to alleviating symptoms and preventing the progression of disease. First-line management of extragenital LSA is potent topical steroids.¹ Adjuvant topical calcineurin inhibitors may be used as steroid-sparing agents.² Phototherapy is a second-line therapy and even narrowband UVB phototherapy has demonstrated efficacy in managing extragenital LSA.^15,16 Our patient was started on mometasone ointment and calcipotriene cream with slight improvement after a 6-month trial. Ongoing management is focused on optimizing application of topical therapies.  

The Diagnosis: Cutaneous Metaplastic Synovial Cyst 

Gross examination of the excised nodule revealed a 2.5×1.2×1.0-cm, intact, gray-white, thin-walled, smooth-lined nodule filled with clear mucinouslike material. Hematoxylin and eosin-stained sections demonstrated a dermal-based cystlike structure composed of a lining of connective tissue with hyalinized material and fibrin as well as spindle and epithelioid cells with a mild mixed inflammatory infiltrate (Figure). These histopathologic findings led to the diagnosis of cutaneous metaplastic synovial cyst (CMSC).  

Cutaneous metaplastic synovial cyst, also known as synovial metaplasia of the skin, is an uncommon benign cystic lesion that was first reported by Gonzalez et al¹ in 1987. Histologically, CMSC lacks an epithelial lining and therefore is not a true cyst but rather a pseudocyst.² Clinically, the lesion typically presents as a solitary subcutaneous nodule that may be tender or painless. In a literature review of CMSC cases performed by Fukuyama et al,³ distribution of reported cases according to body site varied; however, limbs were found to be the most commonly involved area. A PubMed search of articles indexed for MEDLINE as well as a Google Scholar search using the term cutaneous metaplastic synovial cyst revealed at least 37 cases reported in the English-language literature,^3-9 including our present case. The pathogenesis remains uncertain; however, a majority of previously reported cases of CMSC characteristically have been associated with a pre-existing lesion, with most presentations developing at surgical scar sites secondary to operation or trauma.⁵ Relative tissue fragility secondary to rheumatoid arthritis¹⁰ and Ehlers-Danlos syndrome^9,11,12 has been linked to CMSC in some documented reports, while a minority of cases report no antecedent events triggering formation of the lesion.^13-15 

As evidenced by our patient, CMSC clinically mimics several other benign entities; histopathologic examination is necessary to confirm the diagnosis. Although nodular hidradenoma also may clinically present as a solitary firm intradermal nodule, microscopy reveals a dermal-based lobulated tumor containing cystic spaces and solid areas composed of basophilic polyhedral cells and round glycogen-filled clear cells.¹⁶ Epidermoid cysts are differentiated from CMSC by the presence of a cyst wall lining composed of stratified squamous epithelium and associated laminated keratin within the lumen,¹⁷ which corresponds to its pearly white appearance on gross examination. Cutaneous ciliated cysts predominantly occur on the lower extremities of young women and are lined by simple cuboidal or columnar ciliated cells that resemble müllerian epithelium.¹⁸ Similar to CMSC, ganglion cysts are pseudocysts that lack a true epithelial lining but differ in appearance due to their mucin-filled synovial-lined sac.¹⁹ Additionally, ganglion cysts most often occur on the dorsal and volar aspects of the wrist. 

Excisional biopsy is indicated as the preferred treatment of CMSC, given the lesion's benign behavior and low recurrence rate.⁶ Our case highlights this rare entity and reinforces its inclusion in the differential diagnosis of subcutaneous mobile nodules, especially in the setting of prior tissue injury secondary to trauma, surgical procedures, or conditions such as rheumatoid arthritis or Ehlers-Danlos syndrome. Unlike most previously reported cases, our patient reported no preceding tissue injury associated with formation of the lesion, and she was largely asymptomatic on presentation. Considering the limited number of CMSC cases demonstrated in the literature, it is important to continue reporting new cases to better understand characteristics and presentations of this uncommon lesion. 

The Diagnosis: Cutaneous Metaplastic Synovial Cyst 

Gross examination of the excised nodule revealed a 2.5×1.2×1.0-cm, intact, gray-white, thin-walled, smooth-lined nodule filled with clear mucinouslike material. Hematoxylin and eosin-stained sections demonstrated a dermal-based cystlike structure composed of a lining of connective tissue with hyalinized material and fibrin as well as spindle and epithelioid cells with a mild mixed inflammatory infiltrate (Figure). These histopathologic findings led to the diagnosis of cutaneous metaplastic synovial cyst (CMSC).  

Cutaneous metaplastic synovial cyst, also known as synovial metaplasia of the skin, is an uncommon benign cystic lesion that was first reported by Gonzalez et al¹ in 1987. Histologically, CMSC lacks an epithelial lining and therefore is not a true cyst but rather a pseudocyst.² Clinically, the lesion typically presents as a solitary subcutaneous nodule that may be tender or painless. In a literature review of CMSC cases performed by Fukuyama et al,³ distribution of reported cases according to body site varied; however, limbs were found to be the most commonly involved area. A PubMed search of articles indexed for MEDLINE as well as a Google Scholar search using the term cutaneous metaplastic synovial cyst revealed at least 37 cases reported in the English-language literature,^3-9 including our present case. The pathogenesis remains uncertain; however, a majority of previously reported cases of CMSC characteristically have been associated with a pre-existing lesion, with most presentations developing at surgical scar sites secondary to operation or trauma.⁵ Relative tissue fragility secondary to rheumatoid arthritis¹⁰ and Ehlers-Danlos syndrome^9,11,12 has been linked to CMSC in some documented reports, while a minority of cases report no antecedent events triggering formation of the lesion.^13-15 

As evidenced by our patient, CMSC clinically mimics several other benign entities; histopathologic examination is necessary to confirm the diagnosis. Although nodular hidradenoma also may clinically present as a solitary firm intradermal nodule, microscopy reveals a dermal-based lobulated tumor containing cystic spaces and solid areas composed of basophilic polyhedral cells and round glycogen-filled clear cells.¹⁶ Epidermoid cysts are differentiated from CMSC by the presence of a cyst wall lining composed of stratified squamous epithelium and associated laminated keratin within the lumen,¹⁷ which corresponds to its pearly white appearance on gross examination. Cutaneous ciliated cysts predominantly occur on the lower extremities of young women and are lined by simple cuboidal or columnar ciliated cells that resemble müllerian epithelium.¹⁸ Similar to CMSC, ganglion cysts are pseudocysts that lack a true epithelial lining but differ in appearance due to their mucin-filled synovial-lined sac.¹⁹ Additionally, ganglion cysts most often occur on the dorsal and volar aspects of the wrist. 

Excisional biopsy is indicated as the preferred treatment of CMSC, given the lesion's benign behavior and low recurrence rate.⁶ Our case highlights this rare entity and reinforces its inclusion in the differential diagnosis of subcutaneous mobile nodules, especially in the setting of prior tissue injury secondary to trauma, surgical procedures, or conditions such as rheumatoid arthritis or Ehlers-Danlos syndrome. Unlike most previously reported cases, our patient reported no preceding tissue injury associated with formation of the lesion, and she was largely asymptomatic on presentation. Considering the limited number of CMSC cases demonstrated in the literature, it is important to continue reporting new cases to better understand characteristics and presentations of this uncommon lesion. 

The Diagnosis: Cutaneous Metaplastic Synovial Cyst 

Gross examination of the excised nodule revealed a 2.5×1.2×1.0-cm, intact, gray-white, thin-walled, smooth-lined nodule filled with clear mucinouslike material. Hematoxylin and eosin-stained sections demonstrated a dermal-based cystlike structure composed of a lining of connective tissue with hyalinized material and fibrin as well as spindle and epithelioid cells with a mild mixed inflammatory infiltrate (Figure). These histopathologic findings led to the diagnosis of cutaneous metaplastic synovial cyst (CMSC).  

Cutaneous metaplastic synovial cyst, also known as synovial metaplasia of the skin, is an uncommon benign cystic lesion that was first reported by Gonzalez et al¹ in 1987. Histologically, CMSC lacks an epithelial lining and therefore is not a true cyst but rather a pseudocyst.² Clinically, the lesion typically presents as a solitary subcutaneous nodule that may be tender or painless. In a literature review of CMSC cases performed by Fukuyama et al,³ distribution of reported cases according to body site varied; however, limbs were found to be the most commonly involved area. A PubMed search of articles indexed for MEDLINE as well as a Google Scholar search using the term cutaneous metaplastic synovial cyst revealed at least 37 cases reported in the English-language literature,^3-9 including our present case. The pathogenesis remains uncertain; however, a majority of previously reported cases of CMSC characteristically have been associated with a pre-existing lesion, with most presentations developing at surgical scar sites secondary to operation or trauma.⁵ Relative tissue fragility secondary to rheumatoid arthritis¹⁰ and Ehlers-Danlos syndrome^9,11,12 has been linked to CMSC in some documented reports, while a minority of cases report no antecedent events triggering formation of the lesion.^13-15 

As evidenced by our patient, CMSC clinically mimics several other benign entities; histopathologic examination is necessary to confirm the diagnosis. Although nodular hidradenoma also may clinically present as a solitary firm intradermal nodule, microscopy reveals a dermal-based lobulated tumor containing cystic spaces and solid areas composed of basophilic polyhedral cells and round glycogen-filled clear cells.¹⁶ Epidermoid cysts are differentiated from CMSC by the presence of a cyst wall lining composed of stratified squamous epithelium and associated laminated keratin within the lumen,¹⁷ which corresponds to its pearly white appearance on gross examination. Cutaneous ciliated cysts predominantly occur on the lower extremities of young women and are lined by simple cuboidal or columnar ciliated cells that resemble müllerian epithelium.¹⁸ Similar to CMSC, ganglion cysts are pseudocysts that lack a true epithelial lining but differ in appearance due to their mucin-filled synovial-lined sac.¹⁹ Additionally, ganglion cysts most often occur on the dorsal and volar aspects of the wrist. 

Excisional biopsy is indicated as the preferred treatment of CMSC, given the lesion's benign behavior and low recurrence rate.⁶ Our case highlights this rare entity and reinforces its inclusion in the differential diagnosis of subcutaneous mobile nodules, especially in the setting of prior tissue injury secondary to trauma, surgical procedures, or conditions such as rheumatoid arthritis or Ehlers-Danlos syndrome. Unlike most previously reported cases, our patient reported no preceding tissue injury associated with formation of the lesion, and she was largely asymptomatic on presentation. Considering the limited number of CMSC cases demonstrated in the literature, it is important to continue reporting new cases to better understand characteristics and presentations of this uncommon lesion. 

The Diagnosis: Epidermodysplasia Verruciformis 

Histopathologic examination of our patient's biopsy specimen revealed mild acanthosis with prominent hypergranulosis and enlarged keratinocytes with blue-gray cytoplasm (Figure). A diagnosis of acquired epidermodysplasia verruciformis (EV) was rendered. The patient was treated with photodynamic therapy utilizing 5-aminolevulinic acid. 

Epidermodysplasia verruciformis is characterized by susceptibility to human papillomavirus (HPV) infections via a defect in cellular immunity. Epidermodysplasia verruciformis was first described as an autosomal-recessive genodermatosis, but it can be acquired in immunosuppressed states with an atypical clinical appearance.¹ There are few case reports in skin of color. Acquired EV appears in patients with acquired immunodeficiencies that are susceptible to EV-causing HPVs via a similar mechanism found in inherited EV.² The most common HPV serotypes involved in EV are HPV-5 and HPV-8. The duration of immunosuppression has been found to be positively correlated with the risk for EV development, with the majority of patients developing lesions after 5 years of immunosuppression.³ There is an approximately 60% risk of malignant transformation of EV lesions into nonmelanoma skin cancer.² This risk is believed to be lower in patients with darker skin.⁴  

Preventative measures including sun protection and annual surveillance are crucial in EV patients given the high rate of malignant transformation in sun-exposed lesions.⁵ Treatment options for EV are anecdotal and have variable results, ranging from topicals including 5-fluorouracil and imiquimod to systemic medications including acitretin and interferon.³ Photodynamic therapy can be used for extensive EV. Surgical modalities and other destructive methods also have been tried.⁶ 

Epidermodysplasia verruciformis often can be confused with similar dermatoses. Porokeratosis appears as annular pink papules with waferlike peripheral scales. Tinea versicolor is a dermatophyte infection caused by Malassezia furfur and presents as multiple dyspigmented, finely scaling, thin papules and plaques. Subacute cutaneous lupus erythematosus presents as pink, scaly, annular or psoriasiform papules and plaques most commonly on the trunk. Discoid lupus erythematosus presents as pink, hypopigmented or depigmented, atrophic plaques with a peripheral rim of erythema that indicates activity. Secondary syphilis, commonly denoted as the "great mimicker," presents as psoriasiform papules and plaques among other variable morphologies. 

The Diagnosis: Epidermodysplasia Verruciformis 

Histopathologic examination of our patient's biopsy specimen revealed mild acanthosis with prominent hypergranulosis and enlarged keratinocytes with blue-gray cytoplasm (Figure). A diagnosis of acquired epidermodysplasia verruciformis (EV) was rendered. The patient was treated with photodynamic therapy utilizing 5-aminolevulinic acid. 

Epidermodysplasia verruciformis is characterized by susceptibility to human papillomavirus (HPV) infections via a defect in cellular immunity. Epidermodysplasia verruciformis was first described as an autosomal-recessive genodermatosis, but it can be acquired in immunosuppressed states with an atypical clinical appearance.¹ There are few case reports in skin of color. Acquired EV appears in patients with acquired immunodeficiencies that are susceptible to EV-causing HPVs via a similar mechanism found in inherited EV.² The most common HPV serotypes involved in EV are HPV-5 and HPV-8. The duration of immunosuppression has been found to be positively correlated with the risk for EV development, with the majority of patients developing lesions after 5 years of immunosuppression.³ There is an approximately 60% risk of malignant transformation of EV lesions into nonmelanoma skin cancer.² This risk is believed to be lower in patients with darker skin.⁴  

Preventative measures including sun protection and annual surveillance are crucial in EV patients given the high rate of malignant transformation in sun-exposed lesions.⁵ Treatment options for EV are anecdotal and have variable results, ranging from topicals including 5-fluorouracil and imiquimod to systemic medications including acitretin and interferon.³ Photodynamic therapy can be used for extensive EV. Surgical modalities and other destructive methods also have been tried.⁶ 

Epidermodysplasia verruciformis often can be confused with similar dermatoses. Porokeratosis appears as annular pink papules with waferlike peripheral scales. Tinea versicolor is a dermatophyte infection caused by Malassezia furfur and presents as multiple dyspigmented, finely scaling, thin papules and plaques. Subacute cutaneous lupus erythematosus presents as pink, scaly, annular or psoriasiform papules and plaques most commonly on the trunk. Discoid lupus erythematosus presents as pink, hypopigmented or depigmented, atrophic plaques with a peripheral rim of erythema that indicates activity. Secondary syphilis, commonly denoted as the "great mimicker," presents as psoriasiform papules and plaques among other variable morphologies. 

The Diagnosis: Epidermodysplasia Verruciformis 

Histopathologic examination of our patient's biopsy specimen revealed mild acanthosis with prominent hypergranulosis and enlarged keratinocytes with blue-gray cytoplasm (Figure). A diagnosis of acquired epidermodysplasia verruciformis (EV) was rendered. The patient was treated with photodynamic therapy utilizing 5-aminolevulinic acid. 

Epidermodysplasia verruciformis is characterized by susceptibility to human papillomavirus (HPV) infections via a defect in cellular immunity. Epidermodysplasia verruciformis was first described as an autosomal-recessive genodermatosis, but it can be acquired in immunosuppressed states with an atypical clinical appearance.¹ There are few case reports in skin of color. Acquired EV appears in patients with acquired immunodeficiencies that are susceptible to EV-causing HPVs via a similar mechanism found in inherited EV.² The most common HPV serotypes involved in EV are HPV-5 and HPV-8. The duration of immunosuppression has been found to be positively correlated with the risk for EV development, with the majority of patients developing lesions after 5 years of immunosuppression.³ There is an approximately 60% risk of malignant transformation of EV lesions into nonmelanoma skin cancer.² This risk is believed to be lower in patients with darker skin.⁴  

Preventative measures including sun protection and annual surveillance are crucial in EV patients given the high rate of malignant transformation in sun-exposed lesions.⁵ Treatment options for EV are anecdotal and have variable results, ranging from topicals including 5-fluorouracil and imiquimod to systemic medications including acitretin and interferon.³ Photodynamic therapy can be used for extensive EV. Surgical modalities and other destructive methods also have been tried.⁶ 

Epidermodysplasia verruciformis often can be confused with similar dermatoses. Porokeratosis appears as annular pink papules with waferlike peripheral scales. Tinea versicolor is a dermatophyte infection caused by Malassezia furfur and presents as multiple dyspigmented, finely scaling, thin papules and plaques. Subacute cutaneous lupus erythematosus presents as pink, scaly, annular or psoriasiform papules and plaques most commonly on the trunk. Discoid lupus erythematosus presents as pink, hypopigmented or depigmented, atrophic plaques with a peripheral rim of erythema that indicates activity. Secondary syphilis, commonly denoted as the "great mimicker," presents as psoriasiform papules and plaques among other variable morphologies. 

The Diagnosis: Disseminated Erythema Chronicum Migrans 

Empiric treatment with doxycycline 100 mg twice daily for 14 days was initiated for suspected early disseminated Lyme disease manifesting as disseminated multifocal erythema chronicum migrans (Figure). Lyme screening immunoassay and confirmatory IgM Western blot testing subsequently were found to be positive. The clinical history of recent travel to an endemic area and tick bite combined with the recent onset of multifocal erythema migrans lesions, systemic symptoms, elevated erythrocyte sedimentation rate, and positive Lyme serology supported the diagnosis of Lyme disease.

The appropriate clinical context and cutaneous morphology are key when considering the differential diagnosis for multifocal annular lesions. Several entities comprised the differential diagnosis considered in our patient. Sweet syndrome is a neutrophilic dermatosis that can present with fever and varying painful cutaneous lesions. It often is associated with certain medications, underlying illnesses, and infections.¹ Our patient’s lesions were not painful, and she had no notable medical history, recent infections, or new medication use, making Sweet syndrome unlikely. A fixed drug eruption was low on the differential, as the patient denied starting any new medications within the 3 months prior to presentation. Erythema multiforme is an acute-onset immunemediated condition of the skin and mucous membranes that typically affects young adults and often is associated with infection (eg, herpes simplex virus, Mycoplasma pneumoniae) or medication use. Cutaneous lesions typically are self-limited, less than 3 cm targets with 3 concentric distinct color zones, often with central bullae or erosions. Although erythema multiforme was higher on the differential, it was less likely, as the patient lacked mucosal lesions and did not have symptoms of underlying herpetic or mycoplasma infection, and the clinical picture was more consistent with Lyme disease. Lastly, the failure for individual skin lesions to resolve within 
 24 hours excluded the diagnosis of urticaria.

Lyme disease is a tick-borne illness caused by 3 species of the Borrelia spirochete: Borrelia burgdorferi, Borrelia afzelii, and Borrelia garinii.² In the United States, the disease predominantly is caused by B burgdorferi that is endemic in the upper Midwest and Northeast regions.3 There are 3 stages of Lyme disease: early localized, early disseminated, and late disseminated disease. Early localized disease typically presents with a characteristic single erythema migrans (EM) lesion 3 to 30 days following a bite by the tick Ixodes scapularis.² The EM lesion gradually can enlarge over a period of several days, reaching up to 12 inches in diameter.² Early disseminated disease can occur weeks to months following a tick bite and may present with systemic symptoms, multiple widespread 
EM lesions, neurologic features such as meningitis or facial nerve palsy, and/or cardiac manifestations such as atrioventricular block or myocarditis. Late disseminated disease can present with chronic arthritis or encephalopathy after months to years if the disease is left untreated.⁴

Early localized Lyme disease can be diagnosed clinically if the characteristic EM lesion is present in a patient who visited an endemic area. Laboratory testing and Lyme serology are neither required nor recommended in these cases, as the lesion often appears before adequate time has lapsed to develop an adaptive immune response to the organism.5 In contrast, Lyme serology should be ordered in any patient who meets all of the following criteria: (1) patient lives in or has recently traveled to an area endemic for Lyme disease, (2) presence of a risk factor for tick exposure, and (3) symptoms consistent with early disseminated or late Lyme disease. Patients with signs of early or late disseminated disease typically are seropositive, as IgM antibodies can be detected within 2 weeks of onset of the EM lesion and IgG antibodies within 2 to 6 weeks.⁶ The Centers for Disease Control and Prevention recommends a 2-tiered approach when testing for Lyme disease.⁷ A screening test with high sensitivity such as an enzyme-linked immunosorbent assay or an immunofluorescence assay initially should be performed.⁷ If results of the screening test are equivocal or positive, secondary confirmatory testing should be performed via IgM, with or without IgG Western immunoblot assay.⁷ Biopsy with histologic evaluation can reveal nonspecific findings of vascular endothelial injury and increased mucin deposition. Patients with suspected Lyme disease should immediately be started on empiric treatment with doxycycline 100 mg twice daily for a minimum of 10 days (14–28 days if there is concern for dissemination) to prevent post-Lyme sequelae.⁵ Our patient’s cutaneous lesions responded to oral doxycycline. 

The Diagnosis: Disseminated Erythema Chronicum Migrans 

Empiric treatment with doxycycline 100 mg twice daily for 14 days was initiated for suspected early disseminated Lyme disease manifesting as disseminated multifocal erythema chronicum migrans (Figure). Lyme screening immunoassay and confirmatory IgM Western blot testing subsequently were found to be positive. The clinical history of recent travel to an endemic area and tick bite combined with the recent onset of multifocal erythema migrans lesions, systemic symptoms, elevated erythrocyte sedimentation rate, and positive Lyme serology supported the diagnosis of Lyme disease.

The appropriate clinical context and cutaneous morphology are key when considering the differential diagnosis for multifocal annular lesions. Several entities comprised the differential diagnosis considered in our patient. Sweet syndrome is a neutrophilic dermatosis that can present with fever and varying painful cutaneous lesions. It often is associated with certain medications, underlying illnesses, and infections.¹ Our patient’s lesions were not painful, and she had no notable medical history, recent infections, or new medication use, making Sweet syndrome unlikely. A fixed drug eruption was low on the differential, as the patient denied starting any new medications within the 3 months prior to presentation. Erythema multiforme is an acute-onset immunemediated condition of the skin and mucous membranes that typically affects young adults and often is associated with infection (eg, herpes simplex virus, Mycoplasma pneumoniae) or medication use. Cutaneous lesions typically are self-limited, less than 3 cm targets with 3 concentric distinct color zones, often with central bullae or erosions. Although erythema multiforme was higher on the differential, it was less likely, as the patient lacked mucosal lesions and did not have symptoms of underlying herpetic or mycoplasma infection, and the clinical picture was more consistent with Lyme disease. Lastly, the failure for individual skin lesions to resolve within 
 24 hours excluded the diagnosis of urticaria.

Lyme disease is a tick-borne illness caused by 3 species of the Borrelia spirochete: Borrelia burgdorferi, Borrelia afzelii, and Borrelia garinii.² In the United States, the disease predominantly is caused by B burgdorferi that is endemic in the upper Midwest and Northeast regions.3 There are 3 stages of Lyme disease: early localized, early disseminated, and late disseminated disease. Early localized disease typically presents with a characteristic single erythema migrans (EM) lesion 3 to 30 days following a bite by the tick Ixodes scapularis.² The EM lesion gradually can enlarge over a period of several days, reaching up to 12 inches in diameter.² Early disseminated disease can occur weeks to months following a tick bite and may present with systemic symptoms, multiple widespread 
EM lesions, neurologic features such as meningitis or facial nerve palsy, and/or cardiac manifestations such as atrioventricular block or myocarditis. Late disseminated disease can present with chronic arthritis or encephalopathy after months to years if the disease is left untreated.⁴

Early localized Lyme disease can be diagnosed clinically if the characteristic EM lesion is present in a patient who visited an endemic area. Laboratory testing and Lyme serology are neither required nor recommended in these cases, as the lesion often appears before adequate time has lapsed to develop an adaptive immune response to the organism.5 In contrast, Lyme serology should be ordered in any patient who meets all of the following criteria: (1) patient lives in or has recently traveled to an area endemic for Lyme disease, (2) presence of a risk factor for tick exposure, and (3) symptoms consistent with early disseminated or late Lyme disease. Patients with signs of early or late disseminated disease typically are seropositive, as IgM antibodies can be detected within 2 weeks of onset of the EM lesion and IgG antibodies within 2 to 6 weeks.⁶ The Centers for Disease Control and Prevention recommends a 2-tiered approach when testing for Lyme disease.⁷ A screening test with high sensitivity such as an enzyme-linked immunosorbent assay or an immunofluorescence assay initially should be performed.⁷ If results of the screening test are equivocal or positive, secondary confirmatory testing should be performed via IgM, with or without IgG Western immunoblot assay.⁷ Biopsy with histologic evaluation can reveal nonspecific findings of vascular endothelial injury and increased mucin deposition. Patients with suspected Lyme disease should immediately be started on empiric treatment with doxycycline 100 mg twice daily for a minimum of 10 days (14–28 days if there is concern for dissemination) to prevent post-Lyme sequelae.⁵ Our patient’s cutaneous lesions responded to oral doxycycline. 

The Diagnosis: Disseminated Erythema Chronicum Migrans 

Empiric treatment with doxycycline 100 mg twice daily for 14 days was initiated for suspected early disseminated Lyme disease manifesting as disseminated multifocal erythema chronicum migrans (Figure). Lyme screening immunoassay and confirmatory IgM Western blot testing subsequently were found to be positive. The clinical history of recent travel to an endemic area and tick bite combined with the recent onset of multifocal erythema migrans lesions, systemic symptoms, elevated erythrocyte sedimentation rate, and positive Lyme serology supported the diagnosis of Lyme disease.

The appropriate clinical context and cutaneous morphology are key when considering the differential diagnosis for multifocal annular lesions. Several entities comprised the differential diagnosis considered in our patient. Sweet syndrome is a neutrophilic dermatosis that can present with fever and varying painful cutaneous lesions. It often is associated with certain medications, underlying illnesses, and infections.¹ Our patient’s lesions were not painful, and she had no notable medical history, recent infections, or new medication use, making Sweet syndrome unlikely. A fixed drug eruption was low on the differential, as the patient denied starting any new medications within the 3 months prior to presentation. Erythema multiforme is an acute-onset immunemediated condition of the skin and mucous membranes that typically affects young adults and often is associated with infection (eg, herpes simplex virus, Mycoplasma pneumoniae) or medication use. Cutaneous lesions typically are self-limited, less than 3 cm targets with 3 concentric distinct color zones, often with central bullae or erosions. Although erythema multiforme was higher on the differential, it was less likely, as the patient lacked mucosal lesions and did not have symptoms of underlying herpetic or mycoplasma infection, and the clinical picture was more consistent with Lyme disease. Lastly, the failure for individual skin lesions to resolve within 
 24 hours excluded the diagnosis of urticaria.

Lyme disease is a tick-borne illness caused by 3 species of the Borrelia spirochete: Borrelia burgdorferi, Borrelia afzelii, and Borrelia garinii.² In the United States, the disease predominantly is caused by B burgdorferi that is endemic in the upper Midwest and Northeast regions.3 There are 3 stages of Lyme disease: early localized, early disseminated, and late disseminated disease. Early localized disease typically presents with a characteristic single erythema migrans (EM) lesion 3 to 30 days following a bite by the tick Ixodes scapularis.² The EM lesion gradually can enlarge over a period of several days, reaching up to 12 inches in diameter.² Early disseminated disease can occur weeks to months following a tick bite and may present with systemic symptoms, multiple widespread 
EM lesions, neurologic features such as meningitis or facial nerve palsy, and/or cardiac manifestations such as atrioventricular block or myocarditis. Late disseminated disease can present with chronic arthritis or encephalopathy after months to years if the disease is left untreated.⁴

Early localized Lyme disease can be diagnosed clinically if the characteristic EM lesion is present in a patient who visited an endemic area. Laboratory testing and Lyme serology are neither required nor recommended in these cases, as the lesion often appears before adequate time has lapsed to develop an adaptive immune response to the organism.5 In contrast, Lyme serology should be ordered in any patient who meets all of the following criteria: (1) patient lives in or has recently traveled to an area endemic for Lyme disease, (2) presence of a risk factor for tick exposure, and (3) symptoms consistent with early disseminated or late Lyme disease. Patients with signs of early or late disseminated disease typically are seropositive, as IgM antibodies can be detected within 2 weeks of onset of the EM lesion and IgG antibodies within 2 to 6 weeks.⁶ The Centers for Disease Control and Prevention recommends a 2-tiered approach when testing for Lyme disease.⁷ A screening test with high sensitivity such as an enzyme-linked immunosorbent assay or an immunofluorescence assay initially should be performed.⁷ If results of the screening test are equivocal or positive, secondary confirmatory testing should be performed via IgM, with or without IgG Western immunoblot assay.⁷ Biopsy with histologic evaluation can reveal nonspecific findings of vascular endothelial injury and increased mucin deposition. Patients with suspected Lyme disease should immediately be started on empiric treatment with doxycycline 100 mg twice daily for a minimum of 10 days (14–28 days if there is concern for dissemination) to prevent post-Lyme sequelae.⁵ Our patient’s cutaneous lesions responded to oral doxycycline. 

The Diagnosis: Phytophotodermatitis 

A  more detailed patient history revealed that there was beer with limes on the boat, but the partygoers neglected to bring a knife. The patient volunteered to tear the limes apart with his bare hands. Because he was clad only in swim trunks, lime juice splattered over various regions of his body. 

Phytophotodermatitis is a phototoxic blistering rash that follows topical exposure to plant-derived furocoumarins and sunlight. (Figure) Furocoumarins are photosensitizing substances produced by certain plants, possibly as a defense mechanism against predators.¹ They cause a nonimmunologic phototoxic reaction when deposited on the skin and exposed to UVA radiation. Exposure to limes is the most common precipitant of phytophotodermatitis, but other potential culprits include lemons, grapefruit, figs, carrots, parsnips, celery, and dill.²  

Lesions associated with phytophotodermatitis classically present as painful erythematous patches and bullae in regions of furocoumarin exposure. Affected areas are well demarcated and irregularly shaped and heal with a characteristic hyperpigmented rim. They often have a downward streak pattern from the dripping juice.³ If the furocoumarins are transferred by touch, lesions can appear in the shape of handprints, which may raise alarms for physical abuse in children.⁴ 

Photochemical reactions caused by activated furocoumarins cross-link nuclear DNA and damage cell membranes. These changes lead to cellular death resulting in edema and destruction of the epidermis. Other effects include an increase in keratin and thickening of the stratum corneum. The hyperpigmentation is a result of increased concentration of melanosomes and stimulation of melanocytes by activated furocoumarins.⁵ 

Management of phytophotodermatitis depends on the severity of skin injury. Mild cases may not require any treatment, whereas the most severe ones require admission to a burn unit for wound care. Anti-inflammatory medications are the mainstay of therapy. Our patient was prescribed desonide cream 0.05% for application to the affected areas. Sunscreen should be applied to prevent worsening of hyperpigmentation, which may take months to years to fade naturally. If hyperpigmentation is cosmetically troubling to the patient, bleaching agents such as hydroquinone and retinoids or Nd:YAG laser can be used to accelerate the resolution of pigment.⁵ 

Phototoxicity differs from less common photoallergic reactions caused by preformed antibodies or a delayed cell-mediated response to a trigger. The classic presentation of photoallergy is apruritic, inflammatory, bullous eruption in a sensitized individual.⁶ Allergic contact dermatitis more commonly is associated with pruritus than pain, and it presents as a papulovesicular eruption that evolves into lichenified plaques.⁷ Porphyria cutanea tarda would likely be accompanied by other cutaneous features such as hypertrichosis and sclerodermoid plaques with dystrophic calcification, in addition to wine-colored urine-containing porphyrins.⁸ Bullous fixed drug eruptions develop within 48 hours of exposure to a causative agent. The patient typically would experience pruritus and burning at the site of clearly demarcated erythematous lesions that healed with hyperpigmentation.⁹ Lesions of bullous lupus erythematosus may appear in areas without sun exposure, and they would be more likely to leave behind hypopigmentation rather than hyperpigmentation.¹⁰ 

The Diagnosis: Phytophotodermatitis 

A  more detailed patient history revealed that there was beer with limes on the boat, but the partygoers neglected to bring a knife. The patient volunteered to tear the limes apart with his bare hands. Because he was clad only in swim trunks, lime juice splattered over various regions of his body. 

Phytophotodermatitis is a phototoxic blistering rash that follows topical exposure to plant-derived furocoumarins and sunlight. (Figure) Furocoumarins are photosensitizing substances produced by certain plants, possibly as a defense mechanism against predators.¹ They cause a nonimmunologic phototoxic reaction when deposited on the skin and exposed to UVA radiation. Exposure to limes is the most common precipitant of phytophotodermatitis, but other potential culprits include lemons, grapefruit, figs, carrots, parsnips, celery, and dill.²  

Lesions associated with phytophotodermatitis classically present as painful erythematous patches and bullae in regions of furocoumarin exposure. Affected areas are well demarcated and irregularly shaped and heal with a characteristic hyperpigmented rim. They often have a downward streak pattern from the dripping juice.³ If the furocoumarins are transferred by touch, lesions can appear in the shape of handprints, which may raise alarms for physical abuse in children.⁴ 

Photochemical reactions caused by activated furocoumarins cross-link nuclear DNA and damage cell membranes. These changes lead to cellular death resulting in edema and destruction of the epidermis. Other effects include an increase in keratin and thickening of the stratum corneum. The hyperpigmentation is a result of increased concentration of melanosomes and stimulation of melanocytes by activated furocoumarins.⁵ 

Management of phytophotodermatitis depends on the severity of skin injury. Mild cases may not require any treatment, whereas the most severe ones require admission to a burn unit for wound care. Anti-inflammatory medications are the mainstay of therapy. Our patient was prescribed desonide cream 0.05% for application to the affected areas. Sunscreen should be applied to prevent worsening of hyperpigmentation, which may take months to years to fade naturally. If hyperpigmentation is cosmetically troubling to the patient, bleaching agents such as hydroquinone and retinoids or Nd:YAG laser can be used to accelerate the resolution of pigment.⁵ 

Phototoxicity differs from less common photoallergic reactions caused by preformed antibodies or a delayed cell-mediated response to a trigger. The classic presentation of photoallergy is apruritic, inflammatory, bullous eruption in a sensitized individual.⁶ Allergic contact dermatitis more commonly is associated with pruritus than pain, and it presents as a papulovesicular eruption that evolves into lichenified plaques.⁷ Porphyria cutanea tarda would likely be accompanied by other cutaneous features such as hypertrichosis and sclerodermoid plaques with dystrophic calcification, in addition to wine-colored urine-containing porphyrins.⁸ Bullous fixed drug eruptions develop within 48 hours of exposure to a causative agent. The patient typically would experience pruritus and burning at the site of clearly demarcated erythematous lesions that healed with hyperpigmentation.⁹ Lesions of bullous lupus erythematosus may appear in areas without sun exposure, and they would be more likely to leave behind hypopigmentation rather than hyperpigmentation.¹⁰ 

The Diagnosis: Phytophotodermatitis 

A  more detailed patient history revealed that there was beer with limes on the boat, but the partygoers neglected to bring a knife. The patient volunteered to tear the limes apart with his bare hands. Because he was clad only in swim trunks, lime juice splattered over various regions of his body. 

Phytophotodermatitis is a phototoxic blistering rash that follows topical exposure to plant-derived furocoumarins and sunlight. (Figure) Furocoumarins are photosensitizing substances produced by certain plants, possibly as a defense mechanism against predators.¹ They cause a nonimmunologic phototoxic reaction when deposited on the skin and exposed to UVA radiation. Exposure to limes is the most common precipitant of phytophotodermatitis, but other potential culprits include lemons, grapefruit, figs, carrots, parsnips, celery, and dill.²  

Lesions associated with phytophotodermatitis classically present as painful erythematous patches and bullae in regions of furocoumarin exposure. Affected areas are well demarcated and irregularly shaped and heal with a characteristic hyperpigmented rim. They often have a downward streak pattern from the dripping juice.³ If the furocoumarins are transferred by touch, lesions can appear in the shape of handprints, which may raise alarms for physical abuse in children.⁴ 

Photochemical reactions caused by activated furocoumarins cross-link nuclear DNA and damage cell membranes. These changes lead to cellular death resulting in edema and destruction of the epidermis. Other effects include an increase in keratin and thickening of the stratum corneum. The hyperpigmentation is a result of increased concentration of melanosomes and stimulation of melanocytes by activated furocoumarins.⁵ 

Management of phytophotodermatitis depends on the severity of skin injury. Mild cases may not require any treatment, whereas the most severe ones require admission to a burn unit for wound care. Anti-inflammatory medications are the mainstay of therapy. Our patient was prescribed desonide cream 0.05% for application to the affected areas. Sunscreen should be applied to prevent worsening of hyperpigmentation, which may take months to years to fade naturally. If hyperpigmentation is cosmetically troubling to the patient, bleaching agents such as hydroquinone and retinoids or Nd:YAG laser can be used to accelerate the resolution of pigment.⁵ 

Phototoxicity differs from less common photoallergic reactions caused by preformed antibodies or a delayed cell-mediated response to a trigger. The classic presentation of photoallergy is apruritic, inflammatory, bullous eruption in a sensitized individual.⁶ Allergic contact dermatitis more commonly is associated with pruritus than pain, and it presents as a papulovesicular eruption that evolves into lichenified plaques.⁷ Porphyria cutanea tarda would likely be accompanied by other cutaneous features such as hypertrichosis and sclerodermoid plaques with dystrophic calcification, in addition to wine-colored urine-containing porphyrins.⁸ Bullous fixed drug eruptions develop within 48 hours of exposure to a causative agent. The patient typically would experience pruritus and burning at the site of clearly demarcated erythematous lesions that healed with hyperpigmentation.⁹ Lesions of bullous lupus erythematosus may appear in areas without sun exposure, and they would be more likely to leave behind hypopigmentation rather than hyperpigmentation.¹⁰ 

The Diagnosis: Bazex‐Dupré‐Christol Syndrome

Bazex‐Dupré‐Christol syndrome (BDCS) is a rare X-linked dominant genodermatosis characterized by a triad of hypotrichosis, follicular atrophoderma, and multiple basal cell carcinomas (BCCs). Since first being described in 1964,¹ there have been fewer than 200 reported cases of BDCS.² Although a causative gene has not yet been identified, the mutation has been mapped to an 11.4-Mb interval in the Xq25-27.1 region of the X chromosome.³

Classically, congenital hypotrichosis is the first observed symptom and can present shortly after birth.⁴ It typically is widespread, though sometimes it may be confined to the eyebrows, eyelashes, and scalp. Follicular atrophoderma, which occurs due to a laxation and deepening of the follicular ostia, is seen in 80% of cases and typically presents in early childhood as depressions lacking hair.² It commonly is found on the face, extensor surfaces of the elbows and knees, and dorsal aspects of the hands and feet. Physical examination of our patient revealed follicular atrophoderma on both the dorsal surfaces of the hands and the extensor surfaces of the elbows. Hair shaft anomalies including pili torti, pili bifurcati, and trichorrhexis nodosa are infrequently observed symptoms of BDCS.²

Basal cell carcinoma often manifests in the second or third decades of life, though there are reports of BCC developing in BDCS patients as young as 3 years. Basal cell carcinoma typically arises on sun-exposed areas, especially the face, neck, and chest. These lesions can be pigmented or nonpigmented and range from 2 to 20 mm in diameter.⁴ Our patient presented with a BCC on the forehead (Figure 1). Histopathologic evaluation showed a proliferation of basaloid cells with peripheral palisading (Figure 2), confirming the diagnosis of BCC.

Milia, which are not considered part of the classic BDCS triad, are seen in 70% of cases.² They commonly are found on the face and often diminish with age. Milia may precede the formation of follicular atrophoderma and BCC. Hypohidrosis most commonly occurs on the forehead but can be widespread.² Other less commonly observed features include epidermal cysts, hyperpigmentation of the face, and trichoepitheliomas.⁴ The management of BDCS involves frequent clinical examinations, BCC treatment, genetic counseling, and photoprotection.^2,4

Nevoid BCC syndrome (NBCCS), also known as Gorlin-Goltz syndrome, is an autosomal-dominant disease characterized by multiple nevoid BCCs, macrocephaly with a large forehead, cleft lip or palate, jaw keratocysts, palmar and plantar pits, and calcification of the falx cerebri.⁵ Nevoid BCC syndrome is caused by a mutation in the PTCH1 gene in the hedgehog signaling pathway.⁶ The absence of common symptoms of NBCCS including macrocephaly, palmar or plantar pits, and cleft lip or palate, as well as negative genetic testing, suggested that our patient did not have NBCCS.

Rombo syndrome shares features with BDCS. Similar to BDCS, symptoms of Rombo syndrome include follicular atrophy, milialike papules, and BCC. Patients with Rombo syndrome typically present with atrophoderma vermiculatum on the cheeks and forehead in childhood.⁷ This atrophoderma presents with a pitted atrophic appearance in a reticular pattern on sun-exposed areas. Other distinguishing features from BDCS include cyanotic redness of sun-exposed skin and telangiectatic vessels.⁸

Multiple hereditary infundibulocystic BCC is another rare genodermatosis that is characterized by the presence of multiple infundibulocystic BCCs on the face and genitals. Infundibulocystic BCC is a well-differentiated subtype of BCC characterized by buds and cords of basaloid cells with scant stroma. Multiple hereditary infundibulocystic BCC is inherited in an autosomal-dominant fashion and has been linked to ^SUFU mutation in the sonic hedgehog pathway.⁹

Rothmund-Thomson syndrome is an autosomalrecessive disorder characterized by sparse hair, skeletal and dental abnormalities, and a high risk for developing keratinocyte carcinomas. It is differentiated from BDCS clinically by the presence of erythema, edema, and blistering, resulting in poikiloderma, plantar hyperkeratotic lesions, and bone defects.¹⁰

The Diagnosis: Bazex‐Dupré‐Christol Syndrome

Bazex‐Dupré‐Christol syndrome (BDCS) is a rare X-linked dominant genodermatosis characterized by a triad of hypotrichosis, follicular atrophoderma, and multiple basal cell carcinomas (BCCs). Since first being described in 1964,¹ there have been fewer than 200 reported cases of BDCS.² Although a causative gene has not yet been identified, the mutation has been mapped to an 11.4-Mb interval in the Xq25-27.1 region of the X chromosome.³

Classically, congenital hypotrichosis is the first observed symptom and can present shortly after birth.⁴ It typically is widespread, though sometimes it may be confined to the eyebrows, eyelashes, and scalp. Follicular atrophoderma, which occurs due to a laxation and deepening of the follicular ostia, is seen in 80% of cases and typically presents in early childhood as depressions lacking hair.² It commonly is found on the face, extensor surfaces of the elbows and knees, and dorsal aspects of the hands and feet. Physical examination of our patient revealed follicular atrophoderma on both the dorsal surfaces of the hands and the extensor surfaces of the elbows. Hair shaft anomalies including pili torti, pili bifurcati, and trichorrhexis nodosa are infrequently observed symptoms of BDCS.²

Basal cell carcinoma often manifests in the second or third decades of life, though there are reports of BCC developing in BDCS patients as young as 3 years. Basal cell carcinoma typically arises on sun-exposed areas, especially the face, neck, and chest. These lesions can be pigmented or nonpigmented and range from 2 to 20 mm in diameter.⁴ Our patient presented with a BCC on the forehead (Figure 1). Histopathologic evaluation showed a proliferation of basaloid cells with peripheral palisading (Figure 2), confirming the diagnosis of BCC.

Milia, which are not considered part of the classic BDCS triad, are seen in 70% of cases.² They commonly are found on the face and often diminish with age. Milia may precede the formation of follicular atrophoderma and BCC. Hypohidrosis most commonly occurs on the forehead but can be widespread.² Other less commonly observed features include epidermal cysts, hyperpigmentation of the face, and trichoepitheliomas.⁴ The management of BDCS involves frequent clinical examinations, BCC treatment, genetic counseling, and photoprotection.^2,4

Nevoid BCC syndrome (NBCCS), also known as Gorlin-Goltz syndrome, is an autosomal-dominant disease characterized by multiple nevoid BCCs, macrocephaly with a large forehead, cleft lip or palate, jaw keratocysts, palmar and plantar pits, and calcification of the falx cerebri.⁵ Nevoid BCC syndrome is caused by a mutation in the PTCH1 gene in the hedgehog signaling pathway.⁶ The absence of common symptoms of NBCCS including macrocephaly, palmar or plantar pits, and cleft lip or palate, as well as negative genetic testing, suggested that our patient did not have NBCCS.

Rombo syndrome shares features with BDCS. Similar to BDCS, symptoms of Rombo syndrome include follicular atrophy, milialike papules, and BCC. Patients with Rombo syndrome typically present with atrophoderma vermiculatum on the cheeks and forehead in childhood.⁷ This atrophoderma presents with a pitted atrophic appearance in a reticular pattern on sun-exposed areas. Other distinguishing features from BDCS include cyanotic redness of sun-exposed skin and telangiectatic vessels.⁸

Multiple hereditary infundibulocystic BCC is another rare genodermatosis that is characterized by the presence of multiple infundibulocystic BCCs on the face and genitals. Infundibulocystic BCC is a well-differentiated subtype of BCC characterized by buds and cords of basaloid cells with scant stroma. Multiple hereditary infundibulocystic BCC is inherited in an autosomal-dominant fashion and has been linked to ^SUFU mutation in the sonic hedgehog pathway.⁹

Rothmund-Thomson syndrome is an autosomalrecessive disorder characterized by sparse hair, skeletal and dental abnormalities, and a high risk for developing keratinocyte carcinomas. It is differentiated from BDCS clinically by the presence of erythema, edema, and blistering, resulting in poikiloderma, plantar hyperkeratotic lesions, and bone defects.¹⁰

The Diagnosis: Bazex‐Dupré‐Christol Syndrome

Bazex‐Dupré‐Christol syndrome (BDCS) is a rare X-linked dominant genodermatosis characterized by a triad of hypotrichosis, follicular atrophoderma, and multiple basal cell carcinomas (BCCs). Since first being described in 1964,¹ there have been fewer than 200 reported cases of BDCS.² Although a causative gene has not yet been identified, the mutation has been mapped to an 11.4-Mb interval in the Xq25-27.1 region of the X chromosome.³

Classically, congenital hypotrichosis is the first observed symptom and can present shortly after birth.⁴ It typically is widespread, though sometimes it may be confined to the eyebrows, eyelashes, and scalp. Follicular atrophoderma, which occurs due to a laxation and deepening of the follicular ostia, is seen in 80% of cases and typically presents in early childhood as depressions lacking hair.² It commonly is found on the face, extensor surfaces of the elbows and knees, and dorsal aspects of the hands and feet. Physical examination of our patient revealed follicular atrophoderma on both the dorsal surfaces of the hands and the extensor surfaces of the elbows. Hair shaft anomalies including pili torti, pili bifurcati, and trichorrhexis nodosa are infrequently observed symptoms of BDCS.²

Basal cell carcinoma often manifests in the second or third decades of life, though there are reports of BCC developing in BDCS patients as young as 3 years. Basal cell carcinoma typically arises on sun-exposed areas, especially the face, neck, and chest. These lesions can be pigmented or nonpigmented and range from 2 to 20 mm in diameter.⁴ Our patient presented with a BCC on the forehead (Figure 1). Histopathologic evaluation showed a proliferation of basaloid cells with peripheral palisading (Figure 2), confirming the diagnosis of BCC.

Milia, which are not considered part of the classic BDCS triad, are seen in 70% of cases.² They commonly are found on the face and often diminish with age. Milia may precede the formation of follicular atrophoderma and BCC. Hypohidrosis most commonly occurs on the forehead but can be widespread.² Other less commonly observed features include epidermal cysts, hyperpigmentation of the face, and trichoepitheliomas.⁴ The management of BDCS involves frequent clinical examinations, BCC treatment, genetic counseling, and photoprotection.^2,4

Nevoid BCC syndrome (NBCCS), also known as Gorlin-Goltz syndrome, is an autosomal-dominant disease characterized by multiple nevoid BCCs, macrocephaly with a large forehead, cleft lip or palate, jaw keratocysts, palmar and plantar pits, and calcification of the falx cerebri.⁵ Nevoid BCC syndrome is caused by a mutation in the PTCH1 gene in the hedgehog signaling pathway.⁶ The absence of common symptoms of NBCCS including macrocephaly, palmar or plantar pits, and cleft lip or palate, as well as negative genetic testing, suggested that our patient did not have NBCCS.

Rombo syndrome shares features with BDCS. Similar to BDCS, symptoms of Rombo syndrome include follicular atrophy, milialike papules, and BCC. Patients with Rombo syndrome typically present with atrophoderma vermiculatum on the cheeks and forehead in childhood.⁷ This atrophoderma presents with a pitted atrophic appearance in a reticular pattern on sun-exposed areas. Other distinguishing features from BDCS include cyanotic redness of sun-exposed skin and telangiectatic vessels.⁸

Multiple hereditary infundibulocystic BCC is another rare genodermatosis that is characterized by the presence of multiple infundibulocystic BCCs on the face and genitals. Infundibulocystic BCC is a well-differentiated subtype of BCC characterized by buds and cords of basaloid cells with scant stroma. Multiple hereditary infundibulocystic BCC is inherited in an autosomal-dominant fashion and has been linked to ^SUFU mutation in the sonic hedgehog pathway.⁹

Rothmund-Thomson syndrome is an autosomalrecessive disorder characterized by sparse hair, skeletal and dental abnormalities, and a high risk for developing keratinocyte carcinomas. It is differentiated from BDCS clinically by the presence of erythema, edema, and blistering, resulting in poikiloderma, plantar hyperkeratotic lesions, and bone defects.¹⁰

The Diagnosis: Epidermolysis Bullosa Acquisita  

The diagnosis of epidermolysis bullosa acquisita (EBA) was made based on the clinical and pathologic findings. A blistering disorder that resolves with milia is characteristic of EBA. Hematoxylin and eosin staining demonstrated a pauci-inflammatory separation between the epidermis and dermis (Figure 1). Direct immunofluorescence studies showed linear IgG deposition along the basement membrane zone while C3 was negative (Figure 2). Salt-split skin was essential, as it revealed IgG deposition to the floor of the split (Figure 3), a pattern seen in EBA and not bullous pemphigoid (BP).¹ 

Epidermolysis bullosa acquisita is an acquired autoimmune bullous disorder that results from antibodies to type VII collagen, an anchoring fibril that attaches the lamina densa to the dermis. The epidemiology and etiology of the trigger that leads to antibody production are not well known, but an association between EBA and inflammatory bowel disease has been described.² Although this disease may present in childhood, EBA most commonly is a disorder seen in adults and the elderly. A classic noninflammatory mechanobullous form as well as an inflammatory BP-like form are the most commonly encountered presentations. Light microscopy demonstrates subepidermal cleavage without acantholysis. In the inflammatory BP-like subtype, an inflammatory infiltrate may be present. Direct immunofluorescence is remarkable for a linear band of IgG deposits along the basement membrane zone, with or without C3 deposition in a similar pattern.¹ 

Bullous pemphigoid is within the differential of EBA. It can be difficult to differentiate clinically, especially when a patient has the BP-like variant of EBA because, as the name implies, it mimics BP. Patients with BP often will report a pruritic patch that will then develop into an urticarial plaque. Scarring and milia rarely are seen in BP but can be observed in the multiple presentations of EBA. Hematoxylin and eosin staining and direct immunofluorescence may be almost identical, and differentiating between the 2 disorders can be a challenge. Immunodeposition in EBA occurs in a U-shaped, serrated pattern, while the pattern in BP is N-shaped and serrated.³ Although the U-shaped, serrated pattern is relatively specific, it is not always easy to interpret and requires a high-quality biopsy specimen, which can be difficult to discern with certainty in suboptimal preparations. Another way to differentiate between the 2 entities is to utilize the salt-split skin technique, as performed in our patient. With salt-split skin, the biopsy is placed into a solution of 1 mol/L sodium chloride and incubated at 4 °C (39 °F) for 18 to 24 hours. A blister is then produced at the level of the lamina lucida, which allows for the staining of immunoreactants to occur either above or below that split (commonly referred to as staining on the roof or floor of the blister cavity). With EBA, there is immunoreactant deposition on the floor of the blister, while the opposite occurs in BP.⁴ 

Epidermolysis bullosa simplex is the most common type of epidermolysis bullosa, with keratin genes KRT5 and KRT14 as frequent mutations. Patients develop blisters, vesicles, bullae, and milia on traumatized areas of the body such as the hands, elbows, knees, and feet. This disease presents early in childhood. Histology exhibits a cell-poor subepidermal blister.⁵ With porphyria cutanea tarda, reduced activity of uroporphyrinogen decarboxylase, a major enzyme in the heme synthesis pathway, leads to blisters with erosions and milia on sun-exposed areas of the body. Histologic evaluation reveals a subepidermal pauci-inflammatory vesicle with festooning of the dermal papillae and amphophilic basement membrane within the epidermis. Direct immunofluorescence of porphyria cutanea tarda demonstrates IgM and C3 in the vessels.⁶ Sweet syndrome is a neutrophilic dermatosis that presents as erythematous, edematous, hot, and tender plaques along with fever and leukocytosis. It is associated with myeloproliferative disorders. Biopsy demonstrates papillary dermal edema along with diffuse neutrophilic infiltrate.⁷ 

Numerous medications have been recommended for the treatment of EBA, ranging from steroids to steroid-sparing drugs such as colchicine and dapsone.^8,9 Our patient was educated on physical precautions and was started on dapsone alone due to comorbid diabetes mellitus and renal disease. Within a few weeks of initiating dapsone, he observed a reduction in erythema, and within months he experienced a decrease in blister eruption frequency.  

The Diagnosis: Epidermolysis Bullosa Acquisita  

The diagnosis of epidermolysis bullosa acquisita (EBA) was made based on the clinical and pathologic findings. A blistering disorder that resolves with milia is characteristic of EBA. Hematoxylin and eosin staining demonstrated a pauci-inflammatory separation between the epidermis and dermis (Figure 1). Direct immunofluorescence studies showed linear IgG deposition along the basement membrane zone while C3 was negative (Figure 2). Salt-split skin was essential, as it revealed IgG deposition to the floor of the split (Figure 3), a pattern seen in EBA and not bullous pemphigoid (BP).¹ 

Epidermolysis bullosa acquisita is an acquired autoimmune bullous disorder that results from antibodies to type VII collagen, an anchoring fibril that attaches the lamina densa to the dermis. The epidemiology and etiology of the trigger that leads to antibody production are not well known, but an association between EBA and inflammatory bowel disease has been described.² Although this disease may present in childhood, EBA most commonly is a disorder seen in adults and the elderly. A classic noninflammatory mechanobullous form as well as an inflammatory BP-like form are the most commonly encountered presentations. Light microscopy demonstrates subepidermal cleavage without acantholysis. In the inflammatory BP-like subtype, an inflammatory infiltrate may be present. Direct immunofluorescence is remarkable for a linear band of IgG deposits along the basement membrane zone, with or without C3 deposition in a similar pattern.¹ 

Bullous pemphigoid is within the differential of EBA. It can be difficult to differentiate clinically, especially when a patient has the BP-like variant of EBA because, as the name implies, it mimics BP. Patients with BP often will report a pruritic patch that will then develop into an urticarial plaque. Scarring and milia rarely are seen in BP but can be observed in the multiple presentations of EBA. Hematoxylin and eosin staining and direct immunofluorescence may be almost identical, and differentiating between the 2 disorders can be a challenge. Immunodeposition in EBA occurs in a U-shaped, serrated pattern, while the pattern in BP is N-shaped and serrated.³ Although the U-shaped, serrated pattern is relatively specific, it is not always easy to interpret and requires a high-quality biopsy specimen, which can be difficult to discern with certainty in suboptimal preparations. Another way to differentiate between the 2 entities is to utilize the salt-split skin technique, as performed in our patient. With salt-split skin, the biopsy is placed into a solution of 1 mol/L sodium chloride and incubated at 4 °C (39 °F) for 18 to 24 hours. A blister is then produced at the level of the lamina lucida, which allows for the staining of immunoreactants to occur either above or below that split (commonly referred to as staining on the roof or floor of the blister cavity). With EBA, there is immunoreactant deposition on the floor of the blister, while the opposite occurs in BP.⁴ 

Epidermolysis bullosa simplex is the most common type of epidermolysis bullosa, with keratin genes KRT5 and KRT14 as frequent mutations. Patients develop blisters, vesicles, bullae, and milia on traumatized areas of the body such as the hands, elbows, knees, and feet. This disease presents early in childhood. Histology exhibits a cell-poor subepidermal blister.⁵ With porphyria cutanea tarda, reduced activity of uroporphyrinogen decarboxylase, a major enzyme in the heme synthesis pathway, leads to blisters with erosions and milia on sun-exposed areas of the body. Histologic evaluation reveals a subepidermal pauci-inflammatory vesicle with festooning of the dermal papillae and amphophilic basement membrane within the epidermis. Direct immunofluorescence of porphyria cutanea tarda demonstrates IgM and C3 in the vessels.⁶ Sweet syndrome is a neutrophilic dermatosis that presents as erythematous, edematous, hot, and tender plaques along with fever and leukocytosis. It is associated with myeloproliferative disorders. Biopsy demonstrates papillary dermal edema along with diffuse neutrophilic infiltrate.⁷ 

Numerous medications have been recommended for the treatment of EBA, ranging from steroids to steroid-sparing drugs such as colchicine and dapsone.^8,9 Our patient was educated on physical precautions and was started on dapsone alone due to comorbid diabetes mellitus and renal disease. Within a few weeks of initiating dapsone, he observed a reduction in erythema, and within months he experienced a decrease in blister eruption frequency.  

The Diagnosis: Epidermolysis Bullosa Acquisita  

The diagnosis of epidermolysis bullosa acquisita (EBA) was made based on the clinical and pathologic findings. A blistering disorder that resolves with milia is characteristic of EBA. Hematoxylin and eosin staining demonstrated a pauci-inflammatory separation between the epidermis and dermis (Figure 1). Direct immunofluorescence studies showed linear IgG deposition along the basement membrane zone while C3 was negative (Figure 2). Salt-split skin was essential, as it revealed IgG deposition to the floor of the split (Figure 3), a pattern seen in EBA and not bullous pemphigoid (BP).¹ 

Epidermolysis bullosa acquisita is an acquired autoimmune bullous disorder that results from antibodies to type VII collagen, an anchoring fibril that attaches the lamina densa to the dermis. The epidemiology and etiology of the trigger that leads to antibody production are not well known, but an association between EBA and inflammatory bowel disease has been described.² Although this disease may present in childhood, EBA most commonly is a disorder seen in adults and the elderly. A classic noninflammatory mechanobullous form as well as an inflammatory BP-like form are the most commonly encountered presentations. Light microscopy demonstrates subepidermal cleavage without acantholysis. In the inflammatory BP-like subtype, an inflammatory infiltrate may be present. Direct immunofluorescence is remarkable for a linear band of IgG deposits along the basement membrane zone, with or without C3 deposition in a similar pattern.¹ 

Bullous pemphigoid is within the differential of EBA. It can be difficult to differentiate clinically, especially when a patient has the BP-like variant of EBA because, as the name implies, it mimics BP. Patients with BP often will report a pruritic patch that will then develop into an urticarial plaque. Scarring and milia rarely are seen in BP but can be observed in the multiple presentations of EBA. Hematoxylin and eosin staining and direct immunofluorescence may be almost identical, and differentiating between the 2 disorders can be a challenge. Immunodeposition in EBA occurs in a U-shaped, serrated pattern, while the pattern in BP is N-shaped and serrated.³ Although the U-shaped, serrated pattern is relatively specific, it is not always easy to interpret and requires a high-quality biopsy specimen, which can be difficult to discern with certainty in suboptimal preparations. Another way to differentiate between the 2 entities is to utilize the salt-split skin technique, as performed in our patient. With salt-split skin, the biopsy is placed into a solution of 1 mol/L sodium chloride and incubated at 4 °C (39 °F) for 18 to 24 hours. A blister is then produced at the level of the lamina lucida, which allows for the staining of immunoreactants to occur either above or below that split (commonly referred to as staining on the roof or floor of the blister cavity). With EBA, there is immunoreactant deposition on the floor of the blister, while the opposite occurs in BP.⁴ 

Epidermolysis bullosa simplex is the most common type of epidermolysis bullosa, with keratin genes KRT5 and KRT14 as frequent mutations. Patients develop blisters, vesicles, bullae, and milia on traumatized areas of the body such as the hands, elbows, knees, and feet. This disease presents early in childhood. Histology exhibits a cell-poor subepidermal blister.⁵ With porphyria cutanea tarda, reduced activity of uroporphyrinogen decarboxylase, a major enzyme in the heme synthesis pathway, leads to blisters with erosions and milia on sun-exposed areas of the body. Histologic evaluation reveals a subepidermal pauci-inflammatory vesicle with festooning of the dermal papillae and amphophilic basement membrane within the epidermis. Direct immunofluorescence of porphyria cutanea tarda demonstrates IgM and C3 in the vessels.⁶ Sweet syndrome is a neutrophilic dermatosis that presents as erythematous, edematous, hot, and tender plaques along with fever and leukocytosis. It is associated with myeloproliferative disorders. Biopsy demonstrates papillary dermal edema along with diffuse neutrophilic infiltrate.⁷ 

Numerous medications have been recommended for the treatment of EBA, ranging from steroids to steroid-sparing drugs such as colchicine and dapsone.^8,9 Our patient was educated on physical precautions and was started on dapsone alone due to comorbid diabetes mellitus and renal disease. Within a few weeks of initiating dapsone, he observed a reduction in erythema, and within months he experienced a decrease in blister eruption frequency.  

The Diagnosis: Anetoderma of Prematurity 

Anetoderma is a rare benign cutaneous disorder characterized by atrophic patches of skin due to dermal thinning. The term anetoderma is derived from the Greek words anetos (relaxed) and derma (skin).¹ The physical appearance of the skin is associated with a reduction or loss of elastic tissue in the dermal layer, as seen on histolopathology.²  

Two forms of anetoderma have been described. Primary anetoderma is an idiopathic form with no preceding inflammatory lesions. Secondary anetoderma is a reactive process linked to a known preceding inflammatory, infectious, autoimmune, or drug-induced condition.³ On histopathology, both primary and secondary anetoderma are characterized by a loss of elastic tissue or elastin fibers in the superficial to mid dermis.²  

Anetoderma of prematurity was first described in 1996 by Prizant et al⁴ in 9 extremely premature (24-29 weeks' gestation) infants in neonatal intensive care units (NICUs). Although the exact mechanism behind anetoderma of prematurity is still unknown, Prizant et al⁴ and other investigators⁵ postulated that application of adhesive monitoring leads in the NICU played a role in the development of the lesions. 

Iatrogenic anetoderma of prematurity is clinically characterized by circumscribed areas of either wrinkled macular depression or pouchlike herniations, ranging from flesh-colored to violaceous hues. Lesion size varies from a few millimeters to several centimeters in diameter, and they often are oval or round in shape.² Although not common, it is possible for the atrophic patches to be preceded by an area of ecchymosis without necrosis or atrophy and, if present, they usually evolve within a few days to the characteristic appearance of anetoderma.³ They are found at discrete sites where monitoring leads or other medical devices are commonly placed, such as the forehead, abdomen, chest, and proximal limbs. 

Lesions of anetoderma of prematurity are not present at birth, which distinguishes them from congenital anetoderma.⁶ It is unclear if the lesions are associated with the degree of prematurity, extremely low birth weight, or other associated factors of preterm birth. Although often clinically diagnosed, the diagnosis can be confirmed by a loss of elastic fibers on histopathology when stained with Verhoeff-van Gieson stain.¹ Over time, the atrophic patches have the potential to evolve into herniated forms of anetoderma. Self-healing or improvement of the lesions often does not occur. Although the lesion is benign, it often requires surgical correction later in life for cosmesis.  

Infants in the NICU are at risk for iatrogenic cutaneous injuries, which rarely may include anetoderma. Anetoderma of prematurity has been linked to the use of monitoring leads, adhesive tape, and other medical devices placed on the skin. Prizant et al⁴ postulated that the cause of anetoderma in these infants was irritants such as skin cleansers, urine, or sweat that may be trapped under the electrodes. Other hypotheses include local hypoxemia due to prolonged pressure from the electrodes on immature skin or excessive traction used when removing adhesive tape from the skin.^7,8 Premature infants may be more susceptible to these lesions because of the reduced epidermal thickness of premature skin; immaturity of skin structure; or functional immaturity of elastin deposition regulators, such as elastase, lysyl oxidase, the complement system, and decay-accelerating factor.³ The diagnosis should be differentiated from congenital anetoderma, which also has been described in premature neonates but is characterized by lesions that are present at birth. Its origins are still unclear, despite having histopathologic features similar to iatrogenic anetoderma.⁹  

Focal dermal hypoplasia (FDH) is the hallmark cutaneous finding in Goltz syndrome, a rare set of congenital abnormalities of the skin, oral structures, musculoskeletal system, and central nervous system. Similar to congenital anetoderma, FDH also is characterized by atrophic cutaneous lesions; however, the cutaneous lesions in FDH appear as linear, streaky atrophic lesions often with telangiectasias that follow Blaschko lines.¹⁰ The cutaneous lesions in FDH often are associated with other noncutaneous signs such as polydactyly or asymmetric limbs.¹⁰ Cutis laxa is caused by an abnormality in the elastic tissue resulting in a loose sagging appearance of the skin and frequently results in an aged facial appearance. There are both acquired and inherited forms that can be either solely cutaneous or present with extracutaneous features, such as cardiac abnormalities or emphysema.¹¹ 

In contrast to the atrophic appearance of anetodermas, connective tissue nevi and nevus lipomatosus superficialis present as hamartomas that either can be present at birth or arise in infancy. Connective tissue nevi are hamartomas of dermal connective tissue that consist of excessive production of collagen, elastin, or glycosaminoglycans and appear as slightly elevated, flesh-colored to yellow nodules or plaques.¹² Connective tissue nevi often are described in association with other diseases, most commonly tuberous sclerosis (shagreen patches) or familial cutaneous collagenoma. Nevus lipomatosus superficialis is an asymptomatic connective tissue hamartoma composed of mature adipocytes in the dermis. The lesions consist of clusters of flesh-colored to yellow, soft, rubbery papules or nodules with a smooth or verrucoid surface that do not cross the midline and may follow Blaschko lines.¹¹ 

With advances in neonatal infant medical care, survival of extremely premature infants is increasing, and it is possible that this rare cutaneous disorder may become more prevalent. Care should be taken to avoid unnecessary pressure on surfaces where electrodes are placed and tightly applied adhesive tape. When electrodes are placed on the ventral side, the child should be placed supine; similarly, place electrodes on the dorsal side when the child is lying prone.⁵ A diagnosis of anetoderma of prematurity later in childhood may be difficult, so knowledge and awareness can help guide pediatricians and dermatologists to a correct diagnosis and prevent unnecessary evaluations and/or concerns. 

The Diagnosis: Anetoderma of Prematurity 

Anetoderma is a rare benign cutaneous disorder characterized by atrophic patches of skin due to dermal thinning. The term anetoderma is derived from the Greek words anetos (relaxed) and derma (skin).¹ The physical appearance of the skin is associated with a reduction or loss of elastic tissue in the dermal layer, as seen on histolopathology.²  

Two forms of anetoderma have been described. Primary anetoderma is an idiopathic form with no preceding inflammatory lesions. Secondary anetoderma is a reactive process linked to a known preceding inflammatory, infectious, autoimmune, or drug-induced condition.³ On histopathology, both primary and secondary anetoderma are characterized by a loss of elastic tissue or elastin fibers in the superficial to mid dermis.²  

Anetoderma of prematurity was first described in 1996 by Prizant et al⁴ in 9 extremely premature (24-29 weeks' gestation) infants in neonatal intensive care units (NICUs). Although the exact mechanism behind anetoderma of prematurity is still unknown, Prizant et al⁴ and other investigators⁵ postulated that application of adhesive monitoring leads in the NICU played a role in the development of the lesions. 

Iatrogenic anetoderma of prematurity is clinically characterized by circumscribed areas of either wrinkled macular depression or pouchlike herniations, ranging from flesh-colored to violaceous hues. Lesion size varies from a few millimeters to several centimeters in diameter, and they often are oval or round in shape.² Although not common, it is possible for the atrophic patches to be preceded by an area of ecchymosis without necrosis or atrophy and, if present, they usually evolve within a few days to the characteristic appearance of anetoderma.³ They are found at discrete sites where monitoring leads or other medical devices are commonly placed, such as the forehead, abdomen, chest, and proximal limbs. 

Lesions of anetoderma of prematurity are not present at birth, which distinguishes them from congenital anetoderma.⁶ It is unclear if the lesions are associated with the degree of prematurity, extremely low birth weight, or other associated factors of preterm birth. Although often clinically diagnosed, the diagnosis can be confirmed by a loss of elastic fibers on histopathology when stained with Verhoeff-van Gieson stain.¹ Over time, the atrophic patches have the potential to evolve into herniated forms of anetoderma. Self-healing or improvement of the lesions often does not occur. Although the lesion is benign, it often requires surgical correction later in life for cosmesis.  

Infants in the NICU are at risk for iatrogenic cutaneous injuries, which rarely may include anetoderma. Anetoderma of prematurity has been linked to the use of monitoring leads, adhesive tape, and other medical devices placed on the skin. Prizant et al⁴ postulated that the cause of anetoderma in these infants was irritants such as skin cleansers, urine, or sweat that may be trapped under the electrodes. Other hypotheses include local hypoxemia due to prolonged pressure from the electrodes on immature skin or excessive traction used when removing adhesive tape from the skin.^7,8 Premature infants may be more susceptible to these lesions because of the reduced epidermal thickness of premature skin; immaturity of skin structure; or functional immaturity of elastin deposition regulators, such as elastase, lysyl oxidase, the complement system, and decay-accelerating factor.³ The diagnosis should be differentiated from congenital anetoderma, which also has been described in premature neonates but is characterized by lesions that are present at birth. Its origins are still unclear, despite having histopathologic features similar to iatrogenic anetoderma.⁹  

Focal dermal hypoplasia (FDH) is the hallmark cutaneous finding in Goltz syndrome, a rare set of congenital abnormalities of the skin, oral structures, musculoskeletal system, and central nervous system. Similar to congenital anetoderma, FDH also is characterized by atrophic cutaneous lesions; however, the cutaneous lesions in FDH appear as linear, streaky atrophic lesions often with telangiectasias that follow Blaschko lines.¹⁰ The cutaneous lesions in FDH often are associated with other noncutaneous signs such as polydactyly or asymmetric limbs.¹⁰ Cutis laxa is caused by an abnormality in the elastic tissue resulting in a loose sagging appearance of the skin and frequently results in an aged facial appearance. There are both acquired and inherited forms that can be either solely cutaneous or present with extracutaneous features, such as cardiac abnormalities or emphysema.¹¹ 

In contrast to the atrophic appearance of anetodermas, connective tissue nevi and nevus lipomatosus superficialis present as hamartomas that either can be present at birth or arise in infancy. Connective tissue nevi are hamartomas of dermal connective tissue that consist of excessive production of collagen, elastin, or glycosaminoglycans and appear as slightly elevated, flesh-colored to yellow nodules or plaques.¹² Connective tissue nevi often are described in association with other diseases, most commonly tuberous sclerosis (shagreen patches) or familial cutaneous collagenoma. Nevus lipomatosus superficialis is an asymptomatic connective tissue hamartoma composed of mature adipocytes in the dermis. The lesions consist of clusters of flesh-colored to yellow, soft, rubbery papules or nodules with a smooth or verrucoid surface that do not cross the midline and may follow Blaschko lines.¹¹ 

With advances in neonatal infant medical care, survival of extremely premature infants is increasing, and it is possible that this rare cutaneous disorder may become more prevalent. Care should be taken to avoid unnecessary pressure on surfaces where electrodes are placed and tightly applied adhesive tape. When electrodes are placed on the ventral side, the child should be placed supine; similarly, place electrodes on the dorsal side when the child is lying prone.⁵ A diagnosis of anetoderma of prematurity later in childhood may be difficult, so knowledge and awareness can help guide pediatricians and dermatologists to a correct diagnosis and prevent unnecessary evaluations and/or concerns. 

The Diagnosis: Anetoderma of Prematurity 

Anetoderma is a rare benign cutaneous disorder characterized by atrophic patches of skin due to dermal thinning. The term anetoderma is derived from the Greek words anetos (relaxed) and derma (skin).¹ The physical appearance of the skin is associated with a reduction or loss of elastic tissue in the dermal layer, as seen on histolopathology.²  

Two forms of anetoderma have been described. Primary anetoderma is an idiopathic form with no preceding inflammatory lesions. Secondary anetoderma is a reactive process linked to a known preceding inflammatory, infectious, autoimmune, or drug-induced condition.³ On histopathology, both primary and secondary anetoderma are characterized by a loss of elastic tissue or elastin fibers in the superficial to mid dermis.²  

Anetoderma of prematurity was first described in 1996 by Prizant et al⁴ in 9 extremely premature (24-29 weeks' gestation) infants in neonatal intensive care units (NICUs). Although the exact mechanism behind anetoderma of prematurity is still unknown, Prizant et al⁴ and other investigators⁵ postulated that application of adhesive monitoring leads in the NICU played a role in the development of the lesions. 

Iatrogenic anetoderma of prematurity is clinically characterized by circumscribed areas of either wrinkled macular depression or pouchlike herniations, ranging from flesh-colored to violaceous hues. Lesion size varies from a few millimeters to several centimeters in diameter, and they often are oval or round in shape.² Although not common, it is possible for the atrophic patches to be preceded by an area of ecchymosis without necrosis or atrophy and, if present, they usually evolve within a few days to the characteristic appearance of anetoderma.³ They are found at discrete sites where monitoring leads or other medical devices are commonly placed, such as the forehead, abdomen, chest, and proximal limbs. 

Lesions of anetoderma of prematurity are not present at birth, which distinguishes them from congenital anetoderma.⁶ It is unclear if the lesions are associated with the degree of prematurity, extremely low birth weight, or other associated factors of preterm birth. Although often clinically diagnosed, the diagnosis can be confirmed by a loss of elastic fibers on histopathology when stained with Verhoeff-van Gieson stain.¹ Over time, the atrophic patches have the potential to evolve into herniated forms of anetoderma. Self-healing or improvement of the lesions often does not occur. Although the lesion is benign, it often requires surgical correction later in life for cosmesis.  

Infants in the NICU are at risk for iatrogenic cutaneous injuries, which rarely may include anetoderma. Anetoderma of prematurity has been linked to the use of monitoring leads, adhesive tape, and other medical devices placed on the skin. Prizant et al⁴ postulated that the cause of anetoderma in these infants was irritants such as skin cleansers, urine, or sweat that may be trapped under the electrodes. Other hypotheses include local hypoxemia due to prolonged pressure from the electrodes on immature skin or excessive traction used when removing adhesive tape from the skin.^7,8 Premature infants may be more susceptible to these lesions because of the reduced epidermal thickness of premature skin; immaturity of skin structure; or functional immaturity of elastin deposition regulators, such as elastase, lysyl oxidase, the complement system, and decay-accelerating factor.³ The diagnosis should be differentiated from congenital anetoderma, which also has been described in premature neonates but is characterized by lesions that are present at birth. Its origins are still unclear, despite having histopathologic features similar to iatrogenic anetoderma.⁹  

Focal dermal hypoplasia (FDH) is the hallmark cutaneous finding in Goltz syndrome, a rare set of congenital abnormalities of the skin, oral structures, musculoskeletal system, and central nervous system. Similar to congenital anetoderma, FDH also is characterized by atrophic cutaneous lesions; however, the cutaneous lesions in FDH appear as linear, streaky atrophic lesions often with telangiectasias that follow Blaschko lines.¹⁰ The cutaneous lesions in FDH often are associated with other noncutaneous signs such as polydactyly or asymmetric limbs.¹⁰ Cutis laxa is caused by an abnormality in the elastic tissue resulting in a loose sagging appearance of the skin and frequently results in an aged facial appearance. There are both acquired and inherited forms that can be either solely cutaneous or present with extracutaneous features, such as cardiac abnormalities or emphysema.¹¹ 

In contrast to the atrophic appearance of anetodermas, connective tissue nevi and nevus lipomatosus superficialis present as hamartomas that either can be present at birth or arise in infancy. Connective tissue nevi are hamartomas of dermal connective tissue that consist of excessive production of collagen, elastin, or glycosaminoglycans and appear as slightly elevated, flesh-colored to yellow nodules or plaques.¹² Connective tissue nevi often are described in association with other diseases, most commonly tuberous sclerosis (shagreen patches) or familial cutaneous collagenoma. Nevus lipomatosus superficialis is an asymptomatic connective tissue hamartoma composed of mature adipocytes in the dermis. The lesions consist of clusters of flesh-colored to yellow, soft, rubbery papules or nodules with a smooth or verrucoid surface that do not cross the midline and may follow Blaschko lines.¹¹ 

With advances in neonatal infant medical care, survival of extremely premature infants is increasing, and it is possible that this rare cutaneous disorder may become more prevalent. Care should be taken to avoid unnecessary pressure on surfaces where electrodes are placed and tightly applied adhesive tape. When electrodes are placed on the ventral side, the child should be placed supine; similarly, place electrodes on the dorsal side when the child is lying prone.⁵ A diagnosis of anetoderma of prematurity later in childhood may be difficult, so knowledge and awareness can help guide pediatricians and dermatologists to a correct diagnosis and prevent unnecessary evaluations and/or concerns.