Dermatopathology

The Diagnosis: Pachydermoperiostosis

Histopathology of the forehead punch biopsy demonstrated sebaceous hyperplasia with an occupation rate of greater than 40%, increased mucin, elastic fiber degeneration, and fibrosis. Pachydermia is graded from 0 to 3 depending on the degree of these changes; our patient met criteria for grade 3 pachydermia (Figure 1). Radiography revealed diffuse cortical thickening of the long bones that was most marked in the left femur (Figure 2); however, no other findings were demonstrative of Paget disease.

Pachydermoperiostosis (PDP)(also known as Touraine-Solente-Golé syndrome or primary hypertrophic osteoarthropathy) is a rare genetic condition that affects both the dermatologic and skeletal systems. Clinical features of the disease include progressive thickening and furrowing of the skin on the scalp and face (known as pachydermia), digital clubbing, and periostosis. Other potential cutaneous features include seborrhea, acne, hyperhidrosis of the palms and soles, cutis verticis gyrata, eczema, and a burning sensation of the hands and feet. Myelofibrosis and gastrointestinal abnormalities also have been reported.¹

The disease typically affects males (7:1 ratio); also, men typically display a more severe phenotype of the disease.² It most commonly begins during puberty and follows a generally progressive course of 5 to 20 years before eventually stabilizing. Both autosomal-dominant with incomplete penetrance and recessive inheritance versions of PDP can occur. Prostaglandin E₂ (PGE₂) has been implicated in the pathogenesis of PDP; PGE₂ is important in the inflammatory response and may evolve from disrupted protein degradation pathways.³ Sasaki et al⁴ additionally reported that the severity of pachydermia clinically and histologically appeared to correlate with the serum PGE₂ levels in affected patients. Prostaglandin E₂ causes a vasodilatory effect, perhaps explaining the clubbing observed in PDP, and also modifies the activity of osteoblasts and osteoclasts, causing the bone remodeling observed in the disease.⁴

In our patient, the initial differential diagnosis included PDP, as well as lepromatous leprosy, acromegaly, Paget disease of the bone, amyloidosis, scleromyxedema, and cutaneous T-cell lymphoma. However, the time course of the disease, lack of numerous symmetric thickened plaques and madarosis, and pathology argued against lepromatous leprosy. Acromegaly was ruled out due to lack of macroglossia as well as laboratory analysis within reference range including IGF-1 levels and thyroid function tests. Biopsy findings ultimately ruled out amyloidosis and cutaneous T-cell lymphoma. The bone scan revealed diffuse cortical thickening consistent with PDP, and there were no other radiologic findings suggestive of Paget disease. Pachydermoperiostosis is diagnosed using the Borochowitz criteria, which entails that 2 of the following 4 fulfillment criteria must be met: familial transmission, pachydermia, digital clubbing, and/or bony involvement with evidence of radiologic alterations or pain. Our patient met all 4 criteria. The clinical manifestations of PDP are variable with respect to skin and bone changes. The various clinical expressions include the complete form (ie, pachydermia, cutis verticis gyrata, periostosis), the incomplete form (ie, absence of cutis verticis gyrata), and forme fruste (ie, pachydermia with minimal or absent periostosis).⁵

Management for PDP involves surgical correction for cosmesis as well as for functional concerns if present. Symptoms secondary to periostosis should be managed with symptomatic treatment such as nonsteroidal antiinflammatory drugs. Patients managed with etoricoxib, a COX-2–selective nonsteroidal anti-inflammatory drug, have had normalized inflammatory markers that resulted in the lessening of forehead skin folds. Oral aescin has been shown to relieve joint pain due to its antiedematous effect.⁶ Our patient received treatment with nonsteroidal anti-inflammatory drugs for symptomatic management of the associated joint pain but unfortunately was lost to follow-up.

The Diagnosis: Pachydermoperiostosis

Histopathology of the forehead punch biopsy demonstrated sebaceous hyperplasia with an occupation rate of greater than 40%, increased mucin, elastic fiber degeneration, and fibrosis. Pachydermia is graded from 0 to 3 depending on the degree of these changes; our patient met criteria for grade 3 pachydermia (Figure 1). Radiography revealed diffuse cortical thickening of the long bones that was most marked in the left femur (Figure 2); however, no other findings were demonstrative of Paget disease.

Pachydermoperiostosis (PDP)(also known as Touraine-Solente-Golé syndrome or primary hypertrophic osteoarthropathy) is a rare genetic condition that affects both the dermatologic and skeletal systems. Clinical features of the disease include progressive thickening and furrowing of the skin on the scalp and face (known as pachydermia), digital clubbing, and periostosis. Other potential cutaneous features include seborrhea, acne, hyperhidrosis of the palms and soles, cutis verticis gyrata, eczema, and a burning sensation of the hands and feet. Myelofibrosis and gastrointestinal abnormalities also have been reported.¹

The disease typically affects males (7:1 ratio); also, men typically display a more severe phenotype of the disease.² It most commonly begins during puberty and follows a generally progressive course of 5 to 20 years before eventually stabilizing. Both autosomal-dominant with incomplete penetrance and recessive inheritance versions of PDP can occur. Prostaglandin E₂ (PGE₂) has been implicated in the pathogenesis of PDP; PGE₂ is important in the inflammatory response and may evolve from disrupted protein degradation pathways.³ Sasaki et al⁴ additionally reported that the severity of pachydermia clinically and histologically appeared to correlate with the serum PGE₂ levels in affected patients. Prostaglandin E₂ causes a vasodilatory effect, perhaps explaining the clubbing observed in PDP, and also modifies the activity of osteoblasts and osteoclasts, causing the bone remodeling observed in the disease.⁴

In our patient, the initial differential diagnosis included PDP, as well as lepromatous leprosy, acromegaly, Paget disease of the bone, amyloidosis, scleromyxedema, and cutaneous T-cell lymphoma. However, the time course of the disease, lack of numerous symmetric thickened plaques and madarosis, and pathology argued against lepromatous leprosy. Acromegaly was ruled out due to lack of macroglossia as well as laboratory analysis within reference range including IGF-1 levels and thyroid function tests. Biopsy findings ultimately ruled out amyloidosis and cutaneous T-cell lymphoma. The bone scan revealed diffuse cortical thickening consistent with PDP, and there were no other radiologic findings suggestive of Paget disease. Pachydermoperiostosis is diagnosed using the Borochowitz criteria, which entails that 2 of the following 4 fulfillment criteria must be met: familial transmission, pachydermia, digital clubbing, and/or bony involvement with evidence of radiologic alterations or pain. Our patient met all 4 criteria. The clinical manifestations of PDP are variable with respect to skin and bone changes. The various clinical expressions include the complete form (ie, pachydermia, cutis verticis gyrata, periostosis), the incomplete form (ie, absence of cutis verticis gyrata), and forme fruste (ie, pachydermia with minimal or absent periostosis).⁵

Management for PDP involves surgical correction for cosmesis as well as for functional concerns if present. Symptoms secondary to periostosis should be managed with symptomatic treatment such as nonsteroidal antiinflammatory drugs. Patients managed with etoricoxib, a COX-2–selective nonsteroidal anti-inflammatory drug, have had normalized inflammatory markers that resulted in the lessening of forehead skin folds. Oral aescin has been shown to relieve joint pain due to its antiedematous effect.⁶ Our patient received treatment with nonsteroidal anti-inflammatory drugs for symptomatic management of the associated joint pain but unfortunately was lost to follow-up.

The Diagnosis: Pachydermoperiostosis

Histopathology of the forehead punch biopsy demonstrated sebaceous hyperplasia with an occupation rate of greater than 40%, increased mucin, elastic fiber degeneration, and fibrosis. Pachydermia is graded from 0 to 3 depending on the degree of these changes; our patient met criteria for grade 3 pachydermia (Figure 1). Radiography revealed diffuse cortical thickening of the long bones that was most marked in the left femur (Figure 2); however, no other findings were demonstrative of Paget disease.

Pachydermoperiostosis (PDP)(also known as Touraine-Solente-Golé syndrome or primary hypertrophic osteoarthropathy) is a rare genetic condition that affects both the dermatologic and skeletal systems. Clinical features of the disease include progressive thickening and furrowing of the skin on the scalp and face (known as pachydermia), digital clubbing, and periostosis. Other potential cutaneous features include seborrhea, acne, hyperhidrosis of the palms and soles, cutis verticis gyrata, eczema, and a burning sensation of the hands and feet. Myelofibrosis and gastrointestinal abnormalities also have been reported.¹

The disease typically affects males (7:1 ratio); also, men typically display a more severe phenotype of the disease.² It most commonly begins during puberty and follows a generally progressive course of 5 to 20 years before eventually stabilizing. Both autosomal-dominant with incomplete penetrance and recessive inheritance versions of PDP can occur. Prostaglandin E₂ (PGE₂) has been implicated in the pathogenesis of PDP; PGE₂ is important in the inflammatory response and may evolve from disrupted protein degradation pathways.³ Sasaki et al⁴ additionally reported that the severity of pachydermia clinically and histologically appeared to correlate with the serum PGE₂ levels in affected patients. Prostaglandin E₂ causes a vasodilatory effect, perhaps explaining the clubbing observed in PDP, and also modifies the activity of osteoblasts and osteoclasts, causing the bone remodeling observed in the disease.⁴

In our patient, the initial differential diagnosis included PDP, as well as lepromatous leprosy, acromegaly, Paget disease of the bone, amyloidosis, scleromyxedema, and cutaneous T-cell lymphoma. However, the time course of the disease, lack of numerous symmetric thickened plaques and madarosis, and pathology argued against lepromatous leprosy. Acromegaly was ruled out due to lack of macroglossia as well as laboratory analysis within reference range including IGF-1 levels and thyroid function tests. Biopsy findings ultimately ruled out amyloidosis and cutaneous T-cell lymphoma. The bone scan revealed diffuse cortical thickening consistent with PDP, and there were no other radiologic findings suggestive of Paget disease. Pachydermoperiostosis is diagnosed using the Borochowitz criteria, which entails that 2 of the following 4 fulfillment criteria must be met: familial transmission, pachydermia, digital clubbing, and/or bony involvement with evidence of radiologic alterations or pain. Our patient met all 4 criteria. The clinical manifestations of PDP are variable with respect to skin and bone changes. The various clinical expressions include the complete form (ie, pachydermia, cutis verticis gyrata, periostosis), the incomplete form (ie, absence of cutis verticis gyrata), and forme fruste (ie, pachydermia with minimal or absent periostosis).⁵

Management for PDP involves surgical correction for cosmesis as well as for functional concerns if present. Symptoms secondary to periostosis should be managed with symptomatic treatment such as nonsteroidal antiinflammatory drugs. Patients managed with etoricoxib, a COX-2–selective nonsteroidal anti-inflammatory drug, have had normalized inflammatory markers that resulted in the lessening of forehead skin folds. Oral aescin has been shown to relieve joint pain due to its antiedematous effect.⁶ Our patient received treatment with nonsteroidal anti-inflammatory drugs for symptomatic management of the associated joint pain but unfortunately was lost to follow-up.

The Diagnosis: Leiomyosarcoma

Cutaneous leiomyosarcomas are relatively rare neoplasms that favor the head, neck, and extremities of older adults.¹ Dermal leiomyosarcomas originate from arrector pili and are locally aggressive, whereas subcutaneous leiomyosarcomas arise from vascular smooth muscle and metastasize in 30% to 60% of cases.² Clinically, leiomyosarcomas present as solitary, firm, well-circumscribed nodules with possible ulceration and crusting.³ Histopathology of leiomyosarcoma shows fascicles of atypical spindle cells with blunt-ended nuclei and perinuclear glycogen vacuoles, variable atypia, and mitotic figures (quiz images). Definitive diagnosis is based on positive immunohistochemical staining for desmin and smooth muscle actin.⁴ Treatment entails complete removal via wide local excision or Mohs micrographic surgery.⁵

Atypical fibroxanthoma (AFX) is a malignant fibrohistiocytic neoplasm that arises in the dermis and preferentially affects the head and neck in older individuals.³ Atypical fibroxanthoma presents as a nonspecific, pinkred, sometimes ulcerated papule on sun-damaged skin that may clinically resemble a squamous cell carcinoma (SCC) or basal cell carcinoma.6 Histopathology shows pleomorphic spindle cells with hyperchromatic nuclei and abundant cytoplasm mixed with multinucleated giant cells and scattered mitotic figures (Figure 1). Immunohistochemistry is essential for distinguishing AFX from other spindle cell neoplasms. Atypical fibroxanthoma stains positively for vimentin, procollagen-1, CD10, and CD68 but is negative for S-100, human melanoma black 45, Melan-A, desmin, cytokeratin, p40, and p63.⁶ Treatment includes wide local excision or Mohs micrographic surgery.

Melanoma is an aggressive cancer with the propensity to metastasize. Both desmoplastic and spindle cell variants demonstrate atypical spindled melanocytes on histology, and desmoplasia is seen in the desmoplastic variant (Figure 2). In some cases, evaluation of the epidermis for melanoma in situ may aid in diagnosis.⁷ Clinical and prognostic features differ between the 2 variants. Desmoplastic melanomas usually present on the head and neck as scarlike nodules with a low rate of nodal involvement, while spindle cell melanomas can occur anywhere on the body, often are amelanotic, and are associated with widespread metastatic disease at the time of presentation.⁸ SOX10 (SRY-box transcription factor 10) and S-100 may be the only markers that are positive in desmoplastic melanoma.^9,10 Treatment depends on the thickness of the lesion.¹¹

Spindle cell SCC is a histologic variant of SCC characterized by spindled epithelial cells. Spindle cell SCC typically presents as an ulcerated or exophytic mass in sun-exposed areas or areas exposed to ionizing radiation, or in immunocompromised individuals. Histopathology shows spindled pleomorphic keratinocytes with elongated nuclei infiltrating the dermis and minimal keratinization (Figure 3).¹² Immunohistochemistry is necessary to distinguish spindle cell SCC from other spindle cell tumors such as spindle cell melanoma, AFX, and leiomyosarcoma. Spindle cell SCC is positive for high-molecular-weight cytokeratin, p40, and p63. Mohs micrographic surgery provides the highest cure rate, and radiation therapy may be considered when clear surgical margins cannot be obtained.⁶

Undifferentiated pleomorphic sarcoma (UPS) (formerly known as malignant fibrous histiocytoma) describes tumors that resemble AFX but are more invasive. They commonly involve the soft tissue with a higher risk for both recurrence and metastasis than AFX.¹³ Histopathology shows marked cytologic pleomorphism, bizarre cellular forms, atypical mitoses, and ulceration (Figure 4).¹⁴ Diagnosis of UPS is by exclusion and is dependent on immunohistochemical studies. In contrast to AFX, UPS is more likely to be positive for LN-2 (CD74).⁶ Undifferentiated pleomorphic sarcoma has been treated with surgical excision in combination with chemical and radiation therapy, but due to limited data, optimal management is less clear compared to AFX.¹⁵ There is a substantial risk for local recurrence and metastasis, and the lungs are the most common sites of distant metastasis.¹³ In a study of 23 individuals with high-grade UPS, 5-year metastasis-free survival and local recurrence-free survival were 26% and 16%, respectively.¹⁰

The Diagnosis: Leiomyosarcoma

Cutaneous leiomyosarcomas are relatively rare neoplasms that favor the head, neck, and extremities of older adults.¹ Dermal leiomyosarcomas originate from arrector pili and are locally aggressive, whereas subcutaneous leiomyosarcomas arise from vascular smooth muscle and metastasize in 30% to 60% of cases.² Clinically, leiomyosarcomas present as solitary, firm, well-circumscribed nodules with possible ulceration and crusting.³ Histopathology of leiomyosarcoma shows fascicles of atypical spindle cells with blunt-ended nuclei and perinuclear glycogen vacuoles, variable atypia, and mitotic figures (quiz images). Definitive diagnosis is based on positive immunohistochemical staining for desmin and smooth muscle actin.⁴ Treatment entails complete removal via wide local excision or Mohs micrographic surgery.⁵

Atypical fibroxanthoma (AFX) is a malignant fibrohistiocytic neoplasm that arises in the dermis and preferentially affects the head and neck in older individuals.³ Atypical fibroxanthoma presents as a nonspecific, pinkred, sometimes ulcerated papule on sun-damaged skin that may clinically resemble a squamous cell carcinoma (SCC) or basal cell carcinoma.6 Histopathology shows pleomorphic spindle cells with hyperchromatic nuclei and abundant cytoplasm mixed with multinucleated giant cells and scattered mitotic figures (Figure 1). Immunohistochemistry is essential for distinguishing AFX from other spindle cell neoplasms. Atypical fibroxanthoma stains positively for vimentin, procollagen-1, CD10, and CD68 but is negative for S-100, human melanoma black 45, Melan-A, desmin, cytokeratin, p40, and p63.⁶ Treatment includes wide local excision or Mohs micrographic surgery.

Melanoma is an aggressive cancer with the propensity to metastasize. Both desmoplastic and spindle cell variants demonstrate atypical spindled melanocytes on histology, and desmoplasia is seen in the desmoplastic variant (Figure 2). In some cases, evaluation of the epidermis for melanoma in situ may aid in diagnosis.⁷ Clinical and prognostic features differ between the 2 variants. Desmoplastic melanomas usually present on the head and neck as scarlike nodules with a low rate of nodal involvement, while spindle cell melanomas can occur anywhere on the body, often are amelanotic, and are associated with widespread metastatic disease at the time of presentation.⁸ SOX10 (SRY-box transcription factor 10) and S-100 may be the only markers that are positive in desmoplastic melanoma.^9,10 Treatment depends on the thickness of the lesion.¹¹

Spindle cell SCC is a histologic variant of SCC characterized by spindled epithelial cells. Spindle cell SCC typically presents as an ulcerated or exophytic mass in sun-exposed areas or areas exposed to ionizing radiation, or in immunocompromised individuals. Histopathology shows spindled pleomorphic keratinocytes with elongated nuclei infiltrating the dermis and minimal keratinization (Figure 3).¹² Immunohistochemistry is necessary to distinguish spindle cell SCC from other spindle cell tumors such as spindle cell melanoma, AFX, and leiomyosarcoma. Spindle cell SCC is positive for high-molecular-weight cytokeratin, p40, and p63. Mohs micrographic surgery provides the highest cure rate, and radiation therapy may be considered when clear surgical margins cannot be obtained.⁶

Undifferentiated pleomorphic sarcoma (UPS) (formerly known as malignant fibrous histiocytoma) describes tumors that resemble AFX but are more invasive. They commonly involve the soft tissue with a higher risk for both recurrence and metastasis than AFX.¹³ Histopathology shows marked cytologic pleomorphism, bizarre cellular forms, atypical mitoses, and ulceration (Figure 4).¹⁴ Diagnosis of UPS is by exclusion and is dependent on immunohistochemical studies. In contrast to AFX, UPS is more likely to be positive for LN-2 (CD74).⁶ Undifferentiated pleomorphic sarcoma has been treated with surgical excision in combination with chemical and radiation therapy, but due to limited data, optimal management is less clear compared to AFX.¹⁵ There is a substantial risk for local recurrence and metastasis, and the lungs are the most common sites of distant metastasis.¹³ In a study of 23 individuals with high-grade UPS, 5-year metastasis-free survival and local recurrence-free survival were 26% and 16%, respectively.¹⁰

The Diagnosis: Leiomyosarcoma

Cutaneous leiomyosarcomas are relatively rare neoplasms that favor the head, neck, and extremities of older adults.¹ Dermal leiomyosarcomas originate from arrector pili and are locally aggressive, whereas subcutaneous leiomyosarcomas arise from vascular smooth muscle and metastasize in 30% to 60% of cases.² Clinically, leiomyosarcomas present as solitary, firm, well-circumscribed nodules with possible ulceration and crusting.³ Histopathology of leiomyosarcoma shows fascicles of atypical spindle cells with blunt-ended nuclei and perinuclear glycogen vacuoles, variable atypia, and mitotic figures (quiz images). Definitive diagnosis is based on positive immunohistochemical staining for desmin and smooth muscle actin.⁴ Treatment entails complete removal via wide local excision or Mohs micrographic surgery.⁵

Atypical fibroxanthoma (AFX) is a malignant fibrohistiocytic neoplasm that arises in the dermis and preferentially affects the head and neck in older individuals.³ Atypical fibroxanthoma presents as a nonspecific, pinkred, sometimes ulcerated papule on sun-damaged skin that may clinically resemble a squamous cell carcinoma (SCC) or basal cell carcinoma.6 Histopathology shows pleomorphic spindle cells with hyperchromatic nuclei and abundant cytoplasm mixed with multinucleated giant cells and scattered mitotic figures (Figure 1). Immunohistochemistry is essential for distinguishing AFX from other spindle cell neoplasms. Atypical fibroxanthoma stains positively for vimentin, procollagen-1, CD10, and CD68 but is negative for S-100, human melanoma black 45, Melan-A, desmin, cytokeratin, p40, and p63.⁶ Treatment includes wide local excision or Mohs micrographic surgery.

Melanoma is an aggressive cancer with the propensity to metastasize. Both desmoplastic and spindle cell variants demonstrate atypical spindled melanocytes on histology, and desmoplasia is seen in the desmoplastic variant (Figure 2). In some cases, evaluation of the epidermis for melanoma in situ may aid in diagnosis.⁷ Clinical and prognostic features differ between the 2 variants. Desmoplastic melanomas usually present on the head and neck as scarlike nodules with a low rate of nodal involvement, while spindle cell melanomas can occur anywhere on the body, often are amelanotic, and are associated with widespread metastatic disease at the time of presentation.⁸ SOX10 (SRY-box transcription factor 10) and S-100 may be the only markers that are positive in desmoplastic melanoma.^9,10 Treatment depends on the thickness of the lesion.¹¹

Spindle cell SCC is a histologic variant of SCC characterized by spindled epithelial cells. Spindle cell SCC typically presents as an ulcerated or exophytic mass in sun-exposed areas or areas exposed to ionizing radiation, or in immunocompromised individuals. Histopathology shows spindled pleomorphic keratinocytes with elongated nuclei infiltrating the dermis and minimal keratinization (Figure 3).¹² Immunohistochemistry is necessary to distinguish spindle cell SCC from other spindle cell tumors such as spindle cell melanoma, AFX, and leiomyosarcoma. Spindle cell SCC is positive for high-molecular-weight cytokeratin, p40, and p63. Mohs micrographic surgery provides the highest cure rate, and radiation therapy may be considered when clear surgical margins cannot be obtained.⁶

Undifferentiated pleomorphic sarcoma (UPS) (formerly known as malignant fibrous histiocytoma) describes tumors that resemble AFX but are more invasive. They commonly involve the soft tissue with a higher risk for both recurrence and metastasis than AFX.¹³ Histopathology shows marked cytologic pleomorphism, bizarre cellular forms, atypical mitoses, and ulceration (Figure 4).¹⁴ Diagnosis of UPS is by exclusion and is dependent on immunohistochemical studies. In contrast to AFX, UPS is more likely to be positive for LN-2 (CD74).⁶ Undifferentiated pleomorphic sarcoma has been treated with surgical excision in combination with chemical and radiation therapy, but due to limited data, optimal management is less clear compared to AFX.¹⁵ There is a substantial risk for local recurrence and metastasis, and the lungs are the most common sites of distant metastasis.¹³ In a study of 23 individuals with high-grade UPS, 5-year metastasis-free survival and local recurrence-free survival were 26% and 16%, respectively.¹⁰

The Diagnosis: Syringoma

Syringomas are benign adnexal tumors with distinct histopathologic features, including the characteristic comma- or tadpole-shaped tail comprised of dilated cystic eccrine ducts. Clinically, syringomas typically present predominantly in the periorbital region in adolescent girls. They may present as solitary or multiple lesions, and sites such as the genital area, palms, scalp, and chest rarely can be involved.¹ Eruptive syringoma is a clinical subtype of syringoma that is seen on the face, neck, chest, and axillae that predominantly occurs in females with skin of color in countries such as Asia and Africa before or during puberty.^2,3 Lesions appear as small, flesh-colored or slightly pigmented, flat-topped papules.³ The condition can be cosmetically disfiguring and difficult to treat, especially in patients with darker skin.

In our patient, dermoscopic evaluation revealed reticular light brown lines, structureless light brown areas, clustered brown dots, globules, and reticular vessels on a faint background (Figure 1A). Glittering yellow-whitish round structures over a fading pink-brown background also were seen at some sites (Figure 1B). Histologic examination of a neck lesion revealed an epidermis with focal acanthosis; the upper dermis had tumor islands and ducts with cells with round to vesicular nuclei and eosinophilic cytoplasm. A well-circumscribed tumor in the dermis composed of tubules of varying sizes lined by cuboidal cells was seen, consistent with syringoma (Figure 2).

Dermoscopic features of syringomas have not been widely studied. Hayashi et al⁴ reported the dermoscopic features of unilateral linear syringomas as a delicate and faint reticular pigmentation network and multiple hypopigmented areas. Sakiyama et al⁵ also defined an incomplete pigment network with faint erythema in 2 eruptive syringoma cases.

Treatment of this condition is for cosmetic reasons only, and there are no reports of long-term morbidity associated with the disease.^6,7 Multiple therapeutic options are available but are associated with complications such as hyperpigmentation and sclerosis in patients with skin of color due to the dermal location of these syringomas. Management of syringomas includes topical and surgical methods, including topical retinoids such as tretinoin and atropine solution 1%; surgical methods include dermabrasion, excision, cryotherapy, electrocautery, electrofulguration, laser therapy, and chemical cautery. However, there is a substantial risk for recurrence with these treatment options. In a case series of 5 patients with periorbital syringomas, treatment using radiofrequency and a CO₂ laser was performed with favorable outcomes, highlighting the use of combination therapies for treatment.8 Seo et al⁹ reported a retrospective case series of 92 patients with periorbital syringomas in which they treated one group with CO₂ laser and the other with botulinum toxin A injection; CO₂ laser combined with botulinum toxin A showed a greater effect than laser treatment alone. The differential diagnosis includes pigmented plane warts, sebaceous hyperplasia, eruptive xanthomas, and hidrocystomas. Pigmented plane warts characteristically present as flat-topped papules with small hemorrhagic dots or tiny pinpoint vessels on dermoscopy. In sebaceous hyperplasia, yellowish umbilicated papular lesions are seen with crown vessels on dermoscopy. Eruptive xanthomas usually are erythematous to yellow, dome-shaped papules that appear mainly over the extensor aspects of the extremities. Hidrocystoma presents as a solitary translucent larger syringomalike lesion commonly seen in the periorbital region and/or on the cheeks.

We report a case of widespread syringomas with multiple close mimickers such as pigmented plane warts; however, dermoscopy of the lesions helped to arrive at the diagnosis. Dermatologists should be aware of this condition and its benign nature to ensure correct diagnosis and appropriate treatment.

The Diagnosis: Syringoma

Syringomas are benign adnexal tumors with distinct histopathologic features, including the characteristic comma- or tadpole-shaped tail comprised of dilated cystic eccrine ducts. Clinically, syringomas typically present predominantly in the periorbital region in adolescent girls. They may present as solitary or multiple lesions, and sites such as the genital area, palms, scalp, and chest rarely can be involved.¹ Eruptive syringoma is a clinical subtype of syringoma that is seen on the face, neck, chest, and axillae that predominantly occurs in females with skin of color in countries such as Asia and Africa before or during puberty.^2,3 Lesions appear as small, flesh-colored or slightly pigmented, flat-topped papules.³ The condition can be cosmetically disfiguring and difficult to treat, especially in patients with darker skin.

In our patient, dermoscopic evaluation revealed reticular light brown lines, structureless light brown areas, clustered brown dots, globules, and reticular vessels on a faint background (Figure 1A). Glittering yellow-whitish round structures over a fading pink-brown background also were seen at some sites (Figure 1B). Histologic examination of a neck lesion revealed an epidermis with focal acanthosis; the upper dermis had tumor islands and ducts with cells with round to vesicular nuclei and eosinophilic cytoplasm. A well-circumscribed tumor in the dermis composed of tubules of varying sizes lined by cuboidal cells was seen, consistent with syringoma (Figure 2).

Dermoscopic features of syringomas have not been widely studied. Hayashi et al⁴ reported the dermoscopic features of unilateral linear syringomas as a delicate and faint reticular pigmentation network and multiple hypopigmented areas. Sakiyama et al⁵ also defined an incomplete pigment network with faint erythema in 2 eruptive syringoma cases.

Treatment of this condition is for cosmetic reasons only, and there are no reports of long-term morbidity associated with the disease.^6,7 Multiple therapeutic options are available but are associated with complications such as hyperpigmentation and sclerosis in patients with skin of color due to the dermal location of these syringomas. Management of syringomas includes topical and surgical methods, including topical retinoids such as tretinoin and atropine solution 1%; surgical methods include dermabrasion, excision, cryotherapy, electrocautery, electrofulguration, laser therapy, and chemical cautery. However, there is a substantial risk for recurrence with these treatment options. In a case series of 5 patients with periorbital syringomas, treatment using radiofrequency and a CO₂ laser was performed with favorable outcomes, highlighting the use of combination therapies for treatment.8 Seo et al⁹ reported a retrospective case series of 92 patients with periorbital syringomas in which they treated one group with CO₂ laser and the other with botulinum toxin A injection; CO₂ laser combined with botulinum toxin A showed a greater effect than laser treatment alone. The differential diagnosis includes pigmented plane warts, sebaceous hyperplasia, eruptive xanthomas, and hidrocystomas. Pigmented plane warts characteristically present as flat-topped papules with small hemorrhagic dots or tiny pinpoint vessels on dermoscopy. In sebaceous hyperplasia, yellowish umbilicated papular lesions are seen with crown vessels on dermoscopy. Eruptive xanthomas usually are erythematous to yellow, dome-shaped papules that appear mainly over the extensor aspects of the extremities. Hidrocystoma presents as a solitary translucent larger syringomalike lesion commonly seen in the periorbital region and/or on the cheeks.

We report a case of widespread syringomas with multiple close mimickers such as pigmented plane warts; however, dermoscopy of the lesions helped to arrive at the diagnosis. Dermatologists should be aware of this condition and its benign nature to ensure correct diagnosis and appropriate treatment.

The Diagnosis: Syringoma

Syringomas are benign adnexal tumors with distinct histopathologic features, including the characteristic comma- or tadpole-shaped tail comprised of dilated cystic eccrine ducts. Clinically, syringomas typically present predominantly in the periorbital region in adolescent girls. They may present as solitary or multiple lesions, and sites such as the genital area, palms, scalp, and chest rarely can be involved.¹ Eruptive syringoma is a clinical subtype of syringoma that is seen on the face, neck, chest, and axillae that predominantly occurs in females with skin of color in countries such as Asia and Africa before or during puberty.^2,3 Lesions appear as small, flesh-colored or slightly pigmented, flat-topped papules.³ The condition can be cosmetically disfiguring and difficult to treat, especially in patients with darker skin.

In our patient, dermoscopic evaluation revealed reticular light brown lines, structureless light brown areas, clustered brown dots, globules, and reticular vessels on a faint background (Figure 1A). Glittering yellow-whitish round structures over a fading pink-brown background also were seen at some sites (Figure 1B). Histologic examination of a neck lesion revealed an epidermis with focal acanthosis; the upper dermis had tumor islands and ducts with cells with round to vesicular nuclei and eosinophilic cytoplasm. A well-circumscribed tumor in the dermis composed of tubules of varying sizes lined by cuboidal cells was seen, consistent with syringoma (Figure 2).

Dermoscopic features of syringomas have not been widely studied. Hayashi et al⁴ reported the dermoscopic features of unilateral linear syringomas as a delicate and faint reticular pigmentation network and multiple hypopigmented areas. Sakiyama et al⁵ also defined an incomplete pigment network with faint erythema in 2 eruptive syringoma cases.

Treatment of this condition is for cosmetic reasons only, and there are no reports of long-term morbidity associated with the disease.^6,7 Multiple therapeutic options are available but are associated with complications such as hyperpigmentation and sclerosis in patients with skin of color due to the dermal location of these syringomas. Management of syringomas includes topical and surgical methods, including topical retinoids such as tretinoin and atropine solution 1%; surgical methods include dermabrasion, excision, cryotherapy, electrocautery, electrofulguration, laser therapy, and chemical cautery. However, there is a substantial risk for recurrence with these treatment options. In a case series of 5 patients with periorbital syringomas, treatment using radiofrequency and a CO₂ laser was performed with favorable outcomes, highlighting the use of combination therapies for treatment.8 Seo et al⁹ reported a retrospective case series of 92 patients with periorbital syringomas in which they treated one group with CO₂ laser and the other with botulinum toxin A injection; CO₂ laser combined with botulinum toxin A showed a greater effect than laser treatment alone. The differential diagnosis includes pigmented plane warts, sebaceous hyperplasia, eruptive xanthomas, and hidrocystomas. Pigmented plane warts characteristically present as flat-topped papules with small hemorrhagic dots or tiny pinpoint vessels on dermoscopy. In sebaceous hyperplasia, yellowish umbilicated papular lesions are seen with crown vessels on dermoscopy. Eruptive xanthomas usually are erythematous to yellow, dome-shaped papules that appear mainly over the extensor aspects of the extremities. Hidrocystoma presents as a solitary translucent larger syringomalike lesion commonly seen in the periorbital region and/or on the cheeks.

We report a case of widespread syringomas with multiple close mimickers such as pigmented plane warts; however, dermoscopy of the lesions helped to arrive at the diagnosis. Dermatologists should be aware of this condition and its benign nature to ensure correct diagnosis and appropriate treatment.

The Diagnosis: Plaque-type Syringoma

A biopsy demonstrated multiple basaloid islands of tumor cells in the reticular dermis with ductal differentiation, some with a commalike tail. The ducts were lined by 2 to 3 layers of small uniform cuboidal cells without atypia and contained inspissated secretions within the lumina of scattered ducts. There was an associated fibrotic collagenous stroma. There was no evidence of perineural invasion and no deep dermal or subcutaneous extension (Figure 1). Additional cytokeratin immunohistochemical staining highlighted the adnexal proliferation (Figure 2). A diagnosis of plaque-type syringoma (PTS) was made.

Syringomas are benign dermal sweat gland tumors that typically present as flesh-colored papules on the cheeks or periorbital area of young females. Plaque-type tumors as well as papulonodular, eruptive, disseminated, urticaria pigmentosa–like, lichen planus–like, or milialike syringomas also have been reported. Syringomas may be associated with certain medical conditions such as Down syndrome, Nicolau-Balus syndrome, and both scarring and nonscarring alopecias.¹ The clear cell variant of syringoma often is associated with diabetes mellitus.² Kikuchi et al³ first described PTS in 1979. Plaque-type syringomas rarely are reported in the literature, and sites of involvement include the head and neck region, upper lip, chest, upper extremities, vulva, penis, and scrotum.^4-6

Histologically, syringomatous lesions are composed of multiple small ducts lined by 2 to 3 layers of cuboidal epithelium. The ducts may be arranged in nests or strands of basaloid cells surrounded by a dense fibrotic stroma. Occasionally, the ducts will form a comma- or teardropshaped tail; however, this also may be observed in desmoplastic trichoepithelioma (DTE).⁷ Perineural invasion is absent in syringomas. Syringomas exhibit a lateral growth pattern that typically is limited to the upper half of the reticular dermis and spares the underlying subcutis, muscle, and bone. The growth pattern may be discontinuous with proliferations juxtaposed by normal-appearing skin.⁸ Syringomas usually express progesterone receptors and are known to proliferate at puberty, suggesting that these neoplasms are under hormonal control.⁹ Although syringomas are benign, various treatment options that may be pursued for cosmetic purposes include radiofrequency, staged excision, laser ablation, and oral isotretinoin.^8,10 If only a superficial biopsy is obtained, syringomas may display features of other adnexal neoplasms, including microcystic adnexal carcinoma (MAC), DTE, morpheaform basal cell carcinoma (BCC), and inflammatory linear verrucous epidermal nevus (ILVEN).

Microcystic adnexal carcinoma is a locally aggressive neoplasm first described by Goldstein et al¹¹ in 1982 an indurated, ill-defined plaque or nodule on the face with a predilection for the upper and lower lip. Prior radiation therapy and immunosuppression are risk factors for the development of MAC.¹² Histologically, the superficial portion displays small cornifying cysts interspersed with islands of basaloid cells and may mimic a syringoma. However, the deeper portions demonstrate ducts lined by a single layer of cells with a background of hyalinized and sclerotic stroma. The tumor cells may occupy the deep dermis and underlying subcutis, muscle, or bone and demonstrate an infiltrative growth pattern and perineural invasion. Treatment includes Mohs micrographic surgery.

Desmoplastic trichoepitheliomas most commonly present as solitary white to yellowish annular papules or plaques with a central dell located on sun-exposed areas of the face, cheeks, or chin. This benign neoplasm has a bimodal age distribution, primarily affecting females either in childhood or adulthood.¹³ Histologically, strands and nests of basaloid epithelial cells proliferate in a dense eosinophilic desmoplastic stroma. The basaloid islands are narrow and cordlike with growth parallel to the surface epidermis and do not dive deeply into the deep dermis or subcutis. Ductal differentiation with associated secretions typically is not seen in DTE.¹ Calcifications and foreign body granulomatous infiltrates may be present. Merkel cells also are present in this tumor and may be highlighted by immunohistochemistry with cytokeratin 20.¹⁴ Rarely, desmoplastic trichoepitheliomas may transform into trichoblastic carcinomas. Treatment may consist of surgical excision or Mohs micrographic surgery.

Morpheaform BCC also is included in the clinical and histopathologic differential diagnosis of infiltrative basaloid neoplasms. It is one of the more aggressive variants of BCC. The use of immunohistochemical staining may aid in differentiating between these sclerosing adnexal neoplasms.¹⁵ For example, pleckstrin homologylike domain family A member 1 (PHLDA1) is a stem cell marker that is heavily expressed in DTE as a specific follicular bulge marker but is not present in a morpheaform BCC. This highlights the follicular nature of DTEs at the molecular level. BerEP4 is a monoclonal antibody that serves as an epithelial marker for 2 glycopolypeptides: 34 and 39 kDa. This antibody may demonstrate positivity in morpheaform BCC but does not stain cells of interest in MAC.

Inflammatory linear verrucous epidermal nevus clinically presents with erythematous and warty papules in a linear distribution following the Blaschko lines. The papules often are reported to be intensely pruritic and usually are localized to one extremity.¹⁶ Although adultonset forms of ILVEN have been described,¹⁷ it most commonly is diagnosed in young children. Histologically, ILVEN consists of psoriasiform epidermal hyperplasia with alternating areas of parakeratosis and orthokeratosis with underlying agranulosis and hypergranulosis, respectively.¹⁸ The upper dermis contains a perivascular lymphocytic infiltrate. Treatment with laser therapy and surgical excision has led to both symptomatic and clinical improvement of ILVEN.¹⁶

Plaque-type syringomas are a rare variant of syringomas that clinically may mimic other common inflammatory and neoplastic conditions. An adequate biopsy is imperative to differentiate between adnexal neoplasms, as a small superficial biopsy of a syringoma may demonstrate features observed in other malignant or locally aggressive neoplasms. In our patient, the small ducts lined by cuboidal epithelium with no cellular atypia and no deep dermal growth or perineural invasion allowed for the diagnosis of PTS. Therapeutic options were reviewed with our patient, including oral isotretinoin, laser therapy, and staged excision. Ultimately, our patient elected not to pursue treatment, and she is being monitored clinically for any changes in appearance or symptoms.

The Diagnosis: Plaque-type Syringoma

A biopsy demonstrated multiple basaloid islands of tumor cells in the reticular dermis with ductal differentiation, some with a commalike tail. The ducts were lined by 2 to 3 layers of small uniform cuboidal cells without atypia and contained inspissated secretions within the lumina of scattered ducts. There was an associated fibrotic collagenous stroma. There was no evidence of perineural invasion and no deep dermal or subcutaneous extension (Figure 1). Additional cytokeratin immunohistochemical staining highlighted the adnexal proliferation (Figure 2). A diagnosis of plaque-type syringoma (PTS) was made.

Syringomas are benign dermal sweat gland tumors that typically present as flesh-colored papules on the cheeks or periorbital area of young females. Plaque-type tumors as well as papulonodular, eruptive, disseminated, urticaria pigmentosa–like, lichen planus–like, or milialike syringomas also have been reported. Syringomas may be associated with certain medical conditions such as Down syndrome, Nicolau-Balus syndrome, and both scarring and nonscarring alopecias.¹ The clear cell variant of syringoma often is associated with diabetes mellitus.² Kikuchi et al³ first described PTS in 1979. Plaque-type syringomas rarely are reported in the literature, and sites of involvement include the head and neck region, upper lip, chest, upper extremities, vulva, penis, and scrotum.^4-6

Histologically, syringomatous lesions are composed of multiple small ducts lined by 2 to 3 layers of cuboidal epithelium. The ducts may be arranged in nests or strands of basaloid cells surrounded by a dense fibrotic stroma. Occasionally, the ducts will form a comma- or teardropshaped tail; however, this also may be observed in desmoplastic trichoepithelioma (DTE).⁷ Perineural invasion is absent in syringomas. Syringomas exhibit a lateral growth pattern that typically is limited to the upper half of the reticular dermis and spares the underlying subcutis, muscle, and bone. The growth pattern may be discontinuous with proliferations juxtaposed by normal-appearing skin.⁸ Syringomas usually express progesterone receptors and are known to proliferate at puberty, suggesting that these neoplasms are under hormonal control.⁹ Although syringomas are benign, various treatment options that may be pursued for cosmetic purposes include radiofrequency, staged excision, laser ablation, and oral isotretinoin.^8,10 If only a superficial biopsy is obtained, syringomas may display features of other adnexal neoplasms, including microcystic adnexal carcinoma (MAC), DTE, morpheaform basal cell carcinoma (BCC), and inflammatory linear verrucous epidermal nevus (ILVEN).

Microcystic adnexal carcinoma is a locally aggressive neoplasm first described by Goldstein et al¹¹ in 1982 an indurated, ill-defined plaque or nodule on the face with a predilection for the upper and lower lip. Prior radiation therapy and immunosuppression are risk factors for the development of MAC.¹² Histologically, the superficial portion displays small cornifying cysts interspersed with islands of basaloid cells and may mimic a syringoma. However, the deeper portions demonstrate ducts lined by a single layer of cells with a background of hyalinized and sclerotic stroma. The tumor cells may occupy the deep dermis and underlying subcutis, muscle, or bone and demonstrate an infiltrative growth pattern and perineural invasion. Treatment includes Mohs micrographic surgery.

Desmoplastic trichoepitheliomas most commonly present as solitary white to yellowish annular papules or plaques with a central dell located on sun-exposed areas of the face, cheeks, or chin. This benign neoplasm has a bimodal age distribution, primarily affecting females either in childhood or adulthood.¹³ Histologically, strands and nests of basaloid epithelial cells proliferate in a dense eosinophilic desmoplastic stroma. The basaloid islands are narrow and cordlike with growth parallel to the surface epidermis and do not dive deeply into the deep dermis or subcutis. Ductal differentiation with associated secretions typically is not seen in DTE.¹ Calcifications and foreign body granulomatous infiltrates may be present. Merkel cells also are present in this tumor and may be highlighted by immunohistochemistry with cytokeratin 20.¹⁴ Rarely, desmoplastic trichoepitheliomas may transform into trichoblastic carcinomas. Treatment may consist of surgical excision or Mohs micrographic surgery.

Morpheaform BCC also is included in the clinical and histopathologic differential diagnosis of infiltrative basaloid neoplasms. It is one of the more aggressive variants of BCC. The use of immunohistochemical staining may aid in differentiating between these sclerosing adnexal neoplasms.¹⁵ For example, pleckstrin homologylike domain family A member 1 (PHLDA1) is a stem cell marker that is heavily expressed in DTE as a specific follicular bulge marker but is not present in a morpheaform BCC. This highlights the follicular nature of DTEs at the molecular level. BerEP4 is a monoclonal antibody that serves as an epithelial marker for 2 glycopolypeptides: 34 and 39 kDa. This antibody may demonstrate positivity in morpheaform BCC but does not stain cells of interest in MAC.

Inflammatory linear verrucous epidermal nevus clinically presents with erythematous and warty papules in a linear distribution following the Blaschko lines. The papules often are reported to be intensely pruritic and usually are localized to one extremity.¹⁶ Although adultonset forms of ILVEN have been described,¹⁷ it most commonly is diagnosed in young children. Histologically, ILVEN consists of psoriasiform epidermal hyperplasia with alternating areas of parakeratosis and orthokeratosis with underlying agranulosis and hypergranulosis, respectively.¹⁸ The upper dermis contains a perivascular lymphocytic infiltrate. Treatment with laser therapy and surgical excision has led to both symptomatic and clinical improvement of ILVEN.¹⁶

Plaque-type syringomas are a rare variant of syringomas that clinically may mimic other common inflammatory and neoplastic conditions. An adequate biopsy is imperative to differentiate between adnexal neoplasms, as a small superficial biopsy of a syringoma may demonstrate features observed in other malignant or locally aggressive neoplasms. In our patient, the small ducts lined by cuboidal epithelium with no cellular atypia and no deep dermal growth or perineural invasion allowed for the diagnosis of PTS. Therapeutic options were reviewed with our patient, including oral isotretinoin, laser therapy, and staged excision. Ultimately, our patient elected not to pursue treatment, and she is being monitored clinically for any changes in appearance or symptoms.

The Diagnosis: Plaque-type Syringoma

A biopsy demonstrated multiple basaloid islands of tumor cells in the reticular dermis with ductal differentiation, some with a commalike tail. The ducts were lined by 2 to 3 layers of small uniform cuboidal cells without atypia and contained inspissated secretions within the lumina of scattered ducts. There was an associated fibrotic collagenous stroma. There was no evidence of perineural invasion and no deep dermal or subcutaneous extension (Figure 1). Additional cytokeratin immunohistochemical staining highlighted the adnexal proliferation (Figure 2). A diagnosis of plaque-type syringoma (PTS) was made.

Syringomas are benign dermal sweat gland tumors that typically present as flesh-colored papules on the cheeks or periorbital area of young females. Plaque-type tumors as well as papulonodular, eruptive, disseminated, urticaria pigmentosa–like, lichen planus–like, or milialike syringomas also have been reported. Syringomas may be associated with certain medical conditions such as Down syndrome, Nicolau-Balus syndrome, and both scarring and nonscarring alopecias.¹ The clear cell variant of syringoma often is associated with diabetes mellitus.² Kikuchi et al³ first described PTS in 1979. Plaque-type syringomas rarely are reported in the literature, and sites of involvement include the head and neck region, upper lip, chest, upper extremities, vulva, penis, and scrotum.^4-6

Histologically, syringomatous lesions are composed of multiple small ducts lined by 2 to 3 layers of cuboidal epithelium. The ducts may be arranged in nests or strands of basaloid cells surrounded by a dense fibrotic stroma. Occasionally, the ducts will form a comma- or teardropshaped tail; however, this also may be observed in desmoplastic trichoepithelioma (DTE).⁷ Perineural invasion is absent in syringomas. Syringomas exhibit a lateral growth pattern that typically is limited to the upper half of the reticular dermis and spares the underlying subcutis, muscle, and bone. The growth pattern may be discontinuous with proliferations juxtaposed by normal-appearing skin.⁸ Syringomas usually express progesterone receptors and are known to proliferate at puberty, suggesting that these neoplasms are under hormonal control.⁹ Although syringomas are benign, various treatment options that may be pursued for cosmetic purposes include radiofrequency, staged excision, laser ablation, and oral isotretinoin.^8,10 If only a superficial biopsy is obtained, syringomas may display features of other adnexal neoplasms, including microcystic adnexal carcinoma (MAC), DTE, morpheaform basal cell carcinoma (BCC), and inflammatory linear verrucous epidermal nevus (ILVEN).

Microcystic adnexal carcinoma is a locally aggressive neoplasm first described by Goldstein et al¹¹ in 1982 an indurated, ill-defined plaque or nodule on the face with a predilection for the upper and lower lip. Prior radiation therapy and immunosuppression are risk factors for the development of MAC.¹² Histologically, the superficial portion displays small cornifying cysts interspersed with islands of basaloid cells and may mimic a syringoma. However, the deeper portions demonstrate ducts lined by a single layer of cells with a background of hyalinized and sclerotic stroma. The tumor cells may occupy the deep dermis and underlying subcutis, muscle, or bone and demonstrate an infiltrative growth pattern and perineural invasion. Treatment includes Mohs micrographic surgery.

Desmoplastic trichoepitheliomas most commonly present as solitary white to yellowish annular papules or plaques with a central dell located on sun-exposed areas of the face, cheeks, or chin. This benign neoplasm has a bimodal age distribution, primarily affecting females either in childhood or adulthood.¹³ Histologically, strands and nests of basaloid epithelial cells proliferate in a dense eosinophilic desmoplastic stroma. The basaloid islands are narrow and cordlike with growth parallel to the surface epidermis and do not dive deeply into the deep dermis or subcutis. Ductal differentiation with associated secretions typically is not seen in DTE.¹ Calcifications and foreign body granulomatous infiltrates may be present. Merkel cells also are present in this tumor and may be highlighted by immunohistochemistry with cytokeratin 20.¹⁴ Rarely, desmoplastic trichoepitheliomas may transform into trichoblastic carcinomas. Treatment may consist of surgical excision or Mohs micrographic surgery.

Morpheaform BCC also is included in the clinical and histopathologic differential diagnosis of infiltrative basaloid neoplasms. It is one of the more aggressive variants of BCC. The use of immunohistochemical staining may aid in differentiating between these sclerosing adnexal neoplasms.¹⁵ For example, pleckstrin homologylike domain family A member 1 (PHLDA1) is a stem cell marker that is heavily expressed in DTE as a specific follicular bulge marker but is not present in a morpheaform BCC. This highlights the follicular nature of DTEs at the molecular level. BerEP4 is a monoclonal antibody that serves as an epithelial marker for 2 glycopolypeptides: 34 and 39 kDa. This antibody may demonstrate positivity in morpheaform BCC but does not stain cells of interest in MAC.

Inflammatory linear verrucous epidermal nevus clinically presents with erythematous and warty papules in a linear distribution following the Blaschko lines. The papules often are reported to be intensely pruritic and usually are localized to one extremity.¹⁶ Although adultonset forms of ILVEN have been described,¹⁷ it most commonly is diagnosed in young children. Histologically, ILVEN consists of psoriasiform epidermal hyperplasia with alternating areas of parakeratosis and orthokeratosis with underlying agranulosis and hypergranulosis, respectively.¹⁸ The upper dermis contains a perivascular lymphocytic infiltrate. Treatment with laser therapy and surgical excision has led to both symptomatic and clinical improvement of ILVEN.¹⁶

Plaque-type syringomas are a rare variant of syringomas that clinically may mimic other common inflammatory and neoplastic conditions. An adequate biopsy is imperative to differentiate between adnexal neoplasms, as a small superficial biopsy of a syringoma may demonstrate features observed in other malignant or locally aggressive neoplasms. In our patient, the small ducts lined by cuboidal epithelium with no cellular atypia and no deep dermal growth or perineural invasion allowed for the diagnosis of PTS. Therapeutic options were reviewed with our patient, including oral isotretinoin, laser therapy, and staged excision. Ultimately, our patient elected not to pursue treatment, and she is being monitored clinically for any changes in appearance or symptoms.

The Diagnosis: Elephantiasis Nostras Verrucosa

Histopathology revealed a benign fibroepithelial polyp demonstrating areas of hyperkeratosis, acanthosis, and focal papillomatosis (Figure, A). Increased superficial vessels with dilated lymphatics, stellate fibroblasts, edematous stroma, and plasmolymphocytosis also were noted (Figure, B). Clinical and histopathological findings led to a diagnosis of lymphedema papules in the setting of elephantiasis nostra verrucosa (ENV).

Elephantiasis nostras verrucosa is a complication of long-standing nonfilarial obstruction of lymphatic drainage leading to grotesque enlargement of the affected areas. Common cutaneous manifestations of ENV include nonpitting edema, dermal fibrosis, and extensive hyperkeratosis with verrucous and papillomatous lesions.¹ In the beginning stages of ENV, the skin has a cobblestonelike appearance. As the disease progresses, the verrucous lesions continue to enlarge, giving the affected area a mossy appearance. Although less common, groupings of large papillomas similar to our patient’s presentation also can form.² Ulcer formation is more likely to occur in advanced disease states, increasing the risk for bacterial and fungal colonization. Elephantiasis nostras verrucosa classically affects the legs; however, this condition can develop in any area with chronic lymphedema. Cases of ENV involving the arms, abdomen, scrotum, and ear have been documented.^3-5

The pathogenesis of ENV involves the proliferation of fibroblasts and fibrosis secondary to lymphostasis and inflammation.⁶ When interstitial fluid builds up in the affected region, the protein-rich fluid is believed to trigger fibrogenesis and increase macrophage, keratinocyte, and adipocyte activity.⁷ Because of this inflammatory process, dilation and fibrosis of the lymphatic channels develop. Lymphatic obstruction can have several etiologies, most notably infection and malignancy. Staphylococcal lymphangitis and erysipelas create fibrosis of the lymphatic system and are the main infectious causes of ENV.⁶ Large tumors or lymphomas are insidious causes of lymphatic obstruction and should be ruled out when investigating for ENV. Other risk factors include obesity, chronic venous insufficiency, surgery, trauma, radiation, and uncontrolled congestive heart failure.^1,6,8

An ENV diagnosis is clinicopathologic, involving a comprehensive metabolic panel and complete blood cell count with differential. A biopsy is needed for pathologic confirmation and to rule out malignancy. Histologically, ENV is characterized by pseudoepitheliomatous hyperplasia, dermal fibrosis, hyperkeratosis of the epidermis, and dilated lymphatic vessels.^6,8 Additional studies for diagnosis include wound and lymph node culture, Wood lamp examination, and lymphoscintigraphy.

Given the chronic and progressive nature of the disease, ENV is difficult to treat. There currently is no standard of treatment, but the mainstay of management involves reducing peripheral edema. Lifestyle changes including weight loss, extremity elevation, and increased ambulation are helpful first-line therapies.³ Compression of the affected extremity using stockings or intermittent pneumatic compression devices has proven to be beneficial with long-term use.⁷ Patients should be followed for wound care to prevent the infection of ulcers.² Pharmacologic treatments include systemic retinoids, which have been shown to reduce the appearance of hyperkeratosis, verrucous lesions, and papillomatous nodules.⁶ Prophylactic antibiotics are reserved for advanced stages of disease or in patients with recurrent infections.^2,7 In severe cases of ENV that are unresponsive to medical management, surgical intervention such as lymphatic anastomosis and debulking may be considered.^9,10

Other diagnoses to consider for ENV include pretibial myxedema, lymphatic filariasis, Stewart-Treves syndrome, and papillomatosis cutis carcinoides. Pretibial myxedema is an uncommon dermatologic manifestation of Graves disease. It is a local autoimmune reaction in the cutaneous tissue characterized by hyperpigmentation, nonpitting edema, and nodules on the anterior leg. Histopathology shows increased hyaluronic acid and chondroitin as well as compression of dermal lymphatics.¹¹

Filariasis is a parasitic infection caused by Wuchereria bancrofti, Brugia malayi or Brugia timori, and Onchocerca volvulus.⁶ This condition presents with elephantiasis of the affected extremities but should be considered in areas endemic for filarial parasites such as tropical and subtropical countries.¹² Eosinophilia and identification of microfilaria in a peripheral blood smear would indicate parasitic infection. Stewart-Treves syndrome is a rare angiosarcoma that arises in areas of chronic lymphedema. This condition classically is seen on the upper extremities following a mastectomy with lymphadenectomy, lymph node irradiation, or both.

Stewart-Treves syndrome presents with coalescing purpuric macules and nodules that eventually coalesce into cutaneous masses. Histopathology reveals proliferating vascular channels that split apart dermal collagen with hyperchromatism and pleomorphism in the tumor endothelial cells that line these channels.¹³

Papillomatosis cutis carcinoides is a low-grade squamous cell carcinoma that occurs secondary to human papillomavirus commonly affecting the mouth, anogenital area, and the plantar surfaces of the feet. It presents with exophytic growths and ulcerated tumors that are unilateral and asymmetrical. The presence of blunt-shaped tumor projections extending deep into the dermis to form sinuses and keratin-filled cysts is characteristic of papillomatosis cutis carcinoides.¹⁴

The Diagnosis: Elephantiasis Nostras Verrucosa

Histopathology revealed a benign fibroepithelial polyp demonstrating areas of hyperkeratosis, acanthosis, and focal papillomatosis (Figure, A). Increased superficial vessels with dilated lymphatics, stellate fibroblasts, edematous stroma, and plasmolymphocytosis also were noted (Figure, B). Clinical and histopathological findings led to a diagnosis of lymphedema papules in the setting of elephantiasis nostra verrucosa (ENV).

Elephantiasis nostras verrucosa is a complication of long-standing nonfilarial obstruction of lymphatic drainage leading to grotesque enlargement of the affected areas. Common cutaneous manifestations of ENV include nonpitting edema, dermal fibrosis, and extensive hyperkeratosis with verrucous and papillomatous lesions.¹ In the beginning stages of ENV, the skin has a cobblestonelike appearance. As the disease progresses, the verrucous lesions continue to enlarge, giving the affected area a mossy appearance. Although less common, groupings of large papillomas similar to our patient’s presentation also can form.² Ulcer formation is more likely to occur in advanced disease states, increasing the risk for bacterial and fungal colonization. Elephantiasis nostras verrucosa classically affects the legs; however, this condition can develop in any area with chronic lymphedema. Cases of ENV involving the arms, abdomen, scrotum, and ear have been documented.^3-5

The pathogenesis of ENV involves the proliferation of fibroblasts and fibrosis secondary to lymphostasis and inflammation.⁶ When interstitial fluid builds up in the affected region, the protein-rich fluid is believed to trigger fibrogenesis and increase macrophage, keratinocyte, and adipocyte activity.⁷ Because of this inflammatory process, dilation and fibrosis of the lymphatic channels develop. Lymphatic obstruction can have several etiologies, most notably infection and malignancy. Staphylococcal lymphangitis and erysipelas create fibrosis of the lymphatic system and are the main infectious causes of ENV.⁶ Large tumors or lymphomas are insidious causes of lymphatic obstruction and should be ruled out when investigating for ENV. Other risk factors include obesity, chronic venous insufficiency, surgery, trauma, radiation, and uncontrolled congestive heart failure.^1,6,8

An ENV diagnosis is clinicopathologic, involving a comprehensive metabolic panel and complete blood cell count with differential. A biopsy is needed for pathologic confirmation and to rule out malignancy. Histologically, ENV is characterized by pseudoepitheliomatous hyperplasia, dermal fibrosis, hyperkeratosis of the epidermis, and dilated lymphatic vessels.^6,8 Additional studies for diagnosis include wound and lymph node culture, Wood lamp examination, and lymphoscintigraphy.

Given the chronic and progressive nature of the disease, ENV is difficult to treat. There currently is no standard of treatment, but the mainstay of management involves reducing peripheral edema. Lifestyle changes including weight loss, extremity elevation, and increased ambulation are helpful first-line therapies.³ Compression of the affected extremity using stockings or intermittent pneumatic compression devices has proven to be beneficial with long-term use.⁷ Patients should be followed for wound care to prevent the infection of ulcers.² Pharmacologic treatments include systemic retinoids, which have been shown to reduce the appearance of hyperkeratosis, verrucous lesions, and papillomatous nodules.⁶ Prophylactic antibiotics are reserved for advanced stages of disease or in patients with recurrent infections.^2,7 In severe cases of ENV that are unresponsive to medical management, surgical intervention such as lymphatic anastomosis and debulking may be considered.^9,10

Other diagnoses to consider for ENV include pretibial myxedema, lymphatic filariasis, Stewart-Treves syndrome, and papillomatosis cutis carcinoides. Pretibial myxedema is an uncommon dermatologic manifestation of Graves disease. It is a local autoimmune reaction in the cutaneous tissue characterized by hyperpigmentation, nonpitting edema, and nodules on the anterior leg. Histopathology shows increased hyaluronic acid and chondroitin as well as compression of dermal lymphatics.¹¹

Filariasis is a parasitic infection caused by Wuchereria bancrofti, Brugia malayi or Brugia timori, and Onchocerca volvulus.⁶ This condition presents with elephantiasis of the affected extremities but should be considered in areas endemic for filarial parasites such as tropical and subtropical countries.¹² Eosinophilia and identification of microfilaria in a peripheral blood smear would indicate parasitic infection. Stewart-Treves syndrome is a rare angiosarcoma that arises in areas of chronic lymphedema. This condition classically is seen on the upper extremities following a mastectomy with lymphadenectomy, lymph node irradiation, or both.

Stewart-Treves syndrome presents with coalescing purpuric macules and nodules that eventually coalesce into cutaneous masses. Histopathology reveals proliferating vascular channels that split apart dermal collagen with hyperchromatism and pleomorphism in the tumor endothelial cells that line these channels.¹³

Papillomatosis cutis carcinoides is a low-grade squamous cell carcinoma that occurs secondary to human papillomavirus commonly affecting the mouth, anogenital area, and the plantar surfaces of the feet. It presents with exophytic growths and ulcerated tumors that are unilateral and asymmetrical. The presence of blunt-shaped tumor projections extending deep into the dermis to form sinuses and keratin-filled cysts is characteristic of papillomatosis cutis carcinoides.¹⁴

The Diagnosis: Elephantiasis Nostras Verrucosa

Histopathology revealed a benign fibroepithelial polyp demonstrating areas of hyperkeratosis, acanthosis, and focal papillomatosis (Figure, A). Increased superficial vessels with dilated lymphatics, stellate fibroblasts, edematous stroma, and plasmolymphocytosis also were noted (Figure, B). Clinical and histopathological findings led to a diagnosis of lymphedema papules in the setting of elephantiasis nostra verrucosa (ENV).

Elephantiasis nostras verrucosa is a complication of long-standing nonfilarial obstruction of lymphatic drainage leading to grotesque enlargement of the affected areas. Common cutaneous manifestations of ENV include nonpitting edema, dermal fibrosis, and extensive hyperkeratosis with verrucous and papillomatous lesions.¹ In the beginning stages of ENV, the skin has a cobblestonelike appearance. As the disease progresses, the verrucous lesions continue to enlarge, giving the affected area a mossy appearance. Although less common, groupings of large papillomas similar to our patient’s presentation also can form.² Ulcer formation is more likely to occur in advanced disease states, increasing the risk for bacterial and fungal colonization. Elephantiasis nostras verrucosa classically affects the legs; however, this condition can develop in any area with chronic lymphedema. Cases of ENV involving the arms, abdomen, scrotum, and ear have been documented.^3-5

The pathogenesis of ENV involves the proliferation of fibroblasts and fibrosis secondary to lymphostasis and inflammation.⁶ When interstitial fluid builds up in the affected region, the protein-rich fluid is believed to trigger fibrogenesis and increase macrophage, keratinocyte, and adipocyte activity.⁷ Because of this inflammatory process, dilation and fibrosis of the lymphatic channels develop. Lymphatic obstruction can have several etiologies, most notably infection and malignancy. Staphylococcal lymphangitis and erysipelas create fibrosis of the lymphatic system and are the main infectious causes of ENV.⁶ Large tumors or lymphomas are insidious causes of lymphatic obstruction and should be ruled out when investigating for ENV. Other risk factors include obesity, chronic venous insufficiency, surgery, trauma, radiation, and uncontrolled congestive heart failure.^1,6,8

An ENV diagnosis is clinicopathologic, involving a comprehensive metabolic panel and complete blood cell count with differential. A biopsy is needed for pathologic confirmation and to rule out malignancy. Histologically, ENV is characterized by pseudoepitheliomatous hyperplasia, dermal fibrosis, hyperkeratosis of the epidermis, and dilated lymphatic vessels.^6,8 Additional studies for diagnosis include wound and lymph node culture, Wood lamp examination, and lymphoscintigraphy.

Given the chronic and progressive nature of the disease, ENV is difficult to treat. There currently is no standard of treatment, but the mainstay of management involves reducing peripheral edema. Lifestyle changes including weight loss, extremity elevation, and increased ambulation are helpful first-line therapies.³ Compression of the affected extremity using stockings or intermittent pneumatic compression devices has proven to be beneficial with long-term use.⁷ Patients should be followed for wound care to prevent the infection of ulcers.² Pharmacologic treatments include systemic retinoids, which have been shown to reduce the appearance of hyperkeratosis, verrucous lesions, and papillomatous nodules.⁶ Prophylactic antibiotics are reserved for advanced stages of disease or in patients with recurrent infections.^2,7 In severe cases of ENV that are unresponsive to medical management, surgical intervention such as lymphatic anastomosis and debulking may be considered.^9,10

Other diagnoses to consider for ENV include pretibial myxedema, lymphatic filariasis, Stewart-Treves syndrome, and papillomatosis cutis carcinoides. Pretibial myxedema is an uncommon dermatologic manifestation of Graves disease. It is a local autoimmune reaction in the cutaneous tissue characterized by hyperpigmentation, nonpitting edema, and nodules on the anterior leg. Histopathology shows increased hyaluronic acid and chondroitin as well as compression of dermal lymphatics.¹¹

Filariasis is a parasitic infection caused by Wuchereria bancrofti, Brugia malayi or Brugia timori, and Onchocerca volvulus.⁶ This condition presents with elephantiasis of the affected extremities but should be considered in areas endemic for filarial parasites such as tropical and subtropical countries.¹² Eosinophilia and identification of microfilaria in a peripheral blood smear would indicate parasitic infection. Stewart-Treves syndrome is a rare angiosarcoma that arises in areas of chronic lymphedema. This condition classically is seen on the upper extremities following a mastectomy with lymphadenectomy, lymph node irradiation, or both.

Stewart-Treves syndrome presents with coalescing purpuric macules and nodules that eventually coalesce into cutaneous masses. Histopathology reveals proliferating vascular channels that split apart dermal collagen with hyperchromatism and pleomorphism in the tumor endothelial cells that line these channels.¹³

Papillomatosis cutis carcinoides is a low-grade squamous cell carcinoma that occurs secondary to human papillomavirus commonly affecting the mouth, anogenital area, and the plantar surfaces of the feet. It presents with exophytic growths and ulcerated tumors that are unilateral and asymmetrical. The presence of blunt-shaped tumor projections extending deep into the dermis to form sinuses and keratin-filled cysts is characteristic of papillomatosis cutis carcinoides.¹⁴

To the Editor:

Focal palmoplantar keratoderma and gingival keratosis (FPGK)(Online Mendelian Inheritance in Man [OMIM] 148730) is a rare autosomal-dominant syndrome featuring focal, pressure-related, painful palmoplantar keratoderma and gingival hyperkeratosis presenting as leukokeratosis. Focal palmoplantar keratoderma and gingival keratosis was first defined by Gorlin¹ in 1976. Since then, only a few cases have been reported, but no causative mutations have been identified.²

Focal pressure-related palmoplantar keratoderma (PPK) and oral hyperkeratosis also are seen in pachyonychia congenita (PC)(OMIM 167200, 615726, 615728, 167210), a rare autosomal-dominant disorder of keratinization characterized by PPK and nail dystrophy. Patients with PC often present with plantar pain; more variable features include oral leukokeratosis, follicular hyperkeratosis, pilosebaceous and epidermal inclusion cysts, hoarseness, hyperhidrosis, and natal teeth. Pachyonychia congenita is caused by mutation in keratin genes KRT6A, KRT6B, KRT16, or KRT17.

Focal palmoplantar keratoderma and gingival keratosis as well as PC are distinct from other forms of PPK with gingival involvement such as Papillon-Lefèvre syndrome (OMIM 245000) and Olmsted syndrome (OMIM 614594). Papillon-Lefèvre syndrome is a rare autosomal-recessive disorder caused by mutations in the cathepsin C, CTSC, gene that exhibits erythematous, diffuse, transgradient PPK and early severe periodontitis. Olmsted syndrome is caused by autosomal-dominant gene mutations in transient receptor potential cation channel, subfamily V, member 3, TRPV3, and is characterized by severe bilateral transgradient PPK with leukoplakia of the tongue and buccal mucosa but also usually exhibits marked periorificial keratotic plaques, which facilitate exclusion of other phenotypically similar syndromes.³

Despite the common features of FPGK and PC, they are considered distinct disorders due to absence of nail changes in FPGK and no prior evidence of a common genetic cause. We present a patient with familial FPGK found by whole exome sequencing to be caused by a mutation in KRT16.

The proband was a 57-year-old man born to unrelated parents (Figure 1). He had no skin problems at birth, and his development was normal. He had painful focal keratoderma since childhood that were most prominent at pressure points on the soles and toes (Figure 2A), in addition to gingival hyperkeratosis and oral leukokeratosis (Figure 2B). He had no associated abnormalities of the skin, hair, or teeth and no nail findings (Figure 2C). He reported that his father and 2 of his 3 sisters were affected with similar symptoms. A punch biopsy of the right fifth toe was consistent with verrucous epidermal hyperplasia with perinuclear keratinization in the spinous layer (Figure 3A). A gingival biopsy showed perinuclear eosinophilic globules and basophilic stranding in the cytoplasm (Figure 3B). His older sister had more severe and painful focal keratoderma of the soles, punctate keratoderma of the palms, gingival hyperkeratosis, and leukokeratosis of the tongue.

Whole exome sequencing of the proband revealed a heterozygous missense mutation in KRT16 (c.380G>A, p.R127H, rs57424749). Sanger sequencing confirmed this mutation and showed that it was heterozygous in both of his affected sisters and absent in his unaffected niece (Figure 1). The patient was treated with topical and systemic retinoids, keratolytics, and mechanical removal to moderate effect, with noted improvement in the appearance and associated pain of the plantar keratoderma.

Phenotypic heterogeneity is common in PC, though PC due to KRT6A mutations demonstrates more severe nail disease with oral lesions, cysts, and follicular hyperkeratosis, while PC caused by KRT16 mutations generally presents with more extensive and painful PPK.⁴KRT16 mutations affecting p.R127 are frequent causes of PC, and genotype-phenotype correlations have been observed. Individuals with p.R127P mutations exhibit more severe disease with earlier age of onset, more extensive nail involvement and oral leukokeratosis, and greater impact on daily quality of life than in individuals with p.R127C mutations.⁵ Cases of PC with KRT16 p.R127S and p.R127G mutations also have been observed. The KRT16 c.380G>A, p.R127H mutation we documented has been reported in one kindred with PC who presented with PPK, oral leukokeratosis, toenail thickening, and pilosebaceous and follicular hyperkeratosis.⁶

Although patients with FPGK lack the thickening of fingernails and/or toenails considered a defining feature of PC, the disorders otherwise are phenotypically similar, suggesting the possibility of common pathogenesis. One linkage study of familial FPGK excluded genetic intervals containing type I and type II keratins but was limited to a single small kindred.² This study and our data together suggest that, similar to PC, there are multiple genes in which mutations cause FPGK.

Murine Krt16 knockouts show distinct phenotypes depending on the mouse strain in which they are propagated, ranging from perinatal lethality to differences in the severity of oral and PPK lesions.⁷ These observations provide evidence that additional genetic variants contribute to Krt16 phenotypes in mice and suggest the same could be true for humans.

We propose that some cases of FPGK are due to mutations in KRT16 and thus share a genetic pathogenesis with PC, underscoring the utility of whole exome sequencing in providing genetic diagnoses for disorders that are genetically and clinically heterogeneous. Further biologic investigation of phenotypes caused by KRT16 mutation may reveal respective contributions of additional genetic variation and environmental effects to the variable clinical presentations.

To the Editor:

Focal palmoplantar keratoderma and gingival keratosis (FPGK)(Online Mendelian Inheritance in Man [OMIM] 148730) is a rare autosomal-dominant syndrome featuring focal, pressure-related, painful palmoplantar keratoderma and gingival hyperkeratosis presenting as leukokeratosis. Focal palmoplantar keratoderma and gingival keratosis was first defined by Gorlin¹ in 1976. Since then, only a few cases have been reported, but no causative mutations have been identified.²

Focal pressure-related palmoplantar keratoderma (PPK) and oral hyperkeratosis also are seen in pachyonychia congenita (PC)(OMIM 167200, 615726, 615728, 167210), a rare autosomal-dominant disorder of keratinization characterized by PPK and nail dystrophy. Patients with PC often present with plantar pain; more variable features include oral leukokeratosis, follicular hyperkeratosis, pilosebaceous and epidermal inclusion cysts, hoarseness, hyperhidrosis, and natal teeth. Pachyonychia congenita is caused by mutation in keratin genes KRT6A, KRT6B, KRT16, or KRT17.

Focal palmoplantar keratoderma and gingival keratosis as well as PC are distinct from other forms of PPK with gingival involvement such as Papillon-Lefèvre syndrome (OMIM 245000) and Olmsted syndrome (OMIM 614594). Papillon-Lefèvre syndrome is a rare autosomal-recessive disorder caused by mutations in the cathepsin C, CTSC, gene that exhibits erythematous, diffuse, transgradient PPK and early severe periodontitis. Olmsted syndrome is caused by autosomal-dominant gene mutations in transient receptor potential cation channel, subfamily V, member 3, TRPV3, and is characterized by severe bilateral transgradient PPK with leukoplakia of the tongue and buccal mucosa but also usually exhibits marked periorificial keratotic plaques, which facilitate exclusion of other phenotypically similar syndromes.³

Despite the common features of FPGK and PC, they are considered distinct disorders due to absence of nail changes in FPGK and no prior evidence of a common genetic cause. We present a patient with familial FPGK found by whole exome sequencing to be caused by a mutation in KRT16.

The proband was a 57-year-old man born to unrelated parents (Figure 1). He had no skin problems at birth, and his development was normal. He had painful focal keratoderma since childhood that were most prominent at pressure points on the soles and toes (Figure 2A), in addition to gingival hyperkeratosis and oral leukokeratosis (Figure 2B). He had no associated abnormalities of the skin, hair, or teeth and no nail findings (Figure 2C). He reported that his father and 2 of his 3 sisters were affected with similar symptoms. A punch biopsy of the right fifth toe was consistent with verrucous epidermal hyperplasia with perinuclear keratinization in the spinous layer (Figure 3A). A gingival biopsy showed perinuclear eosinophilic globules and basophilic stranding in the cytoplasm (Figure 3B). His older sister had more severe and painful focal keratoderma of the soles, punctate keratoderma of the palms, gingival hyperkeratosis, and leukokeratosis of the tongue.

Whole exome sequencing of the proband revealed a heterozygous missense mutation in KRT16 (c.380G>A, p.R127H, rs57424749). Sanger sequencing confirmed this mutation and showed that it was heterozygous in both of his affected sisters and absent in his unaffected niece (Figure 1). The patient was treated with topical and systemic retinoids, keratolytics, and mechanical removal to moderate effect, with noted improvement in the appearance and associated pain of the plantar keratoderma.

Phenotypic heterogeneity is common in PC, though PC due to KRT6A mutations demonstrates more severe nail disease with oral lesions, cysts, and follicular hyperkeratosis, while PC caused by KRT16 mutations generally presents with more extensive and painful PPK.⁴KRT16 mutations affecting p.R127 are frequent causes of PC, and genotype-phenotype correlations have been observed. Individuals with p.R127P mutations exhibit more severe disease with earlier age of onset, more extensive nail involvement and oral leukokeratosis, and greater impact on daily quality of life than in individuals with p.R127C mutations.⁵ Cases of PC with KRT16 p.R127S and p.R127G mutations also have been observed. The KRT16 c.380G>A, p.R127H mutation we documented has been reported in one kindred with PC who presented with PPK, oral leukokeratosis, toenail thickening, and pilosebaceous and follicular hyperkeratosis.⁶

Although patients with FPGK lack the thickening of fingernails and/or toenails considered a defining feature of PC, the disorders otherwise are phenotypically similar, suggesting the possibility of common pathogenesis. One linkage study of familial FPGK excluded genetic intervals containing type I and type II keratins but was limited to a single small kindred.² This study and our data together suggest that, similar to PC, there are multiple genes in which mutations cause FPGK.

Murine Krt16 knockouts show distinct phenotypes depending on the mouse strain in which they are propagated, ranging from perinatal lethality to differences in the severity of oral and PPK lesions.⁷ These observations provide evidence that additional genetic variants contribute to Krt16 phenotypes in mice and suggest the same could be true for humans.

We propose that some cases of FPGK are due to mutations in KRT16 and thus share a genetic pathogenesis with PC, underscoring the utility of whole exome sequencing in providing genetic diagnoses for disorders that are genetically and clinically heterogeneous. Further biologic investigation of phenotypes caused by KRT16 mutation may reveal respective contributions of additional genetic variation and environmental effects to the variable clinical presentations.

To the Editor:

Focal palmoplantar keratoderma and gingival keratosis (FPGK)(Online Mendelian Inheritance in Man [OMIM] 148730) is a rare autosomal-dominant syndrome featuring focal, pressure-related, painful palmoplantar keratoderma and gingival hyperkeratosis presenting as leukokeratosis. Focal palmoplantar keratoderma and gingival keratosis was first defined by Gorlin¹ in 1976. Since then, only a few cases have been reported, but no causative mutations have been identified.²

Focal pressure-related palmoplantar keratoderma (PPK) and oral hyperkeratosis also are seen in pachyonychia congenita (PC)(OMIM 167200, 615726, 615728, 167210), a rare autosomal-dominant disorder of keratinization characterized by PPK and nail dystrophy. Patients with PC often present with plantar pain; more variable features include oral leukokeratosis, follicular hyperkeratosis, pilosebaceous and epidermal inclusion cysts, hoarseness, hyperhidrosis, and natal teeth. Pachyonychia congenita is caused by mutation in keratin genes KRT6A, KRT6B, KRT16, or KRT17.

Focal palmoplantar keratoderma and gingival keratosis as well as PC are distinct from other forms of PPK with gingival involvement such as Papillon-Lefèvre syndrome (OMIM 245000) and Olmsted syndrome (OMIM 614594). Papillon-Lefèvre syndrome is a rare autosomal-recessive disorder caused by mutations in the cathepsin C, CTSC, gene that exhibits erythematous, diffuse, transgradient PPK and early severe periodontitis. Olmsted syndrome is caused by autosomal-dominant gene mutations in transient receptor potential cation channel, subfamily V, member 3, TRPV3, and is characterized by severe bilateral transgradient PPK with leukoplakia of the tongue and buccal mucosa but also usually exhibits marked periorificial keratotic plaques, which facilitate exclusion of other phenotypically similar syndromes.³

Despite the common features of FPGK and PC, they are considered distinct disorders due to absence of nail changes in FPGK and no prior evidence of a common genetic cause. We present a patient with familial FPGK found by whole exome sequencing to be caused by a mutation in KRT16.

The proband was a 57-year-old man born to unrelated parents (Figure 1). He had no skin problems at birth, and his development was normal. He had painful focal keratoderma since childhood that were most prominent at pressure points on the soles and toes (Figure 2A), in addition to gingival hyperkeratosis and oral leukokeratosis (Figure 2B). He had no associated abnormalities of the skin, hair, or teeth and no nail findings (Figure 2C). He reported that his father and 2 of his 3 sisters were affected with similar symptoms. A punch biopsy of the right fifth toe was consistent with verrucous epidermal hyperplasia with perinuclear keratinization in the spinous layer (Figure 3A). A gingival biopsy showed perinuclear eosinophilic globules and basophilic stranding in the cytoplasm (Figure 3B). His older sister had more severe and painful focal keratoderma of the soles, punctate keratoderma of the palms, gingival hyperkeratosis, and leukokeratosis of the tongue.

Whole exome sequencing of the proband revealed a heterozygous missense mutation in KRT16 (c.380G>A, p.R127H, rs57424749). Sanger sequencing confirmed this mutation and showed that it was heterozygous in both of his affected sisters and absent in his unaffected niece (Figure 1). The patient was treated with topical and systemic retinoids, keratolytics, and mechanical removal to moderate effect, with noted improvement in the appearance and associated pain of the plantar keratoderma.

Phenotypic heterogeneity is common in PC, though PC due to KRT6A mutations demonstrates more severe nail disease with oral lesions, cysts, and follicular hyperkeratosis, while PC caused by KRT16 mutations generally presents with more extensive and painful PPK.⁴KRT16 mutations affecting p.R127 are frequent causes of PC, and genotype-phenotype correlations have been observed. Individuals with p.R127P mutations exhibit more severe disease with earlier age of onset, more extensive nail involvement and oral leukokeratosis, and greater impact on daily quality of life than in individuals with p.R127C mutations.⁵ Cases of PC with KRT16 p.R127S and p.R127G mutations also have been observed. The KRT16 c.380G>A, p.R127H mutation we documented has been reported in one kindred with PC who presented with PPK, oral leukokeratosis, toenail thickening, and pilosebaceous and follicular hyperkeratosis.⁶

Although patients with FPGK lack the thickening of fingernails and/or toenails considered a defining feature of PC, the disorders otherwise are phenotypically similar, suggesting the possibility of common pathogenesis. One linkage study of familial FPGK excluded genetic intervals containing type I and type II keratins but was limited to a single small kindred.² This study and our data together suggest that, similar to PC, there are multiple genes in which mutations cause FPGK.

Murine Krt16 knockouts show distinct phenotypes depending on the mouse strain in which they are propagated, ranging from perinatal lethality to differences in the severity of oral and PPK lesions.⁷ These observations provide evidence that additional genetic variants contribute to Krt16 phenotypes in mice and suggest the same could be true for humans.

We propose that some cases of FPGK are due to mutations in KRT16 and thus share a genetic pathogenesis with PC, underscoring the utility of whole exome sequencing in providing genetic diagnoses for disorders that are genetically and clinically heterogeneous. Further biologic investigation of phenotypes caused by KRT16 mutation may reveal respective contributions of additional genetic variation and environmental effects to the variable clinical presentations.

The Diagnosis: Cutaneous Blastomycosis

A skin biopsy and fungal cultures confirmed the diagnosis of cutaneous blastomycosis. Grocott- Gomori methenamine-silver staining highlighted fungal organisms with refractile walls and broad-based budding consistent with cutaneous blastomycosis (Figure 1). The histopathologic specimen also demonstrated marked pseudoepitheliomatous hyperplasia (Figure 2A) with neutrophilic microabscesses (Figure 2B). Acid-fast bacillus and Fite staining were negative for bacterial organisms. A fungal culture was positive for Blastomyces dermatitidis. Urine and serum blastomycosis antigen were positive. Although Histoplasma serum antigen also was positive, this likely was from cross-reactivity. Chest radiography was negative for lung involvement, and the patient displayed no neurologic symptoms. He was started on oral itraconazole therapy for the treatment of cutaneous blastomycosis.

Blastomyces dermatitidis, the causative organism of blastomycosis, is endemic to the Ohio and Mississippi River valleys, Great Lakes region, and southeastern United States. It is a thermally dimorphic fungus found in soils that grows as a mold at 25 °C and yeast at 37 °C. Primary infection of the lungs—blastomycosis pneumonia—often is the only clinical manifestation¹; however, subsequent hematogenous dissemination to extrapulmonary sites such as the skin, bones, and genitourinary system can occur. Cutaneous blastomycosis, the most common extrapulmonary manifestation, typically follows pulmonary infection. In rare cases, it can occur from direct inoculation.^2,3 Skin lesions can occur anywhere but frequently are found on exposed surfaces of the head, neck, and extremities. Lesions classically present as verrucous crusting plaques with draining microabscesses. Violaceous nodules, ulcers, and pustules also may occur.¹

Diagnosis involves obtaining a thorough history of possible environmental exposures such as the patient’s geographic area of residence, occupation, and outdoor activities involving soil or decaying wood. Because blastomycosis can remain latent, remote exposures are relevant. Definitive diagnosis of cutaneous blastomycosis involves skin biopsy of the lesion with fungal culture, but the yeast’s distinctive thick wall and broad-based budding seen with periodic acid–Schiff or Grocott-Gomori methenamine-silver staining provides a rapid presumptive diagnosis.³ Pseudoepitheliomatous hyperplasia and microabscesses also are characteristic features.² Urine antigen testing for a component of the polysaccharide cell wall has a sensitivity of 93% but a lower specificity of 79% due to cross-reactivity with histoplasmosis.⁴ Treatment consists of itraconazole for mild to moderate blastomycosis or amphotericin B for those with severe disease or central nervous system involvement or those who are immunosuppressed.¹

The differential diagnosis for our patient’s lesion included infectious vs neoplastic etiologies. Histoplasma capsulatum, the dimorphic fungus that causes histoplasmosis, also is endemic to the Ohio and Mississippi River valleys. It is found in soil and droppings of some bats and birds such as chickens and pigeons. Similar to blastomycosis, the primary infection site most commonly is the lungs. It subsequently may disseminate to the skin or less commonly via direct inoculation of injured skin. It can present as papules, plaques, ulcers, purpura, or abscesses. Unlike blastomycosis, tissue biopsy of a cutaneous lesion reveals granuloma formation and distinctive oval, narrow-based budding yeast.⁵ Atypical mycobacteria are another source of infection to consider. For example, cutaneous Mycobacterium kansasii may present as papules and pustules forming verrucous or granulomatous plaques and ulceration. Histopathologic findings distinguishing mycobacterial infection from blastomycosis include granulomas and acid-fast bacilli in histiocytes.⁶

Noninfectious etiologies in the differential may include cutaneous squamous cell carcinoma or pemphigus vegetans. Squamous cell carcinoma may present with a broad range of clinical features—papules, plaques, or nodules with smooth, scaly, verrucous, or ulcerative secondary features all are possible presentations.⁷ Fairskinned individuals, such as our patient, would be at a higher risk in sun-damaged skin. Histologically, cutaneous squamous cell carcinoma is defined as an invasion of the dermis by neoplastic squamous epithelial cells in the form of cords, sheets, individual cells, nodules, or cystic structures.⁷ Pemphigus vegetans is the rarest variant of a group of autoimmune vesiculobullous diseases known as pemphigus. It can be differentiated from the most common variant—pemphigus vulgaris—by the presence of vegetative plaques in intertriginous areas. However, these verrucous vegetations can be misleading and make clinical diagnosis difficult. Histopathologic findings of hyperkeratosis, pseudoepitheliomatous hyperplasia, papillomatosis, and acantholysis with a suprabasal cleft would confirm the diagnosis.⁸

In summary, cutaneous blastomycosis classically presents as verrucous crusting plaques, as seen in our patient. It is important to conduct a thorough history for environmental exposures, but definitive diagnosis of cutaneous blastomycosis involves skin biopsy with fungal culture. Treatment depends on the severity of disease and organ involvement. Itraconazole would be appropriate for mild to moderate blastomycosis.

The Diagnosis: Cutaneous Blastomycosis

A skin biopsy and fungal cultures confirmed the diagnosis of cutaneous blastomycosis. Grocott- Gomori methenamine-silver staining highlighted fungal organisms with refractile walls and broad-based budding consistent with cutaneous blastomycosis (Figure 1). The histopathologic specimen also demonstrated marked pseudoepitheliomatous hyperplasia (Figure 2A) with neutrophilic microabscesses (Figure 2B). Acid-fast bacillus and Fite staining were negative for bacterial organisms. A fungal culture was positive for Blastomyces dermatitidis. Urine and serum blastomycosis antigen were positive. Although Histoplasma serum antigen also was positive, this likely was from cross-reactivity. Chest radiography was negative for lung involvement, and the patient displayed no neurologic symptoms. He was started on oral itraconazole therapy for the treatment of cutaneous blastomycosis.

Blastomyces dermatitidis, the causative organism of blastomycosis, is endemic to the Ohio and Mississippi River valleys, Great Lakes region, and southeastern United States. It is a thermally dimorphic fungus found in soils that grows as a mold at 25 °C and yeast at 37 °C. Primary infection of the lungs—blastomycosis pneumonia—often is the only clinical manifestation¹; however, subsequent hematogenous dissemination to extrapulmonary sites such as the skin, bones, and genitourinary system can occur. Cutaneous blastomycosis, the most common extrapulmonary manifestation, typically follows pulmonary infection. In rare cases, it can occur from direct inoculation.^2,3 Skin lesions can occur anywhere but frequently are found on exposed surfaces of the head, neck, and extremities. Lesions classically present as verrucous crusting plaques with draining microabscesses. Violaceous nodules, ulcers, and pustules also may occur.¹

Diagnosis involves obtaining a thorough history of possible environmental exposures such as the patient’s geographic area of residence, occupation, and outdoor activities involving soil or decaying wood. Because blastomycosis can remain latent, remote exposures are relevant. Definitive diagnosis of cutaneous blastomycosis involves skin biopsy of the lesion with fungal culture, but the yeast’s distinctive thick wall and broad-based budding seen with periodic acid–Schiff or Grocott-Gomori methenamine-silver staining provides a rapid presumptive diagnosis.³ Pseudoepitheliomatous hyperplasia and microabscesses also are characteristic features.² Urine antigen testing for a component of the polysaccharide cell wall has a sensitivity of 93% but a lower specificity of 79% due to cross-reactivity with histoplasmosis.⁴ Treatment consists of itraconazole for mild to moderate blastomycosis or amphotericin B for those with severe disease or central nervous system involvement or those who are immunosuppressed.¹

The differential diagnosis for our patient’s lesion included infectious vs neoplastic etiologies. Histoplasma capsulatum, the dimorphic fungus that causes histoplasmosis, also is endemic to the Ohio and Mississippi River valleys. It is found in soil and droppings of some bats and birds such as chickens and pigeons. Similar to blastomycosis, the primary infection site most commonly is the lungs. It subsequently may disseminate to the skin or less commonly via direct inoculation of injured skin. It can present as papules, plaques, ulcers, purpura, or abscesses. Unlike blastomycosis, tissue biopsy of a cutaneous lesion reveals granuloma formation and distinctive oval, narrow-based budding yeast.⁵ Atypical mycobacteria are another source of infection to consider. For example, cutaneous Mycobacterium kansasii may present as papules and pustules forming verrucous or granulomatous plaques and ulceration. Histopathologic findings distinguishing mycobacterial infection from blastomycosis include granulomas and acid-fast bacilli in histiocytes.⁶

Noninfectious etiologies in the differential may include cutaneous squamous cell carcinoma or pemphigus vegetans. Squamous cell carcinoma may present with a broad range of clinical features—papules, plaques, or nodules with smooth, scaly, verrucous, or ulcerative secondary features all are possible presentations.⁷ Fairskinned individuals, such as our patient, would be at a higher risk in sun-damaged skin. Histologically, cutaneous squamous cell carcinoma is defined as an invasion of the dermis by neoplastic squamous epithelial cells in the form of cords, sheets, individual cells, nodules, or cystic structures.⁷ Pemphigus vegetans is the rarest variant of a group of autoimmune vesiculobullous diseases known as pemphigus. It can be differentiated from the most common variant—pemphigus vulgaris—by the presence of vegetative plaques in intertriginous areas. However, these verrucous vegetations can be misleading and make clinical diagnosis difficult. Histopathologic findings of hyperkeratosis, pseudoepitheliomatous hyperplasia, papillomatosis, and acantholysis with a suprabasal cleft would confirm the diagnosis.⁸

In summary, cutaneous blastomycosis classically presents as verrucous crusting plaques, as seen in our patient. It is important to conduct a thorough history for environmental exposures, but definitive diagnosis of cutaneous blastomycosis involves skin biopsy with fungal culture. Treatment depends on the severity of disease and organ involvement. Itraconazole would be appropriate for mild to moderate blastomycosis.

The Diagnosis: Cutaneous Blastomycosis

A skin biopsy and fungal cultures confirmed the diagnosis of cutaneous blastomycosis. Grocott- Gomori methenamine-silver staining highlighted fungal organisms with refractile walls and broad-based budding consistent with cutaneous blastomycosis (Figure 1). The histopathologic specimen also demonstrated marked pseudoepitheliomatous hyperplasia (Figure 2A) with neutrophilic microabscesses (Figure 2B). Acid-fast bacillus and Fite staining were negative for bacterial organisms. A fungal culture was positive for Blastomyces dermatitidis. Urine and serum blastomycosis antigen were positive. Although Histoplasma serum antigen also was positive, this likely was from cross-reactivity. Chest radiography was negative for lung involvement, and the patient displayed no neurologic symptoms. He was started on oral itraconazole therapy for the treatment of cutaneous blastomycosis.

Blastomyces dermatitidis, the causative organism of blastomycosis, is endemic to the Ohio and Mississippi River valleys, Great Lakes region, and southeastern United States. It is a thermally dimorphic fungus found in soils that grows as a mold at 25 °C and yeast at 37 °C. Primary infection of the lungs—blastomycosis pneumonia—often is the only clinical manifestation¹; however, subsequent hematogenous dissemination to extrapulmonary sites such as the skin, bones, and genitourinary system can occur. Cutaneous blastomycosis, the most common extrapulmonary manifestation, typically follows pulmonary infection. In rare cases, it can occur from direct inoculation.^2,3 Skin lesions can occur anywhere but frequently are found on exposed surfaces of the head, neck, and extremities. Lesions classically present as verrucous crusting plaques with draining microabscesses. Violaceous nodules, ulcers, and pustules also may occur.¹

Diagnosis involves obtaining a thorough history of possible environmental exposures such as the patient’s geographic area of residence, occupation, and outdoor activities involving soil or decaying wood. Because blastomycosis can remain latent, remote exposures are relevant. Definitive diagnosis of cutaneous blastomycosis involves skin biopsy of the lesion with fungal culture, but the yeast’s distinctive thick wall and broad-based budding seen with periodic acid–Schiff or Grocott-Gomori methenamine-silver staining provides a rapid presumptive diagnosis.³ Pseudoepitheliomatous hyperplasia and microabscesses also are characteristic features.² Urine antigen testing for a component of the polysaccharide cell wall has a sensitivity of 93% but a lower specificity of 79% due to cross-reactivity with histoplasmosis.⁴ Treatment consists of itraconazole for mild to moderate blastomycosis or amphotericin B for those with severe disease or central nervous system involvement or those who are immunosuppressed.¹

The differential diagnosis for our patient’s lesion included infectious vs neoplastic etiologies. Histoplasma capsulatum, the dimorphic fungus that causes histoplasmosis, also is endemic to the Ohio and Mississippi River valleys. It is found in soil and droppings of some bats and birds such as chickens and pigeons. Similar to blastomycosis, the primary infection site most commonly is the lungs. It subsequently may disseminate to the skin or less commonly via direct inoculation of injured skin. It can present as papules, plaques, ulcers, purpura, or abscesses. Unlike blastomycosis, tissue biopsy of a cutaneous lesion reveals granuloma formation and distinctive oval, narrow-based budding yeast.⁵ Atypical mycobacteria are another source of infection to consider. For example, cutaneous Mycobacterium kansasii may present as papules and pustules forming verrucous or granulomatous plaques and ulceration. Histopathologic findings distinguishing mycobacterial infection from blastomycosis include granulomas and acid-fast bacilli in histiocytes.⁶

Noninfectious etiologies in the differential may include cutaneous squamous cell carcinoma or pemphigus vegetans. Squamous cell carcinoma may present with a broad range of clinical features—papules, plaques, or nodules with smooth, scaly, verrucous, or ulcerative secondary features all are possible presentations.⁷ Fairskinned individuals, such as our patient, would be at a higher risk in sun-damaged skin. Histologically, cutaneous squamous cell carcinoma is defined as an invasion of the dermis by neoplastic squamous epithelial cells in the form of cords, sheets, individual cells, nodules, or cystic structures.⁷ Pemphigus vegetans is the rarest variant of a group of autoimmune vesiculobullous diseases known as pemphigus. It can be differentiated from the most common variant—pemphigus vulgaris—by the presence of vegetative plaques in intertriginous areas. However, these verrucous vegetations can be misleading and make clinical diagnosis difficult. Histopathologic findings of hyperkeratosis, pseudoepitheliomatous hyperplasia, papillomatosis, and acantholysis with a suprabasal cleft would confirm the diagnosis.⁸

In summary, cutaneous blastomycosis classically presents as verrucous crusting plaques, as seen in our patient. It is important to conduct a thorough history for environmental exposures, but definitive diagnosis of cutaneous blastomycosis involves skin biopsy with fungal culture. Treatment depends on the severity of disease and organ involvement. Itraconazole would be appropriate for mild to moderate blastomycosis.

The Diagnosis: Borrelial Lymphocytoma (Lymphocytoma Cutis)

A punch biopsy revealed an atypical lobular lymphoid infiltrate within the dermis and subcutaneous tissue with a mixed composition of CD3⁺ T cells and CD20⁺ B cells (quiz image, bottom). Immunohistochemical studies revealed a normal CD4:CD8 ratio with preservation of CD5 and CD7. CD30 was largely negative. CD21 failed to detect follicular dendritic cell networks, and κ/λ light chain staining confirmed a preserved ratio of polytypic plasma cells. There was limited staining with B-cell lymphoma (Bcl-2 and Bcl-6). Polymerase chain reaction studies for both T- and B-cell receptors were negative (polyclonal).

Lyme disease is the most frequently reported vectorborne infectious disease in the United States, and borrelial lymphocytoma (BL) is a rare clinical sequela. Borrelial lymphocytoma is a variant of lymphocytoma cutis (also known as benign reactive lymphoid hyperplasia), which is an inflammatory lesion that can mimic malignant lymphoma clinically and histologically. Lymphocytoma cutis is considered the prototypical example of cutaneous B-cell pseudolymphoma.¹ Due to suspicion for lymphocytoma cutis based on the histologic findings and characteristic location of the lesions in our patient, Lyme serologies were ordered and were positive for IgM antibodies against p23, p39, and p41 antigens in high titers. Our patient was treated with doxycycline 100 mg twice daily for 3 weeks with complete resolution of the lesions at 3-month follow-up.

Clinically, BL appears as erythematous papules, plaques, or nodules commonly on the lobules of the ears (quiz image, top). Most cases of lymphocytoma cutis are idiopathic but may be triggered by identifiable associated etiologies including Borrelia burgdorferi, Leishmania donovani, molluscum contagiosum, herpes zoster virus, vaccinations, tattoos, insect bites, and drugs. The main differential diagnosis of lymphocytoma cutis is cutaneous B-cell lymphoma. Pseudolymphoma of the skin can mimic nearly all immunohistochemical staining patterns of true B-cell lymphomas.²

Primary cutaneous follicle center lymphoma frequently occurs on the head and neck. This true lymphoma of the skin can demonstrate prominent follicle centers with centrocytes and fragmented germinal centers (Figure 1) or show a diffuse pattern.³ Most cases show conspicuous Bcl-6 staining, and IgH gene rearrangements can detect a clonal B-cell population in more than 50% of cases.⁴

Diffuse large B-cell lymphoma can occur as a primary cutaneous malignancy or as a manifestation of systemic disease.4 When arising in the skin, lesions tend to affect the extremities, and the disease is classified as diffuse large B-cell lymphoma, leg type. Histologically, sheets of large atypical lymphocytes with numerous mitoses are seen (Figure 2). These cells stain positively with Bcl-2 and frequently demonstrate Bcl-6 and MUM-1, none of which were seen in our case.4 Lymphomatoid papulosis (LyP) tends to present with relapsing erythematous papules. Patients occasionally develop LyP in association with mycosis fungoides or other lymphomas. Both LyP and primary cutaneous anaplastic large cell lymphoma demonstrate conspicuous CD30+ large cells that can be multinucleated or resemble the Reed-Sternberg cells seen in Hodgkin lymphoma (Figure 3).4 Arthropod bite reactions are common but may be confused with lymphomas and pseudolymphomas. The perivascular lymphocytic infiltrate seen in arthropod bite reactions may be dense and usually is associated with numerous eosinophils (Figure 4). Occasional plasma cells also can be seen, and if the infiltrate closely adheres to vascular structures, a diagnosis of erythema chronicum migrans also can be considered. Patients with chronic lymphocytic leukemia/lymphoma may demonstrate exaggerated or persistent arthropod bite reactions, and atypical lymphocytes can be detected admixed with the otherwise reactive infiltrate.⁴

Borrelia burgdorferi is primarily endemic to North America and Europe. It is a spirochete bacterium spread by the Ixodes tick that was first recognized as the etiologic agent in 1975 in Old Lyme, Connecticut, where it received its name.⁵ Most reported cases of Lyme disease occur in the northeastern United States, which correlates with this case given our patient’s place of residence.⁶ Borrelial lymphocytoma cutis occurs in areas endemic for the Ixodes tick in Europe and North America.⁷ When describing the genotyping of Borrelia seen in BL, the strain B burgdorferi previously was grouped with Borrelia afzelii and Borrelia garinii.² In the contemporary literature, however, B burgdorferi is referred to as sensu stricto when specifically talking about the strain B burgdorferi, and the term sensu lato is used when referencing the combination of strains (B burgdorferi, B afzelii, B garinii).

A 2016 study by Maraspin et al⁸ comprising 144 patients diagnosed with BL showed that the lesions mainly were located on the breast (106 patients [73.6%]) and the earlobe (27 patients [18.8%]), with the remaining cases occurring elsewhere on the body (11 patients [7.6%]). The Borrelia strains isolated from the BL lesions included B afzelii, Borrelia bissettii, and B garinii, with B afzelii being the most commonly identified (84.6% [11/13]).⁸

Borrelial lymphocytoma usually is categorized as a form of early disseminated Lyme disease and is treated as such. The treatment of choice for early disseminated Lyme disease is doxycycline 100 mg twice daily for 14 to 21 days. Ceftriaxone and azithromycin are reasonable treatment options for patients who have tetracycline allergies or who are pregnant.⁹

In conclusion, the presentation of red papules or nodules on the ears should prompt clinical suspicion of Lyme disease, particularly in endemic areas. Differentiating pseudolymphomas from true lymphomas and other reactive conditions can be challenging.

The Diagnosis: Borrelial Lymphocytoma (Lymphocytoma Cutis)

A punch biopsy revealed an atypical lobular lymphoid infiltrate within the dermis and subcutaneous tissue with a mixed composition of CD3⁺ T cells and CD20⁺ B cells (quiz image, bottom). Immunohistochemical studies revealed a normal CD4:CD8 ratio with preservation of CD5 and CD7. CD30 was largely negative. CD21 failed to detect follicular dendritic cell networks, and κ/λ light chain staining confirmed a preserved ratio of polytypic plasma cells. There was limited staining with B-cell lymphoma (Bcl-2 and Bcl-6). Polymerase chain reaction studies for both T- and B-cell receptors were negative (polyclonal).

Lyme disease is the most frequently reported vectorborne infectious disease in the United States, and borrelial lymphocytoma (BL) is a rare clinical sequela. Borrelial lymphocytoma is a variant of lymphocytoma cutis (also known as benign reactive lymphoid hyperplasia), which is an inflammatory lesion that can mimic malignant lymphoma clinically and histologically. Lymphocytoma cutis is considered the prototypical example of cutaneous B-cell pseudolymphoma.¹ Due to suspicion for lymphocytoma cutis based on the histologic findings and characteristic location of the lesions in our patient, Lyme serologies were ordered and were positive for IgM antibodies against p23, p39, and p41 antigens in high titers. Our patient was treated with doxycycline 100 mg twice daily for 3 weeks with complete resolution of the lesions at 3-month follow-up.

Clinically, BL appears as erythematous papules, plaques, or nodules commonly on the lobules of the ears (quiz image, top). Most cases of lymphocytoma cutis are idiopathic but may be triggered by identifiable associated etiologies including Borrelia burgdorferi, Leishmania donovani, molluscum contagiosum, herpes zoster virus, vaccinations, tattoos, insect bites, and drugs. The main differential diagnosis of lymphocytoma cutis is cutaneous B-cell lymphoma. Pseudolymphoma of the skin can mimic nearly all immunohistochemical staining patterns of true B-cell lymphomas.²

Primary cutaneous follicle center lymphoma frequently occurs on the head and neck. This true lymphoma of the skin can demonstrate prominent follicle centers with centrocytes and fragmented germinal centers (Figure 1) or show a diffuse pattern.³ Most cases show conspicuous Bcl-6 staining, and IgH gene rearrangements can detect a clonal B-cell population in more than 50% of cases.⁴

Diffuse large B-cell lymphoma can occur as a primary cutaneous malignancy or as a manifestation of systemic disease.4 When arising in the skin, lesions tend to affect the extremities, and the disease is classified as diffuse large B-cell lymphoma, leg type. Histologically, sheets of large atypical lymphocytes with numerous mitoses are seen (Figure 2). These cells stain positively with Bcl-2 and frequently demonstrate Bcl-6 and MUM-1, none of which were seen in our case.4 Lymphomatoid papulosis (LyP) tends to present with relapsing erythematous papules. Patients occasionally develop LyP in association with mycosis fungoides or other lymphomas. Both LyP and primary cutaneous anaplastic large cell lymphoma demonstrate conspicuous CD30+ large cells that can be multinucleated or resemble the Reed-Sternberg cells seen in Hodgkin lymphoma (Figure 3).4 Arthropod bite reactions are common but may be confused with lymphomas and pseudolymphomas. The perivascular lymphocytic infiltrate seen in arthropod bite reactions may be dense and usually is associated with numerous eosinophils (Figure 4). Occasional plasma cells also can be seen, and if the infiltrate closely adheres to vascular structures, a diagnosis of erythema chronicum migrans also can be considered. Patients with chronic lymphocytic leukemia/lymphoma may demonstrate exaggerated or persistent arthropod bite reactions, and atypical lymphocytes can be detected admixed with the otherwise reactive infiltrate.⁴

Borrelia burgdorferi is primarily endemic to North America and Europe. It is a spirochete bacterium spread by the Ixodes tick that was first recognized as the etiologic agent in 1975 in Old Lyme, Connecticut, where it received its name.⁵ Most reported cases of Lyme disease occur in the northeastern United States, which correlates with this case given our patient’s place of residence.⁶ Borrelial lymphocytoma cutis occurs in areas endemic for the Ixodes tick in Europe and North America.⁷ When describing the genotyping of Borrelia seen in BL, the strain B burgdorferi previously was grouped with Borrelia afzelii and Borrelia garinii.² In the contemporary literature, however, B burgdorferi is referred to as sensu stricto when specifically talking about the strain B burgdorferi, and the term sensu lato is used when referencing the combination of strains (B burgdorferi, B afzelii, B garinii).

A 2016 study by Maraspin et al⁸ comprising 144 patients diagnosed with BL showed that the lesions mainly were located on the breast (106 patients [73.6%]) and the earlobe (27 patients [18.8%]), with the remaining cases occurring elsewhere on the body (11 patients [7.6%]). The Borrelia strains isolated from the BL lesions included B afzelii, Borrelia bissettii, and B garinii, with B afzelii being the most commonly identified (84.6% [11/13]).⁸

Borrelial lymphocytoma usually is categorized as a form of early disseminated Lyme disease and is treated as such. The treatment of choice for early disseminated Lyme disease is doxycycline 100 mg twice daily for 14 to 21 days. Ceftriaxone and azithromycin are reasonable treatment options for patients who have tetracycline allergies or who are pregnant.⁹

In conclusion, the presentation of red papules or nodules on the ears should prompt clinical suspicion of Lyme disease, particularly in endemic areas. Differentiating pseudolymphomas from true lymphomas and other reactive conditions can be challenging.

The Diagnosis: Borrelial Lymphocytoma (Lymphocytoma Cutis)

A punch biopsy revealed an atypical lobular lymphoid infiltrate within the dermis and subcutaneous tissue with a mixed composition of CD3⁺ T cells and CD20⁺ B cells (quiz image, bottom). Immunohistochemical studies revealed a normal CD4:CD8 ratio with preservation of CD5 and CD7. CD30 was largely negative. CD21 failed to detect follicular dendritic cell networks, and κ/λ light chain staining confirmed a preserved ratio of polytypic plasma cells. There was limited staining with B-cell lymphoma (Bcl-2 and Bcl-6). Polymerase chain reaction studies for both T- and B-cell receptors were negative (polyclonal).

Lyme disease is the most frequently reported vectorborne infectious disease in the United States, and borrelial lymphocytoma (BL) is a rare clinical sequela. Borrelial lymphocytoma is a variant of lymphocytoma cutis (also known as benign reactive lymphoid hyperplasia), which is an inflammatory lesion that can mimic malignant lymphoma clinically and histologically. Lymphocytoma cutis is considered the prototypical example of cutaneous B-cell pseudolymphoma.¹ Due to suspicion for lymphocytoma cutis based on the histologic findings and characteristic location of the lesions in our patient, Lyme serologies were ordered and were positive for IgM antibodies against p23, p39, and p41 antigens in high titers. Our patient was treated with doxycycline 100 mg twice daily for 3 weeks with complete resolution of the lesions at 3-month follow-up.

Clinically, BL appears as erythematous papules, plaques, or nodules commonly on the lobules of the ears (quiz image, top). Most cases of lymphocytoma cutis are idiopathic but may be triggered by identifiable associated etiologies including Borrelia burgdorferi, Leishmania donovani, molluscum contagiosum, herpes zoster virus, vaccinations, tattoos, insect bites, and drugs. The main differential diagnosis of lymphocytoma cutis is cutaneous B-cell lymphoma. Pseudolymphoma of the skin can mimic nearly all immunohistochemical staining patterns of true B-cell lymphomas.²

Primary cutaneous follicle center lymphoma frequently occurs on the head and neck. This true lymphoma of the skin can demonstrate prominent follicle centers with centrocytes and fragmented germinal centers (Figure 1) or show a diffuse pattern.³ Most cases show conspicuous Bcl-6 staining, and IgH gene rearrangements can detect a clonal B-cell population in more than 50% of cases.⁴

Diffuse large B-cell lymphoma can occur as a primary cutaneous malignancy or as a manifestation of systemic disease.4 When arising in the skin, lesions tend to affect the extremities, and the disease is classified as diffuse large B-cell lymphoma, leg type. Histologically, sheets of large atypical lymphocytes with numerous mitoses are seen (Figure 2). These cells stain positively with Bcl-2 and frequently demonstrate Bcl-6 and MUM-1, none of which were seen in our case.4 Lymphomatoid papulosis (LyP) tends to present with relapsing erythematous papules. Patients occasionally develop LyP in association with mycosis fungoides or other lymphomas. Both LyP and primary cutaneous anaplastic large cell lymphoma demonstrate conspicuous CD30+ large cells that can be multinucleated or resemble the Reed-Sternberg cells seen in Hodgkin lymphoma (Figure 3).4 Arthropod bite reactions are common but may be confused with lymphomas and pseudolymphomas. The perivascular lymphocytic infiltrate seen in arthropod bite reactions may be dense and usually is associated with numerous eosinophils (Figure 4). Occasional plasma cells also can be seen, and if the infiltrate closely adheres to vascular structures, a diagnosis of erythema chronicum migrans also can be considered. Patients with chronic lymphocytic leukemia/lymphoma may demonstrate exaggerated or persistent arthropod bite reactions, and atypical lymphocytes can be detected admixed with the otherwise reactive infiltrate.⁴

Borrelia burgdorferi is primarily endemic to North America and Europe. It is a spirochete bacterium spread by the Ixodes tick that was first recognized as the etiologic agent in 1975 in Old Lyme, Connecticut, where it received its name.⁵ Most reported cases of Lyme disease occur in the northeastern United States, which correlates with this case given our patient’s place of residence.⁶ Borrelial lymphocytoma cutis occurs in areas endemic for the Ixodes tick in Europe and North America.⁷ When describing the genotyping of Borrelia seen in BL, the strain B burgdorferi previously was grouped with Borrelia afzelii and Borrelia garinii.² In the contemporary literature, however, B burgdorferi is referred to as sensu stricto when specifically talking about the strain B burgdorferi, and the term sensu lato is used when referencing the combination of strains (B burgdorferi, B afzelii, B garinii).

A 2016 study by Maraspin et al⁸ comprising 144 patients diagnosed with BL showed that the lesions mainly were located on the breast (106 patients [73.6%]) and the earlobe (27 patients [18.8%]), with the remaining cases occurring elsewhere on the body (11 patients [7.6%]). The Borrelia strains isolated from the BL lesions included B afzelii, Borrelia bissettii, and B garinii, with B afzelii being the most commonly identified (84.6% [11/13]).⁸

Borrelial lymphocytoma usually is categorized as a form of early disseminated Lyme disease and is treated as such. The treatment of choice for early disseminated Lyme disease is doxycycline 100 mg twice daily for 14 to 21 days. Ceftriaxone and azithromycin are reasonable treatment options for patients who have tetracycline allergies or who are pregnant.⁹

In conclusion, the presentation of red papules or nodules on the ears should prompt clinical suspicion of Lyme disease, particularly in endemic areas. Differentiating pseudolymphomas from true lymphomas and other reactive conditions can be challenging.

To the Editor:

A 57-year-old woman presented to an outpatient clinic with severe pruritus and burning of the skin as well as subjective fevers and chills. She had been discharged from a psychiatric hospital for attempted suicide 1 day prior. There were no recent changes in the medication regimen, which consisted of linaclotide, fluoxetine, lorazepam, and gabapentin. While admitted, the patient was started on the atypical antipsychotic cariprazine. Within 24 hours of the first dose, she developed severe facial erythema that progressed to diffuse erythema over more than 60% of the body surface area. The attending psychiatrist promptly discontinued cariprazine. During the next 24 hours, there were no reports of fever, leukocytosis, or signs of systemic organ involvement. Given the patient’s mental and medical stability, she was discharged with instructions to follow up with the outpatient dermatology clinic.

At the current presentation, physical examination revealed innumerable 1- to 4-mm pustules coalescing to lakes of pus on an erythematous base over more than 60% of the body surface area (Figure 1). The mucous membranes were clear of lesions, the Nikolsky sign was negative, and the patient’s temperature was 99.6 °F in the office. Complete blood cell count and complete metabolic panel results were within reference range.

A 4-mm abdominal punch biopsy showed subcorneal neutrophilic pustules, papillary dermal edema, and superficial dermal lymphohistiocytic inflammation with numerous neutrophils, eosinophils, and extravasated red blood cells, consistent with acute generalized exanthematous pustulosis (AGEP)(Figure 2). The patient was started on wet wraps with triamcinolone cream 0.1%.

Two days later, physical examination revealed the erythema noted on initial examination had notably decreased, and the patient no longer reported burning or pruritus. One week after initial presentation to the clinic, the patient’s rash had resolved, and only a few small areas of desquamation remained.

Acute generalized exanthematous pustulosis is a severe cutaneous adverse reaction characterized by the development of numerous nonfollicular sterile pustules on an edematous and erythematous base. In almost 90% of reported cases, the cause is related to use of antibiotics, antifungals, antimalarials, or diltiazem (a calcium channel blocker). This rare cutaneous reaction occurs in 1 to 5 patients per million per year¹; it carries a 1% to 2% mortality rate with proper supportive treatment.

The clinical symptoms of AGEP typically present 24 to 48 hours after drug initiation with the rapid development of dozens to thousands of 1- to 4-mm pustules, typically localized to the flexor surfaces and face. In the setting of AGEP, acute onset of fever and leukocytosis typically occur at the time of the cutaneous eruption. These features were absent in this patient. The eruption usually starts on the face and then migrates to the trunk and extremities, sparing the palms and soles. Systemic involvement most commonly presents as hepatic, renal, or pulmonary insufficiency, which has been seen in 20% of cases.²

The immunologic response associated with the reaction has been studied in vitro. Drug-specific CD8 T cells use perforin/granzyme B and Fas ligand mechanisms to induce apoptosis of the keratinocytes within the epidermis, leading to vesicle formation.³ During the very first stages of formation, vesicles mainly comprise CD8 T cells and keratinocytes. These cells then begin producing CXC-18, a potent neutrophil chemokine, leading to extensive chemotaxis of neutrophils into vesicles, which then rapidly transform to pustules.³ This rapid transformation leads to the lakes of pustules, a description often associated with AGEP.

Treatment of AGEP is mainly supportive and consists of discontinuing use of the causative agent. Topical corticosteroids can be used during the pustular phase for symptom management. There is no evidence that systemic steroids reduce the duration of the disease.² Other supportive measures such as application of wet wraps can be used to provide comfort.

Cutaneous adverse drug reactions commonly are associated with psychiatric pharmacotherapy, but first-and second-generation antipsychotics rarely are associated with these types of reactions. In this patient, the causative agent of the AGEP was cariprazine, an atypical antipsychotic that had no reported association with AGEP or cutaneous adverse drug reactions prior to this presentation.

To the Editor:

A 57-year-old woman presented to an outpatient clinic with severe pruritus and burning of the skin as well as subjective fevers and chills. She had been discharged from a psychiatric hospital for attempted suicide 1 day prior. There were no recent changes in the medication regimen, which consisted of linaclotide, fluoxetine, lorazepam, and gabapentin. While admitted, the patient was started on the atypical antipsychotic cariprazine. Within 24 hours of the first dose, she developed severe facial erythema that progressed to diffuse erythema over more than 60% of the body surface area. The attending psychiatrist promptly discontinued cariprazine. During the next 24 hours, there were no reports of fever, leukocytosis, or signs of systemic organ involvement. Given the patient’s mental and medical stability, she was discharged with instructions to follow up with the outpatient dermatology clinic.

At the current presentation, physical examination revealed innumerable 1- to 4-mm pustules coalescing to lakes of pus on an erythematous base over more than 60% of the body surface area (Figure 1). The mucous membranes were clear of lesions, the Nikolsky sign was negative, and the patient’s temperature was 99.6 °F in the office. Complete blood cell count and complete metabolic panel results were within reference range.

A 4-mm abdominal punch biopsy showed subcorneal neutrophilic pustules, papillary dermal edema, and superficial dermal lymphohistiocytic inflammation with numerous neutrophils, eosinophils, and extravasated red blood cells, consistent with acute generalized exanthematous pustulosis (AGEP)(Figure 2). The patient was started on wet wraps with triamcinolone cream 0.1%.

Two days later, physical examination revealed the erythema noted on initial examination had notably decreased, and the patient no longer reported burning or pruritus. One week after initial presentation to the clinic, the patient’s rash had resolved, and only a few small areas of desquamation remained.

Acute generalized exanthematous pustulosis is a severe cutaneous adverse reaction characterized by the development of numerous nonfollicular sterile pustules on an edematous and erythematous base. In almost 90% of reported cases, the cause is related to use of antibiotics, antifungals, antimalarials, or diltiazem (a calcium channel blocker). This rare cutaneous reaction occurs in 1 to 5 patients per million per year¹; it carries a 1% to 2% mortality rate with proper supportive treatment.

The clinical symptoms of AGEP typically present 24 to 48 hours after drug initiation with the rapid development of dozens to thousands of 1- to 4-mm pustules, typically localized to the flexor surfaces and face. In the setting of AGEP, acute onset of fever and leukocytosis typically occur at the time of the cutaneous eruption. These features were absent in this patient. The eruption usually starts on the face and then migrates to the trunk and extremities, sparing the palms and soles. Systemic involvement most commonly presents as hepatic, renal, or pulmonary insufficiency, which has been seen in 20% of cases.²

The immunologic response associated with the reaction has been studied in vitro. Drug-specific CD8 T cells use perforin/granzyme B and Fas ligand mechanisms to induce apoptosis of the keratinocytes within the epidermis, leading to vesicle formation.³ During the very first stages of formation, vesicles mainly comprise CD8 T cells and keratinocytes. These cells then begin producing CXC-18, a potent neutrophil chemokine, leading to extensive chemotaxis of neutrophils into vesicles, which then rapidly transform to pustules.³ This rapid transformation leads to the lakes of pustules, a description often associated with AGEP.

Treatment of AGEP is mainly supportive and consists of discontinuing use of the causative agent. Topical corticosteroids can be used during the pustular phase for symptom management. There is no evidence that systemic steroids reduce the duration of the disease.² Other supportive measures such as application of wet wraps can be used to provide comfort.

Cutaneous adverse drug reactions commonly are associated with psychiatric pharmacotherapy, but first-and second-generation antipsychotics rarely are associated with these types of reactions. In this patient, the causative agent of the AGEP was cariprazine, an atypical antipsychotic that had no reported association with AGEP or cutaneous adverse drug reactions prior to this presentation.

To the Editor:

A 57-year-old woman presented to an outpatient clinic with severe pruritus and burning of the skin as well as subjective fevers and chills. She had been discharged from a psychiatric hospital for attempted suicide 1 day prior. There were no recent changes in the medication regimen, which consisted of linaclotide, fluoxetine, lorazepam, and gabapentin. While admitted, the patient was started on the atypical antipsychotic cariprazine. Within 24 hours of the first dose, she developed severe facial erythema that progressed to diffuse erythema over more than 60% of the body surface area. The attending psychiatrist promptly discontinued cariprazine. During the next 24 hours, there were no reports of fever, leukocytosis, or signs of systemic organ involvement. Given the patient’s mental and medical stability, she was discharged with instructions to follow up with the outpatient dermatology clinic.

At the current presentation, physical examination revealed innumerable 1- to 4-mm pustules coalescing to lakes of pus on an erythematous base over more than 60% of the body surface area (Figure 1). The mucous membranes were clear of lesions, the Nikolsky sign was negative, and the patient’s temperature was 99.6 °F in the office. Complete blood cell count and complete metabolic panel results were within reference range.

A 4-mm abdominal punch biopsy showed subcorneal neutrophilic pustules, papillary dermal edema, and superficial dermal lymphohistiocytic inflammation with numerous neutrophils, eosinophils, and extravasated red blood cells, consistent with acute generalized exanthematous pustulosis (AGEP)(Figure 2). The patient was started on wet wraps with triamcinolone cream 0.1%.

Two days later, physical examination revealed the erythema noted on initial examination had notably decreased, and the patient no longer reported burning or pruritus. One week after initial presentation to the clinic, the patient’s rash had resolved, and only a few small areas of desquamation remained.

Acute generalized exanthematous pustulosis is a severe cutaneous adverse reaction characterized by the development of numerous nonfollicular sterile pustules on an edematous and erythematous base. In almost 90% of reported cases, the cause is related to use of antibiotics, antifungals, antimalarials, or diltiazem (a calcium channel blocker). This rare cutaneous reaction occurs in 1 to 5 patients per million per year¹; it carries a 1% to 2% mortality rate with proper supportive treatment.

The clinical symptoms of AGEP typically present 24 to 48 hours after drug initiation with the rapid development of dozens to thousands of 1- to 4-mm pustules, typically localized to the flexor surfaces and face. In the setting of AGEP, acute onset of fever and leukocytosis typically occur at the time of the cutaneous eruption. These features were absent in this patient. The eruption usually starts on the face and then migrates to the trunk and extremities, sparing the palms and soles. Systemic involvement most commonly presents as hepatic, renal, or pulmonary insufficiency, which has been seen in 20% of cases.²

The immunologic response associated with the reaction has been studied in vitro. Drug-specific CD8 T cells use perforin/granzyme B and Fas ligand mechanisms to induce apoptosis of the keratinocytes within the epidermis, leading to vesicle formation.³ During the very first stages of formation, vesicles mainly comprise CD8 T cells and keratinocytes. These cells then begin producing CXC-18, a potent neutrophil chemokine, leading to extensive chemotaxis of neutrophils into vesicles, which then rapidly transform to pustules.³ This rapid transformation leads to the lakes of pustules, a description often associated with AGEP.

Treatment of AGEP is mainly supportive and consists of discontinuing use of the causative agent. Topical corticosteroids can be used during the pustular phase for symptom management. There is no evidence that systemic steroids reduce the duration of the disease.² Other supportive measures such as application of wet wraps can be used to provide comfort.

Cutaneous adverse drug reactions commonly are associated with psychiatric pharmacotherapy, but first-and second-generation antipsychotics rarely are associated with these types of reactions. In this patient, the causative agent of the AGEP was cariprazine, an atypical antipsychotic that had no reported association with AGEP or cutaneous adverse drug reactions prior to this presentation.

The Diagnosis: Tinea Corporis Bullosa

At the time of presentation, a potassium hydroxide (KOH) preparation, fungal culture, and punch biopsy of the right ventral wrist was performed. The KOH preparation was positive for fungal hyphae characteristic of dermatophyte infections. Histologically, the biopsy showed intraepidermal and subepidermal blisters with neutrophil- and lymphocyte-rich contents (Figure 1). Fungal hyphae and spores were present within the stratum corneum and superficial epidermis (Figure 2), and fungal cultures grew Microsporum canis. The extent of the rash (upper and lower extremities, chest, and back), positive fungal culture, and KOH preparation all supported the diagnosis of tinea corporis bullosa, which was confirmed with biopsy. Oral prednisone use was discouraged and triamcinolone ointment was discontinued given that inappropriate treatment with steroids in the setting of fungal infection suppresses an inflammatory response and alters clinical appearance, obviating the persistent underlying infection.

Tinea corporis bullosa is a rare superficial dermatophyte fungal infection that often is acquired by close personto- person contact or contact with domestic animals. The infection begins as a circular pruritic plaque, generally with raised borders, which may be erythematous or hyperpigmented. By definition, tinea corporis occurs in sites other than the face, feet, hands, or groin area. Bullae formation is thought to be secondary to a delayed hypersensitivity reaction provoked by the presence of a dermatophyte antigen.¹

Linear IgA bullous dermatosis is an immunemediated disease characterized by IgA deposition at the dermoepidermal junction. Linear IgA bullous dermatosis classically presents as widespread tense vesicles in an arciform or annular pattern. Mucosal involvement is common and typically presents with erosions, ulcerations, and scarring.² Given the absence of mucosal involvement in our patient and a positive KOH preparation, linear IgA bullous dermatosis was an unlikely diagnosis.

Benign inoculation lymphoreticulosis, more commonly known as cat scratch disease (CSD), is a Bartonella henselae infection that results from a cat scratch or bite. Cat scratch disease can present as localized cutaneous and nodal involvement (lymphadenopathy) near the site of inoculation, or it may present as disseminated disease. Cutaneous lesions generally progress through vesicular, erythematous, and papular phases. Regional lymphadenopathy proximal to the inoculation site is the hallmark of CSD.³ Given the absence of lymphadenopathy in our patient as well as the sporadic distribution of lesions, CSD was an unlikely diagnosis.

Dermatitis herpetiformis (DH) is an autoimmune disorder with cutaneous manifestations of gluten sensitivity. Dermatitis herpetiformis presents as extremely pruritic papules and vesicles arranged in groups on areas such as the elbows, dorsal aspects of the forearms, knees, scalp, back, and buttocks. Most patients with DH have celiac disease or small bowel disease related to gluten sensitivity.4 Given our patient’s acute presentation in adulthood and lack of gluten sensitivity, DH was an unlikely diagnosis.

Bullous fixed drug reaction is a cutaneous eruption that typically presents in the setting of exposure to an offending drug/agent. Drug reactions can have various cutaneous presentations, with the most common being pigmented macules that progress into plaques.⁵ Given the isolated nature of our patient’s episode and apparent lack of association with medication, bullous fixed drug reaction was an unlikely diagnosis.

Tinea corporis bullosa is a rare clinical variant of tinea corporis that has only been reported in patients with a history of contact with different animals. There are many causative organisms related to tinea corporis; Trichophyton rubrum is the most common etiology of tinea corporis, while tinea corporis due to close contact with domesticated animals often is caused by M canis.⁶ The immunoinhibitory properties of the mannans in the fungal cell wall allow the organisms to adhere to the skin prior to invasion. Cutaneous invasion into dead cornified layers of the skin is credited to the proteases, subtilisinlike proteases (subtilases), and keratinases produced by the fungus.¹ There are many different clinical presentations of tinea corporis due to the variability of causative organisms. An annular (ring-shaped) lesion with a central plaque and advancing border is the most typical presentation. Tinea corporis bullosa is characterized by the presence of bullae or vesicles in the borders of the scaly plaque. Rupture of the bullae subsequently leads to erosions and crusts over the plaque.

The diagnosis of tinea corporis bullosa often is clinical if the lesion is typical and can be confirmed using KOH preparation and fungal culture. Once the diagnosis is confirmed, topical antifungals are the standard treatment approach for localized superficial tinea corporis. Systemic antifungal treatment can be initiated if the lesion is extensive, recurrent, chronic, or unresponsive to topical treatment.¹ Given our patient’s characteristic presentation, she was managed with an over-the-counter topical antifungal (terbinafine). The patient’s lesions dramatically improved, rendering oral therapy unnecessary. At 1-month follow-up, the rash had nearly resolved.

The Diagnosis: Tinea Corporis Bullosa

At the time of presentation, a potassium hydroxide (KOH) preparation, fungal culture, and punch biopsy of the right ventral wrist was performed. The KOH preparation was positive for fungal hyphae characteristic of dermatophyte infections. Histologically, the biopsy showed intraepidermal and subepidermal blisters with neutrophil- and lymphocyte-rich contents (Figure 1). Fungal hyphae and spores were present within the stratum corneum and superficial epidermis (Figure 2), and fungal cultures grew Microsporum canis. The extent of the rash (upper and lower extremities, chest, and back), positive fungal culture, and KOH preparation all supported the diagnosis of tinea corporis bullosa, which was confirmed with biopsy. Oral prednisone use was discouraged and triamcinolone ointment was discontinued given that inappropriate treatment with steroids in the setting of fungal infection suppresses an inflammatory response and alters clinical appearance, obviating the persistent underlying infection.

Tinea corporis bullosa is a rare superficial dermatophyte fungal infection that often is acquired by close personto- person contact or contact with domestic animals. The infection begins as a circular pruritic plaque, generally with raised borders, which may be erythematous or hyperpigmented. By definition, tinea corporis occurs in sites other than the face, feet, hands, or groin area. Bullae formation is thought to be secondary to a delayed hypersensitivity reaction provoked by the presence of a dermatophyte antigen.¹

Linear IgA bullous dermatosis is an immunemediated disease characterized by IgA deposition at the dermoepidermal junction. Linear IgA bullous dermatosis classically presents as widespread tense vesicles in an arciform or annular pattern. Mucosal involvement is common and typically presents with erosions, ulcerations, and scarring.² Given the absence of mucosal involvement in our patient and a positive KOH preparation, linear IgA bullous dermatosis was an unlikely diagnosis.

Benign inoculation lymphoreticulosis, more commonly known as cat scratch disease (CSD), is a Bartonella henselae infection that results from a cat scratch or bite. Cat scratch disease can present as localized cutaneous and nodal involvement (lymphadenopathy) near the site of inoculation, or it may present as disseminated disease. Cutaneous lesions generally progress through vesicular, erythematous, and papular phases. Regional lymphadenopathy proximal to the inoculation site is the hallmark of CSD.³ Given the absence of lymphadenopathy in our patient as well as the sporadic distribution of lesions, CSD was an unlikely diagnosis.

Dermatitis herpetiformis (DH) is an autoimmune disorder with cutaneous manifestations of gluten sensitivity. Dermatitis herpetiformis presents as extremely pruritic papules and vesicles arranged in groups on areas such as the elbows, dorsal aspects of the forearms, knees, scalp, back, and buttocks. Most patients with DH have celiac disease or small bowel disease related to gluten sensitivity.4 Given our patient’s acute presentation in adulthood and lack of gluten sensitivity, DH was an unlikely diagnosis.

Bullous fixed drug reaction is a cutaneous eruption that typically presents in the setting of exposure to an offending drug/agent. Drug reactions can have various cutaneous presentations, with the most common being pigmented macules that progress into plaques.⁵ Given the isolated nature of our patient’s episode and apparent lack of association with medication, bullous fixed drug reaction was an unlikely diagnosis.

Tinea corporis bullosa is a rare clinical variant of tinea corporis that has only been reported in patients with a history of contact with different animals. There are many causative organisms related to tinea corporis; Trichophyton rubrum is the most common etiology of tinea corporis, while tinea corporis due to close contact with domesticated animals often is caused by M canis.⁶ The immunoinhibitory properties of the mannans in the fungal cell wall allow the organisms to adhere to the skin prior to invasion. Cutaneous invasion into dead cornified layers of the skin is credited to the proteases, subtilisinlike proteases (subtilases), and keratinases produced by the fungus.¹ There are many different clinical presentations of tinea corporis due to the variability of causative organisms. An annular (ring-shaped) lesion with a central plaque and advancing border is the most typical presentation. Tinea corporis bullosa is characterized by the presence of bullae or vesicles in the borders of the scaly plaque. Rupture of the bullae subsequently leads to erosions and crusts over the plaque.

The diagnosis of tinea corporis bullosa often is clinical if the lesion is typical and can be confirmed using KOH preparation and fungal culture. Once the diagnosis is confirmed, topical antifungals are the standard treatment approach for localized superficial tinea corporis. Systemic antifungal treatment can be initiated if the lesion is extensive, recurrent, chronic, or unresponsive to topical treatment.¹ Given our patient’s characteristic presentation, she was managed with an over-the-counter topical antifungal (terbinafine). The patient’s lesions dramatically improved, rendering oral therapy unnecessary. At 1-month follow-up, the rash had nearly resolved.

The Diagnosis: Tinea Corporis Bullosa

At the time of presentation, a potassium hydroxide (KOH) preparation, fungal culture, and punch biopsy of the right ventral wrist was performed. The KOH preparation was positive for fungal hyphae characteristic of dermatophyte infections. Histologically, the biopsy showed intraepidermal and subepidermal blisters with neutrophil- and lymphocyte-rich contents (Figure 1). Fungal hyphae and spores were present within the stratum corneum and superficial epidermis (Figure 2), and fungal cultures grew Microsporum canis. The extent of the rash (upper and lower extremities, chest, and back), positive fungal culture, and KOH preparation all supported the diagnosis of tinea corporis bullosa, which was confirmed with biopsy. Oral prednisone use was discouraged and triamcinolone ointment was discontinued given that inappropriate treatment with steroids in the setting of fungal infection suppresses an inflammatory response and alters clinical appearance, obviating the persistent underlying infection.

Tinea corporis bullosa is a rare superficial dermatophyte fungal infection that often is acquired by close personto- person contact or contact with domestic animals. The infection begins as a circular pruritic plaque, generally with raised borders, which may be erythematous or hyperpigmented. By definition, tinea corporis occurs in sites other than the face, feet, hands, or groin area. Bullae formation is thought to be secondary to a delayed hypersensitivity reaction provoked by the presence of a dermatophyte antigen.¹

Linear IgA bullous dermatosis is an immunemediated disease characterized by IgA deposition at the dermoepidermal junction. Linear IgA bullous dermatosis classically presents as widespread tense vesicles in an arciform or annular pattern. Mucosal involvement is common and typically presents with erosions, ulcerations, and scarring.² Given the absence of mucosal involvement in our patient and a positive KOH preparation, linear IgA bullous dermatosis was an unlikely diagnosis.

Benign inoculation lymphoreticulosis, more commonly known as cat scratch disease (CSD), is a Bartonella henselae infection that results from a cat scratch or bite. Cat scratch disease can present as localized cutaneous and nodal involvement (lymphadenopathy) near the site of inoculation, or it may present as disseminated disease. Cutaneous lesions generally progress through vesicular, erythematous, and papular phases. Regional lymphadenopathy proximal to the inoculation site is the hallmark of CSD.³ Given the absence of lymphadenopathy in our patient as well as the sporadic distribution of lesions, CSD was an unlikely diagnosis.

Dermatitis herpetiformis (DH) is an autoimmune disorder with cutaneous manifestations of gluten sensitivity. Dermatitis herpetiformis presents as extremely pruritic papules and vesicles arranged in groups on areas such as the elbows, dorsal aspects of the forearms, knees, scalp, back, and buttocks. Most patients with DH have celiac disease or small bowel disease related to gluten sensitivity.4 Given our patient’s acute presentation in adulthood and lack of gluten sensitivity, DH was an unlikely diagnosis.

Bullous fixed drug reaction is a cutaneous eruption that typically presents in the setting of exposure to an offending drug/agent. Drug reactions can have various cutaneous presentations, with the most common being pigmented macules that progress into plaques.⁵ Given the isolated nature of our patient’s episode and apparent lack of association with medication, bullous fixed drug reaction was an unlikely diagnosis.

Tinea corporis bullosa is a rare clinical variant of tinea corporis that has only been reported in patients with a history of contact with different animals. There are many causative organisms related to tinea corporis; Trichophyton rubrum is the most common etiology of tinea corporis, while tinea corporis due to close contact with domesticated animals often is caused by M canis.⁶ The immunoinhibitory properties of the mannans in the fungal cell wall allow the organisms to adhere to the skin prior to invasion. Cutaneous invasion into dead cornified layers of the skin is credited to the proteases, subtilisinlike proteases (subtilases), and keratinases produced by the fungus.¹ There are many different clinical presentations of tinea corporis due to the variability of causative organisms. An annular (ring-shaped) lesion with a central plaque and advancing border is the most typical presentation. Tinea corporis bullosa is characterized by the presence of bullae or vesicles in the borders of the scaly plaque. Rupture of the bullae subsequently leads to erosions and crusts over the plaque.

The diagnosis of tinea corporis bullosa often is clinical if the lesion is typical and can be confirmed using KOH preparation and fungal culture. Once the diagnosis is confirmed, topical antifungals are the standard treatment approach for localized superficial tinea corporis. Systemic antifungal treatment can be initiated if the lesion is extensive, recurrent, chronic, or unresponsive to topical treatment.¹ Given our patient’s characteristic presentation, she was managed with an over-the-counter topical antifungal (terbinafine). The patient’s lesions dramatically improved, rendering oral therapy unnecessary. At 1-month follow-up, the rash had nearly resolved.