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The Diagnosis: Pemphigus Foliaceous

Laboratory workup including a complete blood cell count with differential, comprehensive metabolic panel, antinuclear antibodies, Sjögren syndrome A and B antibodies, hepatitis profile, rapid plasma reagin, HIV screen, aldolase, anti–Jo-1, T-Spot TB test (Quest Diagnostics), and tissue cultures was unremarkable. Two 4-mm punch biopsies were obtained from the left cheek and upper back, both of which demonstrated intragranular acantholysis suggestive of pemphigus foliaceous (Figure 1A). A subsequent punch biopsy from the right lower abdomen sent for direct immunofluorescence demonstrated netlike positivity of IgG and C3 in the upper epidermis (Figure 1B), and serum sent for indirect immunofluorescence demonstrated intercellular IgG antibodies to desmoglein (Dsg) 1 on monkey esophagus and positive Dsg-1 antibodies on enzyme-linked immunosorbent assay, confirming the diagnosis.

The patient was started on a 60-mg prednisone taper as well as dapsone 50 mg daily; the dapsone was titrated up to 100 mg daily. After tapering down to 10 mg daily of prednisone over 2 months and continuing dapsone with minimal improvement, he was given 2 infusions of rituximab 1000 mg 2 weeks apart. The scalp plaque was dramatically improved at 3-month follow-up (Figure 2), with partial improvement of the cheek plaques (Figure 3). Dapsone was increased to 150 mg daily, and he was encouraged to use triamcinolone acetonide ointment 0.1% twice daily, which led to further improvement.

Pemphigus foliaceus is an autoimmune blistering disease that most commonly occurs in middle-aged adults. It generally is less common than pemphigus vulgaris, except in Finland, Tunisia, and Brazil, where there is an endemic condition with an identical clinical and histological presentation known as fogo selvagem.¹

The pathogenesis of pemphigus foliaceous is characterized by IgG autoantibodies against Dsg-1, a transmembrane glycoprotein involved in the cellular adhesion of keratinocytes, which is preferentially expressed in the superficial epidermis.^2-7 Dysfunction of Dsg-1 results in the separation of superficial epidermal cells, resulting in intraepidermal blisters.^2,7 In contrast to pemphigus vulgaris, there typically is a lack of oral mucosal involvement due to compensation by Dsg-3 in the mucosa.⁴ Potential triggers for pemphigus foliaceous include exposure to UV radiation; radiotherapy; pregnancy; physiologic stress; and drugs, most commonly captopril, penicillamine, and thiols.⁸

Pemphigus foliaceous lesions clinically appear as eroded and crusted lesions on an erythematous base, commonly in a seborrheic distribution on the face, scalp, and trunk with sparing of the oral mucosa,^2,6 but lesions can progress to a widespread and more severe exfoliative dermatitis.⁷ Lesions also can appear as psoriasiform plaques and often are initially misdiagnosed as psoriasis, particularly in patients with skin of color.^9,10

Diagnosis of pemphigus foliaceous typically is made using a combination of histology as well as both direct and indirect immunofluorescence. Histologically, pemphigus foliaceus presents with subcorneal acantholysis, which is most prominent in the granular layer and occasionally the presence of neutrophils and eosinophils in the blister cavity.⁷ Direct immunofluorescence demonstrates netlike intercellular IgG and C3 in the upper portion of the epidermis.¹¹ Indirect immunofluorescence can help detect circulating IgG antibodies to Dsg-1, with guinea pig esophagus being the ideal substrate.^11,12

First-line treatment of pemphigus foliaceus consists of systemic glucocorticoid therapy, often administered with azathioprine, methotrexate, or mycophenolate mofetil.^2,6,13 Although first-line treatment is effective in 60% to 80% of patients,² relapsing cases can be treated with cyclophosphamide, intravenous immunoglobulin, immunoadsorption, plasmapheresis, or rituximab.²

Rituximab is a chimeric monoclonal antibody targeting CD20⁺ B cells, leading to decreased antibody production, which has been shown to be effective in treating severe and refractory cases of pemphigus foliaceus.^6,13Rituximab with short-course prednisone has been found to be more effective in achieving complete remission at 24 months than prednisone alone.¹⁴ In patients with contraindications to systemic glucocorticoid therapy, rituximab has been shown as an effective first-line therapy.¹⁵ One-quarter of patients treated with rituximab relapsed within 2 years of treatment⁶ (average time to relapse, 6–26 months).¹⁶ High-dose rituximab regimens, along with a higher number of rituximab treatment cycles, have been shown to prolong time to relapse.⁶ Further, higher baseline levels of Dsg-1 antibody have been correlated to earlier relapse and can be used following rituximab therapy to monitor disease progression.^6,16

The differential diagnosis for pemphigus foliaceous includes disseminated blastomycosis, hypertrophic lupus erythematosus, sebopsoriasis, and secondary syphilis. Disseminated blastomycosis presents with cutaneous manifestations such as nodules, papules, or pustules evolving over weeks to months into ulcers with subsequent scarring.¹⁷ Hypertrophic lupus erythematosus presents with papules and nodules with associated keratotic scaling on the face, palms, and extensor surfaces of the limbs.¹⁸ Sebopsoriasis is characterized by well-defined lesions with an overlying scale distributed on the scalp, face, and chest.¹⁹ Secondary syphilis presents as early hyperpigmented macules transitioning to acral papulosquamous lesions involving the palms and soles.²⁰

The Diagnosis: Pemphigus Foliaceous

Laboratory workup including a complete blood cell count with differential, comprehensive metabolic panel, antinuclear antibodies, Sjögren syndrome A and B antibodies, hepatitis profile, rapid plasma reagin, HIV screen, aldolase, anti–Jo-1, T-Spot TB test (Quest Diagnostics), and tissue cultures was unremarkable. Two 4-mm punch biopsies were obtained from the left cheek and upper back, both of which demonstrated intragranular acantholysis suggestive of pemphigus foliaceous (Figure 1A). A subsequent punch biopsy from the right lower abdomen sent for direct immunofluorescence demonstrated netlike positivity of IgG and C3 in the upper epidermis (Figure 1B), and serum sent for indirect immunofluorescence demonstrated intercellular IgG antibodies to desmoglein (Dsg) 1 on monkey esophagus and positive Dsg-1 antibodies on enzyme-linked immunosorbent assay, confirming the diagnosis.

The patient was started on a 60-mg prednisone taper as well as dapsone 50 mg daily; the dapsone was titrated up to 100 mg daily. After tapering down to 10 mg daily of prednisone over 2 months and continuing dapsone with minimal improvement, he was given 2 infusions of rituximab 1000 mg 2 weeks apart. The scalp plaque was dramatically improved at 3-month follow-up (Figure 2), with partial improvement of the cheek plaques (Figure 3). Dapsone was increased to 150 mg daily, and he was encouraged to use triamcinolone acetonide ointment 0.1% twice daily, which led to further improvement.

Pemphigus foliaceus is an autoimmune blistering disease that most commonly occurs in middle-aged adults. It generally is less common than pemphigus vulgaris, except in Finland, Tunisia, and Brazil, where there is an endemic condition with an identical clinical and histological presentation known as fogo selvagem.¹

The pathogenesis of pemphigus foliaceous is characterized by IgG autoantibodies against Dsg-1, a transmembrane glycoprotein involved in the cellular adhesion of keratinocytes, which is preferentially expressed in the superficial epidermis.^2-7 Dysfunction of Dsg-1 results in the separation of superficial epidermal cells, resulting in intraepidermal blisters.^2,7 In contrast to pemphigus vulgaris, there typically is a lack of oral mucosal involvement due to compensation by Dsg-3 in the mucosa.⁴ Potential triggers for pemphigus foliaceous include exposure to UV radiation; radiotherapy; pregnancy; physiologic stress; and drugs, most commonly captopril, penicillamine, and thiols.⁸

Pemphigus foliaceous lesions clinically appear as eroded and crusted lesions on an erythematous base, commonly in a seborrheic distribution on the face, scalp, and trunk with sparing of the oral mucosa,^2,6 but lesions can progress to a widespread and more severe exfoliative dermatitis.⁷ Lesions also can appear as psoriasiform plaques and often are initially misdiagnosed as psoriasis, particularly in patients with skin of color.^9,10

Diagnosis of pemphigus foliaceous typically is made using a combination of histology as well as both direct and indirect immunofluorescence. Histologically, pemphigus foliaceus presents with subcorneal acantholysis, which is most prominent in the granular layer and occasionally the presence of neutrophils and eosinophils in the blister cavity.⁷ Direct immunofluorescence demonstrates netlike intercellular IgG and C3 in the upper portion of the epidermis.¹¹ Indirect immunofluorescence can help detect circulating IgG antibodies to Dsg-1, with guinea pig esophagus being the ideal substrate.^11,12

First-line treatment of pemphigus foliaceus consists of systemic glucocorticoid therapy, often administered with azathioprine, methotrexate, or mycophenolate mofetil.^2,6,13 Although first-line treatment is effective in 60% to 80% of patients,² relapsing cases can be treated with cyclophosphamide, intravenous immunoglobulin, immunoadsorption, plasmapheresis, or rituximab.²

Rituximab is a chimeric monoclonal antibody targeting CD20⁺ B cells, leading to decreased antibody production, which has been shown to be effective in treating severe and refractory cases of pemphigus foliaceus.^6,13Rituximab with short-course prednisone has been found to be more effective in achieving complete remission at 24 months than prednisone alone.¹⁴ In patients with contraindications to systemic glucocorticoid therapy, rituximab has been shown as an effective first-line therapy.¹⁵ One-quarter of patients treated with rituximab relapsed within 2 years of treatment⁶ (average time to relapse, 6–26 months).¹⁶ High-dose rituximab regimens, along with a higher number of rituximab treatment cycles, have been shown to prolong time to relapse.⁶ Further, higher baseline levels of Dsg-1 antibody have been correlated to earlier relapse and can be used following rituximab therapy to monitor disease progression.^6,16

The differential diagnosis for pemphigus foliaceous includes disseminated blastomycosis, hypertrophic lupus erythematosus, sebopsoriasis, and secondary syphilis. Disseminated blastomycosis presents with cutaneous manifestations such as nodules, papules, or pustules evolving over weeks to months into ulcers with subsequent scarring.¹⁷ Hypertrophic lupus erythematosus presents with papules and nodules with associated keratotic scaling on the face, palms, and extensor surfaces of the limbs.¹⁸ Sebopsoriasis is characterized by well-defined lesions with an overlying scale distributed on the scalp, face, and chest.¹⁹ Secondary syphilis presents as early hyperpigmented macules transitioning to acral papulosquamous lesions involving the palms and soles.²⁰

The Diagnosis: Pemphigus Foliaceous

Laboratory workup including a complete blood cell count with differential, comprehensive metabolic panel, antinuclear antibodies, Sjögren syndrome A and B antibodies, hepatitis profile, rapid plasma reagin, HIV screen, aldolase, anti–Jo-1, T-Spot TB test (Quest Diagnostics), and tissue cultures was unremarkable. Two 4-mm punch biopsies were obtained from the left cheek and upper back, both of which demonstrated intragranular acantholysis suggestive of pemphigus foliaceous (Figure 1A). A subsequent punch biopsy from the right lower abdomen sent for direct immunofluorescence demonstrated netlike positivity of IgG and C3 in the upper epidermis (Figure 1B), and serum sent for indirect immunofluorescence demonstrated intercellular IgG antibodies to desmoglein (Dsg) 1 on monkey esophagus and positive Dsg-1 antibodies on enzyme-linked immunosorbent assay, confirming the diagnosis.

The patient was started on a 60-mg prednisone taper as well as dapsone 50 mg daily; the dapsone was titrated up to 100 mg daily. After tapering down to 10 mg daily of prednisone over 2 months and continuing dapsone with minimal improvement, he was given 2 infusions of rituximab 1000 mg 2 weeks apart. The scalp plaque was dramatically improved at 3-month follow-up (Figure 2), with partial improvement of the cheek plaques (Figure 3). Dapsone was increased to 150 mg daily, and he was encouraged to use triamcinolone acetonide ointment 0.1% twice daily, which led to further improvement.

Pemphigus foliaceus is an autoimmune blistering disease that most commonly occurs in middle-aged adults. It generally is less common than pemphigus vulgaris, except in Finland, Tunisia, and Brazil, where there is an endemic condition with an identical clinical and histological presentation known as fogo selvagem.¹

The pathogenesis of pemphigus foliaceous is characterized by IgG autoantibodies against Dsg-1, a transmembrane glycoprotein involved in the cellular adhesion of keratinocytes, which is preferentially expressed in the superficial epidermis.^2-7 Dysfunction of Dsg-1 results in the separation of superficial epidermal cells, resulting in intraepidermal blisters.^2,7 In contrast to pemphigus vulgaris, there typically is a lack of oral mucosal involvement due to compensation by Dsg-3 in the mucosa.⁴ Potential triggers for pemphigus foliaceous include exposure to UV radiation; radiotherapy; pregnancy; physiologic stress; and drugs, most commonly captopril, penicillamine, and thiols.⁸

Pemphigus foliaceous lesions clinically appear as eroded and crusted lesions on an erythematous base, commonly in a seborrheic distribution on the face, scalp, and trunk with sparing of the oral mucosa,^2,6 but lesions can progress to a widespread and more severe exfoliative dermatitis.⁷ Lesions also can appear as psoriasiform plaques and often are initially misdiagnosed as psoriasis, particularly in patients with skin of color.^9,10

Diagnosis of pemphigus foliaceous typically is made using a combination of histology as well as both direct and indirect immunofluorescence. Histologically, pemphigus foliaceus presents with subcorneal acantholysis, which is most prominent in the granular layer and occasionally the presence of neutrophils and eosinophils in the blister cavity.⁷ Direct immunofluorescence demonstrates netlike intercellular IgG and C3 in the upper portion of the epidermis.¹¹ Indirect immunofluorescence can help detect circulating IgG antibodies to Dsg-1, with guinea pig esophagus being the ideal substrate.^11,12

First-line treatment of pemphigus foliaceus consists of systemic glucocorticoid therapy, often administered with azathioprine, methotrexate, or mycophenolate mofetil.^2,6,13 Although first-line treatment is effective in 60% to 80% of patients,² relapsing cases can be treated with cyclophosphamide, intravenous immunoglobulin, immunoadsorption, plasmapheresis, or rituximab.²

Rituximab is a chimeric monoclonal antibody targeting CD20⁺ B cells, leading to decreased antibody production, which has been shown to be effective in treating severe and refractory cases of pemphigus foliaceus.^6,13Rituximab with short-course prednisone has been found to be more effective in achieving complete remission at 24 months than prednisone alone.¹⁴ In patients with contraindications to systemic glucocorticoid therapy, rituximab has been shown as an effective first-line therapy.¹⁵ One-quarter of patients treated with rituximab relapsed within 2 years of treatment⁶ (average time to relapse, 6–26 months).¹⁶ High-dose rituximab regimens, along with a higher number of rituximab treatment cycles, have been shown to prolong time to relapse.⁶ Further, higher baseline levels of Dsg-1 antibody have been correlated to earlier relapse and can be used following rituximab therapy to monitor disease progression.^6,16

The differential diagnosis for pemphigus foliaceous includes disseminated blastomycosis, hypertrophic lupus erythematosus, sebopsoriasis, and secondary syphilis. Disseminated blastomycosis presents with cutaneous manifestations such as nodules, papules, or pustules evolving over weeks to months into ulcers with subsequent scarring.¹⁷ Hypertrophic lupus erythematosus presents with papules and nodules with associated keratotic scaling on the face, palms, and extensor surfaces of the limbs.¹⁸ Sebopsoriasis is characterized by well-defined lesions with an overlying scale distributed on the scalp, face, and chest.¹⁹ Secondary syphilis presents as early hyperpigmented macules transitioning to acral papulosquamous lesions involving the palms and soles.²⁰

The Diagnosis: Generalized Bullous Fixed Drug Eruption

A punch biopsy from the left thigh revealed a vacuolar interface dermatitis with full-thickness necrosis of the epidermis and a patchy lichenoid inflammatory cell infiltrate in the superficial dermis consistent with a generalized bullous fixed drug eruption (GBFDE). The patient received supportive care and methylprednisolone with improvement of symptoms.

Generalized bullous fixed drug eruption is a rare, potentially life-threatening form of a fixed drug eruption (FDE), a cutaneous drug reaction that occurs in response to a causative medication. It typically presents with welldemarcated, dusky, erythematous patches or plaques that recur in the same sites with repeat exposure.¹ The pathogenesis of FDE has been hypothesized to involve epidermal CD8+ T cells, which are activated by drug exposure and release cytotoxic molecules including Fas, Fas ligand, perforin, and granzyme B, resulting in lysis of the surrounding keratinocytes.^1-3 Common eliciting drugs include nonsteroidal anti-inflammatory drugs, antibacterial agents (particularly trimethoprim-sulfamethoxazole), barbiturates, acetaminophen, and antimalarials.1 In addition to the findings seen in FDE, GBFDE is characterized by widespread bullous skin lesions.^1-4 Typical histologic patterns seen in GBFDE are dispersed epidermal apoptotic keratinocytes, prominent dermal eosinophilic and lymphocytic infiltrates, and dermal melanophages.³ Discontinuing the causative agent and diligent prevention of re-exposure are the most important steps in management, as additional exposures can increase the number of lesions and overall severity. Symptoms typically resolve 7 to 14 days after drug discontinuation, often with postinflammatory hyperpigmentation.³

Generalized bullous fixed drug eruption presents a diagnostic challenge, as it sometimes involves the oral mucosa and can exhibit the Nikolsky sign. Thus, it often is confused with Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN).^1,4 Stevens-Johnson syndrome and TEN are severe cutaneous drug eruptions that also can present with diffuse bullous skin lesions. Stevens-Johnson syndrome and TEN are thought to be a spectrum of the same disease that initially presents with dusky red macules that can coalesce, develop central blistering, and lead to skin detachment.⁵ Stevens-Johnson syndrome is defined as skin detachment of less than 10% body surface area (BSA); TEN is defined as skin detachment of more than 30% BSA. Stevens-Johnson syndrome/TEN overlap syndrome includes skin detachment of 10% to 30% BSA.⁵

Causative medications overlap substantially with GBFDE and include anticonvulsants, sulfa-containing drugs, antibiotics, nonsteroidal anti-inflammatory drugs, and uric acid–lowering agents. The histology of SJS/TEN also is quite similar to GBFDE, and these entities may be indistinguishable without clinical information.⁵ Lee et al¹ found that absence of grouped necrotic keratinocytes (fire flag sign), deep inflammatory infiltrates, notable pigment incontinence, and higher eosinophil counts appear to be more common in GBFDE than SJS/TEN. Constitutional symptoms and mucosal involvement also were more frequent in SJS/TEN.

The timing of clinical presentation and medical history can be useful in differentiating between SJS/TEN and GBFDE. In SJS/TEN, drug exposure typically occurs 1 to 3 weeks before onset of symptoms vs 30 minutes to 24 hours in GBFDE.³ Additionally, a history of similar eruption in the same location is pathognomonic for GBFDE. Although GBFDE has been thought to have a better prognosis than SJS/TEN, more recent data suggest mortality rates may be similar.³ A case-control study found a mortality rate of 22% (13/58) in patients with GBFDE compared to 28% (n=170) in SJS/TEN patients.⁴

Erythema multiforme (EM) is an uncommon immunemediated disorder that typically presents as targetoid lesions with central epidermal necrosis in an acral distribution. Erythema multiforme can arise from a variety of factors, but up to 90% of cases are due to infection, most commonly herpes simplex virus; medications account for less than 10% of cases.⁶ Previously, EM has been thought to be on the same disease spectrum as SJS and TEN. It is now clear that EM is a separate entity with similar mucosal erosions but different cutaneous findings,⁶ mainly typical target lesions that differ from the atypical targets seen in SJS.

Staphylococcal scalded skin syndrome is a blistering skin disorder associated with local Staphylococcus aureus infection. It most commonly is seen in children and rarely occurs in adults who are not on dialysis. Some Staphylococcus strains produce exfoliative toxins A and B, which are serine proteases that target and cleave desmoglein 1, a mediator of keratinocyte adhesion. Staphylococcal scalded skin syndrome initially presents with erythema accentuated in the skin folds that becomes generalized. The disruption of keratinocyte adhesion leads to bullae formation in areas of erythema and diffuse sheetlike desquamation. Pathology reveals subcorneal rather than subepidermal blistering, which is seen in GBFDE and SJS/TEN. Treatment involves antistaphylococcal antibiotics and supportive care. With proper treatment, most cases resolve within 2 to 3 weeks.⁷

Mycoplasma pneumoniae–induced rash and mucositis presents with prominent mucositis and can have cutaneous findings of sparse vesiculobullous or targetoid eruption.⁸Mycoplasma pneumoniae typically infects the lungs and is a leading cause of community-acquired pneumonia. However, a subset of patients can have extrapulmonary disease presenting as mucocutaneous eruptions, which is preceded by an approximately weeklong prodrome of fever, cough, and malaise.⁷Mycoplasma pneumoniae–induced rash and mucositis also affect children and young patients and is more common in males.⁸

The Diagnosis: Generalized Bullous Fixed Drug Eruption

A punch biopsy from the left thigh revealed a vacuolar interface dermatitis with full-thickness necrosis of the epidermis and a patchy lichenoid inflammatory cell infiltrate in the superficial dermis consistent with a generalized bullous fixed drug eruption (GBFDE). The patient received supportive care and methylprednisolone with improvement of symptoms.

Generalized bullous fixed drug eruption is a rare, potentially life-threatening form of a fixed drug eruption (FDE), a cutaneous drug reaction that occurs in response to a causative medication. It typically presents with welldemarcated, dusky, erythematous patches or plaques that recur in the same sites with repeat exposure.¹ The pathogenesis of FDE has been hypothesized to involve epidermal CD8+ T cells, which are activated by drug exposure and release cytotoxic molecules including Fas, Fas ligand, perforin, and granzyme B, resulting in lysis of the surrounding keratinocytes.^1-3 Common eliciting drugs include nonsteroidal anti-inflammatory drugs, antibacterial agents (particularly trimethoprim-sulfamethoxazole), barbiturates, acetaminophen, and antimalarials.1 In addition to the findings seen in FDE, GBFDE is characterized by widespread bullous skin lesions.^1-4 Typical histologic patterns seen in GBFDE are dispersed epidermal apoptotic keratinocytes, prominent dermal eosinophilic and lymphocytic infiltrates, and dermal melanophages.³ Discontinuing the causative agent and diligent prevention of re-exposure are the most important steps in management, as additional exposures can increase the number of lesions and overall severity. Symptoms typically resolve 7 to 14 days after drug discontinuation, often with postinflammatory hyperpigmentation.³

Generalized bullous fixed drug eruption presents a diagnostic challenge, as it sometimes involves the oral mucosa and can exhibit the Nikolsky sign. Thus, it often is confused with Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN).^1,4 Stevens-Johnson syndrome and TEN are severe cutaneous drug eruptions that also can present with diffuse bullous skin lesions. Stevens-Johnson syndrome and TEN are thought to be a spectrum of the same disease that initially presents with dusky red macules that can coalesce, develop central blistering, and lead to skin detachment.⁵ Stevens-Johnson syndrome is defined as skin detachment of less than 10% body surface area (BSA); TEN is defined as skin detachment of more than 30% BSA. Stevens-Johnson syndrome/TEN overlap syndrome includes skin detachment of 10% to 30% BSA.⁵

Causative medications overlap substantially with GBFDE and include anticonvulsants, sulfa-containing drugs, antibiotics, nonsteroidal anti-inflammatory drugs, and uric acid–lowering agents. The histology of SJS/TEN also is quite similar to GBFDE, and these entities may be indistinguishable without clinical information.⁵ Lee et al¹ found that absence of grouped necrotic keratinocytes (fire flag sign), deep inflammatory infiltrates, notable pigment incontinence, and higher eosinophil counts appear to be more common in GBFDE than SJS/TEN. Constitutional symptoms and mucosal involvement also were more frequent in SJS/TEN.

The timing of clinical presentation and medical history can be useful in differentiating between SJS/TEN and GBFDE. In SJS/TEN, drug exposure typically occurs 1 to 3 weeks before onset of symptoms vs 30 minutes to 24 hours in GBFDE.³ Additionally, a history of similar eruption in the same location is pathognomonic for GBFDE. Although GBFDE has been thought to have a better prognosis than SJS/TEN, more recent data suggest mortality rates may be similar.³ A case-control study found a mortality rate of 22% (13/58) in patients with GBFDE compared to 28% (n=170) in SJS/TEN patients.⁴

Erythema multiforme (EM) is an uncommon immunemediated disorder that typically presents as targetoid lesions with central epidermal necrosis in an acral distribution. Erythema multiforme can arise from a variety of factors, but up to 90% of cases are due to infection, most commonly herpes simplex virus; medications account for less than 10% of cases.⁶ Previously, EM has been thought to be on the same disease spectrum as SJS and TEN. It is now clear that EM is a separate entity with similar mucosal erosions but different cutaneous findings,⁶ mainly typical target lesions that differ from the atypical targets seen in SJS.

Staphylococcal scalded skin syndrome is a blistering skin disorder associated with local Staphylococcus aureus infection. It most commonly is seen in children and rarely occurs in adults who are not on dialysis. Some Staphylococcus strains produce exfoliative toxins A and B, which are serine proteases that target and cleave desmoglein 1, a mediator of keratinocyte adhesion. Staphylococcal scalded skin syndrome initially presents with erythema accentuated in the skin folds that becomes generalized. The disruption of keratinocyte adhesion leads to bullae formation in areas of erythema and diffuse sheetlike desquamation. Pathology reveals subcorneal rather than subepidermal blistering, which is seen in GBFDE and SJS/TEN. Treatment involves antistaphylococcal antibiotics and supportive care. With proper treatment, most cases resolve within 2 to 3 weeks.⁷

Mycoplasma pneumoniae–induced rash and mucositis presents with prominent mucositis and can have cutaneous findings of sparse vesiculobullous or targetoid eruption.⁸Mycoplasma pneumoniae typically infects the lungs and is a leading cause of community-acquired pneumonia. However, a subset of patients can have extrapulmonary disease presenting as mucocutaneous eruptions, which is preceded by an approximately weeklong prodrome of fever, cough, and malaise.⁷Mycoplasma pneumoniae–induced rash and mucositis also affect children and young patients and is more common in males.⁸

The Diagnosis: Generalized Bullous Fixed Drug Eruption

A punch biopsy from the left thigh revealed a vacuolar interface dermatitis with full-thickness necrosis of the epidermis and a patchy lichenoid inflammatory cell infiltrate in the superficial dermis consistent with a generalized bullous fixed drug eruption (GBFDE). The patient received supportive care and methylprednisolone with improvement of symptoms.

Generalized bullous fixed drug eruption is a rare, potentially life-threatening form of a fixed drug eruption (FDE), a cutaneous drug reaction that occurs in response to a causative medication. It typically presents with welldemarcated, dusky, erythematous patches or plaques that recur in the same sites with repeat exposure.¹ The pathogenesis of FDE has been hypothesized to involve epidermal CD8+ T cells, which are activated by drug exposure and release cytotoxic molecules including Fas, Fas ligand, perforin, and granzyme B, resulting in lysis of the surrounding keratinocytes.^1-3 Common eliciting drugs include nonsteroidal anti-inflammatory drugs, antibacterial agents (particularly trimethoprim-sulfamethoxazole), barbiturates, acetaminophen, and antimalarials.1 In addition to the findings seen in FDE, GBFDE is characterized by widespread bullous skin lesions.^1-4 Typical histologic patterns seen in GBFDE are dispersed epidermal apoptotic keratinocytes, prominent dermal eosinophilic and lymphocytic infiltrates, and dermal melanophages.³ Discontinuing the causative agent and diligent prevention of re-exposure are the most important steps in management, as additional exposures can increase the number of lesions and overall severity. Symptoms typically resolve 7 to 14 days after drug discontinuation, often with postinflammatory hyperpigmentation.³

Generalized bullous fixed drug eruption presents a diagnostic challenge, as it sometimes involves the oral mucosa and can exhibit the Nikolsky sign. Thus, it often is confused with Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN).^1,4 Stevens-Johnson syndrome and TEN are severe cutaneous drug eruptions that also can present with diffuse bullous skin lesions. Stevens-Johnson syndrome and TEN are thought to be a spectrum of the same disease that initially presents with dusky red macules that can coalesce, develop central blistering, and lead to skin detachment.⁵ Stevens-Johnson syndrome is defined as skin detachment of less than 10% body surface area (BSA); TEN is defined as skin detachment of more than 30% BSA. Stevens-Johnson syndrome/TEN overlap syndrome includes skin detachment of 10% to 30% BSA.⁵

Causative medications overlap substantially with GBFDE and include anticonvulsants, sulfa-containing drugs, antibiotics, nonsteroidal anti-inflammatory drugs, and uric acid–lowering agents. The histology of SJS/TEN also is quite similar to GBFDE, and these entities may be indistinguishable without clinical information.⁵ Lee et al¹ found that absence of grouped necrotic keratinocytes (fire flag sign), deep inflammatory infiltrates, notable pigment incontinence, and higher eosinophil counts appear to be more common in GBFDE than SJS/TEN. Constitutional symptoms and mucosal involvement also were more frequent in SJS/TEN.

The timing of clinical presentation and medical history can be useful in differentiating between SJS/TEN and GBFDE. In SJS/TEN, drug exposure typically occurs 1 to 3 weeks before onset of symptoms vs 30 minutes to 24 hours in GBFDE.³ Additionally, a history of similar eruption in the same location is pathognomonic for GBFDE. Although GBFDE has been thought to have a better prognosis than SJS/TEN, more recent data suggest mortality rates may be similar.³ A case-control study found a mortality rate of 22% (13/58) in patients with GBFDE compared to 28% (n=170) in SJS/TEN patients.⁴

Erythema multiforme (EM) is an uncommon immunemediated disorder that typically presents as targetoid lesions with central epidermal necrosis in an acral distribution. Erythema multiforme can arise from a variety of factors, but up to 90% of cases are due to infection, most commonly herpes simplex virus; medications account for less than 10% of cases.⁶ Previously, EM has been thought to be on the same disease spectrum as SJS and TEN. It is now clear that EM is a separate entity with similar mucosal erosions but different cutaneous findings,⁶ mainly typical target lesions that differ from the atypical targets seen in SJS.

Staphylococcal scalded skin syndrome is a blistering skin disorder associated with local Staphylococcus aureus infection. It most commonly is seen in children and rarely occurs in adults who are not on dialysis. Some Staphylococcus strains produce exfoliative toxins A and B, which are serine proteases that target and cleave desmoglein 1, a mediator of keratinocyte adhesion. Staphylococcal scalded skin syndrome initially presents with erythema accentuated in the skin folds that becomes generalized. The disruption of keratinocyte adhesion leads to bullae formation in areas of erythema and diffuse sheetlike desquamation. Pathology reveals subcorneal rather than subepidermal blistering, which is seen in GBFDE and SJS/TEN. Treatment involves antistaphylococcal antibiotics and supportive care. With proper treatment, most cases resolve within 2 to 3 weeks.⁷

Mycoplasma pneumoniae–induced rash and mucositis presents with prominent mucositis and can have cutaneous findings of sparse vesiculobullous or targetoid eruption.⁸Mycoplasma pneumoniae typically infects the lungs and is a leading cause of community-acquired pneumonia. However, a subset of patients can have extrapulmonary disease presenting as mucocutaneous eruptions, which is preceded by an approximately weeklong prodrome of fever, cough, and malaise.⁷Mycoplasma pneumoniae–induced rash and mucositis also affect children and young patients and is more common in males.⁸

The Diagnosis: Disseminated Coccidioidomycosis

A6-mm punch biopsy was performed at the periphery of the ulcerated cutaneous lesion on the chest revealing extensive spherules. Serum antibody immunodiffusion for histoplasmosis and blastomycoses both were negative; however, B-D-glucan assay was positive at 364 pg/mL (reference range: <60 pg/mL, negative). Initial HIV-1 and HIV-2 antibody and antigen testing was negative as well as repeat testing at 3 weeks. Immunodiffusion for Coccidioides IgM and IgG was positive, and cocci antibody IgG complement fixation assays were positive at titers of 1:64 (reference range: <1:2, negative). A computed tomography needle-guided biopsy of the paravertebral soft tissue was performed. Gram stains and bacterial cultures of the biopsies were negative; however, fungal cultures were notable for growth of Coccidioides. Given the pertinent testing, a diagnosis of disseminated coccidioidomycosis was made.

Cutaneous coccidioidomycosis can occur in 3 situations: direct inoculation (primary cutaneous coccidioidomycosis), disseminated infection (disseminated cutaneous coccidioidomycosis), or as a reactive component of pulmonary infection.^1,2 Of them, primary and disseminated cutaneous coccidioidomycosis are organism specific and display characteristic spherules and fungus on histopathology and cultures, respectively. Reactive coccidioidomycosis differs from organism-specific disease, as it does not contain spherules in histopathologic sections of tissue biopsies.¹ Reactive skin manifestations occur in 12% to 50% of patients with primary pulmonary infection and include erythema nodosum, erythema multiforme, acute generalized exanthema, reactive interstitial granulomatous dermatitis, and Sweet syndrome.³

Organism-specific cutaneous coccidioidomycosis most often is correlated with hematogenous dissemination of primary pulmonary disease rather than direct inoculation of skin.¹ The skin is the most common site of extrapulmonary involvement in disseminated coccidioidomycosis, and cutaneous lesions have been reported in 15% to 67% of cases of disseminated disease.^1,4 In cutaneous disseminated disease, nodules, papules, macules, and verrucous plaques have been described. In a case series of disseminated cutaneous coccidioidomycosis, nodules were the most common cutaneous presentation and occurred in 39% (7/18) of patients, while verrucous plaques were the rarest and occurred in only 6% (1/18) of patients.⁵

The rate of coccidioidomycosis dissemination varies based on exposure and patient characteristics. Increased rates of dissemination have been reported in patients of African and Filipino descent, along with individuals that are immunosuppressed due to disease or medical therapy. Dissemination is clinically significant, as patients with multifocal dissemination have a greater than 50% risk for mortality.⁶

Disseminated coccidioidomycosis is a relatively rare manifestation of Coccidioides infection; approximately 1.6% of patients exposed to and infected with Coccidioides ultimately will develop systemic or disseminated disease.^7,8 Although the rates of primary pulmonary infection are similar between patients of varying ethnicities, the rates of dissemination are higher in patients of African and Filipino ethnicity.⁸ In population studies of coccidioidomycosis (N=332), Black patients represented 33.3% (4/12) of disseminated cases but only 8.7% of Coccidioides cases overall.⁷

Population studies of Black patients with coccidioidomycosis have shown a 4-fold higher predisposition for severe disease compared to mild disease.⁹ Spondylitis and meningitis also are disproportionately more common in Black patients.⁸ Black patients comprised 75% of all spondylitis cases in a cohort where only 25% of patients were Black. Additionally, 33% of all meningitis cases occurred in Black patients in a cohort where 8% of total cases were Black patients.⁸ Within the United States, the highest rates of coccidioidomycosis meningitis are seen in Black patients.¹⁰

The pathophysiology underlying the increased susceptibility of individuals of African or Filipino descent to disseminated and severe coccidioidomycosis remains unknown.⁸ The level of vulnerability within this patient population has no association with increased environmental exposure or poor immunologic response to Coccidioides, as demonstrated by the ability of these populations to respond to experimental vaccination and skin testing (spherulin, coccidioidin) to a similar extent as other ethnicities.⁸ Class II HLA-DRB1*1301 alleles have been associated with an increased risk for severe disseminated Coccidioides infection regardless of ethnicity; however, these alleles are not overrepresented in these patient populations.⁸

In patients with primary pulmonary coccidioidomycosis with no evidence of dissemination, guidelines generally recommend offering treatment to groups at high risk of dissemination, such as pregnant women and patients with diabetes mellitus. Given the high incidence of disseminated and severe disease in Black and Filipino patients, some guidelines endorse treatment of all cases of coccidioidomycosis in this patient population.⁸ No current data are available to help determine whether this broad treatment approach reduces the development of disseminated infection in these populations. Frequent monitoring for disease progression and/or dissemination involving clinical and laboratory reevaluation every 3 months for 2 years is highly recommended.⁸

Treatment generally is based on location and severity of infection, with disseminated nonmeningeal infection being treated with oral azole therapy (ketoconazole, itraconazole, or fluconazole).¹¹ If there is involvement of the central nervous system structures or rapidly worsening disease despite azole therapy, amphotericin B is recommended at 0.5 to 0.7 mg/kg daily. In patients with disseminated meningeal infection, oral fluconazole (800–1000 mg/d) or a combination of an azole with intrathecal amphotericin B (0.01–1.5 mg/dose, interval ranging from daily to 1 week) is recommended to improve response.¹¹

The differential diagnosis of cutaneous disseminated coccidioidomycosis is broad and includes other systemic endemic mycoses (histoplasmosis, blastomycosis) and infections (mycobacteria, leishmania). Lupus vulgaris, a form of cutaneous tuberculosis, presents as a palpable tubercular lesion that may coalesce into erythematous plaques, which may mimic endemic mycoses, especially in patients with risk factors for both infectious etiologies such as our patient.¹² Disseminated histoplasmosis may present as polymorphic plaques, pustules, nodules, and ulcerated skin lesions, whereas disseminated blastomycosis characteristically presents as a crusted verrucous lesion with raised borders and painful ulcers, both of which may mimic coccidioidomycosis.¹³ Biopsy would reveal the characteristic intracellular yeast in Histoplasma capsulatum and broad-based budding yeast form of Blastomyces dermatitidis in histoplasmosis and blastomycosis, respectively, in contrast to the spherules seen in our patient’s biopsy.¹³ Localized cutaneous leishmaniasis initially develops as a nodular or papular lesion and can progress to open ulcerations with raised borders. Biopsy and histopathology would reveal round protozoal amastigotes.¹⁴ Other diagnoses that should be considered include mycetoma, nocardiosis, and sporotrichosis.¹⁵ As the cutaneous manifestations of Coccidioides infections are varied, a broad differential diagnosis should be maintained, and probable environmental and infectious exposures should be considered prior to ordering diagnostic studies.

The Diagnosis: Disseminated Coccidioidomycosis

A6-mm punch biopsy was performed at the periphery of the ulcerated cutaneous lesion on the chest revealing extensive spherules. Serum antibody immunodiffusion for histoplasmosis and blastomycoses both were negative; however, B-D-glucan assay was positive at 364 pg/mL (reference range: <60 pg/mL, negative). Initial HIV-1 and HIV-2 antibody and antigen testing was negative as well as repeat testing at 3 weeks. Immunodiffusion for Coccidioides IgM and IgG was positive, and cocci antibody IgG complement fixation assays were positive at titers of 1:64 (reference range: <1:2, negative). A computed tomography needle-guided biopsy of the paravertebral soft tissue was performed. Gram stains and bacterial cultures of the biopsies were negative; however, fungal cultures were notable for growth of Coccidioides. Given the pertinent testing, a diagnosis of disseminated coccidioidomycosis was made.

Cutaneous coccidioidomycosis can occur in 3 situations: direct inoculation (primary cutaneous coccidioidomycosis), disseminated infection (disseminated cutaneous coccidioidomycosis), or as a reactive component of pulmonary infection.^1,2 Of them, primary and disseminated cutaneous coccidioidomycosis are organism specific and display characteristic spherules and fungus on histopathology and cultures, respectively. Reactive coccidioidomycosis differs from organism-specific disease, as it does not contain spherules in histopathologic sections of tissue biopsies.¹ Reactive skin manifestations occur in 12% to 50% of patients with primary pulmonary infection and include erythema nodosum, erythema multiforme, acute generalized exanthema, reactive interstitial granulomatous dermatitis, and Sweet syndrome.³

Organism-specific cutaneous coccidioidomycosis most often is correlated with hematogenous dissemination of primary pulmonary disease rather than direct inoculation of skin.¹ The skin is the most common site of extrapulmonary involvement in disseminated coccidioidomycosis, and cutaneous lesions have been reported in 15% to 67% of cases of disseminated disease.^1,4 In cutaneous disseminated disease, nodules, papules, macules, and verrucous plaques have been described. In a case series of disseminated cutaneous coccidioidomycosis, nodules were the most common cutaneous presentation and occurred in 39% (7/18) of patients, while verrucous plaques were the rarest and occurred in only 6% (1/18) of patients.⁵

The rate of coccidioidomycosis dissemination varies based on exposure and patient characteristics. Increased rates of dissemination have been reported in patients of African and Filipino descent, along with individuals that are immunosuppressed due to disease or medical therapy. Dissemination is clinically significant, as patients with multifocal dissemination have a greater than 50% risk for mortality.⁶

Disseminated coccidioidomycosis is a relatively rare manifestation of Coccidioides infection; approximately 1.6% of patients exposed to and infected with Coccidioides ultimately will develop systemic or disseminated disease.^7,8 Although the rates of primary pulmonary infection are similar between patients of varying ethnicities, the rates of dissemination are higher in patients of African and Filipino ethnicity.⁸ In population studies of coccidioidomycosis (N=332), Black patients represented 33.3% (4/12) of disseminated cases but only 8.7% of Coccidioides cases overall.⁷

Population studies of Black patients with coccidioidomycosis have shown a 4-fold higher predisposition for severe disease compared to mild disease.⁹ Spondylitis and meningitis also are disproportionately more common in Black patients.⁸ Black patients comprised 75% of all spondylitis cases in a cohort where only 25% of patients were Black. Additionally, 33% of all meningitis cases occurred in Black patients in a cohort where 8% of total cases were Black patients.⁸ Within the United States, the highest rates of coccidioidomycosis meningitis are seen in Black patients.¹⁰

The pathophysiology underlying the increased susceptibility of individuals of African or Filipino descent to disseminated and severe coccidioidomycosis remains unknown.⁸ The level of vulnerability within this patient population has no association with increased environmental exposure or poor immunologic response to Coccidioides, as demonstrated by the ability of these populations to respond to experimental vaccination and skin testing (spherulin, coccidioidin) to a similar extent as other ethnicities.⁸ Class II HLA-DRB1*1301 alleles have been associated with an increased risk for severe disseminated Coccidioides infection regardless of ethnicity; however, these alleles are not overrepresented in these patient populations.⁸

In patients with primary pulmonary coccidioidomycosis with no evidence of dissemination, guidelines generally recommend offering treatment to groups at high risk of dissemination, such as pregnant women and patients with diabetes mellitus. Given the high incidence of disseminated and severe disease in Black and Filipino patients, some guidelines endorse treatment of all cases of coccidioidomycosis in this patient population.⁸ No current data are available to help determine whether this broad treatment approach reduces the development of disseminated infection in these populations. Frequent monitoring for disease progression and/or dissemination involving clinical and laboratory reevaluation every 3 months for 2 years is highly recommended.⁸

Treatment generally is based on location and severity of infection, with disseminated nonmeningeal infection being treated with oral azole therapy (ketoconazole, itraconazole, or fluconazole).¹¹ If there is involvement of the central nervous system structures or rapidly worsening disease despite azole therapy, amphotericin B is recommended at 0.5 to 0.7 mg/kg daily. In patients with disseminated meningeal infection, oral fluconazole (800–1000 mg/d) or a combination of an azole with intrathecal amphotericin B (0.01–1.5 mg/dose, interval ranging from daily to 1 week) is recommended to improve response.¹¹

The differential diagnosis of cutaneous disseminated coccidioidomycosis is broad and includes other systemic endemic mycoses (histoplasmosis, blastomycosis) and infections (mycobacteria, leishmania). Lupus vulgaris, a form of cutaneous tuberculosis, presents as a palpable tubercular lesion that may coalesce into erythematous plaques, which may mimic endemic mycoses, especially in patients with risk factors for both infectious etiologies such as our patient.¹² Disseminated histoplasmosis may present as polymorphic plaques, pustules, nodules, and ulcerated skin lesions, whereas disseminated blastomycosis characteristically presents as a crusted verrucous lesion with raised borders and painful ulcers, both of which may mimic coccidioidomycosis.¹³ Biopsy would reveal the characteristic intracellular yeast in Histoplasma capsulatum and broad-based budding yeast form of Blastomyces dermatitidis in histoplasmosis and blastomycosis, respectively, in contrast to the spherules seen in our patient’s biopsy.¹³ Localized cutaneous leishmaniasis initially develops as a nodular or papular lesion and can progress to open ulcerations with raised borders. Biopsy and histopathology would reveal round protozoal amastigotes.¹⁴ Other diagnoses that should be considered include mycetoma, nocardiosis, and sporotrichosis.¹⁵ As the cutaneous manifestations of Coccidioides infections are varied, a broad differential diagnosis should be maintained, and probable environmental and infectious exposures should be considered prior to ordering diagnostic studies.

The Diagnosis: Disseminated Coccidioidomycosis

A6-mm punch biopsy was performed at the periphery of the ulcerated cutaneous lesion on the chest revealing extensive spherules. Serum antibody immunodiffusion for histoplasmosis and blastomycoses both were negative; however, B-D-glucan assay was positive at 364 pg/mL (reference range: <60 pg/mL, negative). Initial HIV-1 and HIV-2 antibody and antigen testing was negative as well as repeat testing at 3 weeks. Immunodiffusion for Coccidioides IgM and IgG was positive, and cocci antibody IgG complement fixation assays were positive at titers of 1:64 (reference range: <1:2, negative). A computed tomography needle-guided biopsy of the paravertebral soft tissue was performed. Gram stains and bacterial cultures of the biopsies were negative; however, fungal cultures were notable for growth of Coccidioides. Given the pertinent testing, a diagnosis of disseminated coccidioidomycosis was made.

Cutaneous coccidioidomycosis can occur in 3 situations: direct inoculation (primary cutaneous coccidioidomycosis), disseminated infection (disseminated cutaneous coccidioidomycosis), or as a reactive component of pulmonary infection.^1,2 Of them, primary and disseminated cutaneous coccidioidomycosis are organism specific and display characteristic spherules and fungus on histopathology and cultures, respectively. Reactive coccidioidomycosis differs from organism-specific disease, as it does not contain spherules in histopathologic sections of tissue biopsies.¹ Reactive skin manifestations occur in 12% to 50% of patients with primary pulmonary infection and include erythema nodosum, erythema multiforme, acute generalized exanthema, reactive interstitial granulomatous dermatitis, and Sweet syndrome.³

Organism-specific cutaneous coccidioidomycosis most often is correlated with hematogenous dissemination of primary pulmonary disease rather than direct inoculation of skin.¹ The skin is the most common site of extrapulmonary involvement in disseminated coccidioidomycosis, and cutaneous lesions have been reported in 15% to 67% of cases of disseminated disease.^1,4 In cutaneous disseminated disease, nodules, papules, macules, and verrucous plaques have been described. In a case series of disseminated cutaneous coccidioidomycosis, nodules were the most common cutaneous presentation and occurred in 39% (7/18) of patients, while verrucous plaques were the rarest and occurred in only 6% (1/18) of patients.⁵

The rate of coccidioidomycosis dissemination varies based on exposure and patient characteristics. Increased rates of dissemination have been reported in patients of African and Filipino descent, along with individuals that are immunosuppressed due to disease or medical therapy. Dissemination is clinically significant, as patients with multifocal dissemination have a greater than 50% risk for mortality.⁶

Disseminated coccidioidomycosis is a relatively rare manifestation of Coccidioides infection; approximately 1.6% of patients exposed to and infected with Coccidioides ultimately will develop systemic or disseminated disease.^7,8 Although the rates of primary pulmonary infection are similar between patients of varying ethnicities, the rates of dissemination are higher in patients of African and Filipino ethnicity.⁸ In population studies of coccidioidomycosis (N=332), Black patients represented 33.3% (4/12) of disseminated cases but only 8.7% of Coccidioides cases overall.⁷

Population studies of Black patients with coccidioidomycosis have shown a 4-fold higher predisposition for severe disease compared to mild disease.⁹ Spondylitis and meningitis also are disproportionately more common in Black patients.⁸ Black patients comprised 75% of all spondylitis cases in a cohort where only 25% of patients were Black. Additionally, 33% of all meningitis cases occurred in Black patients in a cohort where 8% of total cases were Black patients.⁸ Within the United States, the highest rates of coccidioidomycosis meningitis are seen in Black patients.¹⁰

The pathophysiology underlying the increased susceptibility of individuals of African or Filipino descent to disseminated and severe coccidioidomycosis remains unknown.⁸ The level of vulnerability within this patient population has no association with increased environmental exposure or poor immunologic response to Coccidioides, as demonstrated by the ability of these populations to respond to experimental vaccination and skin testing (spherulin, coccidioidin) to a similar extent as other ethnicities.⁸ Class II HLA-DRB1*1301 alleles have been associated with an increased risk for severe disseminated Coccidioides infection regardless of ethnicity; however, these alleles are not overrepresented in these patient populations.⁸

In patients with primary pulmonary coccidioidomycosis with no evidence of dissemination, guidelines generally recommend offering treatment to groups at high risk of dissemination, such as pregnant women and patients with diabetes mellitus. Given the high incidence of disseminated and severe disease in Black and Filipino patients, some guidelines endorse treatment of all cases of coccidioidomycosis in this patient population.⁸ No current data are available to help determine whether this broad treatment approach reduces the development of disseminated infection in these populations. Frequent monitoring for disease progression and/or dissemination involving clinical and laboratory reevaluation every 3 months for 2 years is highly recommended.⁸

Treatment generally is based on location and severity of infection, with disseminated nonmeningeal infection being treated with oral azole therapy (ketoconazole, itraconazole, or fluconazole).¹¹ If there is involvement of the central nervous system structures or rapidly worsening disease despite azole therapy, amphotericin B is recommended at 0.5 to 0.7 mg/kg daily. In patients with disseminated meningeal infection, oral fluconazole (800–1000 mg/d) or a combination of an azole with intrathecal amphotericin B (0.01–1.5 mg/dose, interval ranging from daily to 1 week) is recommended to improve response.¹¹

The differential diagnosis of cutaneous disseminated coccidioidomycosis is broad and includes other systemic endemic mycoses (histoplasmosis, blastomycosis) and infections (mycobacteria, leishmania). Lupus vulgaris, a form of cutaneous tuberculosis, presents as a palpable tubercular lesion that may coalesce into erythematous plaques, which may mimic endemic mycoses, especially in patients with risk factors for both infectious etiologies such as our patient.¹² Disseminated histoplasmosis may present as polymorphic plaques, pustules, nodules, and ulcerated skin lesions, whereas disseminated blastomycosis characteristically presents as a crusted verrucous lesion with raised borders and painful ulcers, both of which may mimic coccidioidomycosis.¹³ Biopsy would reveal the characteristic intracellular yeast in Histoplasma capsulatum and broad-based budding yeast form of Blastomyces dermatitidis in histoplasmosis and blastomycosis, respectively, in contrast to the spherules seen in our patient’s biopsy.¹³ Localized cutaneous leishmaniasis initially develops as a nodular or papular lesion and can progress to open ulcerations with raised borders. Biopsy and histopathology would reveal round protozoal amastigotes.¹⁴ Other diagnoses that should be considered include mycetoma, nocardiosis, and sporotrichosis.¹⁵ As the cutaneous manifestations of Coccidioides infections are varied, a broad differential diagnosis should be maintained, and probable environmental and infectious exposures should be considered prior to ordering diagnostic studies.

The Diagnosis: Erythema Ab Igne

Based on the clinical findings and history, a diagnosis of erythema ab igne (EAI), a skin reaction to chronic infrared radiation exposure, was made. The name of this condition translates from Latin as “redness from fire”; other names include toasted skin syndrome and fire stains. The most common presentation is reticulated hyperpigmentation, erythema, and cutaneous atrophy, as well as possible crusting, scaling, or telangiectasia. The rash also typically presents in areas of heat exposure—from heated blankets, heating pads, or the use of infrared heaters or lamps.^1,2 The patient usually will have pain and pruritus over the affected areas. The diagnosis of EAI largely is clinical and based on the patient’s history of exposure; it rarely requires biopsy and histologic analysis. However, some of the common histopathologic findings include hyperkeratosis, a hyperpigmented basal layer, hemosiderin deposits, prominent melanophages, basal cell degeneration, course collagen, and elastosis.^2,3 These changes are common with UV radiation exposure and thermal damage. The primary treatment in all cases is to remove or reduce the source of infrared radiation. However, EAI has been reported to be successfully treated with removal of the insult as well as topical agents such as imiquimod and 5-fluorouracil.⁴ Possible complications include increased risk for malignancies such as squamous cell carcinoma in the affected area.¹

The possible differential for EAI includes livedo reticularis, livedo racemosa, cutis marmorata, and cutis marmorata telangiectatica congenita. All of these conditions are related to dysfunction of the cutaneous vasculature that creates a reticular, mottled, reddish purple rash. When the livedo is reversible and idiopathic, it is referred to as livedo reticularis, but when it is generalized and permanent it is referred to as livedo racemosa. Livedo racemosa can be caused by a variety of conditions, including systemic lupus erythematosus and antiphospholipid syndrome.¹ Physiologic livedo reticularis that is more transient and can be reversed by warming is referred to as cutis marmorata. Finally, cutis marmorata telangiectatica congenita primarily is found in neonates, and although persistent, it usually improves with age. Erythema ab igne also is a type of livedo with a known heat exposure and localized distribution.

Our patient was educated on the etiology of the rash, specifically related to heating pad usage for multiple years, and the risk for cutaneous malignancy after longstanding EAI. It was recommended that she discontinue use of a heating pad on the affected areas to allow them to properly heal. If she found that heating pad usage was necessary, she was advised to limit use to 5 to 10 minutes with 2 to 3 hours in between applications. In addition, she was advised to apply petroleum jelly daily for assistance with wound healing as well as anti-itch sensitive lotion twice daily on the arms and back to alleviate some of the tingling pain. We explained that areas of hyperpigmentation may improve with time; however, areas of erythema/ atrophy may be long-lasting.

The Diagnosis: Erythema Ab Igne

Based on the clinical findings and history, a diagnosis of erythema ab igne (EAI), a skin reaction to chronic infrared radiation exposure, was made. The name of this condition translates from Latin as “redness from fire”; other names include toasted skin syndrome and fire stains. The most common presentation is reticulated hyperpigmentation, erythema, and cutaneous atrophy, as well as possible crusting, scaling, or telangiectasia. The rash also typically presents in areas of heat exposure—from heated blankets, heating pads, or the use of infrared heaters or lamps.^1,2 The patient usually will have pain and pruritus over the affected areas. The diagnosis of EAI largely is clinical and based on the patient’s history of exposure; it rarely requires biopsy and histologic analysis. However, some of the common histopathologic findings include hyperkeratosis, a hyperpigmented basal layer, hemosiderin deposits, prominent melanophages, basal cell degeneration, course collagen, and elastosis.^2,3 These changes are common with UV radiation exposure and thermal damage. The primary treatment in all cases is to remove or reduce the source of infrared radiation. However, EAI has been reported to be successfully treated with removal of the insult as well as topical agents such as imiquimod and 5-fluorouracil.⁴ Possible complications include increased risk for malignancies such as squamous cell carcinoma in the affected area.¹

The possible differential for EAI includes livedo reticularis, livedo racemosa, cutis marmorata, and cutis marmorata telangiectatica congenita. All of these conditions are related to dysfunction of the cutaneous vasculature that creates a reticular, mottled, reddish purple rash. When the livedo is reversible and idiopathic, it is referred to as livedo reticularis, but when it is generalized and permanent it is referred to as livedo racemosa. Livedo racemosa can be caused by a variety of conditions, including systemic lupus erythematosus and antiphospholipid syndrome.¹ Physiologic livedo reticularis that is more transient and can be reversed by warming is referred to as cutis marmorata. Finally, cutis marmorata telangiectatica congenita primarily is found in neonates, and although persistent, it usually improves with age. Erythema ab igne also is a type of livedo with a known heat exposure and localized distribution.

Our patient was educated on the etiology of the rash, specifically related to heating pad usage for multiple years, and the risk for cutaneous malignancy after longstanding EAI. It was recommended that she discontinue use of a heating pad on the affected areas to allow them to properly heal. If she found that heating pad usage was necessary, she was advised to limit use to 5 to 10 minutes with 2 to 3 hours in between applications. In addition, she was advised to apply petroleum jelly daily for assistance with wound healing as well as anti-itch sensitive lotion twice daily on the arms and back to alleviate some of the tingling pain. We explained that areas of hyperpigmentation may improve with time; however, areas of erythema/ atrophy may be long-lasting.

The Diagnosis: Erythema Ab Igne

Based on the clinical findings and history, a diagnosis of erythema ab igne (EAI), a skin reaction to chronic infrared radiation exposure, was made. The name of this condition translates from Latin as “redness from fire”; other names include toasted skin syndrome and fire stains. The most common presentation is reticulated hyperpigmentation, erythema, and cutaneous atrophy, as well as possible crusting, scaling, or telangiectasia. The rash also typically presents in areas of heat exposure—from heated blankets, heating pads, or the use of infrared heaters or lamps.^1,2 The patient usually will have pain and pruritus over the affected areas. The diagnosis of EAI largely is clinical and based on the patient’s history of exposure; it rarely requires biopsy and histologic analysis. However, some of the common histopathologic findings include hyperkeratosis, a hyperpigmented basal layer, hemosiderin deposits, prominent melanophages, basal cell degeneration, course collagen, and elastosis.^2,3 These changes are common with UV radiation exposure and thermal damage. The primary treatment in all cases is to remove or reduce the source of infrared radiation. However, EAI has been reported to be successfully treated with removal of the insult as well as topical agents such as imiquimod and 5-fluorouracil.⁴ Possible complications include increased risk for malignancies such as squamous cell carcinoma in the affected area.¹

The possible differential for EAI includes livedo reticularis, livedo racemosa, cutis marmorata, and cutis marmorata telangiectatica congenita. All of these conditions are related to dysfunction of the cutaneous vasculature that creates a reticular, mottled, reddish purple rash. When the livedo is reversible and idiopathic, it is referred to as livedo reticularis, but when it is generalized and permanent it is referred to as livedo racemosa. Livedo racemosa can be caused by a variety of conditions, including systemic lupus erythematosus and antiphospholipid syndrome.¹ Physiologic livedo reticularis that is more transient and can be reversed by warming is referred to as cutis marmorata. Finally, cutis marmorata telangiectatica congenita primarily is found in neonates, and although persistent, it usually improves with age. Erythema ab igne also is a type of livedo with a known heat exposure and localized distribution.

Our patient was educated on the etiology of the rash, specifically related to heating pad usage for multiple years, and the risk for cutaneous malignancy after longstanding EAI. It was recommended that she discontinue use of a heating pad on the affected areas to allow them to properly heal. If she found that heating pad usage was necessary, she was advised to limit use to 5 to 10 minutes with 2 to 3 hours in between applications. In addition, she was advised to apply petroleum jelly daily for assistance with wound healing as well as anti-itch sensitive lotion twice daily on the arms and back to alleviate some of the tingling pain. We explained that areas of hyperpigmentation may improve with time; however, areas of erythema/ atrophy may be long-lasting.

The Diagnosis: Tinea Pseudoimbricata

Tinea pseudoimbricata and tinea indecisiva are synonyms describing cases of tinea corporis that manifest in scaly plaques in concentric rings evocative of those present in tinea imbricata. However, in contrast to tinea imbricata, cases of tinea pseudoimbricata are caused by dermatophytes other than Trichophyton concentricum. ¹ Tinea pseudoimbricata usually presents in association with immunosuppression, either systemic or local, and can be produced by application of topical medications such as corticosteroids.² Mask-Bull et al³ reported the case of a 21-year-old man in the United States with no history of immunosuppressive conditions who presented with scaly erythematous annular plaques on the lateral neck that resolved with 2 pulsed doses of terbinafine. Potassium hydroxide preparation and fungal culture were both consistent with Trichophyton tonsurans.³

Trichophyton concentricum is an anthropophilic species of dermatophyte endemic to areas within the South Pacific, Southeast Asia, and Central and South America. Infection with T concentricum produces tinea imbricata, which presents with concentric, scaly, annular rings. Cutaneous lesions of tinea imbricata caused by T concentricum have a more generalized distribution and more densely grouped, concentric circles than the cutaneous findings seen in patients with tinea pseudoimbricata.⁴ Affected patients typically demonstrate negative delayed-type hypersensitivity to T concentricum cytoplasmic antigen and T-lymphocyte hyporeactivity, which may contribute to the development of sequential waves of scaling observed in tinea imbricata.⁵

Trichophyton rubrum, the most common cause of tinea corporis, has been reported to cause some cases of tinea pseudoimbricata (indecisiva).^1,2 It utilizes keratinases such as subtilisins (Sub3 and Sub4), leucine aminopeptidases (Lap1 and Lap2), and dipeptidyl peptidases (DppIV and DppV) to invade the skin. Once inside, mannans, glycoprotein constituents of the cell wall, are released and bind to the cell surface of mononuclear phagocytes, subsequently moving into the cell by phagocytosis, thereafter interfering with RNA synthesis that is necessary for presentation of antigens to appropriate T cells and allowing for initiation of chronic infection.^6,7 The cytotoxic response to superficial dermatophyte infection is triggered by major histocompatibility complex class I molecule activation of CD8⁺ cells.^6,8

Our case is of interest given the localization of the superficial dermatophyte infection to only vitiliginous skin. This distribution and appearance while undergoing narrowband UVB (NB-UVB) treatment is rare. We postulate that our patient likely represents a case of locus minoris resistentiae, a phenomenon in which an area of skin exhibits a compromised immune microenvironment that predisposes it to disease.⁹

In vitiligo, NB-UVB modulates the immune response by increasing IL-10, thereby promoting regulatory T-cell differentiation with suppression of autoreactive T cells and induction of direct T-lymphocyte apoptosis.^10,11 Although the mechanism accounting for our patient’s presentation is unknown, we suspect NB-UVB–induced immunosuppression enabled persistence of the dermatophyte infection. The localization of the infection to the vitiliginous patches may result from the greater penetration of the UV light relative to the surrounding, normally pigmented skin. This relative difference in UV penetration would be expected to result in increased immunosuppression in the vitiliginous lesions and enhanced susceptibility to the fungal organisms.

Erythema annulare centrifugum is characterized by annular lesions with a trailing scale instead of the concentric rings seen in tinea pseudoimbricata. Erythema marginatum is seen in acute rheumatic fever and presents with a transient nonpruritic rash, usually on the trunk or extremities. Erythema migrans presents with fewer lesions that are less circinate in shape, and the patient often has a history of a tick bite. Tinea imbricata is caused by T concentricum, while tinea pseudoimbricata is caused by T tonsurans and other dermatophytes.

With the increasing use of immunosuppressant drugs, the prevalence of tinea pseudoimbricata is hypothesized to increase.¹ The presence of tinea pseudoimbricata should alert dermatologists to the possible overuse of topical corticosteroids, and other forms of immunosuppression also should be considered.

The Diagnosis: Tinea Pseudoimbricata

Tinea pseudoimbricata and tinea indecisiva are synonyms describing cases of tinea corporis that manifest in scaly plaques in concentric rings evocative of those present in tinea imbricata. However, in contrast to tinea imbricata, cases of tinea pseudoimbricata are caused by dermatophytes other than Trichophyton concentricum. ¹ Tinea pseudoimbricata usually presents in association with immunosuppression, either systemic or local, and can be produced by application of topical medications such as corticosteroids.² Mask-Bull et al³ reported the case of a 21-year-old man in the United States with no history of immunosuppressive conditions who presented with scaly erythematous annular plaques on the lateral neck that resolved with 2 pulsed doses of terbinafine. Potassium hydroxide preparation and fungal culture were both consistent with Trichophyton tonsurans.³

Trichophyton concentricum is an anthropophilic species of dermatophyte endemic to areas within the South Pacific, Southeast Asia, and Central and South America. Infection with T concentricum produces tinea imbricata, which presents with concentric, scaly, annular rings. Cutaneous lesions of tinea imbricata caused by T concentricum have a more generalized distribution and more densely grouped, concentric circles than the cutaneous findings seen in patients with tinea pseudoimbricata.⁴ Affected patients typically demonstrate negative delayed-type hypersensitivity to T concentricum cytoplasmic antigen and T-lymphocyte hyporeactivity, which may contribute to the development of sequential waves of scaling observed in tinea imbricata.⁵

Trichophyton rubrum, the most common cause of tinea corporis, has been reported to cause some cases of tinea pseudoimbricata (indecisiva).^1,2 It utilizes keratinases such as subtilisins (Sub3 and Sub4), leucine aminopeptidases (Lap1 and Lap2), and dipeptidyl peptidases (DppIV and DppV) to invade the skin. Once inside, mannans, glycoprotein constituents of the cell wall, are released and bind to the cell surface of mononuclear phagocytes, subsequently moving into the cell by phagocytosis, thereafter interfering with RNA synthesis that is necessary for presentation of antigens to appropriate T cells and allowing for initiation of chronic infection.^6,7 The cytotoxic response to superficial dermatophyte infection is triggered by major histocompatibility complex class I molecule activation of CD8⁺ cells.^6,8

Our case is of interest given the localization of the superficial dermatophyte infection to only vitiliginous skin. This distribution and appearance while undergoing narrowband UVB (NB-UVB) treatment is rare. We postulate that our patient likely represents a case of locus minoris resistentiae, a phenomenon in which an area of skin exhibits a compromised immune microenvironment that predisposes it to disease.⁹

In vitiligo, NB-UVB modulates the immune response by increasing IL-10, thereby promoting regulatory T-cell differentiation with suppression of autoreactive T cells and induction of direct T-lymphocyte apoptosis.^10,11 Although the mechanism accounting for our patient’s presentation is unknown, we suspect NB-UVB–induced immunosuppression enabled persistence of the dermatophyte infection. The localization of the infection to the vitiliginous patches may result from the greater penetration of the UV light relative to the surrounding, normally pigmented skin. This relative difference in UV penetration would be expected to result in increased immunosuppression in the vitiliginous lesions and enhanced susceptibility to the fungal organisms.

Erythema annulare centrifugum is characterized by annular lesions with a trailing scale instead of the concentric rings seen in tinea pseudoimbricata. Erythema marginatum is seen in acute rheumatic fever and presents with a transient nonpruritic rash, usually on the trunk or extremities. Erythema migrans presents with fewer lesions that are less circinate in shape, and the patient often has a history of a tick bite. Tinea imbricata is caused by T concentricum, while tinea pseudoimbricata is caused by T tonsurans and other dermatophytes.

With the increasing use of immunosuppressant drugs, the prevalence of tinea pseudoimbricata is hypothesized to increase.¹ The presence of tinea pseudoimbricata should alert dermatologists to the possible overuse of topical corticosteroids, and other forms of immunosuppression also should be considered.

The Diagnosis: Tinea Pseudoimbricata

Tinea pseudoimbricata and tinea indecisiva are synonyms describing cases of tinea corporis that manifest in scaly plaques in concentric rings evocative of those present in tinea imbricata. However, in contrast to tinea imbricata, cases of tinea pseudoimbricata are caused by dermatophytes other than Trichophyton concentricum. ¹ Tinea pseudoimbricata usually presents in association with immunosuppression, either systemic or local, and can be produced by application of topical medications such as corticosteroids.² Mask-Bull et al³ reported the case of a 21-year-old man in the United States with no history of immunosuppressive conditions who presented with scaly erythematous annular plaques on the lateral neck that resolved with 2 pulsed doses of terbinafine. Potassium hydroxide preparation and fungal culture were both consistent with Trichophyton tonsurans.³

Trichophyton concentricum is an anthropophilic species of dermatophyte endemic to areas within the South Pacific, Southeast Asia, and Central and South America. Infection with T concentricum produces tinea imbricata, which presents with concentric, scaly, annular rings. Cutaneous lesions of tinea imbricata caused by T concentricum have a more generalized distribution and more densely grouped, concentric circles than the cutaneous findings seen in patients with tinea pseudoimbricata.⁴ Affected patients typically demonstrate negative delayed-type hypersensitivity to T concentricum cytoplasmic antigen and T-lymphocyte hyporeactivity, which may contribute to the development of sequential waves of scaling observed in tinea imbricata.⁵

Trichophyton rubrum, the most common cause of tinea corporis, has been reported to cause some cases of tinea pseudoimbricata (indecisiva).^1,2 It utilizes keratinases such as subtilisins (Sub3 and Sub4), leucine aminopeptidases (Lap1 and Lap2), and dipeptidyl peptidases (DppIV and DppV) to invade the skin. Once inside, mannans, glycoprotein constituents of the cell wall, are released and bind to the cell surface of mononuclear phagocytes, subsequently moving into the cell by phagocytosis, thereafter interfering with RNA synthesis that is necessary for presentation of antigens to appropriate T cells and allowing for initiation of chronic infection.^6,7 The cytotoxic response to superficial dermatophyte infection is triggered by major histocompatibility complex class I molecule activation of CD8⁺ cells.^6,8

Our case is of interest given the localization of the superficial dermatophyte infection to only vitiliginous skin. This distribution and appearance while undergoing narrowband UVB (NB-UVB) treatment is rare. We postulate that our patient likely represents a case of locus minoris resistentiae, a phenomenon in which an area of skin exhibits a compromised immune microenvironment that predisposes it to disease.⁹

In vitiligo, NB-UVB modulates the immune response by increasing IL-10, thereby promoting regulatory T-cell differentiation with suppression of autoreactive T cells and induction of direct T-lymphocyte apoptosis.^10,11 Although the mechanism accounting for our patient’s presentation is unknown, we suspect NB-UVB–induced immunosuppression enabled persistence of the dermatophyte infection. The localization of the infection to the vitiliginous patches may result from the greater penetration of the UV light relative to the surrounding, normally pigmented skin. This relative difference in UV penetration would be expected to result in increased immunosuppression in the vitiliginous lesions and enhanced susceptibility to the fungal organisms.

Erythema annulare centrifugum is characterized by annular lesions with a trailing scale instead of the concentric rings seen in tinea pseudoimbricata. Erythema marginatum is seen in acute rheumatic fever and presents with a transient nonpruritic rash, usually on the trunk or extremities. Erythema migrans presents with fewer lesions that are less circinate in shape, and the patient often has a history of a tick bite. Tinea imbricata is caused by T concentricum, while tinea pseudoimbricata is caused by T tonsurans and other dermatophytes.

With the increasing use of immunosuppressant drugs, the prevalence of tinea pseudoimbricata is hypothesized to increase.¹ The presence of tinea pseudoimbricata should alert dermatologists to the possible overuse of topical corticosteroids, and other forms of immunosuppression also should be considered.

The Diagnosis: Hidradenocarcinoma

An excisional biopsy revealed a neoplasm in the dermis with focal invasion into the adjacent soft tissue (Figure 1). The tumor consisted of sheets of cells with cytoplasmic vacuoles and ductal differentiation (Figure 2), as well as cells with mild atypia, mild pleomorphism, rare mitotic figures, and abundant pale cytoplasm. Immunohistochemical staining was positive for cytokeratin (CK) 5, CK7, CK20, CK AE1/AE3, and p63 (Figure 3). The culmination of features including the large tumor size, immunohistochemical staining pattern, and mild pleomorphism with focal invasion into the soft tissue supported the diagnosis of hidradenocarcinoma.

Hidradenocarcinoma is an exceedingly rare malignant tumor of eccrine and/or apocrine origin.¹ It accounts for less than 0.001% of all tumors and 1 of 13,000 skin biopsies.² It usually arises in the head and neck region and most commonly affects older adults aged 50 to 70 years.³ The size of hidradenocarcinomas can vary; however, they typically are large, often growing to be greater than 5 cm in diameter.² It tends to be an aggressive tumor that generally spreads to regional lymph nodes and distant viscera.⁴ Although it most commonly arises de novo, it may occasionally derive from a benign hidradenoma.¹ The diagnosis of hidradenocarcinoma is made based on the tumor’s morphologic and pathologic characteristics. Histologically, it is characterized by an infiltrative and invasive proliferation of lobules made of large clear cells with atypical mitotic figures and nuclear pleomorphism as well as immunohistochemical features displaying various positive markers, such as carcinoembryonic antigen, epithelial membrane antigen, S-100 protein, and CKs AE1/AE3 and 5/6.² Invasion of the adjacent soft tissue can be present and helps to confirm the diagnosis.

The differential diagnosis for hidradenocarcinoma primarily is the benign hidradenoma, which is similar both clinically and histologically with a few important differences. Hidradenocarcinomas often are larger and ulcerated. Histologically, they usually are more pleomorphic with the presence of mitotic figures in clear cells and tend to invade locally into the surrounding soft tissue. Other similar lesions such as spiradenoma, Merkel cell carcinoma, lymphangioma, cutaneous Crohn disease, tumors metastatic to the skin, and metastatic clear cell carcinomas originating from other organs also are included in the differential diagnosis.²

Spiradenomas are dermal tumors originating from the sweat glands. They typically present as bluish, painful, solitary nodules on the ventral surfaces of the upper body, though multiple nodules also are reported.⁵ Spiradenomas manifest as a central constellation of pale large cells surrounded by small, dark, basaloid cells containing hyperchromatic nuclei. The microscopic appearance of the blue basaloid cells contrasts with the clear cells seen in hidradenoma.⁵

Merkel cell carcinoma is a cutaneous neuroendocrine tumor affecting elderly or immunosuppressed individuals. It arises in sun-exposed areas and often is associated with Merkel cell polyomavirus infection. The histologic features display small and round cells that stain positive for CK8, CK18, CK19, and CK20 but stain negative for CK7, a marker that often is positive in hidradenocarcinoma.⁶

Lymphangioma, particularly cavernous lymphangioma, may resemble the gross appearance of hidradenoma/ hidradenocarcinoma. It usually presents as irregular clear blue papules and nodules in the skin and subcutaneous tissue.⁷ The key histopathologic finding in this tumor is the endothelium-lined channels that stain positive for D2-40, a lymphatic endothelium marker.^7,8

Cutaneous Crohn disease is classified as noncaseating granulomatous skin lesions that are noncontinuous with the gastrointestinal tract.⁹ Clinical presentations in addition to skin edema include erythematous plaques, ulcerations, and erosions. Histopathology reveals sterile noncaseating granulomas made of Langerhans giant cells, epithelioid histocytes, and plasma cells.⁹

Metastatic clear cell carcinomas, such as renal cell carcinoma, can be differentiated by a history of primary carcinoma, demonstration of histologic vascular stroma, and other features related to metastatic clear cell carcinoma.²

There are no well-established therapeutic guidelines for hidradenocarcinoma. Wide local excision with margins greater than 2 cm is the preferred initial treatment and often is performed in conjunction with sentinel lymph node biopsy. External beam radiotherapy and adjunctive chemotherapy have been used for tumors that could not be surgically cleared. However, the efficacy of these treatments has not been well established.² Targeted therapies recently have emerged as an alternative treatment choice for hidradenocarcinoma due to the utilization of immunohistochemical and genomic testing. The discovery of specific gene mutations or the expression of hormonal receptors in this tumor have paved the way for targeting HER2-expressing hidradenocarcinomas with trastuzumab and those expressing estrogen receptor with the estrogen receptor inhibitor tamoxifen.¹ Epidermal growth factor receptor inhibitors and PI3K/Akt/mTOR (phosphatidylinositol-3-kinase/AKT/mammalian target of rapamycin) pathway inhibitors also have been used to target various signal transduction pathways.²

Wide excision with 2.5-cm margins was performed on our patient, and a positron emission tomography– computed tomography scan revealed no metastatic disease. She declined sentinel lymph node biopsy and additional treatment. Due to the risk for recurrence, she was monitored closely with skin examinations and positron emission tomography–computed tomography every 3 months for the first year and every 6 months thereafter. Thus far, she has had no evidence of local or regional recurrence.

The Diagnosis: Hidradenocarcinoma

An excisional biopsy revealed a neoplasm in the dermis with focal invasion into the adjacent soft tissue (Figure 1). The tumor consisted of sheets of cells with cytoplasmic vacuoles and ductal differentiation (Figure 2), as well as cells with mild atypia, mild pleomorphism, rare mitotic figures, and abundant pale cytoplasm. Immunohistochemical staining was positive for cytokeratin (CK) 5, CK7, CK20, CK AE1/AE3, and p63 (Figure 3). The culmination of features including the large tumor size, immunohistochemical staining pattern, and mild pleomorphism with focal invasion into the soft tissue supported the diagnosis of hidradenocarcinoma.

Hidradenocarcinoma is an exceedingly rare malignant tumor of eccrine and/or apocrine origin.¹ It accounts for less than 0.001% of all tumors and 1 of 13,000 skin biopsies.² It usually arises in the head and neck region and most commonly affects older adults aged 50 to 70 years.³ The size of hidradenocarcinomas can vary; however, they typically are large, often growing to be greater than 5 cm in diameter.² It tends to be an aggressive tumor that generally spreads to regional lymph nodes and distant viscera.⁴ Although it most commonly arises de novo, it may occasionally derive from a benign hidradenoma.¹ The diagnosis of hidradenocarcinoma is made based on the tumor’s morphologic and pathologic characteristics. Histologically, it is characterized by an infiltrative and invasive proliferation of lobules made of large clear cells with atypical mitotic figures and nuclear pleomorphism as well as immunohistochemical features displaying various positive markers, such as carcinoembryonic antigen, epithelial membrane antigen, S-100 protein, and CKs AE1/AE3 and 5/6.² Invasion of the adjacent soft tissue can be present and helps to confirm the diagnosis.

The differential diagnosis for hidradenocarcinoma primarily is the benign hidradenoma, which is similar both clinically and histologically with a few important differences. Hidradenocarcinomas often are larger and ulcerated. Histologically, they usually are more pleomorphic with the presence of mitotic figures in clear cells and tend to invade locally into the surrounding soft tissue. Other similar lesions such as spiradenoma, Merkel cell carcinoma, lymphangioma, cutaneous Crohn disease, tumors metastatic to the skin, and metastatic clear cell carcinomas originating from other organs also are included in the differential diagnosis.²

Spiradenomas are dermal tumors originating from the sweat glands. They typically present as bluish, painful, solitary nodules on the ventral surfaces of the upper body, though multiple nodules also are reported.⁵ Spiradenomas manifest as a central constellation of pale large cells surrounded by small, dark, basaloid cells containing hyperchromatic nuclei. The microscopic appearance of the blue basaloid cells contrasts with the clear cells seen in hidradenoma.⁵

Merkel cell carcinoma is a cutaneous neuroendocrine tumor affecting elderly or immunosuppressed individuals. It arises in sun-exposed areas and often is associated with Merkel cell polyomavirus infection. The histologic features display small and round cells that stain positive for CK8, CK18, CK19, and CK20 but stain negative for CK7, a marker that often is positive in hidradenocarcinoma.⁶

Lymphangioma, particularly cavernous lymphangioma, may resemble the gross appearance of hidradenoma/ hidradenocarcinoma. It usually presents as irregular clear blue papules and nodules in the skin and subcutaneous tissue.⁷ The key histopathologic finding in this tumor is the endothelium-lined channels that stain positive for D2-40, a lymphatic endothelium marker.^7,8

Cutaneous Crohn disease is classified as noncaseating granulomatous skin lesions that are noncontinuous with the gastrointestinal tract.⁹ Clinical presentations in addition to skin edema include erythematous plaques, ulcerations, and erosions. Histopathology reveals sterile noncaseating granulomas made of Langerhans giant cells, epithelioid histocytes, and plasma cells.⁹

Metastatic clear cell carcinomas, such as renal cell carcinoma, can be differentiated by a history of primary carcinoma, demonstration of histologic vascular stroma, and other features related to metastatic clear cell carcinoma.²

There are no well-established therapeutic guidelines for hidradenocarcinoma. Wide local excision with margins greater than 2 cm is the preferred initial treatment and often is performed in conjunction with sentinel lymph node biopsy. External beam radiotherapy and adjunctive chemotherapy have been used for tumors that could not be surgically cleared. However, the efficacy of these treatments has not been well established.² Targeted therapies recently have emerged as an alternative treatment choice for hidradenocarcinoma due to the utilization of immunohistochemical and genomic testing. The discovery of specific gene mutations or the expression of hormonal receptors in this tumor have paved the way for targeting HER2-expressing hidradenocarcinomas with trastuzumab and those expressing estrogen receptor with the estrogen receptor inhibitor tamoxifen.¹ Epidermal growth factor receptor inhibitors and PI3K/Akt/mTOR (phosphatidylinositol-3-kinase/AKT/mammalian target of rapamycin) pathway inhibitors also have been used to target various signal transduction pathways.²

Wide excision with 2.5-cm margins was performed on our patient, and a positron emission tomography– computed tomography scan revealed no metastatic disease. She declined sentinel lymph node biopsy and additional treatment. Due to the risk for recurrence, she was monitored closely with skin examinations and positron emission tomography–computed tomography every 3 months for the first year and every 6 months thereafter. Thus far, she has had no evidence of local or regional recurrence.

The Diagnosis: Hidradenocarcinoma

An excisional biopsy revealed a neoplasm in the dermis with focal invasion into the adjacent soft tissue (Figure 1). The tumor consisted of sheets of cells with cytoplasmic vacuoles and ductal differentiation (Figure 2), as well as cells with mild atypia, mild pleomorphism, rare mitotic figures, and abundant pale cytoplasm. Immunohistochemical staining was positive for cytokeratin (CK) 5, CK7, CK20, CK AE1/AE3, and p63 (Figure 3). The culmination of features including the large tumor size, immunohistochemical staining pattern, and mild pleomorphism with focal invasion into the soft tissue supported the diagnosis of hidradenocarcinoma.

Hidradenocarcinoma is an exceedingly rare malignant tumor of eccrine and/or apocrine origin.¹ It accounts for less than 0.001% of all tumors and 1 of 13,000 skin biopsies.² It usually arises in the head and neck region and most commonly affects older adults aged 50 to 70 years.³ The size of hidradenocarcinomas can vary; however, they typically are large, often growing to be greater than 5 cm in diameter.² It tends to be an aggressive tumor that generally spreads to regional lymph nodes and distant viscera.⁴ Although it most commonly arises de novo, it may occasionally derive from a benign hidradenoma.¹ The diagnosis of hidradenocarcinoma is made based on the tumor’s morphologic and pathologic characteristics. Histologically, it is characterized by an infiltrative and invasive proliferation of lobules made of large clear cells with atypical mitotic figures and nuclear pleomorphism as well as immunohistochemical features displaying various positive markers, such as carcinoembryonic antigen, epithelial membrane antigen, S-100 protein, and CKs AE1/AE3 and 5/6.² Invasion of the adjacent soft tissue can be present and helps to confirm the diagnosis.

The differential diagnosis for hidradenocarcinoma primarily is the benign hidradenoma, which is similar both clinically and histologically with a few important differences. Hidradenocarcinomas often are larger and ulcerated. Histologically, they usually are more pleomorphic with the presence of mitotic figures in clear cells and tend to invade locally into the surrounding soft tissue. Other similar lesions such as spiradenoma, Merkel cell carcinoma, lymphangioma, cutaneous Crohn disease, tumors metastatic to the skin, and metastatic clear cell carcinomas originating from other organs also are included in the differential diagnosis.²

Spiradenomas are dermal tumors originating from the sweat glands. They typically present as bluish, painful, solitary nodules on the ventral surfaces of the upper body, though multiple nodules also are reported.⁵ Spiradenomas manifest as a central constellation of pale large cells surrounded by small, dark, basaloid cells containing hyperchromatic nuclei. The microscopic appearance of the blue basaloid cells contrasts with the clear cells seen in hidradenoma.⁵

Merkel cell carcinoma is a cutaneous neuroendocrine tumor affecting elderly or immunosuppressed individuals. It arises in sun-exposed areas and often is associated with Merkel cell polyomavirus infection. The histologic features display small and round cells that stain positive for CK8, CK18, CK19, and CK20 but stain negative for CK7, a marker that often is positive in hidradenocarcinoma.⁶

Lymphangioma, particularly cavernous lymphangioma, may resemble the gross appearance of hidradenoma/ hidradenocarcinoma. It usually presents as irregular clear blue papules and nodules in the skin and subcutaneous tissue.⁷ The key histopathologic finding in this tumor is the endothelium-lined channels that stain positive for D2-40, a lymphatic endothelium marker.^7,8

Cutaneous Crohn disease is classified as noncaseating granulomatous skin lesions that are noncontinuous with the gastrointestinal tract.⁹ Clinical presentations in addition to skin edema include erythematous plaques, ulcerations, and erosions. Histopathology reveals sterile noncaseating granulomas made of Langerhans giant cells, epithelioid histocytes, and plasma cells.⁹

Metastatic clear cell carcinomas, such as renal cell carcinoma, can be differentiated by a history of primary carcinoma, demonstration of histologic vascular stroma, and other features related to metastatic clear cell carcinoma.²

There are no well-established therapeutic guidelines for hidradenocarcinoma. Wide local excision with margins greater than 2 cm is the preferred initial treatment and often is performed in conjunction with sentinel lymph node biopsy. External beam radiotherapy and adjunctive chemotherapy have been used for tumors that could not be surgically cleared. However, the efficacy of these treatments has not been well established.² Targeted therapies recently have emerged as an alternative treatment choice for hidradenocarcinoma due to the utilization of immunohistochemical and genomic testing. The discovery of specific gene mutations or the expression of hormonal receptors in this tumor have paved the way for targeting HER2-expressing hidradenocarcinomas with trastuzumab and those expressing estrogen receptor with the estrogen receptor inhibitor tamoxifen.¹ Epidermal growth factor receptor inhibitors and PI3K/Akt/mTOR (phosphatidylinositol-3-kinase/AKT/mammalian target of rapamycin) pathway inhibitors also have been used to target various signal transduction pathways.²

Wide excision with 2.5-cm margins was performed on our patient, and a positron emission tomography– computed tomography scan revealed no metastatic disease. She declined sentinel lymph node biopsy and additional treatment. Due to the risk for recurrence, she was monitored closely with skin examinations and positron emission tomography–computed tomography every 3 months for the first year and every 6 months thereafter. Thus far, she has had no evidence of local or regional recurrence.

The Diagnosis: Cutaneous Angiosarcoma 

Biopsy revealed a cellular neoplasm consisting of atypical polygonal cells with a hobnailed appearance, vasoformative characteristics, and rare extravasated erythrocytes. The tumor had an infiltrative growth pattern as demonstrated by dissecting dermal collagen and a poorly defined border with adjacent normal tissue (Figure 1). Immunohistochemistry revealed that the lesion was positive for CD31 and D2-40 (Figure 2) but negative for cytokeratin, CD10, CD68, human herpesvirus 8, CD34, and Melan A, thus confirming the endothelial origin of the tumor cells and the diagnosis of cutaneous angiosarcoma (CAS). The patient was treated with extended surgical excision and radiation therapy. No recurrence or metastasis was found throughout 2 years of follow-up.  

Radical resection with a negative margin is considered the first-line treatment of choice. Although there is a paucity of studies assessing the specific width of surgical margins, application of no less than a 3-cm peripheral margin as well as a clear deep margin is recommended.⁵ Adjuvant radiation therapy also is essential to prevent local recurrence. Patients receiving combination therapy have a superior overall survival rate when compared to those undergoing surgery or radiation therapy alone.⁴  

Cutaneous follicle center lymphoma also may present as 1 or more localized erythematous papules, plaques, and/or nodules, commonly arising on the scalp/forehead or trunk of middle-aged men. Despite being a low-grade lymphoma with a favorable prognosis, it may have a relatively fast growth and locally aggressive course if left untreated. The distinguishing histologic feature is a dense proliferation of neoplastic infiltrates in the dermis, which is separated from the epidermis by the grenz zone.⁶ 

The clinical presentation of cutaneous metastatic carcinomas varies greatly, with 1 or multiple localized or widespread lesions commonly involving the abdominal wall, scalp, and face. The lesions also may mimic benign dermatologic conditions, thus potentially resulting in erroneous clinical diagnosis and delayed therapy of the primary malignancy. Obtaining clinical history is crucial; however, a precise diagnosis may require histologic examination.⁷ 

Atypical fibroxanthoma is a rare superficial cutaneous sarcoma that typically occurs on the head and neck in sun-damaged elderly individuals. Clinically, AFX presents as well-circumscribed red or pink nodules or plaques with or without ulceration, crust, or scale.⁸ Atypical fibroxanthoma lesions usually are small, with a median diameter of 1 cm, while those greater than 2 cm reportedly account for less than 5% of cases.⁹ Atypical fibroxanthoma typically grows rapidly with no pain or discomfort. Histologically, AFX is characterized by a well-circumscribed dermal nodule consisting of pleomorphic spindle cells and multinucleated giant cells that can stain positively for CD10 and procollagen 1.¹⁰ 

Cutaneous pseudolymphoma is a benign inflammatory response process that stimulates polyclonal T- or B-cell lymphoproliferation. The clinical presentation may appear as localized or disseminated flesh-colored or red papules, infiltrated plaques, and nodules.¹¹ Histopathology will show mixtures of B and T cells along with dendritic cells and macrophages, but irregular vascular structure and dissecting dermal collagen are not involved. 

We present an unusual case of CAS with multiple pink nodules on the scalp. Early biopsy of these lesions is important to reach a correct diagnosis and to initiate appropriate treatment. 

The Diagnosis: Cutaneous Angiosarcoma 

Biopsy revealed a cellular neoplasm consisting of atypical polygonal cells with a hobnailed appearance, vasoformative characteristics, and rare extravasated erythrocytes. The tumor had an infiltrative growth pattern as demonstrated by dissecting dermal collagen and a poorly defined border with adjacent normal tissue (Figure 1). Immunohistochemistry revealed that the lesion was positive for CD31 and D2-40 (Figure 2) but negative for cytokeratin, CD10, CD68, human herpesvirus 8, CD34, and Melan A, thus confirming the endothelial origin of the tumor cells and the diagnosis of cutaneous angiosarcoma (CAS). The patient was treated with extended surgical excision and radiation therapy. No recurrence or metastasis was found throughout 2 years of follow-up.  

Radical resection with a negative margin is considered the first-line treatment of choice. Although there is a paucity of studies assessing the specific width of surgical margins, application of no less than a 3-cm peripheral margin as well as a clear deep margin is recommended.⁵ Adjuvant radiation therapy also is essential to prevent local recurrence. Patients receiving combination therapy have a superior overall survival rate when compared to those undergoing surgery or radiation therapy alone.⁴  

Cutaneous follicle center lymphoma also may present as 1 or more localized erythematous papules, plaques, and/or nodules, commonly arising on the scalp/forehead or trunk of middle-aged men. Despite being a low-grade lymphoma with a favorable prognosis, it may have a relatively fast growth and locally aggressive course if left untreated. The distinguishing histologic feature is a dense proliferation of neoplastic infiltrates in the dermis, which is separated from the epidermis by the grenz zone.⁶ 

The clinical presentation of cutaneous metastatic carcinomas varies greatly, with 1 or multiple localized or widespread lesions commonly involving the abdominal wall, scalp, and face. The lesions also may mimic benign dermatologic conditions, thus potentially resulting in erroneous clinical diagnosis and delayed therapy of the primary malignancy. Obtaining clinical history is crucial; however, a precise diagnosis may require histologic examination.⁷ 

Atypical fibroxanthoma is a rare superficial cutaneous sarcoma that typically occurs on the head and neck in sun-damaged elderly individuals. Clinically, AFX presents as well-circumscribed red or pink nodules or plaques with or without ulceration, crust, or scale.⁸ Atypical fibroxanthoma lesions usually are small, with a median diameter of 1 cm, while those greater than 2 cm reportedly account for less than 5% of cases.⁹ Atypical fibroxanthoma typically grows rapidly with no pain or discomfort. Histologically, AFX is characterized by a well-circumscribed dermal nodule consisting of pleomorphic spindle cells and multinucleated giant cells that can stain positively for CD10 and procollagen 1.¹⁰ 

Cutaneous pseudolymphoma is a benign inflammatory response process that stimulates polyclonal T- or B-cell lymphoproliferation. The clinical presentation may appear as localized or disseminated flesh-colored or red papules, infiltrated plaques, and nodules.¹¹ Histopathology will show mixtures of B and T cells along with dendritic cells and macrophages, but irregular vascular structure and dissecting dermal collagen are not involved. 

We present an unusual case of CAS with multiple pink nodules on the scalp. Early biopsy of these lesions is important to reach a correct diagnosis and to initiate appropriate treatment. 

The Diagnosis: Cutaneous Angiosarcoma 

Biopsy revealed a cellular neoplasm consisting of atypical polygonal cells with a hobnailed appearance, vasoformative characteristics, and rare extravasated erythrocytes. The tumor had an infiltrative growth pattern as demonstrated by dissecting dermal collagen and a poorly defined border with adjacent normal tissue (Figure 1). Immunohistochemistry revealed that the lesion was positive for CD31 and D2-40 (Figure 2) but negative for cytokeratin, CD10, CD68, human herpesvirus 8, CD34, and Melan A, thus confirming the endothelial origin of the tumor cells and the diagnosis of cutaneous angiosarcoma (CAS). The patient was treated with extended surgical excision and radiation therapy. No recurrence or metastasis was found throughout 2 years of follow-up.  

Radical resection with a negative margin is considered the first-line treatment of choice. Although there is a paucity of studies assessing the specific width of surgical margins, application of no less than a 3-cm peripheral margin as well as a clear deep margin is recommended.⁵ Adjuvant radiation therapy also is essential to prevent local recurrence. Patients receiving combination therapy have a superior overall survival rate when compared to those undergoing surgery or radiation therapy alone.⁴  

Cutaneous follicle center lymphoma also may present as 1 or more localized erythematous papules, plaques, and/or nodules, commonly arising on the scalp/forehead or trunk of middle-aged men. Despite being a low-grade lymphoma with a favorable prognosis, it may have a relatively fast growth and locally aggressive course if left untreated. The distinguishing histologic feature is a dense proliferation of neoplastic infiltrates in the dermis, which is separated from the epidermis by the grenz zone.⁶ 

The clinical presentation of cutaneous metastatic carcinomas varies greatly, with 1 or multiple localized or widespread lesions commonly involving the abdominal wall, scalp, and face. The lesions also may mimic benign dermatologic conditions, thus potentially resulting in erroneous clinical diagnosis and delayed therapy of the primary malignancy. Obtaining clinical history is crucial; however, a precise diagnosis may require histologic examination.⁷ 

Atypical fibroxanthoma is a rare superficial cutaneous sarcoma that typically occurs on the head and neck in sun-damaged elderly individuals. Clinically, AFX presents as well-circumscribed red or pink nodules or plaques with or without ulceration, crust, or scale.⁸ Atypical fibroxanthoma lesions usually are small, with a median diameter of 1 cm, while those greater than 2 cm reportedly account for less than 5% of cases.⁹ Atypical fibroxanthoma typically grows rapidly with no pain or discomfort. Histologically, AFX is characterized by a well-circumscribed dermal nodule consisting of pleomorphic spindle cells and multinucleated giant cells that can stain positively for CD10 and procollagen 1.¹⁰ 

Cutaneous pseudolymphoma is a benign inflammatory response process that stimulates polyclonal T- or B-cell lymphoproliferation. The clinical presentation may appear as localized or disseminated flesh-colored or red papules, infiltrated plaques, and nodules.¹¹ Histopathology will show mixtures of B and T cells along with dendritic cells and macrophages, but irregular vascular structure and dissecting dermal collagen are not involved. 

We present an unusual case of CAS with multiple pink nodules on the scalp. Early biopsy of these lesions is important to reach a correct diagnosis and to initiate appropriate treatment. 

Congenital onychodysplasia of the index finger (COIF), or Iso-Kikuchi syndrome, is a rare disorder characterized by malformation of one or both nails of the index fingers. The various anomalies described are anonychia, micronychia, polyonychia, malalignment, or hemi-onychogryphosis. It may be associated with abnormalities of the underlying phalangeal bone, the most masked being bifurcation of the terminal phalange.¹ Initially thought to be nonhereditary and nonfamilial,² it is now known that COIF can be inherited in an autosomal-dominant fashion.³ Millman and Strier³ described a family of 9 patients with COIF. It rarely is described outside of Japan. Padmavathy et al⁴ described a case in an Indian patient with COIF that was associated with the absence of a ring finger in addition to anomalies of the metacarpal bones.

Congenital onychodysplasia of the index finger has a broad spectrum regarding its etiology and clinical features.⁵ The pathogenesis of COIF still is poorly understood. Deficient circulation in digital arteries is thought to be a putative mechanism for developing a deformed nail. The nail is affected on the radial side of the index finger, likely because of the smaller caliber of the artery on that side.⁵ Hereditary as well as nonhereditary sporadic cases have been reported. In addition to the various fingernail anomalies, skeletal abnormalities also have been reported. Baran and Stroud⁶ have reported deformed lunulae as a manifestation of COIF.

The Diagnosis: Congenital Onychodysplasia of the Index Finger

The differential diagnosis of COIF includes hidrotic ectodermal dysplasia, nail-patella syndrome, Poland syndrome, and DOOR syndrome. Hidrotic ectodermal dysplasia exhibits onychodystrophy, generalized hypotrichosis, palmoplantar keratoderma, and dental anomalies.⁷ Nail-patella syndrome presents with hypoplasia of the fingernails and toenails, triangular nail lunulae, absent or hypoplastic patellae, and elbow and iliac horn dysplasia. Poland syndrome is distinguished from COIF by the congenital absence of the pectoralis major muscle on the ipsilateral side of the involved digits. The DOOR syndrome tetrad is comprised of deafness, onychodystrophy, osteodystrophy, and mental retardation.⁸ Unlike these conditions, COIF does not involve systems other than the nails and phalanges.

Treatment of this condition is mainly conservative, as patients typically do not have symptoms.⁹ Surgical interventions can be considered for cosmetic concerns. Knowledge of this congenital entity and its clinical findings is essential to prevent unnecessary procedures and workup.

Congenital onychodysplasia of the index finger (COIF), or Iso-Kikuchi syndrome, is a rare disorder characterized by malformation of one or both nails of the index fingers. The various anomalies described are anonychia, micronychia, polyonychia, malalignment, or hemi-onychogryphosis. It may be associated with abnormalities of the underlying phalangeal bone, the most masked being bifurcation of the terminal phalange.¹ Initially thought to be nonhereditary and nonfamilial,² it is now known that COIF can be inherited in an autosomal-dominant fashion.³ Millman and Strier³ described a family of 9 patients with COIF. It rarely is described outside of Japan. Padmavathy et al⁴ described a case in an Indian patient with COIF that was associated with the absence of a ring finger in addition to anomalies of the metacarpal bones.

Congenital onychodysplasia of the index finger has a broad spectrum regarding its etiology and clinical features.⁵ The pathogenesis of COIF still is poorly understood. Deficient circulation in digital arteries is thought to be a putative mechanism for developing a deformed nail. The nail is affected on the radial side of the index finger, likely because of the smaller caliber of the artery on that side.⁵ Hereditary as well as nonhereditary sporadic cases have been reported. In addition to the various fingernail anomalies, skeletal abnormalities also have been reported. Baran and Stroud⁶ have reported deformed lunulae as a manifestation of COIF.

The Diagnosis: Congenital Onychodysplasia of the Index Finger

The differential diagnosis of COIF includes hidrotic ectodermal dysplasia, nail-patella syndrome, Poland syndrome, and DOOR syndrome. Hidrotic ectodermal dysplasia exhibits onychodystrophy, generalized hypotrichosis, palmoplantar keratoderma, and dental anomalies.⁷ Nail-patella syndrome presents with hypoplasia of the fingernails and toenails, triangular nail lunulae, absent or hypoplastic patellae, and elbow and iliac horn dysplasia. Poland syndrome is distinguished from COIF by the congenital absence of the pectoralis major muscle on the ipsilateral side of the involved digits. The DOOR syndrome tetrad is comprised of deafness, onychodystrophy, osteodystrophy, and mental retardation.⁸ Unlike these conditions, COIF does not involve systems other than the nails and phalanges.

Treatment of this condition is mainly conservative, as patients typically do not have symptoms.⁹ Surgical interventions can be considered for cosmetic concerns. Knowledge of this congenital entity and its clinical findings is essential to prevent unnecessary procedures and workup.

Congenital onychodysplasia of the index finger (COIF), or Iso-Kikuchi syndrome, is a rare disorder characterized by malformation of one or both nails of the index fingers. The various anomalies described are anonychia, micronychia, polyonychia, malalignment, or hemi-onychogryphosis. It may be associated with abnormalities of the underlying phalangeal bone, the most masked being bifurcation of the terminal phalange.¹ Initially thought to be nonhereditary and nonfamilial,² it is now known that COIF can be inherited in an autosomal-dominant fashion.³ Millman and Strier³ described a family of 9 patients with COIF. It rarely is described outside of Japan. Padmavathy et al⁴ described a case in an Indian patient with COIF that was associated with the absence of a ring finger in addition to anomalies of the metacarpal bones.

Congenital onychodysplasia of the index finger has a broad spectrum regarding its etiology and clinical features.⁵ The pathogenesis of COIF still is poorly understood. Deficient circulation in digital arteries is thought to be a putative mechanism for developing a deformed nail. The nail is affected on the radial side of the index finger, likely because of the smaller caliber of the artery on that side.⁵ Hereditary as well as nonhereditary sporadic cases have been reported. In addition to the various fingernail anomalies, skeletal abnormalities also have been reported. Baran and Stroud⁶ have reported deformed lunulae as a manifestation of COIF.

The Diagnosis: Congenital Onychodysplasia of the Index Finger

The differential diagnosis of COIF includes hidrotic ectodermal dysplasia, nail-patella syndrome, Poland syndrome, and DOOR syndrome. Hidrotic ectodermal dysplasia exhibits onychodystrophy, generalized hypotrichosis, palmoplantar keratoderma, and dental anomalies.⁷ Nail-patella syndrome presents with hypoplasia of the fingernails and toenails, triangular nail lunulae, absent or hypoplastic patellae, and elbow and iliac horn dysplasia. Poland syndrome is distinguished from COIF by the congenital absence of the pectoralis major muscle on the ipsilateral side of the involved digits. The DOOR syndrome tetrad is comprised of deafness, onychodystrophy, osteodystrophy, and mental retardation.⁸ Unlike these conditions, COIF does not involve systems other than the nails and phalanges.

Treatment of this condition is mainly conservative, as patients typically do not have symptoms.⁹ Surgical interventions can be considered for cosmetic concerns. Knowledge of this congenital entity and its clinical findings is essential to prevent unnecessary procedures and workup.

The Diagnosis: Dowling-Degos Disease

Histopathology demonstrated elongation of the epidermal rete ridges with increased basal pigmentation, suprapapillary epithelial thinning, dermal melanophages, and a mild lymphocytic infiltrate (Figure). Given the clinical and histologic findings, a diagnosis of Dowling-Degos disease (DDD) was made. The patient was counseled on the increased risk for her children developing DDD. Treatment with the erbium:YAG (Er:YAG) laser subsequently was initiated.

Dowling-Degos disease (also known as reticulate pigmented anomaly of the flexures) is an uncommon autosomal-dominant condition characterized by reticular hyperpigmentation involving the flexural and intertriginous sites. Classic DDD commonly is caused by lossof-function mutations in the keratin 5 gene, KRT5¹; however, DDD also may result from loss-of-function mutations in the protein O-fucosyltransferase 1, POFUT1, and protein O-glucosyltransferase 1, POGLUT1, genes.²

Rare cases of DDD associated with hidradenitis suppurativa are caused by mutations in the presenilin enhancer protein 2 gene, PSENEN.³

Of note, a missense mutation in KRT5 is implicated in epidermolysis bullosa simplex with mottled pigmentation. Onset of DDD typically occurs during the third to fourth decades of life. Reticulated hyperpigmented macules initially occur in the axillae and groin and progressively increase over time to involve the neck, inframammary folds, trunk, and flexural surfaces of the arms and thighs. Patients additionally may present with pitted perioral scars, comedolike lesions on the back and neck, epidermoid cysts, and hidradenitis suppurativa. Keratoacanthoma and squamous cell carcinoma rarely have been reported in association with classic DDD.^4,5

Dowling-Degos disease usually is asymptomatic, though pruritus seldom may occur in the affected flexural areas. Histologically, the epidermal rete ridges are elongated in a filiform or antlerlike pattern with increased pigmentation of the basal layer and thinning of the suprapapillary epithelium. Dermal melanosis and a mild perivascular lymphohistiocytic infiltrate also are present with no increase in the number of melanocytes.^6,7 Galli-Galli disease is a variant of DDD that shares similar clinical and histologic features of DDD but is distinguished from DDD by suprabasilar nondyskeratotic acantholysis on histology.⁸

Regarding other differential diagnoses for our patient, acanthosis nigricans may be distinguished clinically by the presence of velvety and/or verrucous plaques, commonly in the neck folds and axillae. Histologically, acanthosis nigricans is distinct from DDD and involves hyperkeratosis, acanthosis, and epidermal papillomatosis. Our patient had no history of diabetes mellitus or insulin resistance. Granular parakeratosis presents with hyperpigmented hyperkeratotic papules and plaques classically confined to the axillary region; however, the involvement of other intertriginous areas may occur. Histologically, granular parakeratosis demonstrates compact parakeratosis with small bluish keratohyalin granules within the stratum corneum. Confluent and reticulated papillomatosis presents with red-brown keratotic papules that initially appear in the intermammary region and spread laterally forming a reticulated pattern. Histology is similar to acanthosis nigricans and demonstrates hyperkeratosis, acanthosis, and papillomatosis. Inverse psoriasis presents with symmetric and sharply demarcated, erythematous, nonscaly plaques in the intertriginous areas. The plaques of inverse psoriasis may be pruritic and/or sore and occasionally may become macerated. Inverse psoriasis shares similar histologic findings compared to classic plaque psoriasis but may have less confluent parakeratosis.

Treatment of DDD essentially is reserved for cosmetic reasons. Topical hydroquinone, tretinoin, and corticosteroids have been used with limited to no success.^5,9 Beneficial results after treatment with the Er:YAG laser have been reported.¹⁰

The Diagnosis: Dowling-Degos Disease

Histopathology demonstrated elongation of the epidermal rete ridges with increased basal pigmentation, suprapapillary epithelial thinning, dermal melanophages, and a mild lymphocytic infiltrate (Figure). Given the clinical and histologic findings, a diagnosis of Dowling-Degos disease (DDD) was made. The patient was counseled on the increased risk for her children developing DDD. Treatment with the erbium:YAG (Er:YAG) laser subsequently was initiated.

Dowling-Degos disease (also known as reticulate pigmented anomaly of the flexures) is an uncommon autosomal-dominant condition characterized by reticular hyperpigmentation involving the flexural and intertriginous sites. Classic DDD commonly is caused by lossof-function mutations in the keratin 5 gene, KRT5¹; however, DDD also may result from loss-of-function mutations in the protein O-fucosyltransferase 1, POFUT1, and protein O-glucosyltransferase 1, POGLUT1, genes.²

Rare cases of DDD associated with hidradenitis suppurativa are caused by mutations in the presenilin enhancer protein 2 gene, PSENEN.³

Of note, a missense mutation in KRT5 is implicated in epidermolysis bullosa simplex with mottled pigmentation. Onset of DDD typically occurs during the third to fourth decades of life. Reticulated hyperpigmented macules initially occur in the axillae and groin and progressively increase over time to involve the neck, inframammary folds, trunk, and flexural surfaces of the arms and thighs. Patients additionally may present with pitted perioral scars, comedolike lesions on the back and neck, epidermoid cysts, and hidradenitis suppurativa. Keratoacanthoma and squamous cell carcinoma rarely have been reported in association with classic DDD.^4,5

Dowling-Degos disease usually is asymptomatic, though pruritus seldom may occur in the affected flexural areas. Histologically, the epidermal rete ridges are elongated in a filiform or antlerlike pattern with increased pigmentation of the basal layer and thinning of the suprapapillary epithelium. Dermal melanosis and a mild perivascular lymphohistiocytic infiltrate also are present with no increase in the number of melanocytes.^6,7 Galli-Galli disease is a variant of DDD that shares similar clinical and histologic features of DDD but is distinguished from DDD by suprabasilar nondyskeratotic acantholysis on histology.⁸

Regarding other differential diagnoses for our patient, acanthosis nigricans may be distinguished clinically by the presence of velvety and/or verrucous plaques, commonly in the neck folds and axillae. Histologically, acanthosis nigricans is distinct from DDD and involves hyperkeratosis, acanthosis, and epidermal papillomatosis. Our patient had no history of diabetes mellitus or insulin resistance. Granular parakeratosis presents with hyperpigmented hyperkeratotic papules and plaques classically confined to the axillary region; however, the involvement of other intertriginous areas may occur. Histologically, granular parakeratosis demonstrates compact parakeratosis with small bluish keratohyalin granules within the stratum corneum. Confluent and reticulated papillomatosis presents with red-brown keratotic papules that initially appear in the intermammary region and spread laterally forming a reticulated pattern. Histology is similar to acanthosis nigricans and demonstrates hyperkeratosis, acanthosis, and papillomatosis. Inverse psoriasis presents with symmetric and sharply demarcated, erythematous, nonscaly plaques in the intertriginous areas. The plaques of inverse psoriasis may be pruritic and/or sore and occasionally may become macerated. Inverse psoriasis shares similar histologic findings compared to classic plaque psoriasis but may have less confluent parakeratosis.

Treatment of DDD essentially is reserved for cosmetic reasons. Topical hydroquinone, tretinoin, and corticosteroids have been used with limited to no success.^5,9 Beneficial results after treatment with the Er:YAG laser have been reported.¹⁰

The Diagnosis: Dowling-Degos Disease

Histopathology demonstrated elongation of the epidermal rete ridges with increased basal pigmentation, suprapapillary epithelial thinning, dermal melanophages, and a mild lymphocytic infiltrate (Figure). Given the clinical and histologic findings, a diagnosis of Dowling-Degos disease (DDD) was made. The patient was counseled on the increased risk for her children developing DDD. Treatment with the erbium:YAG (Er:YAG) laser subsequently was initiated.

Dowling-Degos disease (also known as reticulate pigmented anomaly of the flexures) is an uncommon autosomal-dominant condition characterized by reticular hyperpigmentation involving the flexural and intertriginous sites. Classic DDD commonly is caused by lossof-function mutations in the keratin 5 gene, KRT5¹; however, DDD also may result from loss-of-function mutations in the protein O-fucosyltransferase 1, POFUT1, and protein O-glucosyltransferase 1, POGLUT1, genes.²

Rare cases of DDD associated with hidradenitis suppurativa are caused by mutations in the presenilin enhancer protein 2 gene, PSENEN.³

Of note, a missense mutation in KRT5 is implicated in epidermolysis bullosa simplex with mottled pigmentation. Onset of DDD typically occurs during the third to fourth decades of life. Reticulated hyperpigmented macules initially occur in the axillae and groin and progressively increase over time to involve the neck, inframammary folds, trunk, and flexural surfaces of the arms and thighs. Patients additionally may present with pitted perioral scars, comedolike lesions on the back and neck, epidermoid cysts, and hidradenitis suppurativa. Keratoacanthoma and squamous cell carcinoma rarely have been reported in association with classic DDD.^4,5

Dowling-Degos disease usually is asymptomatic, though pruritus seldom may occur in the affected flexural areas. Histologically, the epidermal rete ridges are elongated in a filiform or antlerlike pattern with increased pigmentation of the basal layer and thinning of the suprapapillary epithelium. Dermal melanosis and a mild perivascular lymphohistiocytic infiltrate also are present with no increase in the number of melanocytes.^6,7 Galli-Galli disease is a variant of DDD that shares similar clinical and histologic features of DDD but is distinguished from DDD by suprabasilar nondyskeratotic acantholysis on histology.⁸

Regarding other differential diagnoses for our patient, acanthosis nigricans may be distinguished clinically by the presence of velvety and/or verrucous plaques, commonly in the neck folds and axillae. Histologically, acanthosis nigricans is distinct from DDD and involves hyperkeratosis, acanthosis, and epidermal papillomatosis. Our patient had no history of diabetes mellitus or insulin resistance. Granular parakeratosis presents with hyperpigmented hyperkeratotic papules and plaques classically confined to the axillary region; however, the involvement of other intertriginous areas may occur. Histologically, granular parakeratosis demonstrates compact parakeratosis with small bluish keratohyalin granules within the stratum corneum. Confluent and reticulated papillomatosis presents with red-brown keratotic papules that initially appear in the intermammary region and spread laterally forming a reticulated pattern. Histology is similar to acanthosis nigricans and demonstrates hyperkeratosis, acanthosis, and papillomatosis. Inverse psoriasis presents with symmetric and sharply demarcated, erythematous, nonscaly plaques in the intertriginous areas. The plaques of inverse psoriasis may be pruritic and/or sore and occasionally may become macerated. Inverse psoriasis shares similar histologic findings compared to classic plaque psoriasis but may have less confluent parakeratosis.

Treatment of DDD essentially is reserved for cosmetic reasons. Topical hydroquinone, tretinoin, and corticosteroids have been used with limited to no success.^5,9 Beneficial results after treatment with the Er:YAG laser have been reported.¹⁰

The Diagnosis: Platelike Osteoma Cutis 

Histopathologic examination revealed extensive cutaneous ossification in the dermis and subcutis with dermal fibrosis and minimal surrounding inflammation (Figure 1). There was no evidence of infection or neoplasm. Further evaluation did not demonstrate any additional physical dysmorphia, and there were no imbalances of calcium-phosphate metabolism or abnormalities in parathyroid hormone or thyroid hormone function. A diagnosis of platelike osteoma cutis (PLOC) was favored. Computed tomography of the head showed material at the posterior skull of similar density to the adjacent calvarial skull and centered within the dermis, consistent with osteoma cutis (Figure 2). 

Osteoma cutis describes the formation of bone within the skin. It occurs when hydroxyapatite crystals in a proteinaceous matrix are deposited within the skin, ultimately leading to the formation of bone ultrastructure. Ossification of the skin most often occurs secondary to trauma, inflammation, or neoplasm; however, it rarely may be a primary event.^1,2 

Platelike osteoma cutis is a rare form of primary cutaneous ossification in which bone forms within the skin in a platelike manner. It most frequently affects the scalp but also has been observed on the trunk and extremities.¹ A driving metabolic or endocrine abnormality typically is not identified.² 

Platelike osteoma cutis can occur as an isolated finding or as a feature of Albright hereditary osteodystrophy (AHO) or progressive osseous heteroplasia (POH). In addition to cutaneous ossification, AHO involves short stature, endocrinopathy, obesity, shortened fourth and fifth metacarpals, and mental retardation. Progressive osseous heteroplasia is characterized by progressive ossification of the skin and deeper tissues such as muscle and fascia, leading to severe movement restriction; it is believed to be a localized nonprogressive variant of POH.^3,4 Mutations in the guanine nucleotide binding protein, alpha stimulating activity polypeptide 1 gene, GNAS1, a key regulatory gene involved in AHO and POH, have been found in several cases of PLOC.³ Our patient lacked any dysmorphic features or laboratory abnormalities suggestive of AHO or POH. Moreover, testing of the tissue and blood for the GNAS1 mutation was negative. Treatment of PLOC often is difficult. Our patient underwent a trial of ablative fractional laser resurfacing, which failed to lead to perceivable improvement.  

The differential diagnoses include a kerion, dissecting cellulitis of the scalp, folliculitis decalvans, and acne keloidalis nuchae. A kerion is a manifestation of tinea capitis characterized by an inflammatory plaque, often with pain or tenderness. Kerions most frequently occur in children aged 5 to 10 years.⁵ Failure to treat a kerion may result in scarring alopecia. Treatment consists of oral antifungals.  

Dissecting cellulitis of the scalp is thought to occur secondary to follicular occlusion. It is characterized by boggy suppurative nodules primarily on the posterior and vertex scalp. Patchy hair loss is present and typically progresses to cicatricial alopecia. Histology characteristically shows areas of dense, predominantly neutrophilic, perifollicular dermal infiltrates.⁶ 

Folliculitis decalvans is a primary neutrophilic cicatricial alopecia that primarily occurs in adults. Patients with folliculitis decalvans tend to have multiple pustules on the periphery of confluent areas of scarring alopecia. It is theorized that an immune response to staphylococcal superantigens contributes to this disease process.⁷  

The clinical findings of acne keloidalis nuchae include inflammatory pustules and papules with keloidlike plaques on the posterior neck and scalp. It occurs predominantly in teenaged and adult males of African ancestry.⁸ Treatment is aimed at reducing inflammation and preventing exacerbating factors. Severe disease courses may lead to scarring alopecia.

The Diagnosis: Platelike Osteoma Cutis 

Histopathologic examination revealed extensive cutaneous ossification in the dermis and subcutis with dermal fibrosis and minimal surrounding inflammation (Figure 1). There was no evidence of infection or neoplasm. Further evaluation did not demonstrate any additional physical dysmorphia, and there were no imbalances of calcium-phosphate metabolism or abnormalities in parathyroid hormone or thyroid hormone function. A diagnosis of platelike osteoma cutis (PLOC) was favored. Computed tomography of the head showed material at the posterior skull of similar density to the adjacent calvarial skull and centered within the dermis, consistent with osteoma cutis (Figure 2). 

Osteoma cutis describes the formation of bone within the skin. It occurs when hydroxyapatite crystals in a proteinaceous matrix are deposited within the skin, ultimately leading to the formation of bone ultrastructure. Ossification of the skin most often occurs secondary to trauma, inflammation, or neoplasm; however, it rarely may be a primary event.^1,2 

Platelike osteoma cutis is a rare form of primary cutaneous ossification in which bone forms within the skin in a platelike manner. It most frequently affects the scalp but also has been observed on the trunk and extremities.¹ A driving metabolic or endocrine abnormality typically is not identified.² 

Platelike osteoma cutis can occur as an isolated finding or as a feature of Albright hereditary osteodystrophy (AHO) or progressive osseous heteroplasia (POH). In addition to cutaneous ossification, AHO involves short stature, endocrinopathy, obesity, shortened fourth and fifth metacarpals, and mental retardation. Progressive osseous heteroplasia is characterized by progressive ossification of the skin and deeper tissues such as muscle and fascia, leading to severe movement restriction; it is believed to be a localized nonprogressive variant of POH.^3,4 Mutations in the guanine nucleotide binding protein, alpha stimulating activity polypeptide 1 gene, GNAS1, a key regulatory gene involved in AHO and POH, have been found in several cases of PLOC.³ Our patient lacked any dysmorphic features or laboratory abnormalities suggestive of AHO or POH. Moreover, testing of the tissue and blood for the GNAS1 mutation was negative. Treatment of PLOC often is difficult. Our patient underwent a trial of ablative fractional laser resurfacing, which failed to lead to perceivable improvement.  

The differential diagnoses include a kerion, dissecting cellulitis of the scalp, folliculitis decalvans, and acne keloidalis nuchae. A kerion is a manifestation of tinea capitis characterized by an inflammatory plaque, often with pain or tenderness. Kerions most frequently occur in children aged 5 to 10 years.⁵ Failure to treat a kerion may result in scarring alopecia. Treatment consists of oral antifungals.  

Dissecting cellulitis of the scalp is thought to occur secondary to follicular occlusion. It is characterized by boggy suppurative nodules primarily on the posterior and vertex scalp. Patchy hair loss is present and typically progresses to cicatricial alopecia. Histology characteristically shows areas of dense, predominantly neutrophilic, perifollicular dermal infiltrates.⁶ 

Folliculitis decalvans is a primary neutrophilic cicatricial alopecia that primarily occurs in adults. Patients with folliculitis decalvans tend to have multiple pustules on the periphery of confluent areas of scarring alopecia. It is theorized that an immune response to staphylococcal superantigens contributes to this disease process.⁷  

The clinical findings of acne keloidalis nuchae include inflammatory pustules and papules with keloidlike plaques on the posterior neck and scalp. It occurs predominantly in teenaged and adult males of African ancestry.⁸ Treatment is aimed at reducing inflammation and preventing exacerbating factors. Severe disease courses may lead to scarring alopecia.

The Diagnosis: Platelike Osteoma Cutis 

Histopathologic examination revealed extensive cutaneous ossification in the dermis and subcutis with dermal fibrosis and minimal surrounding inflammation (Figure 1). There was no evidence of infection or neoplasm. Further evaluation did not demonstrate any additional physical dysmorphia, and there were no imbalances of calcium-phosphate metabolism or abnormalities in parathyroid hormone or thyroid hormone function. A diagnosis of platelike osteoma cutis (PLOC) was favored. Computed tomography of the head showed material at the posterior skull of similar density to the adjacent calvarial skull and centered within the dermis, consistent with osteoma cutis (Figure 2). 

Osteoma cutis describes the formation of bone within the skin. It occurs when hydroxyapatite crystals in a proteinaceous matrix are deposited within the skin, ultimately leading to the formation of bone ultrastructure. Ossification of the skin most often occurs secondary to trauma, inflammation, or neoplasm; however, it rarely may be a primary event.^1,2 

Platelike osteoma cutis is a rare form of primary cutaneous ossification in which bone forms within the skin in a platelike manner. It most frequently affects the scalp but also has been observed on the trunk and extremities.¹ A driving metabolic or endocrine abnormality typically is not identified.² 

Platelike osteoma cutis can occur as an isolated finding or as a feature of Albright hereditary osteodystrophy (AHO) or progressive osseous heteroplasia (POH). In addition to cutaneous ossification, AHO involves short stature, endocrinopathy, obesity, shortened fourth and fifth metacarpals, and mental retardation. Progressive osseous heteroplasia is characterized by progressive ossification of the skin and deeper tissues such as muscle and fascia, leading to severe movement restriction; it is believed to be a localized nonprogressive variant of POH.^3,4 Mutations in the guanine nucleotide binding protein, alpha stimulating activity polypeptide 1 gene, GNAS1, a key regulatory gene involved in AHO and POH, have been found in several cases of PLOC.³ Our patient lacked any dysmorphic features or laboratory abnormalities suggestive of AHO or POH. Moreover, testing of the tissue and blood for the GNAS1 mutation was negative. Treatment of PLOC often is difficult. Our patient underwent a trial of ablative fractional laser resurfacing, which failed to lead to perceivable improvement.  

The differential diagnoses include a kerion, dissecting cellulitis of the scalp, folliculitis decalvans, and acne keloidalis nuchae. A kerion is a manifestation of tinea capitis characterized by an inflammatory plaque, often with pain or tenderness. Kerions most frequently occur in children aged 5 to 10 years.⁵ Failure to treat a kerion may result in scarring alopecia. Treatment consists of oral antifungals.  

Dissecting cellulitis of the scalp is thought to occur secondary to follicular occlusion. It is characterized by boggy suppurative nodules primarily on the posterior and vertex scalp. Patchy hair loss is present and typically progresses to cicatricial alopecia. Histology characteristically shows areas of dense, predominantly neutrophilic, perifollicular dermal infiltrates.⁶ 

Folliculitis decalvans is a primary neutrophilic cicatricial alopecia that primarily occurs in adults. Patients with folliculitis decalvans tend to have multiple pustules on the periphery of confluent areas of scarring alopecia. It is theorized that an immune response to staphylococcal superantigens contributes to this disease process.⁷  

The clinical findings of acne keloidalis nuchae include inflammatory pustules and papules with keloidlike plaques on the posterior neck and scalp. It occurs predominantly in teenaged and adult males of African ancestry.⁸ Treatment is aimed at reducing inflammation and preventing exacerbating factors. Severe disease courses may lead to scarring alopecia.