Cindy Wassef, MD

The Diagnosis: Cutaneous Rosai-Dorfman Disease

Rosai-Dorfman disease is a rare benign non- Langerhans cell histiocytopathy that can manifest initially with lymph node involvement—classically, massive painless cervical lymphadenopathy.¹ Cutaneous Rosai-Dorfman disease (CRDD) is a variant that can be associated with lymph node and internal involvement, but more than 80% of cases lack extracutaneous involvement.^2,3 In cases with extracutaneous involvement, lymph node disease is most frequent.3 Cutaneous Rosai-Dorfman disease unassociated with extracutaneous disease is a benign self-limiting histiocytopathy that manifests as painless red-brown, yellow, or fleshcolored nodules, plaques, or papules that may become tender or ulcerated.⁴

Cutaneous Rosai-Dorfman disease represents a benign histiocytopathy of resident dendritic cell derivation.³ A characteristic immunohistochemical finding is S-100 positivity, which might suggest a Langerhans cell transdifferentiation phenotype, but other markers corroborative of a Langerhans cell phenotype—namely CD1a and langerin—will be negative. Biopsies typically show a mid to deep dermal histiocytic infiltration in a variably dense polymorphous inflammatory cell background comprised of a mixture of lymphocytes, plasma cells, and neutrophils.³ At times the extent of lymphocytic infiltration can be to a magnitude that resembles a lymphoma on histopathology. In our patient, lymphoma was excluded based on clinical presentation, as this patient lacked the typical symptoms of lymphadenopathy or B symptoms that come with B-cell lymphoma.⁵

The histiocytes in CRDD are characteristically large mononuclear cells exhibiting a low nuclear to cytoplasmic ratio reflective of the voluminous, nonvacuolated, watery cytoplasm. They have ill-defined cytoplasmic membranes resulting in a seemingly syncytial growth pattern. A hallmark of the histiocytes is emperipolesis characterized by intracytoplasmic localization of intact inflammatory cells including neutrophils, lymphocytes, and plasma cells.³

The differential diagnosis of CRDD includes Langerhans cell histiocytosis (LCH), indeterminate cell histiocytosis, xanthogranuloma, and reticulohistiocytoma. All of these conditions can be differentiated by their unique histopathologic and phenotypic characteristics.

Langerhans cell histiocytosis is a distinct clonal histiocytopathy that has a varied presentation ranging from cutaneous confined cases manifesting as a solitary lesion to one of disseminated cutaneous disease with the potential for multiorgan involvement. Regardless of the variant of LCH, the hallmark cell is one showing an eccentrically disposed, reniform nucleus with an open chromatin and abundant eosinophilic cytoplasm (Figure 1).⁶ Both LCH and CRDD stain positive for S-100. However, unlike the histiocytes in CRDD, those seen in LCH stain positive for CD1a and langerin and would not express factor XIIIA. Additionally, the neoplastic cells would not exhibit the same extent of CD68 positivity seen in CRDD.⁶ Treatment of LCH depends on the extent of disease, especially for the presence or absence of extracutaneous disease.⁷

A variant of LCH is indeterminate cell histiocytosis, which can be seen in neonates or adults. It represents a neoplastic proliferation of Langerhans cells that are devoid of Birbeck granules, reflective of an immature early phase of differentiation in the skin prior to the cells acquiring the Birbeck granule (as would be seen in neonates) or a later phase of differentiation after the mature Langerhans cell has encountered antigen and is en route to the lymph node (typically seen in adults).⁸ The phenotypic profile is identical to conventional LCH except the cells do not express langerin. Microscopically, the infiltrates are composed of Langerhans cells that are morphologically indistinguishable from classic LCH but without epidermotropism and exhibit a dominant localization in the dermis typically unassociated with other inflammatory cell elements (Figure 2).⁹

Xanthogranuloma is seen in young children (juvenile xanthogranuloma) as a solitary lesion, though a multifocal cutaneous variant and extracutaneous presentations have been described. Similar lesions can be seen in adults.¹⁰ These lesions are evolutionary in their morphology. In the inception of a juvenile xanthogranuloma, the lesions are highly cellular, and the histiocytes typically are poorly lipidized; there may be a dearth of other inflammatory cell elements. As the lesions mature, the histiocytes become lipidized, and characteristic Touton giant cells that exhibit a wreath of nuclei with peripheral lipidization may develop (Figure 3). In the later stages, there is considerable hyalinizing fibrosis, and the cells can acquire a spindled appearance. The absence of emperipolesis and the presence of notable lipidization are useful light microscopy features differentiating xanthogranuloma from CRDD.¹¹ Treatment of xanthogranuloma can range from a conservative monitoring approach to an aggressive approach combining various antineoplastic therapies with immunosuppressive agents.¹²

Solitary and multicentric reticulohistiocytoma is another form of resident dendritic cell histiocytopathy that can resemble Rosai-Dorfman disease. It is a dermal histiocytic infiltrate accompanied by a polymorphous inflammatory cell infiltrate (Figure 4) and can show variable fibrosis.¹³ One of the hallmarks is the distinct amphophilic cytoplasms, possibly attributable to nuclear DNA released into the cytoplasm from effete nuclei.¹³ The solitary form is unassociated with systemic disease, whereas the multicentric variant can be a paraneoplastic syndrome in the setting of solid and hematologic malignancies.¹⁴ In addition, in the multicentric variant, similar lesions can affect any organ but there can be a proclivity to involve the hand and knee joints, leading to a crippling arthritis.¹⁵ We presented a case of CRDD, a benign resident dendritic cell histiocytopathy that can manifest as a cutaneous confined process in the skin where the clinical course is characteristically benign. It potentially can be confused with LCH, indeterminate cell histiocytosis, xanthogranuloma, and reticulohistiocytoma. For a solitary lesion, intralesional triamcinolone injection and excision are options. Multifocal cutaneous disease or CRDD with notable extracutaneous disease may require systemic treatment.16 In our patient, one intralesional triamcinolone injection was performed with notable resolution.

The Diagnosis: Cutaneous Rosai-Dorfman Disease

Rosai-Dorfman disease is a rare benign non- Langerhans cell histiocytopathy that can manifest initially with lymph node involvement—classically, massive painless cervical lymphadenopathy.¹ Cutaneous Rosai-Dorfman disease (CRDD) is a variant that can be associated with lymph node and internal involvement, but more than 80% of cases lack extracutaneous involvement.^2,3 In cases with extracutaneous involvement, lymph node disease is most frequent.3 Cutaneous Rosai-Dorfman disease unassociated with extracutaneous disease is a benign self-limiting histiocytopathy that manifests as painless red-brown, yellow, or fleshcolored nodules, plaques, or papules that may become tender or ulcerated.⁴

Cutaneous Rosai-Dorfman disease represents a benign histiocytopathy of resident dendritic cell derivation.³ A characteristic immunohistochemical finding is S-100 positivity, which might suggest a Langerhans cell transdifferentiation phenotype, but other markers corroborative of a Langerhans cell phenotype—namely CD1a and langerin—will be negative. Biopsies typically show a mid to deep dermal histiocytic infiltration in a variably dense polymorphous inflammatory cell background comprised of a mixture of lymphocytes, plasma cells, and neutrophils.³ At times the extent of lymphocytic infiltration can be to a magnitude that resembles a lymphoma on histopathology. In our patient, lymphoma was excluded based on clinical presentation, as this patient lacked the typical symptoms of lymphadenopathy or B symptoms that come with B-cell lymphoma.⁵

The histiocytes in CRDD are characteristically large mononuclear cells exhibiting a low nuclear to cytoplasmic ratio reflective of the voluminous, nonvacuolated, watery cytoplasm. They have ill-defined cytoplasmic membranes resulting in a seemingly syncytial growth pattern. A hallmark of the histiocytes is emperipolesis characterized by intracytoplasmic localization of intact inflammatory cells including neutrophils, lymphocytes, and plasma cells.³

The differential diagnosis of CRDD includes Langerhans cell histiocytosis (LCH), indeterminate cell histiocytosis, xanthogranuloma, and reticulohistiocytoma. All of these conditions can be differentiated by their unique histopathologic and phenotypic characteristics.

Langerhans cell histiocytosis is a distinct clonal histiocytopathy that has a varied presentation ranging from cutaneous confined cases manifesting as a solitary lesion to one of disseminated cutaneous disease with the potential for multiorgan involvement. Regardless of the variant of LCH, the hallmark cell is one showing an eccentrically disposed, reniform nucleus with an open chromatin and abundant eosinophilic cytoplasm (Figure 1).⁶ Both LCH and CRDD stain positive for S-100. However, unlike the histiocytes in CRDD, those seen in LCH stain positive for CD1a and langerin and would not express factor XIIIA. Additionally, the neoplastic cells would not exhibit the same extent of CD68 positivity seen in CRDD.⁶ Treatment of LCH depends on the extent of disease, especially for the presence or absence of extracutaneous disease.⁷

A variant of LCH is indeterminate cell histiocytosis, which can be seen in neonates or adults. It represents a neoplastic proliferation of Langerhans cells that are devoid of Birbeck granules, reflective of an immature early phase of differentiation in the skin prior to the cells acquiring the Birbeck granule (as would be seen in neonates) or a later phase of differentiation after the mature Langerhans cell has encountered antigen and is en route to the lymph node (typically seen in adults).⁸ The phenotypic profile is identical to conventional LCH except the cells do not express langerin. Microscopically, the infiltrates are composed of Langerhans cells that are morphologically indistinguishable from classic LCH but without epidermotropism and exhibit a dominant localization in the dermis typically unassociated with other inflammatory cell elements (Figure 2).⁹

Xanthogranuloma is seen in young children (juvenile xanthogranuloma) as a solitary lesion, though a multifocal cutaneous variant and extracutaneous presentations have been described. Similar lesions can be seen in adults.¹⁰ These lesions are evolutionary in their morphology. In the inception of a juvenile xanthogranuloma, the lesions are highly cellular, and the histiocytes typically are poorly lipidized; there may be a dearth of other inflammatory cell elements. As the lesions mature, the histiocytes become lipidized, and characteristic Touton giant cells that exhibit a wreath of nuclei with peripheral lipidization may develop (Figure 3). In the later stages, there is considerable hyalinizing fibrosis, and the cells can acquire a spindled appearance. The absence of emperipolesis and the presence of notable lipidization are useful light microscopy features differentiating xanthogranuloma from CRDD.¹¹ Treatment of xanthogranuloma can range from a conservative monitoring approach to an aggressive approach combining various antineoplastic therapies with immunosuppressive agents.¹²

Solitary and multicentric reticulohistiocytoma is another form of resident dendritic cell histiocytopathy that can resemble Rosai-Dorfman disease. It is a dermal histiocytic infiltrate accompanied by a polymorphous inflammatory cell infiltrate (Figure 4) and can show variable fibrosis.¹³ One of the hallmarks is the distinct amphophilic cytoplasms, possibly attributable to nuclear DNA released into the cytoplasm from effete nuclei.¹³ The solitary form is unassociated with systemic disease, whereas the multicentric variant can be a paraneoplastic syndrome in the setting of solid and hematologic malignancies.¹⁴ In addition, in the multicentric variant, similar lesions can affect any organ but there can be a proclivity to involve the hand and knee joints, leading to a crippling arthritis.¹⁵ We presented a case of CRDD, a benign resident dendritic cell histiocytopathy that can manifest as a cutaneous confined process in the skin where the clinical course is characteristically benign. It potentially can be confused with LCH, indeterminate cell histiocytosis, xanthogranuloma, and reticulohistiocytoma. For a solitary lesion, intralesional triamcinolone injection and excision are options. Multifocal cutaneous disease or CRDD with notable extracutaneous disease may require systemic treatment.16 In our patient, one intralesional triamcinolone injection was performed with notable resolution.

The Diagnosis: Cutaneous Rosai-Dorfman Disease

Rosai-Dorfman disease is a rare benign non- Langerhans cell histiocytopathy that can manifest initially with lymph node involvement—classically, massive painless cervical lymphadenopathy.¹ Cutaneous Rosai-Dorfman disease (CRDD) is a variant that can be associated with lymph node and internal involvement, but more than 80% of cases lack extracutaneous involvement.^2,3 In cases with extracutaneous involvement, lymph node disease is most frequent.3 Cutaneous Rosai-Dorfman disease unassociated with extracutaneous disease is a benign self-limiting histiocytopathy that manifests as painless red-brown, yellow, or fleshcolored nodules, plaques, or papules that may become tender or ulcerated.⁴

Cutaneous Rosai-Dorfman disease represents a benign histiocytopathy of resident dendritic cell derivation.³ A characteristic immunohistochemical finding is S-100 positivity, which might suggest a Langerhans cell transdifferentiation phenotype, but other markers corroborative of a Langerhans cell phenotype—namely CD1a and langerin—will be negative. Biopsies typically show a mid to deep dermal histiocytic infiltration in a variably dense polymorphous inflammatory cell background comprised of a mixture of lymphocytes, plasma cells, and neutrophils.³ At times the extent of lymphocytic infiltration can be to a magnitude that resembles a lymphoma on histopathology. In our patient, lymphoma was excluded based on clinical presentation, as this patient lacked the typical symptoms of lymphadenopathy or B symptoms that come with B-cell lymphoma.⁵

The histiocytes in CRDD are characteristically large mononuclear cells exhibiting a low nuclear to cytoplasmic ratio reflective of the voluminous, nonvacuolated, watery cytoplasm. They have ill-defined cytoplasmic membranes resulting in a seemingly syncytial growth pattern. A hallmark of the histiocytes is emperipolesis characterized by intracytoplasmic localization of intact inflammatory cells including neutrophils, lymphocytes, and plasma cells.³

The differential diagnosis of CRDD includes Langerhans cell histiocytosis (LCH), indeterminate cell histiocytosis, xanthogranuloma, and reticulohistiocytoma. All of these conditions can be differentiated by their unique histopathologic and phenotypic characteristics.

Langerhans cell histiocytosis is a distinct clonal histiocytopathy that has a varied presentation ranging from cutaneous confined cases manifesting as a solitary lesion to one of disseminated cutaneous disease with the potential for multiorgan involvement. Regardless of the variant of LCH, the hallmark cell is one showing an eccentrically disposed, reniform nucleus with an open chromatin and abundant eosinophilic cytoplasm (Figure 1).⁶ Both LCH and CRDD stain positive for S-100. However, unlike the histiocytes in CRDD, those seen in LCH stain positive for CD1a and langerin and would not express factor XIIIA. Additionally, the neoplastic cells would not exhibit the same extent of CD68 positivity seen in CRDD.⁶ Treatment of LCH depends on the extent of disease, especially for the presence or absence of extracutaneous disease.⁷

A variant of LCH is indeterminate cell histiocytosis, which can be seen in neonates or adults. It represents a neoplastic proliferation of Langerhans cells that are devoid of Birbeck granules, reflective of an immature early phase of differentiation in the skin prior to the cells acquiring the Birbeck granule (as would be seen in neonates) or a later phase of differentiation after the mature Langerhans cell has encountered antigen and is en route to the lymph node (typically seen in adults).⁸ The phenotypic profile is identical to conventional LCH except the cells do not express langerin. Microscopically, the infiltrates are composed of Langerhans cells that are morphologically indistinguishable from classic LCH but without epidermotropism and exhibit a dominant localization in the dermis typically unassociated with other inflammatory cell elements (Figure 2).⁹

Xanthogranuloma is seen in young children (juvenile xanthogranuloma) as a solitary lesion, though a multifocal cutaneous variant and extracutaneous presentations have been described. Similar lesions can be seen in adults.¹⁰ These lesions are evolutionary in their morphology. In the inception of a juvenile xanthogranuloma, the lesions are highly cellular, and the histiocytes typically are poorly lipidized; there may be a dearth of other inflammatory cell elements. As the lesions mature, the histiocytes become lipidized, and characteristic Touton giant cells that exhibit a wreath of nuclei with peripheral lipidization may develop (Figure 3). In the later stages, there is considerable hyalinizing fibrosis, and the cells can acquire a spindled appearance. The absence of emperipolesis and the presence of notable lipidization are useful light microscopy features differentiating xanthogranuloma from CRDD.¹¹ Treatment of xanthogranuloma can range from a conservative monitoring approach to an aggressive approach combining various antineoplastic therapies with immunosuppressive agents.¹²

Solitary and multicentric reticulohistiocytoma is another form of resident dendritic cell histiocytopathy that can resemble Rosai-Dorfman disease. It is a dermal histiocytic infiltrate accompanied by a polymorphous inflammatory cell infiltrate (Figure 4) and can show variable fibrosis.¹³ One of the hallmarks is the distinct amphophilic cytoplasms, possibly attributable to nuclear DNA released into the cytoplasm from effete nuclei.¹³ The solitary form is unassociated with systemic disease, whereas the multicentric variant can be a paraneoplastic syndrome in the setting of solid and hematologic malignancies.¹⁴ In addition, in the multicentric variant, similar lesions can affect any organ but there can be a proclivity to involve the hand and knee joints, leading to a crippling arthritis.¹⁵ We presented a case of CRDD, a benign resident dendritic cell histiocytopathy that can manifest as a cutaneous confined process in the skin where the clinical course is characteristically benign. It potentially can be confused with LCH, indeterminate cell histiocytosis, xanthogranuloma, and reticulohistiocytoma. For a solitary lesion, intralesional triamcinolone injection and excision are options. Multifocal cutaneous disease or CRDD with notable extracutaneous disease may require systemic treatment.16 In our patient, one intralesional triamcinolone injection was performed with notable resolution.

The Diagnosis: Mycobacterium abscessus Infection

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

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

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

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

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

The Diagnosis: Mycobacterium abscessus Infection

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

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

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

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

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

The Diagnosis: Mycobacterium abscessus Infection

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

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

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

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

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

To the Editor:

Dermatology is one of the most competitive residencies for matching, with a 57.5% match rate in 2022.¹ Our prior study of research-mentor relationships among matched dermatology applicants corroborated the importance of home programs (HPs) and program connections.² Therefore, our current objective was to compare profiles of matched dermatology applicants without HPs vs those with HPs.

We searched websites of 139 dermatology programs nationwide and found 1736 matched applicants from 2016 to 2020; of them, 323 did not have HPs. We determined program rank by research output using Doximity Residency Navigator (https://www.doximity.com/residency/). Advanced degrees (ADs) of applicants were identified using program websites and LinkedIn. A PubMed search was conducted for number of articles published by each applicant before September 15 of their match year. For applicants without HPs, we identified the senior author on each publication. The senior author publishing with an applicant most often was considered the research mentor. Two-tailed independent t tests and χ² tests were used to determine statistical significance (P<.05).

On average, matched applicants without HPs matched in lower-ranked (74.4) and smaller (12.4) programs compared with matched applicants with HPs (45.3 [P<.0001] and 15.1 [P<.0001], respectively)(eTable). The mean number of publications was similar between matched applicants with HPs and without HPs (5.64 and 4.80, respectively; P=.0525) as well as the percentage with ADs (14.7% and 11.5%, respectively; P=.0953). Overall, 14.8% of matched applicants without HPs matched at their mentors’ institutions.

Data were obtained for matched international applicants as a subset of non-HP applicants. Despite attending medical schools without associated HPs in the United States, international applicants matched at similarly ranked (44.3) and sized (15.0) programs, on average, compared with HP applicants. The mean number of publications was higher for international applicants (11.4) vs domestic applicants (5.33). International applicants more often had ADs (23.8%) and 60.1% of them held doctor of philosophy degrees. Overall, 40.5% of international applicants matched at their mentors’ institutions.

Our study suggests that matched dermatology applicants with and without HPs had similar achievements, on average, for the number of publications and percentage with ADs. However, non-HP applicants matched at lower-ranked programs than HP applicants. Therefore, applicants without HPs should strongly consider cultivating program connections, especially if they desire to match at higher-ranked dermatology programs. To illustrate, the rate of matching at research mentors’ institutions was approximately 3-times higher for international applicants than non-HP applicants overall. Despite the disadvantages of applying as international applicants, they were able to match at substantially higher-ranked dermatology programs than non-HP applicants. International applicants may have a longer time investment—the number of years from obtaining their medical degree or US medical license to matching—giving them time to produce quality research and develop meaningful relationships at an institution. Additionally, our prior study of the top 25 dermatology residencies showed that 26.2% of successful applicants matched at their research mentors’ institutions, with almost half of this subset matching at their HPs, where their mentors also practiced.² Because of the potential benefits of having program connections, applicants without HPs should seek dermatology research mentors, especially via highly beneficial in-person networking opportunities (eg, away rotations, conferences) that had previously been limited during the COVID-19 pandemic.³ Formal mentorship programs giving priority to students without HPs recently have been developed, which only begins to address the inequities in the dermatology residency application process.⁴

Study limitations include lack of resident information on 15 program websites, missed publications due to applicant name changes, not accounting for abstracts and posters, and inability to collect data on unmatched applicants.

We hope that our study alleviates some concerns that applicants without HPs may have regarding applying for dermatology residency and encourages those with a genuine interest in dermatology to pursue the specialty, provided they find a strong research mentor. Residency programs should be cognizant of the unique challenges that non-HP applicants face for matching.

To the Editor:

Dermatology is one of the most competitive residencies for matching, with a 57.5% match rate in 2022.¹ Our prior study of research-mentor relationships among matched dermatology applicants corroborated the importance of home programs (HPs) and program connections.² Therefore, our current objective was to compare profiles of matched dermatology applicants without HPs vs those with HPs.

We searched websites of 139 dermatology programs nationwide and found 1736 matched applicants from 2016 to 2020; of them, 323 did not have HPs. We determined program rank by research output using Doximity Residency Navigator (https://www.doximity.com/residency/). Advanced degrees (ADs) of applicants were identified using program websites and LinkedIn. A PubMed search was conducted for number of articles published by each applicant before September 15 of their match year. For applicants without HPs, we identified the senior author on each publication. The senior author publishing with an applicant most often was considered the research mentor. Two-tailed independent t tests and χ² tests were used to determine statistical significance (P<.05).

On average, matched applicants without HPs matched in lower-ranked (74.4) and smaller (12.4) programs compared with matched applicants with HPs (45.3 [P<.0001] and 15.1 [P<.0001], respectively)(eTable). The mean number of publications was similar between matched applicants with HPs and without HPs (5.64 and 4.80, respectively; P=.0525) as well as the percentage with ADs (14.7% and 11.5%, respectively; P=.0953). Overall, 14.8% of matched applicants without HPs matched at their mentors’ institutions.

Data were obtained for matched international applicants as a subset of non-HP applicants. Despite attending medical schools without associated HPs in the United States, international applicants matched at similarly ranked (44.3) and sized (15.0) programs, on average, compared with HP applicants. The mean number of publications was higher for international applicants (11.4) vs domestic applicants (5.33). International applicants more often had ADs (23.8%) and 60.1% of them held doctor of philosophy degrees. Overall, 40.5% of international applicants matched at their mentors’ institutions.

Our study suggests that matched dermatology applicants with and without HPs had similar achievements, on average, for the number of publications and percentage with ADs. However, non-HP applicants matched at lower-ranked programs than HP applicants. Therefore, applicants without HPs should strongly consider cultivating program connections, especially if they desire to match at higher-ranked dermatology programs. To illustrate, the rate of matching at research mentors’ institutions was approximately 3-times higher for international applicants than non-HP applicants overall. Despite the disadvantages of applying as international applicants, they were able to match at substantially higher-ranked dermatology programs than non-HP applicants. International applicants may have a longer time investment—the number of years from obtaining their medical degree or US medical license to matching—giving them time to produce quality research and develop meaningful relationships at an institution. Additionally, our prior study of the top 25 dermatology residencies showed that 26.2% of successful applicants matched at their research mentors’ institutions, with almost half of this subset matching at their HPs, where their mentors also practiced.² Because of the potential benefits of having program connections, applicants without HPs should seek dermatology research mentors, especially via highly beneficial in-person networking opportunities (eg, away rotations, conferences) that had previously been limited during the COVID-19 pandemic.³ Formal mentorship programs giving priority to students without HPs recently have been developed, which only begins to address the inequities in the dermatology residency application process.⁴

Study limitations include lack of resident information on 15 program websites, missed publications due to applicant name changes, not accounting for abstracts and posters, and inability to collect data on unmatched applicants.

We hope that our study alleviates some concerns that applicants without HPs may have regarding applying for dermatology residency and encourages those with a genuine interest in dermatology to pursue the specialty, provided they find a strong research mentor. Residency programs should be cognizant of the unique challenges that non-HP applicants face for matching.

To the Editor:

Dermatology is one of the most competitive residencies for matching, with a 57.5% match rate in 2022.¹ Our prior study of research-mentor relationships among matched dermatology applicants corroborated the importance of home programs (HPs) and program connections.² Therefore, our current objective was to compare profiles of matched dermatology applicants without HPs vs those with HPs.

We searched websites of 139 dermatology programs nationwide and found 1736 matched applicants from 2016 to 2020; of them, 323 did not have HPs. We determined program rank by research output using Doximity Residency Navigator (https://www.doximity.com/residency/). Advanced degrees (ADs) of applicants were identified using program websites and LinkedIn. A PubMed search was conducted for number of articles published by each applicant before September 15 of their match year. For applicants without HPs, we identified the senior author on each publication. The senior author publishing with an applicant most often was considered the research mentor. Two-tailed independent t tests and χ² tests were used to determine statistical significance (P<.05).

On average, matched applicants without HPs matched in lower-ranked (74.4) and smaller (12.4) programs compared with matched applicants with HPs (45.3 [P<.0001] and 15.1 [P<.0001], respectively)(eTable). The mean number of publications was similar between matched applicants with HPs and without HPs (5.64 and 4.80, respectively; P=.0525) as well as the percentage with ADs (14.7% and 11.5%, respectively; P=.0953). Overall, 14.8% of matched applicants without HPs matched at their mentors’ institutions.

Data were obtained for matched international applicants as a subset of non-HP applicants. Despite attending medical schools without associated HPs in the United States, international applicants matched at similarly ranked (44.3) and sized (15.0) programs, on average, compared with HP applicants. The mean number of publications was higher for international applicants (11.4) vs domestic applicants (5.33). International applicants more often had ADs (23.8%) and 60.1% of them held doctor of philosophy degrees. Overall, 40.5% of international applicants matched at their mentors’ institutions.

Our study suggests that matched dermatology applicants with and without HPs had similar achievements, on average, for the number of publications and percentage with ADs. However, non-HP applicants matched at lower-ranked programs than HP applicants. Therefore, applicants without HPs should strongly consider cultivating program connections, especially if they desire to match at higher-ranked dermatology programs. To illustrate, the rate of matching at research mentors’ institutions was approximately 3-times higher for international applicants than non-HP applicants overall. Despite the disadvantages of applying as international applicants, they were able to match at substantially higher-ranked dermatology programs than non-HP applicants. International applicants may have a longer time investment—the number of years from obtaining their medical degree or US medical license to matching—giving them time to produce quality research and develop meaningful relationships at an institution. Additionally, our prior study of the top 25 dermatology residencies showed that 26.2% of successful applicants matched at their research mentors’ institutions, with almost half of this subset matching at their HPs, where their mentors also practiced.² Because of the potential benefits of having program connections, applicants without HPs should seek dermatology research mentors, especially via highly beneficial in-person networking opportunities (eg, away rotations, conferences) that had previously been limited during the COVID-19 pandemic.³ Formal mentorship programs giving priority to students without HPs recently have been developed, which only begins to address the inequities in the dermatology residency application process.⁴

Study limitations include lack of resident information on 15 program websites, missed publications due to applicant name changes, not accounting for abstracts and posters, and inability to collect data on unmatched applicants.

We hope that our study alleviates some concerns that applicants without HPs may have regarding applying for dermatology residency and encourages those with a genuine interest in dermatology to pursue the specialty, provided they find a strong research mentor. Residency programs should be cognizant of the unique challenges that non-HP applicants face for matching.

To the Editor:

With a steady increase in dermatology publications over recent decades, there is an expanding pool of evidence to address clinical questions.¹ Residency training is the time when appraising the medical literature and practicing evidence-based medicine is most honed. Evidence-based medicine is an essential component of Practice-based Learning and Improvement, a required core competency of the Accreditation Council for Graduate Medical Education.² Assimilation of new research evidence is traditionally taught through didactics and journal club discussions in residency.

However, at a time when the demand for information overwhelms safeguards that exist to evaluate its quality, it is more important than ever to be equipped with the proper tools to critically appraise novel literature. Beyond accepting a scientific article at face value, physicians must learn to ask targeted questions of the study design, results, and clinical relevance. These questions change based on the type of study, and organizations such as the Oxford Centre for Evidence-Based Medicine provide guidance through critical appraisal worksheets.³

To investigate the utility of using guided questions to evaluate the reliability, significance, and applicability of clinical evidence, we beta tested a novel web-based application in an academic dermatology setting to design and run a journal club for residents. Six dermatology residents participated in this institutional review board–approved study comprised of 3 phases: (1) independent article appraisal through the web-based application, (2) group discussion, and (3) anonymous postsurvey.

Using this platform, we uploaded a recent article into the interactive reader, which contained an integrated tool for appraisal based on specific questions. Because the article described the results of a randomized clinical trial, we used questions from the Centre for Evidence-Based Medicine’s Randomised Controlled Trials Critical Appraisal Worksheet, which has a series of questions to evaluate internal validity, results, and external validity and applicability.³

Residents used the platform to independently read the article, highlight areas of the text that corresponded to 8 critical appraisal questions, and answer yes or no to these questions. Based on residents’ answers, a final appraisal score (on a scale of 1% to 100%) was generated. Simultaneously, the attending dermatologist leading the journal club (C.W.) also completed the assignment to establish an expert score.

Scores from the residents’ independent appraisal ranged from 75% to 100% (mean, 85.4%). Upon discussing the article in a group setting, the residents established a consensus score of 75%. This consensus score matched the expert score, which suggested to us that both independently reviewing the article using guided questions and conducting a group debriefing were necessary to match the expert level of critical appraisal.

Of note, the residents’ average independent appraisal score was higher than both the consensus and expert scores, indicating that the residents evaluated the article less critically on their own. With more practice using this method, it is possible that the precision and accuracy of the residents’ critical appraisal of scientific articles will improve.

In the postsurvey, we asked residents about the critical appraisal of the medical literature. All residents agreed that evaluating the quality of evidence when reading a scientific article was somewhat important or very important to them; however, only 2 of 6 evaluated the quality of evidence all the time, and the other 4 did so half of the time or less than half of the time.

When critically appraising articles, 2 of 6 residents used specific rubrics half of the time; 4 of 6 less than half of the time. Most important, 5 of 6 residents agreed that the quality of evidence affected their management decisions more than half of the time or all of the time. Although it is clear that residents value evidence-based medicine and understand the importance of evaluating the quality of evidence, doing so currently might not be simple or practical.

An organized framework for appraising articles would streamline the process. Five of 6 residents agreed that the use of specific questions as a guide made it easier to appraise an article for the quality of its evidence. Four of 6 residents found that juxtaposing specific questions with the interactive reader was helpful; 5 of 6 agreed that they would use a web-based journal club platform if given the option.

Lastly, 5 of 6 residents agreed that if such a tool were available, a platform containing all major dermatology publications in an interactive reader format, along with relevant appraisal questions on the side, would be useful.

This pilot study augmented the typical journal club experience by emphasizing goal-directed reading and the importance of analyzing the quality of evidence. The combination of independent appraisal of an article using targeted questions and a group debrief led to better understanding of the evidence and its clinical applicability. The COVID-19 pandemic may be a better time than ever to explore innovative ways to teach evidence-based medicine in residency training.

To the Editor:

With a steady increase in dermatology publications over recent decades, there is an expanding pool of evidence to address clinical questions.¹ Residency training is the time when appraising the medical literature and practicing evidence-based medicine is most honed. Evidence-based medicine is an essential component of Practice-based Learning and Improvement, a required core competency of the Accreditation Council for Graduate Medical Education.² Assimilation of new research evidence is traditionally taught through didactics and journal club discussions in residency.

However, at a time when the demand for information overwhelms safeguards that exist to evaluate its quality, it is more important than ever to be equipped with the proper tools to critically appraise novel literature. Beyond accepting a scientific article at face value, physicians must learn to ask targeted questions of the study design, results, and clinical relevance. These questions change based on the type of study, and organizations such as the Oxford Centre for Evidence-Based Medicine provide guidance through critical appraisal worksheets.³

To investigate the utility of using guided questions to evaluate the reliability, significance, and applicability of clinical evidence, we beta tested a novel web-based application in an academic dermatology setting to design and run a journal club for residents. Six dermatology residents participated in this institutional review board–approved study comprised of 3 phases: (1) independent article appraisal through the web-based application, (2) group discussion, and (3) anonymous postsurvey.

Using this platform, we uploaded a recent article into the interactive reader, which contained an integrated tool for appraisal based on specific questions. Because the article described the results of a randomized clinical trial, we used questions from the Centre for Evidence-Based Medicine’s Randomised Controlled Trials Critical Appraisal Worksheet, which has a series of questions to evaluate internal validity, results, and external validity and applicability.³

Residents used the platform to independently read the article, highlight areas of the text that corresponded to 8 critical appraisal questions, and answer yes or no to these questions. Based on residents’ answers, a final appraisal score (on a scale of 1% to 100%) was generated. Simultaneously, the attending dermatologist leading the journal club (C.W.) also completed the assignment to establish an expert score.

Scores from the residents’ independent appraisal ranged from 75% to 100% (mean, 85.4%). Upon discussing the article in a group setting, the residents established a consensus score of 75%. This consensus score matched the expert score, which suggested to us that both independently reviewing the article using guided questions and conducting a group debriefing were necessary to match the expert level of critical appraisal.

Of note, the residents’ average independent appraisal score was higher than both the consensus and expert scores, indicating that the residents evaluated the article less critically on their own. With more practice using this method, it is possible that the precision and accuracy of the residents’ critical appraisal of scientific articles will improve.

In the postsurvey, we asked residents about the critical appraisal of the medical literature. All residents agreed that evaluating the quality of evidence when reading a scientific article was somewhat important or very important to them; however, only 2 of 6 evaluated the quality of evidence all the time, and the other 4 did so half of the time or less than half of the time.

When critically appraising articles, 2 of 6 residents used specific rubrics half of the time; 4 of 6 less than half of the time. Most important, 5 of 6 residents agreed that the quality of evidence affected their management decisions more than half of the time or all of the time. Although it is clear that residents value evidence-based medicine and understand the importance of evaluating the quality of evidence, doing so currently might not be simple or practical.

An organized framework for appraising articles would streamline the process. Five of 6 residents agreed that the use of specific questions as a guide made it easier to appraise an article for the quality of its evidence. Four of 6 residents found that juxtaposing specific questions with the interactive reader was helpful; 5 of 6 agreed that they would use a web-based journal club platform if given the option.

Lastly, 5 of 6 residents agreed that if such a tool were available, a platform containing all major dermatology publications in an interactive reader format, along with relevant appraisal questions on the side, would be useful.

This pilot study augmented the typical journal club experience by emphasizing goal-directed reading and the importance of analyzing the quality of evidence. The combination of independent appraisal of an article using targeted questions and a group debrief led to better understanding of the evidence and its clinical applicability. The COVID-19 pandemic may be a better time than ever to explore innovative ways to teach evidence-based medicine in residency training.

To the Editor:

With a steady increase in dermatology publications over recent decades, there is an expanding pool of evidence to address clinical questions.¹ Residency training is the time when appraising the medical literature and practicing evidence-based medicine is most honed. Evidence-based medicine is an essential component of Practice-based Learning and Improvement, a required core competency of the Accreditation Council for Graduate Medical Education.² Assimilation of new research evidence is traditionally taught through didactics and journal club discussions in residency.

However, at a time when the demand for information overwhelms safeguards that exist to evaluate its quality, it is more important than ever to be equipped with the proper tools to critically appraise novel literature. Beyond accepting a scientific article at face value, physicians must learn to ask targeted questions of the study design, results, and clinical relevance. These questions change based on the type of study, and organizations such as the Oxford Centre for Evidence-Based Medicine provide guidance through critical appraisal worksheets.³

To investigate the utility of using guided questions to evaluate the reliability, significance, and applicability of clinical evidence, we beta tested a novel web-based application in an academic dermatology setting to design and run a journal club for residents. Six dermatology residents participated in this institutional review board–approved study comprised of 3 phases: (1) independent article appraisal through the web-based application, (2) group discussion, and (3) anonymous postsurvey.

Using this platform, we uploaded a recent article into the interactive reader, which contained an integrated tool for appraisal based on specific questions. Because the article described the results of a randomized clinical trial, we used questions from the Centre for Evidence-Based Medicine’s Randomised Controlled Trials Critical Appraisal Worksheet, which has a series of questions to evaluate internal validity, results, and external validity and applicability.³

Residents used the platform to independently read the article, highlight areas of the text that corresponded to 8 critical appraisal questions, and answer yes or no to these questions. Based on residents’ answers, a final appraisal score (on a scale of 1% to 100%) was generated. Simultaneously, the attending dermatologist leading the journal club (C.W.) also completed the assignment to establish an expert score.

Scores from the residents’ independent appraisal ranged from 75% to 100% (mean, 85.4%). Upon discussing the article in a group setting, the residents established a consensus score of 75%. This consensus score matched the expert score, which suggested to us that both independently reviewing the article using guided questions and conducting a group debriefing were necessary to match the expert level of critical appraisal.

Of note, the residents’ average independent appraisal score was higher than both the consensus and expert scores, indicating that the residents evaluated the article less critically on their own. With more practice using this method, it is possible that the precision and accuracy of the residents’ critical appraisal of scientific articles will improve.

In the postsurvey, we asked residents about the critical appraisal of the medical literature. All residents agreed that evaluating the quality of evidence when reading a scientific article was somewhat important or very important to them; however, only 2 of 6 evaluated the quality of evidence all the time, and the other 4 did so half of the time or less than half of the time.

When critically appraising articles, 2 of 6 residents used specific rubrics half of the time; 4 of 6 less than half of the time. Most important, 5 of 6 residents agreed that the quality of evidence affected their management decisions more than half of the time or all of the time. Although it is clear that residents value evidence-based medicine and understand the importance of evaluating the quality of evidence, doing so currently might not be simple or practical.

An organized framework for appraising articles would streamline the process. Five of 6 residents agreed that the use of specific questions as a guide made it easier to appraise an article for the quality of its evidence. Four of 6 residents found that juxtaposing specific questions with the interactive reader was helpful; 5 of 6 agreed that they would use a web-based journal club platform if given the option.

Lastly, 5 of 6 residents agreed that if such a tool were available, a platform containing all major dermatology publications in an interactive reader format, along with relevant appraisal questions on the side, would be useful.

This pilot study augmented the typical journal club experience by emphasizing goal-directed reading and the importance of analyzing the quality of evidence. The combination of independent appraisal of an article using targeted questions and a group debrief led to better understanding of the evidence and its clinical applicability. The COVID-19 pandemic may be a better time than ever to explore innovative ways to teach evidence-based medicine in residency training.

THE DIAGNOSIS:

Acquired Perforating Disorder of Renal Disease

A papule with the central plug removed left a pitlike depression, representing Kyrle disease (Figure 1). A punch biopsy of the left forearm revealed epidermal hyperplasia (Figure 2A) surrounding a keratin plug that contained degenerated basophilic material (Figure 2B), confirming the diagnosis of acquired perforating disorder of renal disease (APDRD), classically described as Kyrle disease.

Acquired perforating disorder of renal disease is an uncommon condition in the general population. It is associated with systemic disease, commonly diabetes mellitus and chronic renal failure, and is seen in up to 10% patients receiving hemodialysis.¹ The underlying etiology and pathogenesis of APDRD remains unknown. It has been proposed to be a variant of prurigo nodularis, representing end-stage excoriated folliculitis.¹ Given that most cases appear in patients with systemic disease and metabolic abnormalities, APDRD also has been classified under the spectrum of acquired perforating dermatoses, a group of disorders defined by transepithelial elimination of dermal connective tissue. Elevated levels of serum and tissue fibronectin, uremia, and hyperphosphatemia have been observed in patients with APDRD.^1,2 Fibronectin stimulates epithelial migration and proliferation and may lead to expulsion of keratin. Furthermore, dermal deposition of excess urea and/or phosphate could initiate transepithelial elimination of material. Alternative hypotheses implicate abnormal keratinization or an imbalance between the rates of epidermal proliferation/ differentiation and keratin production, whereby keratin production outpaces the former. Keratin deposited within the dermis subsequently elicits an inflammatory response along with alterations in the local dermis and connective tissue. These components become intermixed and are extruded through the plug opening.³ Lastly, immune dysregulation resulting from systemic disease could contribute to APDRD through increased expression of IL-31, a cytokine thought to play a role in several pruritic inflammatory skin diseases.⁴

Although standardized treatment guidelines for APDRD have not been established, the mainstay of therapy is control of the underlying systemic disorder. Intense pruritus and repeated scratching may contribute to microtrauma and subsequent koebnerization of new lesions.³ Thus, ameliorating pruritus can provide both symptomatic relief and prevent the development of new lesions. Retinoids, UV light, oral antibiotics, antihistamines, corticosteroids, keratolytic agents, and immunosuppressants (eg, allopurinol, tacrolimus) have shown some benefit.⁴

The differential diagnoses for APDRD include arthropod hypersensitivity reactions, eruptive keratoacanthomas, keratosis pilaris, and prurigo nodularis. Arthropod hypersensitivity reactions are seen in patients with a history of a bite or sting from arthropods such as bees, fleas, mites, ticks, and spiders. These reactions cause symptoms of pain, burning, or pruritus and present heterogeneously. They can be edematous and appear as single or multiple papules, pustules, plaques, vesicles, and/or bullae. A central punctum or crusting also may be present. Eruptive keratoacanthomas are seen in Grzybowski syndrome and Ferguson-Smith disease. Grzybowski syndrome arises in the fifth to seventh decades of life and is characterized by the eruptive onset of hundreds to thousands of pruritic, dome-shaped, follicular papules with or without central keratin plugs. Ectropion, mucosal lesions, and masklike facies are other clinical characteristics of Grzybowski syndrome. Ferguson-Smith disease begins in the second decade of life. The eruption of multiple keratoacanthomas and/or squamous cell carcinomas occurs in crops, rapidly growing over 2 to 4 weeks, and then self-resolves. This disease is inherited in an autosomal-dominant manner and is associated with chromosome 9q22. Keratosis pilaris is a benign condition of follicular hyperkeratosis that can appear in any age group and usually is absent of symptoms. It is not associated with any systemic disease. Clinically, the condition appears as folliculocentric keratotic papules with varying degrees of perifollicular erythema located along the extensor surfaces. Keratosis pilaris and APDRD share features of a follicular hyperkeratosis and dilated infundibulum; however, perforation is absent in keratosis pilaris. Lastly, prurigo nodularis is another intensely pruritic dermatosis associated with renal disease that presents as papulonodules on the extensor surfaces of the arms and legs. A biopsy can help to distinguish prurigo nodularis from APDRD.

THE DIAGNOSIS:

Acquired Perforating Disorder of Renal Disease

A papule with the central plug removed left a pitlike depression, representing Kyrle disease (Figure 1). A punch biopsy of the left forearm revealed epidermal hyperplasia (Figure 2A) surrounding a keratin plug that contained degenerated basophilic material (Figure 2B), confirming the diagnosis of acquired perforating disorder of renal disease (APDRD), classically described as Kyrle disease.

Acquired perforating disorder of renal disease is an uncommon condition in the general population. It is associated with systemic disease, commonly diabetes mellitus and chronic renal failure, and is seen in up to 10% patients receiving hemodialysis.¹ The underlying etiology and pathogenesis of APDRD remains unknown. It has been proposed to be a variant of prurigo nodularis, representing end-stage excoriated folliculitis.¹ Given that most cases appear in patients with systemic disease and metabolic abnormalities, APDRD also has been classified under the spectrum of acquired perforating dermatoses, a group of disorders defined by transepithelial elimination of dermal connective tissue. Elevated levels of serum and tissue fibronectin, uremia, and hyperphosphatemia have been observed in patients with APDRD.^1,2 Fibronectin stimulates epithelial migration and proliferation and may lead to expulsion of keratin. Furthermore, dermal deposition of excess urea and/or phosphate could initiate transepithelial elimination of material. Alternative hypotheses implicate abnormal keratinization or an imbalance between the rates of epidermal proliferation/ differentiation and keratin production, whereby keratin production outpaces the former. Keratin deposited within the dermis subsequently elicits an inflammatory response along with alterations in the local dermis and connective tissue. These components become intermixed and are extruded through the plug opening.³ Lastly, immune dysregulation resulting from systemic disease could contribute to APDRD through increased expression of IL-31, a cytokine thought to play a role in several pruritic inflammatory skin diseases.⁴

Although standardized treatment guidelines for APDRD have not been established, the mainstay of therapy is control of the underlying systemic disorder. Intense pruritus and repeated scratching may contribute to microtrauma and subsequent koebnerization of new lesions.³ Thus, ameliorating pruritus can provide both symptomatic relief and prevent the development of new lesions. Retinoids, UV light, oral antibiotics, antihistamines, corticosteroids, keratolytic agents, and immunosuppressants (eg, allopurinol, tacrolimus) have shown some benefit.⁴

The differential diagnoses for APDRD include arthropod hypersensitivity reactions, eruptive keratoacanthomas, keratosis pilaris, and prurigo nodularis. Arthropod hypersensitivity reactions are seen in patients with a history of a bite or sting from arthropods such as bees, fleas, mites, ticks, and spiders. These reactions cause symptoms of pain, burning, or pruritus and present heterogeneously. They can be edematous and appear as single or multiple papules, pustules, plaques, vesicles, and/or bullae. A central punctum or crusting also may be present. Eruptive keratoacanthomas are seen in Grzybowski syndrome and Ferguson-Smith disease. Grzybowski syndrome arises in the fifth to seventh decades of life and is characterized by the eruptive onset of hundreds to thousands of pruritic, dome-shaped, follicular papules with or without central keratin plugs. Ectropion, mucosal lesions, and masklike facies are other clinical characteristics of Grzybowski syndrome. Ferguson-Smith disease begins in the second decade of life. The eruption of multiple keratoacanthomas and/or squamous cell carcinomas occurs in crops, rapidly growing over 2 to 4 weeks, and then self-resolves. This disease is inherited in an autosomal-dominant manner and is associated with chromosome 9q22. Keratosis pilaris is a benign condition of follicular hyperkeratosis that can appear in any age group and usually is absent of symptoms. It is not associated with any systemic disease. Clinically, the condition appears as folliculocentric keratotic papules with varying degrees of perifollicular erythema located along the extensor surfaces. Keratosis pilaris and APDRD share features of a follicular hyperkeratosis and dilated infundibulum; however, perforation is absent in keratosis pilaris. Lastly, prurigo nodularis is another intensely pruritic dermatosis associated with renal disease that presents as papulonodules on the extensor surfaces of the arms and legs. A biopsy can help to distinguish prurigo nodularis from APDRD.

THE DIAGNOSIS:

Acquired Perforating Disorder of Renal Disease

A papule with the central plug removed left a pitlike depression, representing Kyrle disease (Figure 1). A punch biopsy of the left forearm revealed epidermal hyperplasia (Figure 2A) surrounding a keratin plug that contained degenerated basophilic material (Figure 2B), confirming the diagnosis of acquired perforating disorder of renal disease (APDRD), classically described as Kyrle disease.

Acquired perforating disorder of renal disease is an uncommon condition in the general population. It is associated with systemic disease, commonly diabetes mellitus and chronic renal failure, and is seen in up to 10% patients receiving hemodialysis.¹ The underlying etiology and pathogenesis of APDRD remains unknown. It has been proposed to be a variant of prurigo nodularis, representing end-stage excoriated folliculitis.¹ Given that most cases appear in patients with systemic disease and metabolic abnormalities, APDRD also has been classified under the spectrum of acquired perforating dermatoses, a group of disorders defined by transepithelial elimination of dermal connective tissue. Elevated levels of serum and tissue fibronectin, uremia, and hyperphosphatemia have been observed in patients with APDRD.^1,2 Fibronectin stimulates epithelial migration and proliferation and may lead to expulsion of keratin. Furthermore, dermal deposition of excess urea and/or phosphate could initiate transepithelial elimination of material. Alternative hypotheses implicate abnormal keratinization or an imbalance between the rates of epidermal proliferation/ differentiation and keratin production, whereby keratin production outpaces the former. Keratin deposited within the dermis subsequently elicits an inflammatory response along with alterations in the local dermis and connective tissue. These components become intermixed and are extruded through the plug opening.³ Lastly, immune dysregulation resulting from systemic disease could contribute to APDRD through increased expression of IL-31, a cytokine thought to play a role in several pruritic inflammatory skin diseases.⁴

Although standardized treatment guidelines for APDRD have not been established, the mainstay of therapy is control of the underlying systemic disorder. Intense pruritus and repeated scratching may contribute to microtrauma and subsequent koebnerization of new lesions.³ Thus, ameliorating pruritus can provide both symptomatic relief and prevent the development of new lesions. Retinoids, UV light, oral antibiotics, antihistamines, corticosteroids, keratolytic agents, and immunosuppressants (eg, allopurinol, tacrolimus) have shown some benefit.⁴

The differential diagnoses for APDRD include arthropod hypersensitivity reactions, eruptive keratoacanthomas, keratosis pilaris, and prurigo nodularis. Arthropod hypersensitivity reactions are seen in patients with a history of a bite or sting from arthropods such as bees, fleas, mites, ticks, and spiders. These reactions cause symptoms of pain, burning, or pruritus and present heterogeneously. They can be edematous and appear as single or multiple papules, pustules, plaques, vesicles, and/or bullae. A central punctum or crusting also may be present. Eruptive keratoacanthomas are seen in Grzybowski syndrome and Ferguson-Smith disease. Grzybowski syndrome arises in the fifth to seventh decades of life and is characterized by the eruptive onset of hundreds to thousands of pruritic, dome-shaped, follicular papules with or without central keratin plugs. Ectropion, mucosal lesions, and masklike facies are other clinical characteristics of Grzybowski syndrome. Ferguson-Smith disease begins in the second decade of life. The eruption of multiple keratoacanthomas and/or squamous cell carcinomas occurs in crops, rapidly growing over 2 to 4 weeks, and then self-resolves. This disease is inherited in an autosomal-dominant manner and is associated with chromosome 9q22. Keratosis pilaris is a benign condition of follicular hyperkeratosis that can appear in any age group and usually is absent of symptoms. It is not associated with any systemic disease. Clinically, the condition appears as folliculocentric keratotic papules with varying degrees of perifollicular erythema located along the extensor surfaces. Keratosis pilaris and APDRD share features of a follicular hyperkeratosis and dilated infundibulum; however, perforation is absent in keratosis pilaris. Lastly, prurigo nodularis is another intensely pruritic dermatosis associated with renal disease that presents as papulonodules on the extensor surfaces of the arms and legs. A biopsy can help to distinguish prurigo nodularis from APDRD.

To the Editor:

Annular leukoderma, or the halo phenomenon, is a circular reaction of hypopigmentation that most commonly is observed alongside congenital nevi, acquired melanocytic nevi, blue nevi, Spitz nevi, vitiligo, and rarely melanoma.¹ There is limited literature on the mechanism of the halo phenomenon. Most of the literature proposes a T cell–mediated immune response to antigens, which causes not only surrounding pigment loss but also heralds the regression of central lesions.² Others have suggested a vascular mechanism, with blood shunted away from the lesions.³ Because guidelines discourage biopsy of typical halo nevi, it becomes important to evaluate lesions for worrisome features such as ulceration or asymmetry, especially in older patients. We present a case of a pigmented basal cell carcinoma (BCC) that exhibited the halo phenomenon. Four other cases have been described in the literature.^3-6

A 53-year-old man presented for evaluation of an asymptomatic lesion on the left side of the abdomen of approximately 8 months’ duration. He had no personal or family history of skin cancer. Physical examination revealed a central 1-cm, pink, verrucous papule surrounded by a 2×1.2-cm, depigmented, circular patch on the left side of the inferior abdomen (Figure 1). Upon questioning, the patient produced cell phone photographs of the trunk from 3 years prior, which did not show any lesions present. Full-body skin examination did not reveal any other concerning pigmented lesions. Excisional biopsy was performed due to concern for amelanotic melanoma, and histopathology revealed a superficial and pigmented BCC (Figure 2). Immunohistochemistry with Melan-A was negative for atypical melanocytes, with no uptake in the leukoderma areas.

Our patient’s final histologic diagnosis was pigmented BCC, which comprises only 6% of all BCCs.³ The proposed mechanism is that melanocytes colonize the tumor in the surrounding stroma and produce excess melanin. Basal cell carcinoma with halo phenomenon is a rare presentation. As in our case, 2 prior BCC reports also involved patients older than 50 years,^3,5 with the 2 other cases describing women in their late twenties and early thirties.^4,6 Additionally, 2 of 4 reports described patients with a history of multiple BCCs.^3,5

In summary, the seemingly benign halo phenomenon may accompany malignant processes such as nonmelanoma skin cancer. Careful consideration of lesion time course and atypia is imperative for proper clinical suspicion in such cases.

To the Editor:

Annular leukoderma, or the halo phenomenon, is a circular reaction of hypopigmentation that most commonly is observed alongside congenital nevi, acquired melanocytic nevi, blue nevi, Spitz nevi, vitiligo, and rarely melanoma.¹ There is limited literature on the mechanism of the halo phenomenon. Most of the literature proposes a T cell–mediated immune response to antigens, which causes not only surrounding pigment loss but also heralds the regression of central lesions.² Others have suggested a vascular mechanism, with blood shunted away from the lesions.³ Because guidelines discourage biopsy of typical halo nevi, it becomes important to evaluate lesions for worrisome features such as ulceration or asymmetry, especially in older patients. We present a case of a pigmented basal cell carcinoma (BCC) that exhibited the halo phenomenon. Four other cases have been described in the literature.^3-6

A 53-year-old man presented for evaluation of an asymptomatic lesion on the left side of the abdomen of approximately 8 months’ duration. He had no personal or family history of skin cancer. Physical examination revealed a central 1-cm, pink, verrucous papule surrounded by a 2×1.2-cm, depigmented, circular patch on the left side of the inferior abdomen (Figure 1). Upon questioning, the patient produced cell phone photographs of the trunk from 3 years prior, which did not show any lesions present. Full-body skin examination did not reveal any other concerning pigmented lesions. Excisional biopsy was performed due to concern for amelanotic melanoma, and histopathology revealed a superficial and pigmented BCC (Figure 2). Immunohistochemistry with Melan-A was negative for atypical melanocytes, with no uptake in the leukoderma areas.

Our patient’s final histologic diagnosis was pigmented BCC, which comprises only 6% of all BCCs.³ The proposed mechanism is that melanocytes colonize the tumor in the surrounding stroma and produce excess melanin. Basal cell carcinoma with halo phenomenon is a rare presentation. As in our case, 2 prior BCC reports also involved patients older than 50 years,^3,5 with the 2 other cases describing women in their late twenties and early thirties.^4,6 Additionally, 2 of 4 reports described patients with a history of multiple BCCs.^3,5

In summary, the seemingly benign halo phenomenon may accompany malignant processes such as nonmelanoma skin cancer. Careful consideration of lesion time course and atypia is imperative for proper clinical suspicion in such cases.

To the Editor:

Annular leukoderma, or the halo phenomenon, is a circular reaction of hypopigmentation that most commonly is observed alongside congenital nevi, acquired melanocytic nevi, blue nevi, Spitz nevi, vitiligo, and rarely melanoma.¹ There is limited literature on the mechanism of the halo phenomenon. Most of the literature proposes a T cell–mediated immune response to antigens, which causes not only surrounding pigment loss but also heralds the regression of central lesions.² Others have suggested a vascular mechanism, with blood shunted away from the lesions.³ Because guidelines discourage biopsy of typical halo nevi, it becomes important to evaluate lesions for worrisome features such as ulceration or asymmetry, especially in older patients. We present a case of a pigmented basal cell carcinoma (BCC) that exhibited the halo phenomenon. Four other cases have been described in the literature.^3-6

A 53-year-old man presented for evaluation of an asymptomatic lesion on the left side of the abdomen of approximately 8 months’ duration. He had no personal or family history of skin cancer. Physical examination revealed a central 1-cm, pink, verrucous papule surrounded by a 2×1.2-cm, depigmented, circular patch on the left side of the inferior abdomen (Figure 1). Upon questioning, the patient produced cell phone photographs of the trunk from 3 years prior, which did not show any lesions present. Full-body skin examination did not reveal any other concerning pigmented lesions. Excisional biopsy was performed due to concern for amelanotic melanoma, and histopathology revealed a superficial and pigmented BCC (Figure 2). Immunohistochemistry with Melan-A was negative for atypical melanocytes, with no uptake in the leukoderma areas.

Our patient’s final histologic diagnosis was pigmented BCC, which comprises only 6% of all BCCs.³ The proposed mechanism is that melanocytes colonize the tumor in the surrounding stroma and produce excess melanin. Basal cell carcinoma with halo phenomenon is a rare presentation. As in our case, 2 prior BCC reports also involved patients older than 50 years,^3,5 with the 2 other cases describing women in their late twenties and early thirties.^4,6 Additionally, 2 of 4 reports described patients with a history of multiple BCCs.^3,5

In summary, the seemingly benign halo phenomenon may accompany malignant processes such as nonmelanoma skin cancer. Careful consideration of lesion time course and atypia is imperative for proper clinical suspicion in such cases.

The Diagnosis: Interstitial Granulomatous Dermatitis 

Interstitial granulomatous dermatitis (IGD) is rare, and the exact incidence is unknown, with only a few cases reported in the literature annually.¹ Although IGD may arise in both children and adults, it occurs more commonly in adults, with an age of onset of 52 to 58.5 years. Interstitial granulomatous dermatitis also shows a female predominance.¹  

Interstitial granulomatous dermatitis may present as annular flesh-colored or erythematous to violaceous papules and plaques, or less commonly erythematous linear cordlike subcutaneous nodules (called the rope sign).¹ Lesions often are asymptomatic but may be pruritic or tender. Interstitial granulomatous dermatitis has been associated with autoimmune conditions such as rheumatoid arthritis, systemic lupus erythematosus, and primary biliary cholangitis, and rarely malignancy.² Interstitial granulomatous drug reactions can occur months to years after initiation of therapy with offending agents, and common causes include calcium channel blockers, statins, and tumor necrosis factor α inhibitors.³  

Interstitial granulomatous dermatitis and palisaded neutrophilic and granulomatous dermatitis (PNGD) demonstrate overlapping clinical features and are thought to be part of the same spectrum of granulomatous dermatitis.⁴ Both IGD and PNGD may present with symmetric flesh-colored to erythematous papules or erythematous annular or linear plaques.⁵ Interstitial granulomatous dermatitis and PNGD may be differentiated through histopathologic examination.  

Histopathology of IGD shows an interstitial infiltrate of epithelioid histiocytes in the dermis, often surrounding foci of degenerated collagen resembling palisading granulomas (quiz images).¹ Perivascular and interstitial lymphocytic infiltrates also are present in most cases. Epidermal changes are minimal in IGD but can be associated with interstitial granulomatous drug reactions.¹ There usually is no vasculitis, and mucin typically is absent, unlike granuloma annulare (GA).^3,6 In comparison, histopathologic examination of PNGD shows basophilic degenerated collagen surrounded by palisades of histiocytes, neutrophils, and nuclear debris with focal areas of leukocytoclastic vasculitis and rare mucin.⁵  

No specific treatment is recommended, and lesions may resolve without any therapy. Reported treatments include topical, intralesional, or systemic steroids; nonsteroidal anti-inflammatory drugs; methotrexate; hydroxychloroquine; and cyclosporine.⁶ Due to the strong association with systemic diseases, it is important to evaluate patients with IGD for autoimmune diseases and conduct age-appropriate cancer screening. Furthermore, a review of medications is warranted to assess the possibility of interstitial granulomatous drug reactions.⁶ In our patient, rheumatologic workup and age-appropriate cancer screenings were negative, and the rash spontaneously resolved without treatment. 

Granuloma annulare presents with asymptomatic flesh-colored to erythematous papules and plaques in an annular configuration. In the localized variant of GA, plaques frequently localize to the distal extremities, especially the dorsal hands, as in our patient. Other variants include generalized GA, subcutaneous GA, and perforating GA. Mucin and a palisading or interstitial pattern of granulomatous inflammation are key features on histopathology in all subtypes of GA (Figure 1).⁷ Patch GA is a rare variant that presents with asymptomatic erythematous to brown patches, is associated with interstitial-type inflammation on histopathology, and can be difficult to distinguish from IGD.⁸ Granuloma annulare with interstitial inflammation on histology can be differentiated from IGD by the comparative lack of mucin in IGD.⁷ 

Sweet syndrome (SS) is characterized by sudden-onset, painful, erythematous plaques and/or nodules, commonly associated with fever and leukocytosis. Clinical variants of SS include pustular and bullous SS; giant cellulitis-like SS; necrotizing SS; and neutrophilic dermatosis of the dorsal hands presenting with hemorrhagic bullae, plaques, and pustules.^7-9 Histopathologic examination shows dense nodular or perivascular neutrophilic infiltrate in the dermis without evidence of vasculitis (Figure 2).¹⁰ Histopathologic variants include histiocytoid, lymphocytic, subcutaneous, and cryptococcoid.⁹ The classic variant of SS has a bandlike, predominantly neutrophilic infiltrate with marked leukocytoclasia, which can be differentiated from the histiocytoid infiltrate of IGD.¹¹ It has been shown that the infiltrate of the histiocytoid variant of SS is composed of myeloperoxidase-positive, immature myeloid cells rather than true histiocytes, and therefore can be differentiated from IGD.¹² Lastly, all variants of SS have dermal edema, which typically is absent in IGD, and SS has no evidence of necrobiosis.  

Erythema elevatum diutinum (EED) is a rare disease that presents with bilateral violaceous or erythematous to brown papules, plaques, or nodules. Lesions frequently localize to extensor surfaces, including the hands and fingers, and may be asymptomatic or associated with pruritus, burning, or tingling.¹³ Early EED lesions are characterized by leukocytoclastic vasculitis of the papillary and mid-dermal vessels with a perivascular neutrophilic infiltrate and perivascular fibrinoid necrosis. With older EED lesions, dermal and perivascular onion skin-like fibrosis become more prominent (Figure 3).¹⁴ The neutrophilic infiltrate, dermal fibrosis, and chronic vasculitic changes distinguish EED from IGD. 

Necrobiosis lipoidica (NL) is a rare disease that presents with well-demarcated, yellow to red-brown papules and nodules most commonly localized to the bilateral lower extremities on the pretibial area. Papules and nodules evolve into plaques over time, and ulceration is common.¹⁵ On histopathology, NL primarily exhibits granulomatous inflammation with parallel palisading (Figure 4). The hallmark feature is necrobiosis--or degeneration--of collagen; the alternation of necrobiotic collagen and inflammatory infiltrate creates a layered cake-like appearance on low power.¹⁶ The clinical presentation as well as the dermal necrobiotic granuloma consisting of a large confluent area of necrobiosis centered in the superficial dermis and subcutaneous tissue of NL distinguishes it from the histiocytic infiltrate of IGD.  

The Diagnosis: Interstitial Granulomatous Dermatitis 

Interstitial granulomatous dermatitis (IGD) is rare, and the exact incidence is unknown, with only a few cases reported in the literature annually.¹ Although IGD may arise in both children and adults, it occurs more commonly in adults, with an age of onset of 52 to 58.5 years. Interstitial granulomatous dermatitis also shows a female predominance.¹  

Interstitial granulomatous dermatitis may present as annular flesh-colored or erythematous to violaceous papules and plaques, or less commonly erythematous linear cordlike subcutaneous nodules (called the rope sign).¹ Lesions often are asymptomatic but may be pruritic or tender. Interstitial granulomatous dermatitis has been associated with autoimmune conditions such as rheumatoid arthritis, systemic lupus erythematosus, and primary biliary cholangitis, and rarely malignancy.² Interstitial granulomatous drug reactions can occur months to years after initiation of therapy with offending agents, and common causes include calcium channel blockers, statins, and tumor necrosis factor α inhibitors.³  

Interstitial granulomatous dermatitis and palisaded neutrophilic and granulomatous dermatitis (PNGD) demonstrate overlapping clinical features and are thought to be part of the same spectrum of granulomatous dermatitis.⁴ Both IGD and PNGD may present with symmetric flesh-colored to erythematous papules or erythematous annular or linear plaques.⁵ Interstitial granulomatous dermatitis and PNGD may be differentiated through histopathologic examination.  

Histopathology of IGD shows an interstitial infiltrate of epithelioid histiocytes in the dermis, often surrounding foci of degenerated collagen resembling palisading granulomas (quiz images).¹ Perivascular and interstitial lymphocytic infiltrates also are present in most cases. Epidermal changes are minimal in IGD but can be associated with interstitial granulomatous drug reactions.¹ There usually is no vasculitis, and mucin typically is absent, unlike granuloma annulare (GA).^3,6 In comparison, histopathologic examination of PNGD shows basophilic degenerated collagen surrounded by palisades of histiocytes, neutrophils, and nuclear debris with focal areas of leukocytoclastic vasculitis and rare mucin.⁵  

No specific treatment is recommended, and lesions may resolve without any therapy. Reported treatments include topical, intralesional, or systemic steroids; nonsteroidal anti-inflammatory drugs; methotrexate; hydroxychloroquine; and cyclosporine.⁶ Due to the strong association with systemic diseases, it is important to evaluate patients with IGD for autoimmune diseases and conduct age-appropriate cancer screening. Furthermore, a review of medications is warranted to assess the possibility of interstitial granulomatous drug reactions.⁶ In our patient, rheumatologic workup and age-appropriate cancer screenings were negative, and the rash spontaneously resolved without treatment. 

Granuloma annulare presents with asymptomatic flesh-colored to erythematous papules and plaques in an annular configuration. In the localized variant of GA, plaques frequently localize to the distal extremities, especially the dorsal hands, as in our patient. Other variants include generalized GA, subcutaneous GA, and perforating GA. Mucin and a palisading or interstitial pattern of granulomatous inflammation are key features on histopathology in all subtypes of GA (Figure 1).⁷ Patch GA is a rare variant that presents with asymptomatic erythematous to brown patches, is associated with interstitial-type inflammation on histopathology, and can be difficult to distinguish from IGD.⁸ Granuloma annulare with interstitial inflammation on histology can be differentiated from IGD by the comparative lack of mucin in IGD.⁷ 

Sweet syndrome (SS) is characterized by sudden-onset, painful, erythematous plaques and/or nodules, commonly associated with fever and leukocytosis. Clinical variants of SS include pustular and bullous SS; giant cellulitis-like SS; necrotizing SS; and neutrophilic dermatosis of the dorsal hands presenting with hemorrhagic bullae, plaques, and pustules.^7-9 Histopathologic examination shows dense nodular or perivascular neutrophilic infiltrate in the dermis without evidence of vasculitis (Figure 2).¹⁰ Histopathologic variants include histiocytoid, lymphocytic, subcutaneous, and cryptococcoid.⁹ The classic variant of SS has a bandlike, predominantly neutrophilic infiltrate with marked leukocytoclasia, which can be differentiated from the histiocytoid infiltrate of IGD.¹¹ It has been shown that the infiltrate of the histiocytoid variant of SS is composed of myeloperoxidase-positive, immature myeloid cells rather than true histiocytes, and therefore can be differentiated from IGD.¹² Lastly, all variants of SS have dermal edema, which typically is absent in IGD, and SS has no evidence of necrobiosis.  

Erythema elevatum diutinum (EED) is a rare disease that presents with bilateral violaceous or erythematous to brown papules, plaques, or nodules. Lesions frequently localize to extensor surfaces, including the hands and fingers, and may be asymptomatic or associated with pruritus, burning, or tingling.¹³ Early EED lesions are characterized by leukocytoclastic vasculitis of the papillary and mid-dermal vessels with a perivascular neutrophilic infiltrate and perivascular fibrinoid necrosis. With older EED lesions, dermal and perivascular onion skin-like fibrosis become more prominent (Figure 3).¹⁴ The neutrophilic infiltrate, dermal fibrosis, and chronic vasculitic changes distinguish EED from IGD. 

Necrobiosis lipoidica (NL) is a rare disease that presents with well-demarcated, yellow to red-brown papules and nodules most commonly localized to the bilateral lower extremities on the pretibial area. Papules and nodules evolve into plaques over time, and ulceration is common.¹⁵ On histopathology, NL primarily exhibits granulomatous inflammation with parallel palisading (Figure 4). The hallmark feature is necrobiosis--or degeneration--of collagen; the alternation of necrobiotic collagen and inflammatory infiltrate creates a layered cake-like appearance on low power.¹⁶ The clinical presentation as well as the dermal necrobiotic granuloma consisting of a large confluent area of necrobiosis centered in the superficial dermis and subcutaneous tissue of NL distinguishes it from the histiocytic infiltrate of IGD.  

The Diagnosis: Interstitial Granulomatous Dermatitis 

Interstitial granulomatous dermatitis (IGD) is rare, and the exact incidence is unknown, with only a few cases reported in the literature annually.¹ Although IGD may arise in both children and adults, it occurs more commonly in adults, with an age of onset of 52 to 58.5 years. Interstitial granulomatous dermatitis also shows a female predominance.¹  

Interstitial granulomatous dermatitis may present as annular flesh-colored or erythematous to violaceous papules and plaques, or less commonly erythematous linear cordlike subcutaneous nodules (called the rope sign).¹ Lesions often are asymptomatic but may be pruritic or tender. Interstitial granulomatous dermatitis has been associated with autoimmune conditions such as rheumatoid arthritis, systemic lupus erythematosus, and primary biliary cholangitis, and rarely malignancy.² Interstitial granulomatous drug reactions can occur months to years after initiation of therapy with offending agents, and common causes include calcium channel blockers, statins, and tumor necrosis factor α inhibitors.³  

Interstitial granulomatous dermatitis and palisaded neutrophilic and granulomatous dermatitis (PNGD) demonstrate overlapping clinical features and are thought to be part of the same spectrum of granulomatous dermatitis.⁴ Both IGD and PNGD may present with symmetric flesh-colored to erythematous papules or erythematous annular or linear plaques.⁵ Interstitial granulomatous dermatitis and PNGD may be differentiated through histopathologic examination.  

Histopathology of IGD shows an interstitial infiltrate of epithelioid histiocytes in the dermis, often surrounding foci of degenerated collagen resembling palisading granulomas (quiz images).¹ Perivascular and interstitial lymphocytic infiltrates also are present in most cases. Epidermal changes are minimal in IGD but can be associated with interstitial granulomatous drug reactions.¹ There usually is no vasculitis, and mucin typically is absent, unlike granuloma annulare (GA).^3,6 In comparison, histopathologic examination of PNGD shows basophilic degenerated collagen surrounded by palisades of histiocytes, neutrophils, and nuclear debris with focal areas of leukocytoclastic vasculitis and rare mucin.⁵  

No specific treatment is recommended, and lesions may resolve without any therapy. Reported treatments include topical, intralesional, or systemic steroids; nonsteroidal anti-inflammatory drugs; methotrexate; hydroxychloroquine; and cyclosporine.⁶ Due to the strong association with systemic diseases, it is important to evaluate patients with IGD for autoimmune diseases and conduct age-appropriate cancer screening. Furthermore, a review of medications is warranted to assess the possibility of interstitial granulomatous drug reactions.⁶ In our patient, rheumatologic workup and age-appropriate cancer screenings were negative, and the rash spontaneously resolved without treatment. 

Granuloma annulare presents with asymptomatic flesh-colored to erythematous papules and plaques in an annular configuration. In the localized variant of GA, plaques frequently localize to the distal extremities, especially the dorsal hands, as in our patient. Other variants include generalized GA, subcutaneous GA, and perforating GA. Mucin and a palisading or interstitial pattern of granulomatous inflammation are key features on histopathology in all subtypes of GA (Figure 1).⁷ Patch GA is a rare variant that presents with asymptomatic erythematous to brown patches, is associated with interstitial-type inflammation on histopathology, and can be difficult to distinguish from IGD.⁸ Granuloma annulare with interstitial inflammation on histology can be differentiated from IGD by the comparative lack of mucin in IGD.⁷ 

Sweet syndrome (SS) is characterized by sudden-onset, painful, erythematous plaques and/or nodules, commonly associated with fever and leukocytosis. Clinical variants of SS include pustular and bullous SS; giant cellulitis-like SS; necrotizing SS; and neutrophilic dermatosis of the dorsal hands presenting with hemorrhagic bullae, plaques, and pustules.^7-9 Histopathologic examination shows dense nodular or perivascular neutrophilic infiltrate in the dermis without evidence of vasculitis (Figure 2).¹⁰ Histopathologic variants include histiocytoid, lymphocytic, subcutaneous, and cryptococcoid.⁹ The classic variant of SS has a bandlike, predominantly neutrophilic infiltrate with marked leukocytoclasia, which can be differentiated from the histiocytoid infiltrate of IGD.¹¹ It has been shown that the infiltrate of the histiocytoid variant of SS is composed of myeloperoxidase-positive, immature myeloid cells rather than true histiocytes, and therefore can be differentiated from IGD.¹² Lastly, all variants of SS have dermal edema, which typically is absent in IGD, and SS has no evidence of necrobiosis.  

Erythema elevatum diutinum (EED) is a rare disease that presents with bilateral violaceous or erythematous to brown papules, plaques, or nodules. Lesions frequently localize to extensor surfaces, including the hands and fingers, and may be asymptomatic or associated with pruritus, burning, or tingling.¹³ Early EED lesions are characterized by leukocytoclastic vasculitis of the papillary and mid-dermal vessels with a perivascular neutrophilic infiltrate and perivascular fibrinoid necrosis. With older EED lesions, dermal and perivascular onion skin-like fibrosis become more prominent (Figure 3).¹⁴ The neutrophilic infiltrate, dermal fibrosis, and chronic vasculitic changes distinguish EED from IGD. 

Necrobiosis lipoidica (NL) is a rare disease that presents with well-demarcated, yellow to red-brown papules and nodules most commonly localized to the bilateral lower extremities on the pretibial area. Papules and nodules evolve into plaques over time, and ulceration is common.¹⁵ On histopathology, NL primarily exhibits granulomatous inflammation with parallel palisading (Figure 4). The hallmark feature is necrobiosis--or degeneration--of collagen; the alternation of necrobiotic collagen and inflammatory infiltrate creates a layered cake-like appearance on low power.¹⁶ The clinical presentation as well as the dermal necrobiotic granuloma consisting of a large confluent area of necrobiosis centered in the superficial dermis and subcutaneous tissue of NL distinguishes it from the histiocytic infiltrate of IGD.  

In February 2019, Dayanara Torres announced that she had been diagnosed with metastatic melanoma. Ms. Torres, a Puerto Rican–born former Miss Universe who has more than 1 million followers on Instagram (@dayanarapr), seemed an unlikely candidate for skin cancer, which often is associated with fair-skinned and light-eyed individuals. She shared the news of her diagnosis in an Instagram video that has now received more than 850,000 views. In the video, Ms. Torres described a new mole with uneven surface that had developed on her leg and noted that she had ignored it, even though it had been growing for years. Ultimately, she was diagnosed with melanoma that had already metastasized to regional lymph nodes in her leg. Ms. Torres concluded the video by urging fans and viewers to be mindful of new or changing skin lesions and to be aware of the seriousness of skin cancer. In March 2019, Ms. Torres posted a follow-up educational video on Instagram highlighting the features of melanoma that has now received more than 300,000 views.

Since her announcement, we have noticed that more Hispanic patients with concerns about skin cancer are presenting to our dermatology clinic, which is located in a highly diverse city (New Brunswick, New Jersey) with approximately 50% of residents identifying as Hispanic.¹ Most Hispanic patients typically present to our dermatology clinic for non–skin cancer–related concerns, such as acne, rash, and dyschromia; however, following Ms. Torres’ announcement, many have cited her diagnosis of metastatic melanoma as a cause for concern and a motivating factor in having their skin examined. The diagnosis in a prominent celebrity and Hispanic woman has given a new face to metastatic melanoma.

Although melanoma most commonly occurs in white patients, Hispanic patients experience disproportionately greater morbidity and mortality when diagnosed with melanoma.² Poor prognosis in patients with skin of color is multifactorial and may be due to poor use of sun protection, misconceptions about melanoma risk, atypical clinical presentation, impaired access to care, and delay in diagnosis. The Hispanic community encompasses a wide variety of individuals with varying levels of skin pigmentation and sun sensitivity.³ However, Hispanics report low levels of sun-protective behaviors. They also may have misconceptions that sunscreen is ineffective in preventing skin cancer and that little can be done to decrease the risk for developing skin cancer.^4,5 Additionally, Hispanic patients often have lower perceptions of their personal risk for melanoma and report low rates of clinical and self-examinations compared to non-Hispanic white patients.^6-8 Many Hispanic patients have reported that they were not instructed to perform self-examinations of their skin regularly by dermatologists or other providers and did not know the signs of skin cancer.⁷ Furthermore, a language barrier also may impede communication and education regarding melanoma risk.⁹

Similar to white patients, superficial spreading melanoma is the most common histologic subtype in Hispanic patients, followed by acral lentiginous melanoma, which is the most common subtype in black and Asian patients.^2,4 Compared to non-Hispanic white patients, who most commonly present with truncal melanomas, Hispanic patients (particularly those from Puerto Rico, such as Ms. Torres) are more likely to present with melanoma on the lower extremities.^4,10 Additionally, Hispanic patients have high rates of head, neck, and mucosal melanomas compared to all other racial and ethnic groups.²

Hispanic patients diagnosed with melanoma are more likely to present with thicker primary tumors, later stages of disease, and distant metastases compared to non-Hispanic white patients, all of which are associated with poor prognosis.^2,4,11 Five-year survival rates for melanoma are lower in Hispanic patients compared to non-Hispanic white patients.¹² Although the Hispanic community is diverse in socioeconomic and immigration status as well as occupation, lack of insurance also may contribute to decreased access to care, delayed diagnosis, and ultimately worse survival.

These disparities have spurred suggestions for increased education about skin cancer and the signs and symptoms of melanoma, encouragement of self-examinations, and routine clinical skin examinations for Hispanic patients by dermatologists and other providers.⁸ There is evidence that knowledge-based interventions, especially when presented in Spanish, produce statistically significant improvements in knowledge of skin cancer risk and sun-protective behavior among Hispanic patients.¹² Similarly, we have observed that the videos shared by Ms. Torres regarding her melanoma diagnosis and the features of melanoma, in which she spoke in Spanish, have compelled many Hispanic patients to examine their own skin and have led to increased concern for skin cancer in this patient population. In our practice, we refer to the increase in spot checks and skin examinations requested by Hispanic patients as “The Dayanara Effect,” and we hypothesize that this same effect may be taking place throughout the dermatology community.

In February 2019, Dayanara Torres announced that she had been diagnosed with metastatic melanoma. Ms. Torres, a Puerto Rican–born former Miss Universe who has more than 1 million followers on Instagram (@dayanarapr), seemed an unlikely candidate for skin cancer, which often is associated with fair-skinned and light-eyed individuals. She shared the news of her diagnosis in an Instagram video that has now received more than 850,000 views. In the video, Ms. Torres described a new mole with uneven surface that had developed on her leg and noted that she had ignored it, even though it had been growing for years. Ultimately, she was diagnosed with melanoma that had already metastasized to regional lymph nodes in her leg. Ms. Torres concluded the video by urging fans and viewers to be mindful of new or changing skin lesions and to be aware of the seriousness of skin cancer. In March 2019, Ms. Torres posted a follow-up educational video on Instagram highlighting the features of melanoma that has now received more than 300,000 views.

Since her announcement, we have noticed that more Hispanic patients with concerns about skin cancer are presenting to our dermatology clinic, which is located in a highly diverse city (New Brunswick, New Jersey) with approximately 50% of residents identifying as Hispanic.¹ Most Hispanic patients typically present to our dermatology clinic for non–skin cancer–related concerns, such as acne, rash, and dyschromia; however, following Ms. Torres’ announcement, many have cited her diagnosis of metastatic melanoma as a cause for concern and a motivating factor in having their skin examined. The diagnosis in a prominent celebrity and Hispanic woman has given a new face to metastatic melanoma.

Although melanoma most commonly occurs in white patients, Hispanic patients experience disproportionately greater morbidity and mortality when diagnosed with melanoma.² Poor prognosis in patients with skin of color is multifactorial and may be due to poor use of sun protection, misconceptions about melanoma risk, atypical clinical presentation, impaired access to care, and delay in diagnosis. The Hispanic community encompasses a wide variety of individuals with varying levels of skin pigmentation and sun sensitivity.³ However, Hispanics report low levels of sun-protective behaviors. They also may have misconceptions that sunscreen is ineffective in preventing skin cancer and that little can be done to decrease the risk for developing skin cancer.^4,5 Additionally, Hispanic patients often have lower perceptions of their personal risk for melanoma and report low rates of clinical and self-examinations compared to non-Hispanic white patients.^6-8 Many Hispanic patients have reported that they were not instructed to perform self-examinations of their skin regularly by dermatologists or other providers and did not know the signs of skin cancer.⁷ Furthermore, a language barrier also may impede communication and education regarding melanoma risk.⁹

Similar to white patients, superficial spreading melanoma is the most common histologic subtype in Hispanic patients, followed by acral lentiginous melanoma, which is the most common subtype in black and Asian patients.^2,4 Compared to non-Hispanic white patients, who most commonly present with truncal melanomas, Hispanic patients (particularly those from Puerto Rico, such as Ms. Torres) are more likely to present with melanoma on the lower extremities.^4,10 Additionally, Hispanic patients have high rates of head, neck, and mucosal melanomas compared to all other racial and ethnic groups.²

Hispanic patients diagnosed with melanoma are more likely to present with thicker primary tumors, later stages of disease, and distant metastases compared to non-Hispanic white patients, all of which are associated with poor prognosis.^2,4,11 Five-year survival rates for melanoma are lower in Hispanic patients compared to non-Hispanic white patients.¹² Although the Hispanic community is diverse in socioeconomic and immigration status as well as occupation, lack of insurance also may contribute to decreased access to care, delayed diagnosis, and ultimately worse survival.

These disparities have spurred suggestions for increased education about skin cancer and the signs and symptoms of melanoma, encouragement of self-examinations, and routine clinical skin examinations for Hispanic patients by dermatologists and other providers.⁸ There is evidence that knowledge-based interventions, especially when presented in Spanish, produce statistically significant improvements in knowledge of skin cancer risk and sun-protective behavior among Hispanic patients.¹² Similarly, we have observed that the videos shared by Ms. Torres regarding her melanoma diagnosis and the features of melanoma, in which she spoke in Spanish, have compelled many Hispanic patients to examine their own skin and have led to increased concern for skin cancer in this patient population. In our practice, we refer to the increase in spot checks and skin examinations requested by Hispanic patients as “The Dayanara Effect,” and we hypothesize that this same effect may be taking place throughout the dermatology community.

In February 2019, Dayanara Torres announced that she had been diagnosed with metastatic melanoma. Ms. Torres, a Puerto Rican–born former Miss Universe who has more than 1 million followers on Instagram (@dayanarapr), seemed an unlikely candidate for skin cancer, which often is associated with fair-skinned and light-eyed individuals. She shared the news of her diagnosis in an Instagram video that has now received more than 850,000 views. In the video, Ms. Torres described a new mole with uneven surface that had developed on her leg and noted that she had ignored it, even though it had been growing for years. Ultimately, she was diagnosed with melanoma that had already metastasized to regional lymph nodes in her leg. Ms. Torres concluded the video by urging fans and viewers to be mindful of new or changing skin lesions and to be aware of the seriousness of skin cancer. In March 2019, Ms. Torres posted a follow-up educational video on Instagram highlighting the features of melanoma that has now received more than 300,000 views.

Since her announcement, we have noticed that more Hispanic patients with concerns about skin cancer are presenting to our dermatology clinic, which is located in a highly diverse city (New Brunswick, New Jersey) with approximately 50% of residents identifying as Hispanic.¹ Most Hispanic patients typically present to our dermatology clinic for non–skin cancer–related concerns, such as acne, rash, and dyschromia; however, following Ms. Torres’ announcement, many have cited her diagnosis of metastatic melanoma as a cause for concern and a motivating factor in having their skin examined. The diagnosis in a prominent celebrity and Hispanic woman has given a new face to metastatic melanoma.

Although melanoma most commonly occurs in white patients, Hispanic patients experience disproportionately greater morbidity and mortality when diagnosed with melanoma.² Poor prognosis in patients with skin of color is multifactorial and may be due to poor use of sun protection, misconceptions about melanoma risk, atypical clinical presentation, impaired access to care, and delay in diagnosis. The Hispanic community encompasses a wide variety of individuals with varying levels of skin pigmentation and sun sensitivity.³ However, Hispanics report low levels of sun-protective behaviors. They also may have misconceptions that sunscreen is ineffective in preventing skin cancer and that little can be done to decrease the risk for developing skin cancer.^4,5 Additionally, Hispanic patients often have lower perceptions of their personal risk for melanoma and report low rates of clinical and self-examinations compared to non-Hispanic white patients.^6-8 Many Hispanic patients have reported that they were not instructed to perform self-examinations of their skin regularly by dermatologists or other providers and did not know the signs of skin cancer.⁷ Furthermore, a language barrier also may impede communication and education regarding melanoma risk.⁹

Similar to white patients, superficial spreading melanoma is the most common histologic subtype in Hispanic patients, followed by acral lentiginous melanoma, which is the most common subtype in black and Asian patients.^2,4 Compared to non-Hispanic white patients, who most commonly present with truncal melanomas, Hispanic patients (particularly those from Puerto Rico, such as Ms. Torres) are more likely to present with melanoma on the lower extremities.^4,10 Additionally, Hispanic patients have high rates of head, neck, and mucosal melanomas compared to all other racial and ethnic groups.²

Hispanic patients diagnosed with melanoma are more likely to present with thicker primary tumors, later stages of disease, and distant metastases compared to non-Hispanic white patients, all of which are associated with poor prognosis.^2,4,11 Five-year survival rates for melanoma are lower in Hispanic patients compared to non-Hispanic white patients.¹² Although the Hispanic community is diverse in socioeconomic and immigration status as well as occupation, lack of insurance also may contribute to decreased access to care, delayed diagnosis, and ultimately worse survival.

These disparities have spurred suggestions for increased education about skin cancer and the signs and symptoms of melanoma, encouragement of self-examinations, and routine clinical skin examinations for Hispanic patients by dermatologists and other providers.⁸ There is evidence that knowledge-based interventions, especially when presented in Spanish, produce statistically significant improvements in knowledge of skin cancer risk and sun-protective behavior among Hispanic patients.¹² Similarly, we have observed that the videos shared by Ms. Torres regarding her melanoma diagnosis and the features of melanoma, in which she spoke in Spanish, have compelled many Hispanic patients to examine their own skin and have led to increased concern for skin cancer in this patient population. In our practice, we refer to the increase in spot checks and skin examinations requested by Hispanic patients as “The Dayanara Effect,” and we hypothesize that this same effect may be taking place throughout the dermatology community.