Abstract

Disseminated histoplasmosis is a systemic mycosis that can be seen in immunocompromised patients, caused by the dimorphic fungus Histoplasma capsulatum, endemic to the Ohio and Mississippi River valleys. We describe a case of disseminated cutaneous histoplasmosis mimicking leishmaniasis. Our patient, a 16 year-old from Egypt with a history Bardet-Biedl syndrome, renal transplant complicated by chronic rejection presented with generalized abdominal pain, and a 5 month history of a 3 cm ovoid pink atrophic plaque on his chest. Given the patient’s country of origin, ongoing immunosuppression and outside GI biopsy concerning for leishmaniasis, this diagnosis moved to the top of the clinical differential. A skin punch biopsy showed an ulcer bed with lymphohistiocytic inflammation and dermal fibrosis. The histiocytes were remarkable for small uniform dot like structures uniformly distributed within the cells, lacking a kinetoplast, and with a capsular dot. Special stains performed were positive for PAS and GMS. The above features along with supporting labs, positive serum Histoplasma antigen and positive Karius were consistent with H. capsulatum infection. In leishmaniasis the nuclei are often located at the periphery and the kinetoplast, a mass of mitochondrial DNA, is present while Histoplasmosis lacks a kinetoplast. Special stains are helpful as Histoplasmosis is positive on silver and PAS stains as noted in this case and leishmaniasis is negative. Definitive diagnosis requires detailed clinico–pathological correlation, fungal culture, and ancillary studies. The case highlights the importance of considering histoplasmosis in cases of solitary ulcerated lesions in immunocompromised hosts and further exploring the histological differential that includes leishmaniasis.

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