An unusual dematiaceous fungal infection of the skin caused by Fonsecaea pedrosoi: a case report and review of the literature

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Abstract
Background: A case of an unusual dematiaceous fungal infection of the skin in a 43‐year‐old man with diabetes mellitus treated with steroids for reactive airway disease is presented. He developed chromoblastomycosis in the left wrist and was treated with antifungals and multiple surgical excisions. Results: Histologic examination of the excised tissue revealed widespread suppurative granulomatous inflammation in the dermis and subcutaneous tissue. Thick‐walled internally septated brown fungal cells were found both inside multinucleated giant cells and extracellularly. Non‐to‐lightly pigmented septate hyphal elements, however, were also identified with special stains and, in retrospect, on one of the routinely stained sections. In culture, the organism was reported to initially grow as soft white colonies that soon turned to black and velvety. Conclusions: The two unusual features of this case include the controversial report of the organism's initial growth in culture as soft white colonies and the presence of hyphal elements in addition to the sclerotic bodies in the dermis and subcutaneous tissue. This has not been reported before in human cases of dermal infection by Fonsecaea pedrosoi.