Atypical Cutaneous Blastomycosis in a Child With Juvenile Idiopathic Arthritis on Infliximab

Blastomyces dermatitidis is a dimorphic fungus endemic to much of North America, particularly the soils of the midwestern and southeastern United States. Human infection typically occurs through inhalation of airborne conidia, which can be followed occasionally by dissemination to the skin, bone, genitourinary system, and central nervous system. A hallmark of the pathogen is that it can cause disease in both immunocompetent and immunosuppressed populations. Blastomycosis is rare in pediatric patients, with cutaneous manifestations occurring even less frequently. Here, we report the case of a 9-year-old boy on iatrogenic immunosuppression with infliximab and methotrexate for juvenile idiopathic arthritis who presented with a nonhealing, indurated plaque of his right ear with significant superficial yellow crusting in the absence of constitutional symptoms. After failing a prolonged course of topical and oral antibiotic therapy, biopsy and tissue culture revealed Blastomyces dermatitidis infection. The area cleared after treatment with oral fluconazole and withdrawal of infliximab. To our knowledge, this is the first report of a pediatric patient developing an infection with B dermatitidis after initiation of therapy with a tumor necrosis factor-α inhibitor. This case also highlights an unusual morphology of cutaneous blastomycosis in an iatrogenically immunosuppressed child.