Cough in Immunosuppressed Patients

Histoplasma capsulatum

A 45 year old man taking corticosteroids for his asthma from the Mississippi River valley presents with pneumonia. He likes to explore bat caves as a hobby and just returned from a vacation trip that involved exploring a bat cave. Chest x-ray shows multiple, small calcified lung nodules.

Labs: Tissue biopsy reveals oval yeast cells within macrophages. Cultures on Sabouraud's agar show hyphae with tuberculate macroconidia. Skin test for histoplasmin positive. The antibody titer of the yeast phase antigen is greater than 1:32.

Discussion: The diagnosis of histoplasmosis by Histoplasma capsulatum is made by clinical presentation and serology and/or skin tests. The organism is associated with the Ohio and Mississippi River valley and bats. It can also occur in immunocompetent individuals.

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