Coccidiomycosis presenting as a popliteal cyst.

Coccidiomycosis is a fungal infection that primarily causes pulmonary disease. Extrapulmonary dissemination can occur to the musculoskeletal system with the knee joint most frequently involved. This case report describes a patient with coccidiomycosis whose initial presentation was of a popliteal cyst. The need for aggressive surgical and antibiotic treatment to eradicate this infection is discussed. Coccidiomycosis should be considered in a differential diagnosis of patients with popliteal cysts without other obvious etiologies.