Blastomycosis presenting as polyarticular septic arthritis.

Articular infection with Blastomyces dermatitidis frequently is difficult to diagnose as it resembles bacterial arthritis in several ways. This report of an elderly man who had initially monoarticular and eventually polyarticular arthritis illustrates the clinical and laboratory findings that should suggest blastomycosis. Treatment with amphotericin B and ketoconazole in sequence led to complete resolution of the infection.