Blastomycosis presenting as monarticular arthritis. The role of synovial fluid cytology

Joint complaints are common among patients with blastomycosis; however, true arthritis is infrequently documented by synovial fluid analysis. Of 72 individuals with blastomycosis who were patients at the Vanderbilt School of Medicine affiliated hospitals during the period 1957–1983, 6 (8%) had arthritis at presentation. In 5 patients (7%), monarticular arthritis was the chief complaint leading to hospitalization. Cytologic examination of synovial fluid was performed in 4 patients and demonstrated characteristic organisms each time. Three patients had negative 10% potassium hydroxide smears, and 2 had negative synovial fluid cultures. Blastomycosis should be considered in the differential diagnosis of acute arthritis. In patients with blastomycotic arthritis, cytologic examination of synovial fluid can add to the diagnostic yield of synovial fluid fungal cultures and potassium hydroxide preparations.