Urinary tract blastomycosis diagnosed by urine cytology

Urinary tract blastomycosis is an uncommon manifestation of disseminated Blastomyces infection. Here, we report a 50-year-old male with common variable immunodeficiency who presented with urinary symptoms and a renal mass concerning for a kidney neoplasm. Urine cytology revealed typical broad-based budding yeasts with thick-walled refractile capsules, leading to diagnosis of urinary tract blastomycosis. In this case, urine cultures were negative, and urine cytology was the main method of diagnosis of blastomycosis. Thus, urine cytology represents a rapid and reliable method of diagnosing blastomycosis, which in the current case led to prompt treatment of this potentially life threatening infection.