Blastomycosis is a rare fungal infection that occurs primarily in the central and southeastern states of the US, Canada, India, Israel, Saudi Arabia, and Africa. It is acquired by inhaling fungal particles found in moist soil, particularly amongst decaying vegetation. People with immune system disorders are at highest risk.

The lungs are the portal of entry for this infection and are the main organ involved. The fungus may disseminate (spread) to other areas of the body after initial infection in the lungs and affect the skin, bone/joints, genitourinary tract and other systems. Skin disease is primarily a manifestation of disseminated (widespread blastomycosis) and occurs in up to 80% of individuals. Skin lesions may be wartlike or appear as ulcers and may affect the nose and mouth as well.