Which fungus is known to cause systemic mycoses and is specifically found in the southwestern region of the US?

• A. Histoplasma capsulatum
• B. Blastomyces dermatitidis
• C. Paracoccidioides brasiliensis
• D. Coccidioides immitis

Answer: (D)

This item tests geographic distribution of systemic fungal infections and which organism is classically tied to a specific region. The fungus known to cause systemic mycoses and is specifically found in the southwestern United States is Coccidioides immitis. It lives in arid desert soils, and inhalation of its airborne arthroconidia from dusty soils leads to coccidioidomycosis, or valley fever. The infection starts in the lungs and can stay localized, or in some cases disseminate to skin, bones, or meninges, making it a true systemic mycosis. Histoplasma capsulatum is more associated with bird or bat guano in the Ohio and Mississippi River valleys; Blastomyces dermatitidis with moist soils of the eastern U.S. and Great Lakes region; Paracoccidioides brasiliensis with Latin American regions like Brazil. So the Southwest-endemic cause of systemic mycoses is Coccidioides immitis.