A patient from the Mississippi River valley with cough, unilateral pulmonary infiltrate, mediastinal lymphadenopathy, and a normal ACE level most likely has which infection?

• A. Histoplasmosis
• B. Pulmonary coccidioidomycosis
• C. Sarcoidosis
• D. Lung cancer

Answer: (A)

This scenario tests recognizing a regional fungal infection and using ACE levels to distinguish it from other granulomatous diseases. Histoplasma capsulatum is endemic in the Mississippi and Ohio River valleys. Inhalation of spores from soil contaminated with bird or bat droppings can produce a pulmonary infection that often presents with a focal or unilateral infiltrate and mediastinal (hilar) lymphadenopathy due to granulomatous inflammation. Importantly, ACE levels are not elevated in histoplasmosis, which helps differentiate it from sarcoidosis, a granulomatous disease where ACE is often increased and the radiographic pattern can include bilateral hilar lymphadenopathy. Pulmonary coccidioidomycosis occurs more in the Southwest, not the Mississippi River valley, and lung cancer would not typically be keyed to the geographic exposure or show this specific ACE pattern. Therefore, the presentation most consistent with this patient is histoplasmosis.