A patient who lived on a farm in Iowa presents with chest radiographs showing both lungs with calcifications in a miliary pattern. What is the most likely diagnosis?

A patient who lived on a farm in Iowa presents with chest radiographs showing both lungs with calcifications in a miliary pattern. What is the most likely diagnosis?

• A. Histoplasmosis
• B. Tuberculosis
• C. Coccidioidomycosis
• D. Sarcoidosis

Answer: (A)

The key idea here is that this pattern and setting point to histoplasmosis. Histoplasma capsulatum thrives in soil enriched with bird or bat droppings and is common in the Midwest, including Iowa. A farmer with exposure to such soil can inhale microconidia, leading to pulmonary infection. When the infection disseminates, the chest x-ray can show numerous tiny nodules distributed throughout both lungs—the so-called miliary pattern. Over time, healed granulomas often calcify, producing calcified nodules seen on imaging. That combination—the Midwest farm exposure, a diffuse miliary pattern on imaging, and calcified granulomas—fits histoplasmosis best. Tuberculosis can also produce diffuse nodules, but the geographic exposure and the classic calcified granulomas after histoplasmosis are more typical here. Coccidioidomycosis is more common in the southwestern desert regions, not Iowa, and sarcoidosis tends to show different patterns such as bilateral hilar lymphadenopathy with less likelihood of a purely infectious exposure pattern.

The key idea here is that this pattern and setting point to histoplasmosis. Histoplasma capsulatum thrives in soil enriched with bird or bat droppings and is common in the Midwest, including Iowa. A farmer with exposure to such soil can inhale microconidia, leading to pulmonary infection. When the infection disseminates, the chest x-ray can show numerous tiny nodules distributed throughout both lungs—the so-called miliary pattern. Over time, healed granulomas often calcify, producing calcified nodules seen on imaging. That combination—the Midwest farm exposure, a diffuse miliary pattern on imaging, and calcified granulomas—fits histoplasmosis best.

Tuberculosis can also produce diffuse nodules, but the geographic exposure and the classic calcified granulomas after histoplasmosis are more typical here. Coccidioidomycosis is more common in the southwestern desert regions, not Iowa, and sarcoidosis tends to show different patterns such as bilateral hilar lymphadenopathy with less likelihood of a purely infectious exposure pattern.