American Board of Family Medicine (ABFM) Practice Exam

What is the most likely cause of BB-sized calcifications in a miliary pattern seen on CXR in a patient with negative PPD and a history of living on a farm?

1. HIV infection

2. Histoplasmosis

3. Coccidioidomycosis

4. Tuberculosis

The correct answer is: Histoplasmosis

The presence of BB-sized calcifications in a miliary pattern on a chest X-ray, particularly in a patient with a history of living on a farm and a negative PPD, is most characteristically associated with histoplasmosis. Histoplasmosis is a fungal infection caused by Histoplasma capsulatum, which is often found in soil, particularly in areas enriched with bird or bat droppings, commonly encountered by individuals living or working in agricultural or rural settings. Patients with histoplasmosis may develop calcifications in a miliary pattern as a result of the body's immune response to the infection. Over time, granulomas (which are small areas of inflammation) can form and calcify, leading to the characteristic imaging findings seen on a chest X-ray. The negative PPD in this case also supports the likelihood that tuberculosis, a common cause of miliary calcifications, is not present; being one of the few infections typically tested against with a PPD. While HIV infection can lead to a variety of pulmonary complications, including opportunistic infections, it is not specifically associated with the BB-sized calcifications seen here. Coccidioidomycosis can lead to pulmonary findings but usually does not present as a miliary pattern in the same way