Histoplasmosis-Induced Lung Calcification

A 40-year-old man, originally an Ohio resident, underwent a chest x-ray study during medical clearance following surgery to repair a hernia. Although the patient had no pulmonary symptoms, the film showed multiple small, punctate calcifications in both lung fields. This, writes Dr Sonia Arunabh of Flushing, NY, was an example of lung calcification following exposure to Histoplasma capsulatum. A skin test was positive for this organism. Histoplasmosis is a fungal infection found worldwide but is especially prevalent in the central portion of the United States along the Mississippi, Ohio, and Missouri river valleys.

Infection does not develop in the majority of persons who inhale H capsulatum. The principal evidence of exposure is residual calcification in the lung (and possibly in the spleen) and a positive skin test. Histoplasmosis is self-limited in most patients, and the pulmonary lesions are encapsulated and calcified. A more serious form of the disease can develop among a small number of infected persons, particularly those who are immunosuppressed. Multiple punctate calcification of the lung may also follow silicosis, varicella pneumonia, and pulmonary alveolar microlithiasis.