Pulmonary histoplasmosis.

Histoplasmosis is a common infection in the central United States and is acquired through inhalation of airborne spores. The majority of infected persons have an asymptomatic, self-limiting illness. Clinical pneumonia occurs in those with exposure to a large number of infecting spores. Resolution of the pneumonia often leaves calcified pulmonary nodules, calcified mediastinal lymph nodes, or splenic calcifications. Chronic disease, which mimics tuberculosis, may develop in those with underlying emphysema. In patients with deficient cell-mediated immunity, Histoplasma capsulatum may disseminate throughout the body; this often is fatal. Delayed manifestations arise months or years after the primary infection. Broncholithiasis occurs when peribronchial calcific nodes produce bronchial obstruction. Mediastinal granuloma is the continued proliferation of fibrous tissue in draining mediastinal lymph nodes. These granulomas may obstruct adjacent veins, arteries, or airways and lead to various clinical symptoms.