Pulmonary function studies in acute pulmonary histoplasmosis.

We performed follow-up pulmonary function studies on three patients with acute pulmonary histoplasmosis over a period of several months, and found that the disease is benign and usually responds well to treatment or is self-limiting. There are four major changes in lung function, namely a restrictive defect, an impairment of diffusing capacity, stiff lung, and obstruction in small airways. These changes usually lead to disturbance of ventilation-perfusion ratios and impaired gas transport across alveolar capillary membranes, resulting in arterial hypoxemia. There is also hypocapnia from alveolar hyperventilation commonly found in restrictive and stiff lung syndrome.