Eosinophilic pneumonia. Physiologic response to steroid therapy and observations on light and electron microscopic findings

A detailed description is presented of 3 cases of chronic eosinophilic pneumonia, including the clinical features, pulmonary physiologic studies before and after treatment with steroid therapy, and light and electron microscopic studies. All patients showed a dramatic clinical response to steroid therapy, with chest roentgenographic clearing of infiltrates in 2 of 3. Physiologic responses included an increase in vital capacity, arterial oxygen pressure, and single breath CO diffusing capacity, and a decrease in percentage of right-to-left shunt. Electron microscopic examination revealed a marked increase in the cellular content of the alveolar wall interstitium. This disease is of unknown cause but responds clinically and physiologically to steroid therapy, adding another incentive to perform lung biopsies on all patients with diffuse lung disease.