Electron microscopic study of chronic eosinophilic pneumonia

Two cases of chronic eoslnophlllc pneumonia were examined electron mlcroscoplcally to study the role of eosinophll granulocytes. Eoslnophlls, together wlth macrophages and lymphocytes, were observed to have Infiltrated prominently in the lung tissues of the two cases. Degeneration and necrosis of pneumocytes were observed, and denuded basement membranes and destroyed alveolar structures were occasionally found. In the alveolar septa, swelling of the endothellal cells of the blood caplllarles, edema of the stroma and fibrin deposition were observed. Eosinophils, released eosinophil granules and macrophages phagocytosing eosinophll granules were found frequently near the degenerated and necrotic alveolar tissues. These findings suggest that the tissue injuries were induced by the cytotoxic effects of the eosinophil granules.