[Pulmonary pneumocystosis]

Sixteen autopsy cases of adults and older children who had contracted pneumocystosis of the lung were observed macro- and microscopically. Electron microscopical observation was done in 5 of these 16 cases. Also experimental studies on the pathogenesis of this disease were carried out on 20 rats. Most of the autopsy cases in this study had hematological neoplasia such as leukemia and malignant lymphoma which had been treated with cortisone and cytostatics. We found that intraalveolar foamy substances in this disease chiefly consisted of thin- and thick-walled Pneumocystis carinii which had many pseudopodias on the surface. Through these pseudopodias, pneumocystis were bound to each other and to the alveolar wall. In many cases desquamation of alveolar epithelial cells, formation of hyaline membrane and organization of alveolar contents were seen. Association with cytomegalovirus pneumonia was found in 12 cases.