A clinical, histopathologic, and electron microscopic study of Pneumocystis carinii choroiditis.

We studied the clinical and histopathologic features of Pneumocystis carinii choroiditis in three patients with acquired immunodeficiency syndrome. In two cases, a provisional diagnosis of disseminated P. carinii infection was made by ophthalmologic examination. The characteristic fundus changes in this infection consisted of numerous slightly elevated, plaque-like, yellow-white lesions located in the choroid and unassociated with signs of intraocular inflammation. The diagnosis was confirmed by postmortem examination of the eyes and other organs. Histopathologically, the globes showed many choroidal infiltrates that were eosinophilic, acellular, vacuolated, and frothy. Several such infiltrates were noted within the choroidal vessels and choriocapillaries. Gomori's methenamine silver stain demonstrated many cystic and crescentic organisms. Electron microscopy disclosed thick-walled cystic organisms and large numbers of trophozoites.