ALVEOLAR DAMAGE IN AIDS-RELATED PNEUMOCYSTIS-CARINII PNEUMONIA

Objective: Pneumocystis carinii pneumonia is the most common and serio us of the pulmonary complications of AIDS. Despite this, many basic as pects in the pathogenesis of HIV-associated P carinii pneumonia are un known. We therefore undertook a light and electron microscopic study o f transbronchial biopsy specimens to compare pathologic features of P carinii pneumonia and other HIV-related lung diseases. Design and pati ents: Thirty-seven consecutive HIV-infected patients undergoing a diag nostic bronchoscopy. Results: P carinii pneumonia was characterized by an increase in inflammation, edema, exudate, fibrosis, type II pneumo cyte proliferation, and cellular infiltration of die alveolar wall whe n compared with other lung diseases (all p <0.05). Electron microscopy showed apposition of the trophozoite to the type I pneumocyte. Erosio n of type I pneumocytes was observed in 13 of 15 patients with P carin ii pneumonia, whereas none without P carinii pneumonia had this findin g (p <0.05). Erosion of the type II pneumocyte was not observed. Concl usion: Inflammation, interstitial fibrosis, and alveolar epithelial er osion are characteristic features of P carinii pneumonia. The changes may form the pathologic basis for the respiratory failure seen in pati ents with P carinii pneumonia, Electron microscopy did not show any di agnostic advantage over conventional light microscopy using routine st ains.