Granulomatous response to Pneumocystis carinii in patients infected with HIV

Pneumocystis carinii is the most frequent manifestation of the acquired immune deficiency syndrome. Typical histologic findings include foamy, acellular eosinophilic intra-alveolar exudate in which the cysts of the organisms are readily demonstrated with silver stains. Granuloma formation is rare. Only nine such cases have been described in the English literature. We reviewed 400 transbronchial biopsies done in patients suspected of having pneumocystis pneumonia at our institution between the period of 1987-1990. Of the 320 biopsy specimens with Pneumocystis carinii identified, 17 cases had granulomatous inflammation with or without Pneumocystis carinii present. All cultures for tuberculosis and fungi were negative during initial admission and follow up in fifteen cases. One was later found to have tuberculosis and another about 6 months later histoplasmosis, when rebronchoscoped for suspicion of recurrent Pneumocystis infection. None of our patients had clinical evidence for sarcoidosis or hypersensitivity pneumonitis. We believe that granulomatous pneumonitis should be included in the list of pulmonary complications associated with Pneumocystis carinii pneumonia. Clinical significance and immunologic nature remains unexplained.