Failure of Transbronchial Biopsy to Diagnose Pneumocystis carinii Pneumonia in an AIDS Patient Receiving Aerosolized Pentamidine

We present an AIDS patient on aerosolized pentamidine prophylaxis whose initial presentation was suggestive of recurrent Pneumocystis carinii pneumonia (PCP). Both bronchoalveolar lavage and transbronchial biopsy were nondiagnostic until development of fulminant PCP several weeks later. This case demonstrates that even transbronchial biopsy may fail to diagnose this infection in the setting of aerosolized pentamidine prophylaxis. Patients with a presentation suggestive of PCP pneumonia must be observed closely despite negative bronchoalveolar lavage and transbronchial biopsy.