In their review of pleural effusions in patients with the acquired immunodeficiency syndrome (AIDS), Joseph and colleagues [1] attribute 15% (nine cases) to Pneumocystis carinii pneumonia. The organism was recovered in sputum or bronchoalveolar lavage, and the pneumonia and effusion resolved after specific therapy. Pleural fluid was obtained from only two of these patients and was not examined with "special stains" for the presence of P. carinii. We describe a case of P. carinii pneumonia that was diagnosed from a finding of organisms in routine stains of pleural fluid.

A 45-year-old, human immunodeficiency virus (HIV)-infected, homosexual man developed low-grade fever, cough, and dyspnea. For 2 years he had received monthly P. carinii pneumonia prophylaxis with aerosolized pentamidine. A chest roentgenogram showed apical cystic lucencies, interstitial opacities in upper lung fields, and small bilateral pleural effusions. A presumptive diagnosis of P. carinii pneumonia was made, and the patient responded to treatment with intravenous pentamidine. Induced sputa processed for P. carinii with the Diff-Quik (Baxter Diagnostics, Inc., McGaw Park, Illinois) (Giemsa-like) stain [2] failed to show the organism. A thoracentesis was done, and the routine (Wright-stained) differential smear of the aspirated fluid showed forms resembling P. carinii trophozoites. The presence of P. carinii was confirmed by staining the fluid with the Diff-Quik method and by cytopathologic analysis of the specimen using Papanicolaou and silver methenamine stains.

Visualizing P. carinii in routine smears of pleural fluid avoids time-consuming, cumbersome staining techniques, cytopathologic preparations, or invasive procedures such as bronchoalveolar lavage. We believe that in patients with equivocal diagnoses of P. carinii pneumonia, accompanying effusions should be aspirated and stained for P. carinii by routine or specific methods [3, 4].