Pneumocystis carinii pleural effusion. Pathogenesis and pleural fluid analysis.

We present three new cases of Pneumocystis carinii in pleural effusions of patients with AIDS, bringing the total number of reported cases to six. In our patients, diagnosis was made by visualization of Pneumocystis in pleural fluid stained with Gomori methenamine silver. LDH was greater than 400, and pleural fluid to serum LDH ratio was greater than 1.0 in all cases at time of presentation. All six reported patients have been associated with aerosolized pentamidine, and five of the six had documented underlying Pneumocystis pneumonia. The sixth patient, which we report, presented with primary pleural infection with Pneumocystis. Although we could not document underlying pneumonia, we suspect it was present. Pneumocystis pleural disease appears to be an anatomic extension of smoldering subpleural Pneumocystis pneumonia, and prognosis is not worse than with pneumonia alone.