Pneumocystis carinii pneumonia in the United States: Epidemiologic, diagnostic, and clinical features

Analysis of 194 patients with confirmed Pneumocystis carinii pneumonia in the United States over a 3 year period revealed that P. carinii pneumonia occurred almost exclusively in the immunosuppressed host who had a serious underlying disease. The epidemiologic features of pneumocystis pneumonia primarily reflected those of the underlying disease. P. carinii was identified antemortem in 81% of the cases usually by biopsy or needle aspiration of the lung, procedures associated with considerable morbidity and mortality. Laboratory identification of P. carinii was usually accurate, but errors resulting from faulty staining technique occurred. Most patients had been ill less than 2 weeks with bilateral diffuse interstitial pneumonia. Leukopenia (white blood cell count ≤3,000/mm³) and probably severe hypoxia were negative prognostic factors. Although treatment with pentamidine was effective, the drug frequently caused adverse reactions, particularly impaired function, when given with other nephrotoxic agents.