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

Study of 194 patients with confirmed Pneumocystis carinii pneumonia in the U.S. during a 3 yr period showed 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. Identification of P. carinii was made antemortem in 81% of the cases, usually by biopsy or needle aspiration of the lung, procedures that were associated with considerable morbidity and mortality. Laboratory identification of P. carinii was usually accurate, but there were errors from faulty staining technique. Most patients had been ill for less than 2 wk with bilateral diffuse interstitial pneumonia. Leukopenia (leukocytes ≤ 3000/mm³) and probably severe hypoxia were negative prognostic factors. Although treatment with pentamidine was effective, it frequently caused adverse reactions, particularly, impaired renal function, when given with other nephrotoxic agents.