Pneumocystis carinii and Toxoplasma gondii infections in patients with AIDS.

Pneumocystis carinii and Toxoplasma gondii are the commonest protozoans causing infections in patients with acquired immunodeficiency syndrome (AIDS). P. carinii is almost exclusively a pulmonary pathogen and caused the commonest serious infection experienced by AIDS patients. The clinical findings are those of progressive pneumonia. Diagnosis requires microscopic examination of lower respiratory secretions or lung tissue. Pentamidine or combinations of trimethoprim and sulfamethoxazole are equally effective (85% recovery), but about one-half of patients thus treated experience severe toxicity. T. gondii infections occur primarily in the brain; patients present with focal seizures or neurologic deficit and have focal abnormalities as assessed by computed tomography. Serologic tests for toxoplasmosis are rarely diagnostic in AIDS patients, and most patients are treated empirically with a combination of pyrimethamine and sulfonamide. Less invasive diagnostic tests and better chemotherapeutic agents are required for both pneumocystosis and toxoplasmosis.