Extrapulmonary Pneumocystis carinii infections in the acquired immunodeficiency syndrome

Pneumocystis carinii is a frequent cause of interstitial pneumonitis in patients with cell-mediated immunodeficiencies. Extrapulmonary P carinii infection is a rare manifestation of disease caused by this organism. Nevertheless, reports of extrapulmonary P carinii infection are increasing in the setting of the acquired immunodeficiency syndrome (AIDS). We report two cases of extrapulmonary P carinii infection in patients with AIDS and review the literature on this subject. We identified 37 such cases: in 19 cases, P carinii pneumonia was present concurrently; in 18 cases, involvement was exclusively extrapulmonary. A minority of patients were receiving aerosolized pentamidine isethionate therapy. Most patients had a history of P carinii pneumonia, and other AIDS-related illnesses, such as cytomegalovirus infection, mycobacterial disease, candidiasis, Kaposi's sarcoma, and cryptococcosis were common. Concurrent cytomegalovirus infection indicated a poor prognosis, while otic pneumocytosis was associated with a favorable outcome. Pathologic evidence suggested that extrapulmonary pneumocystosis occurred by hematogenous and lymphatic dissemination from the lungs in most cases. In other cases, extrapulmonary pneumocystosis appeared to be due either to reactivation of latent infection in extrapulmonary sites or to primary infection of these sites. Further studies are needed to determine the true frequency of extrapulmonary involvement in P carinii infections and to define risk factors for acquisition of extrapulmonary pneumocytosis.