Pneumocystis carinii pneumonia in a HIV-seronegative patient with untreated rheumatoid arthritis and CD4+ T-lymphocytopenia.

Pneumocystis carinii pneumonia (PCP) usually occurs in immunocompromised patients, and it is a life-threatening infection. We report the case of a human immunodeficiency virus (HIV)-seronegative patient with untreated rheumatoid arthritis (RA), who developed fatal PCP related to uncommon CD4+ T-lymphocytopenia. Although extremely rare and of uncertain aetiology, suppression of cellular immunity and subsequent opportunistic infections should be suspected in such patients.