To establish proper management of Pneumocystis jiroveci pneumonia (PCP) in rheumatoid arthritis (RA) patients treated with infliximab. PCP has been observed in 0.4% of patients with RA treated with infliximab in Japan.


Data from patients with RA (n = 21) who were diagnosed with PCP during infliximab treatment and from 102 patients with RA who did not develop PCP during infliximab therapy were collected from 14 rheumatology referral centers in Japan. A retrospective review of these patients and a case–control study to compare patients with and without PCP were performed.


The median length of time from the first infliximab infusion to the development of PCP was 8.5 weeks. At the onset of PCP, the median dosages of prednisolone and methotrexate were 7.5 mg/day and 8 mg/week, respectively. Pneumocystis jiroveci was microscopically identified in only 2 patients, although the polymerase chain reaction test for the organism was positive in 20 patients. The patients with PCP had significantly lower serum albumin levels (P < 0.001) and lower serum IgG levels (P < 0.001) than the patients without PCP. Computed tomography of the chest in all patients with PCP revealed ground-glass opacity either with sharp demarcation by interlobular septa or without interlobular septal boundaries. Sixteen of the 21 patients with PCP developed acute respiratory failure, but all survived.


PCP is a serious complication that may occur early in the course of infliximab therapy in patients with RA. For the proper clinical management of this infectious disease, physicians need to be aware of the possibility of PCP developing during infliximab therapy.