A Cluster of Pneumocystis jirovecii Infection Among Outpatients with Rheumatoid Arthritis

To the Editor: Pneumocystis jirovecii is the causative agent of Pneumocystis pneumonia (PCP), well known to be one of the most frequent and serious complications occurring under immunocompromised conditions such as HIV infection. Accumulating reports have also shown the clinical significance of PCP in patients with malignancy, in transplant recipients, and in patients receiving immunosuppressive therapy. Indeed, a recent postmarketing surveillance report by the Japan College of Rheumatology indicated a high incidence of PCP in patients with rheumatoid arthritis (RA) receiving the anti-tumor necrosis factor-α agents infliximab and etanercept (0.4% and 0.2%, respectively). Despite recent advances in understanding human Pneumocystis infection, the exact mode of its transmission and acquisition remains unclear, and both the source and reservoir for infection in humans have not yet been established1. We describe a cluster of asymptomatic carriage of P. jirovecii and/or PCP occurring among outpatients with RA. Clinical and epidemiological data strongly suggest person-to-person transmission of P. jirovecii in our outpatient facility as the predominant route of acquisition. Kumamoto Saishunsou National Hospital is a 500-bed general hospital consisting of 3 buildings, located in the suburbs of Kumamoto City in western Japan. One building accommodates an outpatient clinic and a radiodiagnostic facility, which are both shared by all outpatients; about 200 outpatients from 12 clinical sections visit this building daily. Accordingly, patients with RA visit this building for regular checkups and … Address correspondence to Dr. Mori. E-mail: moris{at}saisyunsou1.hosp.go.jp