Pneumocystis Pneumonia Associated with Infliximab in Japan

To the Editor: Infliximab, a monoclonal antibody against tumor necrosis factor α (TNF-α), is used in Japan for the treatment of patients with active rheumatoid arthritis that is resistant to methotrexate.1 Methotrexate is used only for patients who do not have a response to or cannot tolerate other disease-modifying antirheumatic drugs, such as sulfasalazine. Infliximab is not used as primary therapy for rheumatoid arthritis in Japan. Strict postmarketing surveillance of infliximab and etanercept, a drug that blocks the action of TNF, revealed incidences of pneumocystis pneumonia in Japanese patients with rheumatoid arthritis that were higher (0.4% and 0.2%, respectively) than . . .