The patient was a 64-year-old woman with rheumatoid arthritis who had been treated with infliximab, prednisolone, and methotrexate. At the end of January 2016, computerized tomography (CT) revealed an infiltrative shadow and ground glass opacity in the middle lobe of the right lung. In March, CT showed some improvement but revealed new infiltrative shadowing and ground glass opacity in the lower lobe of the right lung. Bronchoscopy was performed for further examination with transbronchial lung biopsy and bronchoalveolar lavage. The histological diagnosis was organizing pneumonia. Bronchoalveolar lavage was smear positive for Mycobacterium avium complex (MAC). Infliximab was stopped. Treatment was instituted with tacrolimus, clarithromycin, pyrazinamide, and ethambutol. The infiltrative shadow and ground glass opacity in the lower lobe of the right lung subsequently improved.