Organizing Pneumonia in Rheumatoid Arthritis Patients: A Case-Based Review.

We treated 21 patients with organizing pneumonia (OP) associated with rheumatoid arthritis (RA) or related to biological disease-modifying antirheumatic drugs (DMARDs) at our institution between 2006 and 2014. Among these cases, 3 (14.3%) preceded articular symptoms of RA, 4 (19.0%) developed simultaneously with RA onset, and 14 (66.7%) occurred during follow-up periods for RA. In the case of OP preceding RA, increased levels of anti-cyclic citrullinated peptide antibodies and rheumatoid factor were observed at the OP onset. RA disease activity was related to the development of OP in the simultaneous cases. In the cases of OP developing after RA diagnosis, 10 of 14 patients had maintained low disease activity with biological DMARD therapy at the OP onset, and among them, 6 patients developed OP within the first year of this therapy. In the remaining four patients, RA activity was not controlled at the OP onset. All patients responded well to systemic steroid therapy, but two patients suffered from relapses of articular and pulmonary symptoms upon steroid tapering. In most of the RA patients, DMARD therapy was introduced or restarted during the steroid tapering. We successfully restarted a biological DMARD that had not been previously used for patients whose RA would otherwise have been difficult to control. In this study, we also perform a review of the literature on RA-associated or biological DMARD-related OP and discuss the pathogenesis and management of OP occurring in RA patients.