Idiopathic Organizing Pneumonia: A Relapsing Disease

BACKGROUND: Although organizing pneumonia (OP) is a common pathological finding, studies including a substantial number of patients with idiopathic forms from a unique center and a long follow-up are rare. OBJECTIVES: To determine patients with cryptogenic forms of organizing pneumonia (COP), in order to characterize their clinical course, to identify predictive factors for relapse and to assess their effect on outcome. METHODS: For a 19-year period, all histopathological reports from a community teaching hospital were reviewed, and OP was found in 210 lung specimens belonging to 197 patients. RESULTS: Thirty-three (17%) patients presented cryptogenic forms and 32 of them (97%) responded to steroid therapy. At follow-up, 14 patients presented no relapses (no-relapse group, NR) and 18 (56%) presented relapses (relapsing group, RG) that resolved with ulterior treatment. Multifocal opacities on chest X-ray (RG 83% vs. NR 36%, p = 0.02) appeared to be a predictor for relapse. Patients with relapses showed a shorter time span to chest X-ray normalization (RG 8 +/- 8 weeks vs. NR 13 +/- 9 weeks, p = 0.09) that became significant in patients with 3 or more relapses (multiple-relapse group, MR, 4 +/- 2 weeks vs. NR 13 +/- 9 weeks, p < 0.04). Although the initial prednisone dose was similar in patients with relapsing forms, its maintenance was shorter than in patients without relapses, showing a trend to significance (RG 4 +/- 3 weeks, NR 7 +/- 6 weeks, p = 0.09). Lower levels of lactate dehydrogenase and gamma-glutamyltransferase, although always within the normal range, were found in patients with relapsing forms. CONCLUSION: COP is a specific but infrequent form of OP with a good response to steroid therapy. Relapses are frequent and typical characteristics of COP which resolved with ulterior treatment. Multifocal opacities on chest X-ray and a shorter maintenance of the initial steroid dose may increase the risk of relapse.