Idiopathic organizing pneumonia: a relapsing disease. 19 years of experience in a hospital setting.

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.