ORGANIZING PNEUMONIA - FEATURES AND PROGNOSIS OF CRYPTOGENIC, SECONDARY, AND FOCAL VARIANTS

Background: Organizing pneumonia (OF) is a nonspecific response to man y types of lung injury. Clinicians frequently encounter pathology repo rts of OP in patients with no underlying condition (cryptogenic OF, al so known as BOOP or bronchiolitis obliterans OF) or in association wit h drugs or nonpulmonary disease. The goals of this study are to descri be the clinical course and outcomes in patients with 3 clinical varian ts of OF. Methods: A retrospective study of patients with OP seen at t he Mayo Clinic, Rochester, Minn, from January 1, 1984, through June 30 , 1994, was conducted. Initial features were obtained from medical rec ords. Chest radiographs and pathology specimens were reviewed for this study. Resolution, relapse, and survival were obtained from medical r ecords and a follow-up patient questionnaire. Results: Seventy-four pa tients had pathologically confirmed OF. Organizing pneumonia was class ified into 3 clinical groups: symptomatic cryptogenic OF; symptomatic OP related to underlying hematologic malignant neoplasm, collagen vasc ular disease, or drugs (secondary OF); and asymptomatic OP presenting as a focal nodule (focal OF). Thirty-seven patients (50%) had cryptoge nic OP and 27 patients (36%) had secondary OF. No difference was found between cryptogenic and secondary OP in type or severity of symptoms, signs, laboratory and pulmonary function tests, or radiologic or path ologic findings. Corticosteroids were given at a similar initial dose (prednisone, about 50 mg/d). Resolution of symptoms was more frequent in patients with cryptogenic OP than those with secondary OF. Relapse was infrequent in both of these groups. Five-year survival was higher in patients with cryptogenic OP (73%) than in secondary OP (44%), and respiratory-related deaths were more frequent in patients with seconda ry OF. Organizing pneumonia was an asymptomatic focal rounded opacity in 10 patients (14%), most often detected on chest radiograph and diag nosed on lung biopsy done for suspicion of lung cancer. Patients with focal OP required no treatment and had no relapse or respiratory-relat ed deaths. Conclusions: Clinical classification of OP is useful to pre dict clinical course and outcome. Cryptogenic OP most often was a symp tomatic bilateral lung process that had an overall favorable prognosis with prolonged corticosteroid therapy. Patients with secondary OP had a high mortality rate when the disease was associated with predisposi ng conditions or drugs. Patients with asymptomatic focal OP had an exc ellent prognosis.