BRONCHIOLITIS OBLITERANS ORGANIZING PNEUMONIA

In 50 of 94 patients with bronchiolitis obliterans no apparent cause or associated disease was found; the bronchiolitis obliterans occurred with patchy organizing pneumonia. Histologic characteristics included polypoid masses of granulation tissue in lumens of small airways, alveolar ducts and some alveoli. The fibrosis was uniform in age, suggesting that all repair had begun at the same time. The distribution was patchy, with preservation of background architecture. Clinically, there was cough or flu-like illness for 4-10 wk and crackles were heard in the lungs of 68% of the patients. Radiographs showed an unusual pattern of patchy densities with a ground glass appearance in 81%. Physiologically, there was restriction in 72% of the patients and 86% had impaired diffusing capacity. Obstruction was limited to smokers. The mean follow-up period was 4 yr. With corticosteroids, there was complete clinical and physiologic recovery in 65% of the subjects; 2 died from progressive disease. This disorder differs from bronchiolitis obliterans with irreversible obstruction. It was confused most often with idiopathic pulmonary fibrosis. In view of the benign course and therapeutic response, a histologic distinction is important.