Pulmonary Alveolar Proteinosis

Abstract

Since the original description of pulmonary alveolar proteinosis in 1958 (19), more than 100 cases have been reported. This article indicates the wide spectrum of roentgenographic changes (other than the well known batwing appearance) by reference to 5 patients in the San Francisco area who were examined recently. The classic butterfly pattern formed by infiltrates radiating from the hili and suggestive of pulmonary edema is not seen in as many patients as the earlier case reports suggested. When present, its differentiation from pulmonary edema is based on much less dyspnea in patients with pulmonary alveolar proteinosis (PAP), normal size of heart, and caliber of pulmonary vein. Also, Kerley's B lines or pleural effusion are absent. In patients with longstanding PAP, cor pulmonale may supervene. This adds further diagnostic problems by the presence of cardiomegaly and pleural effusions. The butterfly appearance may resolve almost completely within a week (18), but the overnight clearing seen in some patients with pulmonary edema has never been reported. In view of the viscidity of the alveolar contents, such rapid clearing is hard to explain. It is emphasized that rapid clearing is the exception. Some authors (14, 21) have stressed that enlargement of the hilar node is absent, but this is at variance with other reports (2, 10). Nevertheless, enlargement of the hilar node is rare, although the nodes may be involved histologically without enlargement (12). Although the pleurae have never been primarily involved in pulmonary alveolar proteinosis, pleural effusions have appeared in long-standing cases due to cor pulmonale or secondary bacterial or fungal infections. The most frequent roentgenographic appearance is that of infiltrates in both lower lobes. Separate nodules or confluent areas may progress to complete consolidation of a lobe. The appearance, both roentgenographic and histologic, of infiltrates in chronic cholesterol pneumonitis is similar to that in PAP (9). Occasionally, shifting densities may suggest Loeffler's syndrome (2). The butterfly pattern may also progress to complete consolidation of either one or several lobes. A miliary pattern in the lower lung fields of a patient was reported by Depierre et al. (7). Interstitial pulmonary fibrosis, seen in some patients, adds its own characteristic roentgenographic appearance of lungs of small volume. Thickening of interlobular septa may result in “honeycombing” and, in some cases, Kerley's B lines. In their original report, Rosen, Castleman, and Liebow (19) suggested that several years were required for development of fibrosis. Moretti et al. (12) and Wilkinson et al. (22) described patients, however, in whom pulmonary fibrosis developed as a complication of pulmonary alveolar proteinosis after a much shorter illness. PAP may also be associated with neoplasms and granulomatous and nongranulomatous diseases such as bronchiectasis (3).