Pulmonary alveolar proteinosis

Since the original description of pulmonary alveolar proteinosis (PAP) as bilaterally symmetric, confluent, perihilar infiltrates, no large series evaluating the relative frequency of radiographic findings has been published. The authors reviewed 53 histologically proved cases and found a predominantly confluent pattern in 77.4%; of these, 61% had a nodular component. A predominantly nodular pattern was seen in 22.6% often with some coalescence or reticular shadows. Distribution was perhilar 56.6%, diffuse in 26.4%, basilar in 26.4%, and asymmetric in 35.8%. The classic pattern was seen in 18.9%. The authors conclude that the spectrum of patterns in pulmonary alveolar proteinosis is wider than generally appreciated