Pulmonary alveolar proteinosis: primary and secondary, a report of three cases.

Three cases of the rare disorder pulmonary alveolar proteinosis (PAP) presented to our unit over the past thirteen years. Two of the patients conformed to the classical description of idiopathic or "primary" PAP. One patient appeared to have co-existing extrinsic allergic alveolitis with "secondary" PAP, an association not previously described. This patient has required continued steroid therapy, a mode of treatment usually contraindicated in PAP.