Pulmonary alveolar proteinosis: an overview for internists and hospital physicians

Pulmonary alveolar proteinosis (PAP) is a rare diffuse lung disease characterized by abnormal accumulation of surfactant-associated phospholipoproteinaceous material in the pulmonary alveoli. The clinical findings of slow-onset dyspnea or dyspnea on exertion and persistent dry cough are nonspecific; radiographic findings of "bat-wing configuration" and "crazy paving" appearance in high-resolution computed tomography are suggestive, but not diagnostic of PAP. The current gold standard of PAP diagnosis involves histopathological examination of alveolar specimens obtained from bronchoalveolar lavage and transbronchial lung biopsy. The characteristic histopathological features are intraalveolar periodic acid Schiff (PAS)-positive eosinophilic homogeneous material with well-preserved architecture ofalveolar septa. The current standard medical treatment of PAP involves the physical removal of the surfactant-associated phospholipoproteinaceous alveolar deposit by whole lung lavage, which causes clinical and radiological improvement in a majority of patients. Some patients have been successfully treated with recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF).