Pulmonary alveolar proteinosis: Clinical and morphological overview of a rare disease associated with macrophage dysfunction.

Pulmonary alveolar proteinosis (PAP) is a rare disease characterised by excessive accumulation of surfactant components in alveolar macrophages, alveoli, and peripheral airways. The accumulation of surfactant is associated with only a minimal inflammatory response but can lead to the development of pulmonary fibrosis. Three clinical forms of PAP are distinguished - primary, secondary and congenital.