Hereditary pulmonary alveolar proteinosis

A rare, genetic, interstitial lung disease due to mutations in the CSF2R (colony-stimulating factor 2 receptor) alpha or beta subunits and characterized by alveolar accumulation of pulmonary surfactant, presenting a highly variable clinical presentation, ranging from asymptomatic to severe respiratory failure. Characteristic lung biopsy findings include periodic acid-Schiff-positive, granular eosinophilic material, enlarged foamy alveolar macrophages, and well-preserved alveolar walls. The Granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor function is impaired but GM-CSF receptor autoantibodies are absent.