CSF2RB and pulmonary alveolar proteinosis: Based on the etiopathogenesis, PAP is classified into three major types: 1) Autoimmune PAP (primary)—the most common form accounting for about 90% of cases, 2) Secondary PAP—occurs as a consequence of underlying conditions such as malignancies, inhalational exposure or immunodeficiencies, which impair macrophage function, 3) Hereditary PAP (hPAP)—a rare genetic form caused by mutations in the CSF2RA or CSF2RB genes, leading to impaired surfactant clearance by alveolar macrophages [1].