It is a disease of obscure cause that is characterized by the accumulation of a granular material that contains abundant lipid within the alveoli of lung. Pulmonary alveolar proteinosis (PAP) has been divided into a congenital and an adult form. The acquired form has been subdivided into a idiopathic form and a secondary form associated with a know disorder or exposure as silica, aluminium, titanium. Dyspnea and cough are the most common presenting symptoms. Chest pain, hemoptysis, fever and weight loss are variably reported. Pathogenesis remains unknown, but evidence points to a dysfunction of alveolar macrophages. Mice genetically deficient in granulocyte macrophagecolony stimulating factor (GM-CSF) show an alveolar proteinosis. A neutralizing antibody against GM-CSF was found in bronchoalveolar lavage fluid and serum of patients with idiopathic PAP. Currently, no specific therapy exists for pulmonary alveolar proteinosis, and sequential whole lung lavage is standard treatment.