PAP is a rare lung disease characterized by accumulation of surfactant phospholipids and proteins within the lungs. There is no specific pharmacologic therapy for PAP and the current practice of lung lavage under general anesthesia is invasive and has limitations. Although it is unknown if the anti GM-CSF antibody is related to the disease pathogenesis, observations suggest a role for GM-CSF in lung homeostasis as well as in the pathogenesis of PAP.