CSF2 and pulmonary alveolar proteinosis: An important step in understanding the pathogenesis of pulmonary alveolar proteinosis was made in 1994 with the discovery of a similar pulmonary disease present in mice deficient in granulocyte-macrophage colony-stimulating factor (GM-CSF), thus revealing, as the authors mentioned, a critical role for GM-CSF in pulmonary homeostasis [5].