CSF2 and pulmonary alveolar proteinosis: Rare patients with severe early-onset PAP due to inborn errors of the GM-CSF pathway have been reported since 1997, with AR deficiency of the βc receptor chain (Dirksen et al., 1997) common to the receptors for IL-3, IL-5, and GM-CSF, or AR deficiency of GM-CSFRα, encoded by the CSF2RA gene (Martinez-Moczygemba et al., 2008; Suzuki et al., 2008; Suzuki et al., 2010).