High titers of neutralizing auto-Abs against granulocyte-macrophage colony-stimulating factor (GM-CSF) were first described in adult patients with idiopathic pulmonary alveolar proteinosis (PAP), a severe lung disease characterized by the accumulation of surfactants in the alveoli, progressive respiratory failure, and an increased risk of secondary infections [11]. This evidence concerns the gene CSF2 and pulmonary alveolar proteinosis.