CSF2 and hyperinsulinemic hypoglycemia, familial, 4: However, a small proportion of SCN patients with G-CSF receptor deficiency (i.e., due to biallelic loss-of-function mutations in the CSF3R gene) are refractory to G-CSF but respond to granulocyte macrophage colony-stimulating factor (GM-CSF) treatment (7, 8).