G6PC3 and hyperinsulinemic hypoglycemia, familial, 4: G6PC3 deficiency is characterized by extreme congenital neutropenia that occurs in a phenotypic spectrum from (a) Isolated severe congenital neutropenia (non-syndromic) to (b) Classic G6PC3 deficiency (syndromic), which is severe congenital neutropenia plus cardiovascular and/or urogenital abnormalities [8].