GCK: A de novo variant [p.(Ala456Val)] in GCK that coexisted with a heterozygous paternal ABCC8 variant of uncertain significance [p.(Gly505Cys)] was discovered in 1 macrosomic proband with hypoglycemia (0.1 mmol/L) on the first day of life (Tables 2 and 3). The gene discussed is GCK; the disease is Hypoglycemia.