The molecular basis of CHI involves defects in key genes (ABCC8, KCNJ11, GLUD1, GCK, HADH, SLC16A1, HNF1A, HNF4A, UCP2, HK1, PGM1 and PMM2) which regulate insulin secretion. The gene discussed is HNF4A; the disease is congenital isolated hyperinsulinism.