Huopio et al. report that dominant inactivating mutations in the sulfonylurea receptor (ABCC8), a major component of the beta-cell ATP-regulated potassium channel, result in a similar phenotype: hyperinsulinemic hypoglycemia with macrosomia in infancy, decreased glucose-stimulated insulin secretion in adolescence and young adulthood, and frank diabetes during middle age [15,16]. The gene discussed is ABCC8; the disease is hyperinsulinemic hypoglycemia.