UCDs included arginosuccinate synthetase deficiency (<i>n</i> = 8), arginosuccinate lyase deficiency (<i>n</i> = 6), ornithine carbamoyltransferase deficiency (<i>n</i> = 3), and carbamoyl phosphate synthetase 1 deficiency (<i>n</i> = 3). The gene discussed is OTC; the disease is hyperinsulinemic hypoglycemia, familial, 4.