Some studies that include large series of patients with IEMs and MD are: Tetrahydrobiopterin (BH4) deficiencies (37), cobalamin-related remethylation disorders (38), SERAC1 deficiency (39), mitochondrial disorders (22), PLA2G6-associated neurodegeneration (24), lysosomal storage disorders (40), cerebrotendinous xanthomatosis (9), and congenital disorders of glycosylation (41). The gene discussed is SERAC1; the disease is hyperinsulinemic hypoglycemia, familial, 4.