This group of abnormalities comprised the three enzymatic defects in the synthesis of creatine:arginine:glycine amidinotransferase (AGAT) deficiency (OMIM 612718), guanidinoacetate methyltransferase (GAMT) deficiency (OMIM 612736), and SLC6A8 deficiency (OMIM 300352). Here, GATM is linked to hyperinsulinemic hypoglycemia, familial, 4.