... (arginine:glycine [AGAT; MIM 602360]; guanidinoacetate methyltransferase deficiency [GAMT; MIM 601240]) and of creatine transport (SLC6A8 deficiency [SLC6A8; MIM 300036]). Inborn errors of creatine synthesis-but not, as yet, of transport-can be treated by creatine substitution and are thus treatable causes...