The importance of creatine is highlighted by the genetic creatine deficiency syndromes, encompassing mutations in the genes of AGAT, GAMT or the gene coding for the creatine transporter (SLC6A8), where patients develop neuromuscular and neurological symptoms, including mental retardation, autism, and epilepsy [40]. The gene discussed is SLC6A8; the disease is cerebral creatine deficiency syndrome.