Disorders of Creatine Metabolism

Creatine is a physiological guanidino compound playing a major role in energy metabolism in muscle and implicated in neurotransmission in brain. The three disorders of creatine metabolism (AGAT and GAMT deficiencies and the X-linked creatine transporter defect) are a group of inborn errors of metabolism characterized by a depletion of creatine that could be easily diagnosed by mesasurement of guanidinoacetate and creatine in body fluid or cranial MRS spectroscopy. The main clinical features of these paediatric disorders are intellectual disability and speech delay and some adult patients have been described with severe language impairment and mental retardation. Although the X-linked creatine transporter defect is currently not treatable, the clinical symptoms of the two disorders of creatine synthesis should be improved by creatine supplementation emphasizing the importance of an early diagnostic.