Guanidinoacetate methyltransferase deficiency


What is guanidinoacetate methyltransferase (GAMT) deficiency?

Guanidinoacetate methyltransferase (GAMT) deficiency is a rare genetic neurological disorder. Individuals with GAMT deficiency have a problem with the creation (synthesis) of creatine in the body. Creatine is important to the body because it increases the levels of adenosine triphosphate (ATP), a molecule that provides energy to all the cells in the body, especially those cells in areas of the body that have high energy requirements like the brain or the skeletal muscle. Creatine is necessary to help the body store and use energy and to help the brain and muscles develop. Infants and children with this disorder cannot breakdown a compound called guanidinoacetate; breaking down this compound is a normal step in producing creatine. Without treatment, infants and children will develop neurological symptoms including intellectual disability, which can be mild or severe. Other symptoms include seizures, lack of coordination (ataxia), autistic-like behaviors, and movement disorders. Symptoms occur because of the lack of creatine and because of the buildup of guanidinoacetate. How the disorder affects one child can be very different from how it affects another child. Symptoms can be very severe, or much milder. GAMT deficiency is caused by changes (mutations) in the GAMT gene. The disorder is treated with supplemental creatine and a low-protein or low-arginine diet and sometimes supplements with other substances such as ornithine. If treatment is begun early enough, it can be highly effective and some infants showed normal development.

SOURCE: Emory University - Department of Human Genetics in collaboration with ThinkGenetic • • DATE UPDATED: 2017-04-24


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Guanidinoacetate methyltransferase deficiency. Genetics Home Reference website.

Van Karnebeek C, Stockler-Ipsiroglu S. Congenital Disorders of Creatine Metabolism. UpToDate, Inc. website.

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