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Guanidinoacetate methyltransferase deficiency
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Reviewed June 2011
What is guanidinoacetate methyltransferase deficiency?
Guanidinoacetate methyltransferase deficiency is an inherited disorder that primarily affects the brain and muscles. People with this disorder have intellectual disability that is usually severe, with speech development limited to a few words. Almost all individuals with guanidinoacetate methyltransferase deficiency experience recurrent seizures (epilepsy). Most develop autistic behaviors that affect communication and social interaction; some affected individuals also exhibit self-injurious behaviors such as head-banging. Certain involuntary movements (extrapyramidal dysfunction) such as tremors or facial tics occur in about half of affected individuals.
People with guanidinoacetate methyltransferase deficiency may have weak muscle tone and delayed development of motor skills such as sitting or walking. In severe cases they may lose previously acquired skills such as the ability to support their head or to sit unsupported.
How common is guanidinoacetate methyltransferase deficiency?
Guanidinoacetate methyltransferase deficiency is a very rare disorder. About 80 affected individuals have been reported worldwide. Of these, approximately one third are of Portuguese origin.
What genes are related to guanidinoacetate methyltransferase deficiency?
Mutations in the GAMT gene cause guanidinoacetate methyltransferase deficiency. The GAMT gene provides instructions for making the enzyme guanidinoacetate methyltransferase. This enzyme participates in the two-step production (synthesis) of the compound creatine from the protein building blocks (amino acids) glycine, arginine, and methionine. Specifically, guanidinoacetate methyltransferase controls the second step of this process. In this step, creatine is produced from another compound called guanidinoacetate. Creatine is needed for the body to store and use energy properly.
GAMT gene mutations impair the ability of the guanidinoacetate methyltransferase enzyme to participate in creatine synthesis, resulting in a shortage of creatine. The effects of guanidinoacetate methyltransferase deficiency are most severe in organs and tissues that require large amounts of energy, especially the brain.
Read more about the GAMT gene.
How do people inherit guanidinoacetate methyltransferase deficiency?
This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
Where can I find information about diagnosis or management of guanidinoacetate methyltransferase deficiency?
These resources address the diagnosis or management of guanidinoacetate methyltransferase deficiency and may include treatment providers.
General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.
To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.
Where can I find additional information about guanidinoacetate methyltransferase deficiency?
You may find the following resources about guanidinoacetate methyltransferase deficiency helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
What other names do people use for guanidinoacetate methyltransferase deficiency?
What if I still have specific questions about guanidinoacetate methyltransferase deficiency?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding guanidinoacetate methyltransferase deficiency?
acids ; arginine ; autosomal ; autosomal recessive ; cell ; compound ; creatine ; deficiency ; disability ; enzyme ; epilepsy ; extrapyramidal ; gene ; glycine ; inherited ; involuntary ; methionine ; methyltransferase ; motor ; muscle tone ; protein ; recessive ; syndrome ; synthesis
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (12 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.