This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
Hypermethioninemia due to S-adenosylhomocysteine hydrolase deficiency (SAHH deficiency) is a muscle disease associated with high blood levels of methionine and creatine kinase (CK). The main symptoms are psychomotor delay, behavioral disorders, severe myopathy, and delayed myelination from birth. Myelin is the layer covering the axons of nerves and plays an important role in nerve impulse conduction. SAHH deficiency is caused by mutations in the AHCY gene. Inheritance is autosomal recessive. A methionine-restricted diet, together with creatine supplements, may partly improve the delayed myelination and psychomotor development. The outcome depends upon the severity of the disease.
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