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General Condition Information

Other Names

  • Deficiency of methionine adenosyltransferase
  • Glycine N-methyltransferase deficiency
  • GNMT deficiency
  • Hepatic methionine adenosyltransferase
  • Hypermethionemia
  • Hypermothioninemia
  • MET
  • Methioninemia
  • S-adenosylhomocysteine hydrolase deficiency

Condition Type

Birth Prevalence

  • It is unknown how many babies are born with this rare condition each year in the United States.

Screening Finding

High levels of methionine

What is hypermethioninemia

Hypermethioninemia is an inherited (genetic) condition that prevents the body from processing proteins correctly. Your body breaks up the protein you eat into parts called amino acids. Your body then processes those amino acids to either use or get rid of them.

There are different forms of hypermethioninemia. All forms result in high levels of an amino acid called methionine.

Several enzymes in your body break down methionine. For people with hypermethioninemia, one enzyme does not work correctly. As a result, they have trouble breaking down methionine. Methionine then builds up in their body.

Many people with this condition do not show any signs. Without treatment, however, high levels of methionine can lead to the signs and symptoms of the condition.

Newborn Screening and Follow-Up

Condition Details

Treatment and Management

Most children with hypermethioninemia do not need treatment. It is important to talk to your health care provider about which treatment(s) are best for your baby. The goal of treatment is to prevent the health problems caused by this condition. 

Treatments may include the following:

  • Restricted diet that avoids food with methionine
  • Special foods or formulas
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