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Nonketotic hyperglycinemia

(NAHN-kee-TAH-tik • HIE-puhr-GLIE-see-NEE-mee-uh)

General Condition Information

Other Names

  • Glycine encephalopathy
  • Non-ketotic hyperglycinemia

Condition Type

Birth Prevalence

  • It is estimated that more than 50 babies are born with some form of this condition each year in the United States.
  • Visit GeneReviews to learn more about how often this condition occurs.

Screening Finding

High levels of glycine

What is nonketotic hyperglycinemia

Nonketotic hyperglycinemia (NKH) is an inherited (genetic) condition that prevents your baby’s body from breaking down a substance called glycine in the blood. Glycine is an amino acid, one of the building blocks that makes up proteins. Glycine is also used as a neurotransmitter, which helps send signals from one part of the brain to another.

The glycine cleavage system is a process that uses two enzymes that work together to help break down glycine. If one of the two enzymes is not working well, your baby has trouble breaking down glycine and sending signals in the brain.

There are two types of NKH – severe and attenuated – that differ in signs, symptoms, and age of onset. The severity of the condition depends on how much glycine cleavage system activity is present. Glycine cleavage system activity shows how well your baby can break down glycine.

High glycine can damage your baby’s brain and other organs. Left untreated, this damage leads to the signs and symptoms of the condition.

Newborn Screening and Follow-Up

Condition Details

Treatment and Management

It is important to talk to your health care provider about how to best care for your baby. Currently, the treatment options available cannot stop the progression of the condition. Health care providers will develop a plan that is tailored to the needs of each child.

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