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Pyruvate Metabolism Disorders

By

Matt Demczko

, MD, Sidney Kimmel Medical College of Thomas Jefferson University

Last full review/revision Apr 2020| Content last modified Apr 2020
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Pyruvate metabolism disorders are carbohydrate metabolism disorders that are caused by a lack of the ability to metabolize a substance called pyruvate. These disorders cause a buildup of lactic acid and a variety of neurologic abnormalities. Pyruvate metabolism disorders occur when parents pass the defective genes that cause these disorders on to their children.

  • A deficiency in any one of the enzymes involved in pyruvate metabolism leads to one of many disorders.

  • Symptoms include seizures, intellectual disability, muscle weakness, and coordination problems.

  • Some of these disorders can be fatal.

  • Some specific pyruvate disorders are helped by changes in diet.

There are different types of inherited disorders. In many pyruvate metabolism disorders, both parents of the affected child carry a copy of the abnormal gene. Because usually two copies of the abnormal gene are necessary for the disorder to occur, usually neither parent has the disorder. (See also Overview of Hereditary Metabolic Disorders.)

Pyruvate is a substance that is formed in the processing of carbohydrates and proteins and that serves as an energy source for cells.

Problems with the breaking down (metabolizing) of pyruvate can limit a cell’s ability to produce energy and allow a buildup of a waste product called lactic acid (lactic acidosis). Many enzymes are involved in pyruvate metabolism. A hereditary deficiency in any one of these enzymes results in one of a variety of disorders, depending on which enzyme is deficient.

Symptoms of pyruvate metabolism disorders may develop any time between early infancy and late adulthood. Exercise and infections can worsen symptoms, leading to severe lactic acidosis.

These disorders are diagnosed by measuring enzyme activity in cells from the liver or skin. Genetic testing, which is used to determine whether a couple is at increased risk of having a baby with a hereditary genetic disorder, is also available.

Pyruvate dehydrogenase complex deficiency

This disorder is caused by a lack of a group of enzymes needed to process pyruvate. This deficiency results in a variety of symptoms, ranging from mild to severe. Some newborns with this deficiency have brain malformations. Other children appear normal at birth but develop symptoms, including weak muscles, seizures, poor coordination, and a severe balance problem, later in infancy or childhood. Intellectual disability is common.

This disorder cannot be cured, but some children are helped by a diet that is high in fat and low in carbohydrates. Children may also be given supplements of the vitamin thiamin.

Absence of pyruvate carboxylase (pyruvate carboxylase deficiency)

Pyruvate carboxylase is an enzyme. A lack of this enzyme causes a very rare condition that interferes with or blocks the production of glucose from pyruvate in the body. Lactic acid and ketones build up in the blood. Often, this disease is fatal. Children who survive have seizures and severe intellectual disability, although there are recent reports of children with milder symptoms.

There is no effective treatment for this disorder, but some children may be given supplements of biotin.

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