Isovaleric Acidaemia

What is isovaleric acidaemia?

Isovaleric acidaemia is a rare disorder in which the body is unable to process certain proteins properly. People with this disorder have inadequate levels of an enzyme that helps break down the amino acid leucine, a building block of proteins.

A characteristic feature of isovaleric acidaemia is a distinctive odour of sweaty feet. This odour is caused by the buildup of a compound called isovaleric acid in affected individuals.

In about half of cases, the signs and symptoms of this disorder become apparent within a few days after birth and include poor feeding, vomiting, seizures, and lack of energy (lethargy) that can progress to coma. These medical problems are typically severe and can be life-threatening. In the other half of cases, the signs and symptoms of the disorder appear during childhood and may come and go over time. They are often triggered by an infection or by eating an increased amount of protein-rich foods.

How common is isovaleric acidaemia?

Isovaleric acidaemia is estimated to affect at least 1 in 250,000 births in the United States.

What genes are related to isovaleric acidaemia?

Mutations in the IVD gene cause isovaleric acidaemia.

The enzyme made by the IVD gene plays an essential role in breaking down proteins from the diet. Specifically, the enzyme is responsible for the third step in processing leucine, an amino acid that is part of many proteins. If a mutation in the IVD gene reduces or eliminates the activity of this enzyme, the body is unable to break down leucine properly. As a result, a molecule called isovaleric acid and related compounds build up to harmful levels, damaging the brain and nervous system.

How do people inherit isovaleric acidaemia?

This condition is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. Most often, the parents of an individual with an autosomal recessive disorder are carriers of one copy of the altered gene but do not show signs and symptoms of the disorder.

What other names do people use for isovaleric acidaemia?

  • Isovaleric acid-CoA dehydrogenase deficiency
  • Isovaleryl-CoA dehydrogenase deficiency
  • IVD deficiency

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