Isovaleric acidemia

Alternate names

Isovaleric acid CoA dehydrogenase deficiency; IVA; Isovaleryl CoA carboxylase deficiency; IVD deficiency

Summary

• Isovaleric acidemia (IVA) occurs when the body cannot breakdown certain parts of the proteins found in food. This can cause a build-up of toxic substances which can lead to bouts of serious illness known as metabolic crises.
• The condition is classified as an organic acid disorder, which is a condition that leads to an abnormal buildup of particular acids known as organic acids. Abnormal levels of organic acids in the blood (organic acidemia), urine (organic aciduria), and tissues can be toxic and can cause serious health problems.

Types

There are two types of IVA.

• The acute, neonatal type has more severe symptoms that begin in the newborn period.
• In the chronic, intermittent type; symptoms appear during childhood and can come and go.

Epidemiology

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

Cause

Mutations in the IVD gene cause isovaleric acidemia. The IVD gene provides instructions for making an enzyme that plays an essential role in breaking down proteins from the diet. Specifically, this enzyme helps process the amino acid leucine, which 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, an organic acid called isovaleric acid and related compounds build up to harmful levels in the body. This buildup damages the brain and nervous system, causing serious health problems.

Inheritance

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Signs and symptoms

Symptoms may include:

• Poor feeding
• Vomiting
• Lack of energy
• Low muscle tone
• Tremor
• Odor of sweaty feet

The symptoms of IVA can range from mild to very severe. In severe cases, these symptoms start a few days after birth. These symptoms sometimes progress to more serious medical problems, including seizures, coma, and possibly death. In other cases, the symptoms of IVA appear during childhood and can be triggered by prolonged periods without food (fasting), infections, or eating an increased amount of protein-rich foods. Although IVA can be life-threatening in infancy, with treatment, many children with IVA have normal growth and development. Some people have a form of IVA which does not cause any symptoms of the condition.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Global developmental delay
• Metabolic acidosis

30%-79% of people have these symptoms

• Seizure

5%-29% of people have these symptoms

• Cerebellar hemorrhage

Diagnosis

• Isovaleric acidemia (IVA) is diagnosed based on the symptoms, clinical exam, blood and urine testing. The results of genetic testing may help confirm the diagnosis.
• IVA can also be diagnosed on the newborn screen. However, some people found to have IVA on a newborn screen may have never develop symptoms.

Treatment

Treatment is focused on managing the symptoms and involves a special protein-restricted diet and medications that rid the body of excess isovaleric acid.

NIH genetic and rare disease info

• NIH info on Isovaleric acidemia

Isovaleric acidemia is a rare disease.

Isovaleric acidemia Resources
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