isovaleric acidemia

What is Isovaleric Acidemia?

Isovaleric acidemia (IVA) is an inherited disorder in which the body is unable to properly process proteins, leading to a toxic buildup of isovaleric acid in the blood.

Some people with the genetic mutations that cause IVA do not show symptoms of the disease. The reason for this lack of symptoms is not entirely understood.

As the body digests proteins, it breaks them into smaller parts called amino acids. People with IVA lack a properly-working enzyme necessary to break down a common amino acid called leucine. As a result, an organic acid called isovaleric acid reaches toxic levels in the blood and can cause damage to the brain and nervous system. If left untreated, IVA can lead to seizures, coma, and death. Treatment with an appropriate low-protein diet, however, can lead to fairly normal growth, development, and lifespan.

There are two forms of IVA, one which appears shortly after birth and is rapidly life-threatening, and another which may appear later in childhood as episodes of illness.

The form of IVA seen in newborns appears within two weeks of birth. Initial symptoms include lack of energy, poor appetite, vomiting, and difficulty staying warm. The buildup of isovaleric acid often gives them an odor of sweaty feet. If untreated, these infants will progress to a more serious metabolic crisis, suffering seizures, coma, swelling or bleeding of the brain, and even death.

The childhood form of IVA often appears around the child's first birthday and its symptoms—nearly identical to the infantile form of the disease—may come and go over time, flaring up particularly during times of illness, high protein consumption, or long periods without food. Between periods of crisis, the child can be healthy, however overall these children may show poor growth, muscle weakness, or learning problems. Some infants who have the more severe, early-onset form of the disease can progress to the more episodic form later in life.

IVA is part of a group of diseases known as organic acid disorders.

How common is Isovaleric Acidemia?

IVA affects at least 1 in 250,000 Americans.

How is Isovaleric Acidemia treated?

People with IVA must eat a diet low in proteins, minimizing foods such as dairy products, meat, fish, eggs, legumes, and nuts. The body does need protein, however, and a nutritionist or other medical professional can help devise an appropriate diet. This may include foods made especially for people with organic acid disorders. Supplements of carnitine and/or glycine may be prescribed. These supplements bind with isovaleric acid and turn it into a less harmful compound.

People with IVA should have close contact with a physician during times of illness. At these times, the body may break down its own protein, leading to a buildup of isovaleric acid. Typically people with IVA need to eat more carbohydrates and drink more fluids during times of illness, even if they are not hungry or thirsty.

Any time a child with IVA experiences a metabolic crisis, he or she needs prompt treatment, which may include a hospital visit.

What is the prognosis for a person with Isovaleric Acidemia?

If the disease is recognized promptly and treated diligently, children with IVA can live near-normal lives. It is possible, however, that they will have episodes of metabolic crisis, although these episodes tend to decrease with age. If these episodes are not treated, irreversible learning problems or mental disability can occur.

Those who do not develop any symptoms of the disease can be expected to live a normal lifespan.