Ataxia Telangiectasia

Ataxia-telangiectasia is a rare inherited disorder of childhood that affects the nervous system, immune system, and other body systems. This condition occurs in 1 in 40,000 to 100,000 people worldwide.

Symptoms

Ataxia-telangiectasia is characterized by progressive difficulty with coordinating movements (ataxia) beginning in early childhood. Affected children typically develop difficulty walking, problems with balance, abnormal eye movements, and slurred speech. Small clusters of enlarged blood vessels called telangiectases, which occur in the eyes and on the surface of the skin, are also characteristic of this condition.

People with ataxia-telangiectasia often have weakened immune systems, and many develop chronic lung infections. They are also at an increased risk of developing cancer, particularly cancer of blood-forming tissue (leukemia) and cancer of immune system cells (lymphoma). Affected individuals are very sensitive to the effects of radiation exposure, including medical x-rays. Although people with ataxia-telangiectasia usually live into adulthood, their life expectancy is reduced.

Causes

Mutations in the ATM gene cause ataxia-telangiectasia.

The ATM gene provides instructions for making a protein that helps control cell division and is involved in DNA repair. This protein plays an important role in the normal development and activity of several body systems, including the nervous system and immune system. Mutations in the ATM gene reduce or eliminate the function of the ATM protein. Without this protein, cells in the brain die inappropriately, particularly in a part of the brain involved in coordinating movements (the cerebellum). The loss of these brain cells causes the movement problems characteristic of this disorder. Mutations in the ATM gene also prevent cells from responding correctly to DNA damage, which allows genetic defects to accumulate and can lead to cancer.

How do people inherit ataxia-telangiectasia?

Ataxia-telangiectasia is inherited in an autosomal recessive pattern, which means two copies of the ATM gene in each cell must be altered in order for the disease to occur. 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.

About 1 percent of the United States population (2.5 million people) carry one mutated copy and one normal copy of the ATM gene. Although they do not have ataxia-telangiectasia, they are more likely than people without an ATM mutation to develop cancer, particularly breast cancer. Carriers of a mutation in the ATM gene also may have an increased risk of heart disease.

Treatment

See GeneTests Web site.

Reference:

Genetics Home Reference, U. S. National Library of Medicine