Genetics of Ataxia Telangiectasia: A Detailed Guide

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Ataxia telangiectasia is a rare childhood disorder that affects the brain and other areas of the body. Ataxia is a term used to refer to uncoordinated movements, like walking. Telangiectasias are blood vessels that are enlarged just under the skin’s surface. They look like red, tiny, spider-like veins. Understanding the genetics of ataxia telangiectasia helps both health care providers, patients, and parents better understand how this disorder occurs and affects patients. This disorder is also known as Louis-Bar syndrome. The incidence rate for this genetic disorder throughout the world is about one in 40,000 to 100,000 people.

Genetics

Through understanding the genetics of ataxia telangiectasia, we know that an ATM gene mutation is the cause of this disorder. This gene works to give the instructions necessary for creating a protein that assists in cell division control and it is also involved in the repair of DNA. When this gene is mutated, the function of the ATM protein is eliminated or reduced. If this protein is absent, cells start to become unstable and then die inappropriately. The cells in the cerebellum are particularly affected. This disorder is inherited in an autosomal recessive pattern.

Signs and Symptoms

During late childhood, patients may experience a jerky gait, ataxic gait, or be unsteady. Other possible signs and symptoms may include:

Mental development decreases, stops, or slow after 10 to 12 years of age
Skin discoloration on areas exposed to the sun
Enlarged blood vessels in the areas of the eyes that are white
Hair grays prematurely
Radiation sensitivity, including x-rays
Delayed walking
Skin discoloration
Enlarged blood vessels in the ear, nose, knee, and inside of elbow skin
Late in the disorder, abnormal or jerky eye movements
Seizures
Recurring, severe respiratory infections

Diagnosis

The doctor will start diagnosing this condition by performing a physical exam in which he or she is looking for certain signs, such as:

Tonsils, spleen, and lymph nodes below normal size
Absent or decreased sexual and physical development
Mask-like face
Absent or decreased deep tendon reflexes
Growth failure
Multiple skin texture and coloring changes

Other diagnostic testing may include:

Alpha fetoprotein
Carcinoembryonic antigen
Glucose tolerance test
X-rays may be used to examine thymus gland size
B and T cell screen
Genetic testing may be performed to look for ATM gene mutations
Serum immunoglobulin levels

Treatment

There is no treatment for this disorder, but there are treatments to help alleviate some of the symptoms. Even with treatment, certain complications, such as cancer (like lymphoma), kyphosis, scoliosis, diabetes, progressive movement disorder, and recurrent, severe lung infections may occur. Physical, occupational, and speech and swallowing therapy may benefit patients, as well as assistive devices. Medications may help with cerebellar tremors and drooling. Intravenous immunoglobulin, certain antioxidants, and certain other medications may help patients as well.

Resources

National Institute of Neurological Disorders and Stroke. (2010). NINDS Ataxia Telangiectasia Information Page. Retrieved on December 5, 2010 from the National Institute of Neurological Disorders and Stroke: https://www.ninds.nih.gov/disorders/a_t/a-t.htm

Genetics Home Reference. (2008). Ataxia-Telangiectasia. Retrieved on December 5, 2010 from Genetics Home Reference: https://ghr.nlm.nih.gov/condition/ataxia-telangiectasia