Ataxia-Telangiectasia is a rare genetic condition that affects the nervous system, immune system, and other body systems. Most children with this condition have ataxia, or trouble coordinating their movements. They also have small clusters of enlarged blood vessels called telangiectasias in the eyes and on the surface of the skin. Compared to people who don’t have Ataxia-Telangiectasia, they are at higher risk for developing certain types of blood cancers and immune system cancers.
In people with Ataxia-Telangiectasia, the ataxia often begins in early childhood, typically before age 5, and gets worse over time. Most children with Ataxia-Telangiectasia will eventually find it hard to walk and will have problems with balance and hand coordination. They may have other nervous system problems as well, including:
- Slurred speech
- Oculomotor apraxia (trouble moving the eyes from side to side)
- Chorea (involuntary jerking movements)
- Myoclonus (muscle twitches)
- Neuropathy (disturbances in nerve function)
By adolescence, many people with Ataxia-Telangiectasia will require a wheelchair.
Ataxia-Telangiectasia is caused by changes in a gene known as ATM. Genes carry information telling cells in the body how to work. The ATM gene is needed for cells to fix damaged genetic material (DNA).
Most people without Ataxia-Telangiectasia carry two working copies of the ATM gene in their cells. One copy is inherited from each parent. People with Ataxia-Telangiectasia carry two changed copies of the ATM gene in their cells. One changed copy was inherited from each parent. The changes cause the ATM gene to not work right. These gene changes are called variants.
When both copies of the ATM gene have variants, cells can’t fix damage to their DNA as well as in someone without Ataxia-Telangiectasia. The cells become unstable and sometimes die or grow to form a tumor. That is why people with Ataxia-Telangiectasia are at higher risk of developing some kinds of cancer.
People with only one variant copy of the ATM gene do not have Ataxia-Telangiectasia and do not show the signs and symptoms of the condition. These people are called “carriers.” Female carriers (women with one variant copy of the ATM gene) have a slightly higher risk of developing breast cancer than the general population.
The parents of a child with Ataxia-Telangiectasia have a 25% (1 in 4) chance of having another child with the condition. They have a 50% (1 in 2) chance of having a child who carries just one copy of an ATM variant. That child would be a carrier. Carriers do not have Ataxia-Telangiectasia but could pass on the changed ATM gene to their own children. There is a 25% (1 in 4) chance of having another child with two normal copies of the ATM gene. That child would not have Ataxia-Telangiectasia and would not be a carrier. Children with two normal copies of the ATM gene would pass on only normal copies of the ATM gene to their own children.
A person with Ataxia-Telangiectasia has different risks of having a child with Ataxia-Telangiectasia. A person with Ataxia-Telangiectasia will pass one ATM variant to each of his or her children. This person’s chance of having a child with Ataxia-Telangiectasia depends on whether his or her partner also carries an ATM variant. If the partner carries an ATM variant, the chance of having a child with the condition is 50% (1 in 2). The chance of having a child who carries just one copy of an ATM variant is 50% (1 in 2). If the partner does not carry an ATM variant, none of the children will have Ataxia-Telangiectasia, but all of the children will be carriers.
A doctor may suspect this diagnosis based on physical exam, and/or after looking at a person’s medical or family history. In most cases, a doctor or genetic counselor will ask questions about the person’s health and the health of other family members. Read more about genetic counseling and genetic testing.
Diagnosing Ataxia-Telangiectasia is usually done by sequencing the ATM gene to find variants (gene changes).
Additional lab tests can be used to support a diagnosis of Ataxia-Telangiectasia:
- Specialized tests to measure the amount of ATM protein in cells. The ATM gene makes a protein that is also called ATM. If a person has a variant copy of the ATM gene, that person usually will have ATM protein levels in their cells that are much lower than normal.
- Blood tests to measure the level of a protein called alpha-fetoprotein. More than 95% of people with Ataxia-Telangiectasia have high levels of alpha-fetoprotein, but levels are very low in most people without the condition. Doctors do not know why the level of alpha-fetoprotein is so high in people with this condition.
- Radiosensitivity test to measure how well a cell can fix damaged DNA. Normal cells that have working ATM protein should be able to fix themselves after being exposed to radiation. The cells from people with Ataxia-Telangiectasia do not survive normally after exposure to radiation because they do not fix DNA as well.
- Chromosome analysis to look for what’s called a translocation that can occur in cells treated with a certain chemical. Chromosomes are the part of the cell that contains the genetic material (DNA). A translocation occurs when chromosomes break and the pieces reattach improperly to other chromosomes.
People with Ataxia-Telangiectasia have about a 40% chance of developing cancer. Of those that develop cancer, most will develop leukemia (blood cell cancer) or lymphoma (immune cell cancer, usually in the lymph node). Other types of cancer that may develop include:
- Ovarian cancer
- Breast cancer
- Thyroid cancer
- Parotid (salivary) gland tumors
- Gastric (stomach) cancer
- Melanoma (skin cancer)
- Leiomyomas (smooth muscle tumors)
Female carriers (women with one variant copy of the ATM gene) have a slightly higher risk of developing breast cancer than those who are not carriers. The risk is relatively low (about 2–4 times greater than the general population). Given this risk, some health care providers may recommend that female ATM variant carriers consider breast cancer screening at an earlier age than people who are not carriers. Currently, ATM variant carriers are not thought to be at an increased risk for other types of cancer besides breast cancer.
Cancer screening involves tests to check for cancer before symptoms occur. The goal is to find cancer at the earliest and most treatable stage. Guidelines for cancer screening are available online. Recommended screenings may change over time as doctors learn more about Ataxia-Telangiectasia, so screening tests should be discussed with a health care provider who knows this syndrome well.
For carriers of one copy of a variant ATM gene, early breast cancer screening may be advisable. This should be decided by a doctor who manages patients who have an increased risk for breast cancer.
Other ideas to reduce the risk of cancer include:
- Eat a healthful diet with lots of fruits and vegetables
- Get regular exercise
- Avoid smoking or using tobacco products
- Avoid secondhand smoke
- Avoid excess sun exposure and always wear sunscreen, hat, and protective clothing when out in the sun
- Get medical attention for unusual or ongoing symptoms
If cancer is found, it is very important to get a doctor who is experienced in treating cancer in people with Ataxia-Telangiectasia. Standard doses of some types of chemotherapy and radiation therapy may be more harmful to people with Ataxia-Telangiectasia. Lower doses of chemotherapy or radiation therapy may be needed.
Children with Ataxia-Telangiectasia may have some of the following medical concerns. Not all people with Ataxia-Telangiectasia will have all of these issues—medical issues vary from person to person.
- Weakened immune system resulting in infections more often
- Sensitive to ionizing radiation (such as the radiation used for CT scans and medical X-rays)
- Premature aging with graying of the hair
- Abnormal endocrine (hormone) system, including type 2 diabetes, short stature, and delayed puberty
- Mild learning problems or mild intellectual disability
- Smaller-than-normal cerebellum (a part of the brain), which can be seen on an MRI exam after the age of about 7 or 8 years
- Shortened life span (most people live into their 20s; some people live into their 40s or 50s)
Because of the other medical concerns related to Ataxia-Telangiectasia, specialists in the following areas may need to assess a child with Ataxia-Telangiectasia:
- Neurology
- Immunology
- Supportive therapy (such as physical, occupational, and speech therapies)
Also, children with Ataxia-Telangiectasia should:
- Have regular checks of development and school progress, as doctors believe are needed for the child
- Have their health monitored and adopt healthful habits throughout life, including regular physical checkups and screenings, due to their higher risk of cancer. That way, any cancer can be found early, at the most treatable stage.
- Avoid medical tests that use radiation, such as CT scans, X-rays, and mammograms, when possible, as both people with Ataxia-Telangiectasia and carriers are more sensitive to the effects of radiation. Radiation may increase their risk of developing cancer. A doctor may, at times, decide that these tests are needed if the benefit of the test outweighs the risk of developing cancer as the result of the test.
- Get special care when anesthesia is needed
The severity of the signs and symptoms of Ataxia-Telangiectasia vary among people. However, people with Ataxia-Telangiectasia who are in the same family often have a similar disease course.
- A-T Children’s Project (www.atcp.org)
- National Ataxia Foundation (www.ataxia.org)
- National Organization for Rare Disorders – Ataxia-Telangiectasia (rarediseases.org/rare-diseases/ataxia-telangiectasia/)
Other resources:
- Making Sense of Your Genes: A Guide to Genetic Counseling (www.ncbi.nlm.nih.gov/books/NBK115508/)
Adapted from educational materials developed by the St. Jude Children’s Research Hospital Cancer Predisposition Program