Ataxia telangiectasia syndrome, also known as Louis-Bar syndrome or AT, is an inherited disorder with an autosomal recessive inheritance pattern. This means that for a child to inherit this condition, both parents must pass down a copy of the relevant gene mutation. Therefore, when both parents are carriers, the chances of their child to develop this syndrome are twenty-five percent.
What are the symptoms?
Symptoms of this disease vary. Not all patients suffer from the same symptoms since there is great variation in the clinical manifestation of this disorder.
Symptoms include:
- Involuntary arm movements (Chorea).
- Eye movement abnormalities.
- Dilated blood vessels (Telangiectasias) in the eyes, and occasionally on the skin.
- Increased risk for developing cancer (especially breast cancer, lymphoma, and leukemia) at a young age.
- Weakened immune system, causing recurring infections (especially lung infections).
- Walking difficulties.
- Progressive loss of the ability to walk during patients’ twenties.
- Swallowing and eating difficulties that develop with age.
- Patients’ life expectancy varies, but patients do not usually live past twenty-five years of age.
Which gene mutation causes AT?
Ataxia telangiectasia is caused by mutations to the ATM gene, located on chromosome 11. A variety of mutations may cause this disorder. The disease affects people of all ethnic descents equally.
Genetic testing
Prenatal screening tests for ataxia telangiectasia can be undergone by people with a known family history of this disorder. Tests can be performed using several methods, such as chorionic villus sampling or amniocentesis.
Those undergoing in vitro fertilization (IVF) can choose to use preimplantation genetic diagnosis (PGD) to test embryos for AT before they are transferred to the uterus. This ensures that only healthy embryos, that do not carry the ATM gene mutation, are implanted.
In addition, newborn screening is also offered on some occasions. The disease can also be genetically tested in children who show typical symptoms.
What is the frequency of AT?
The frequency of ataxia telangiectasia is 1 in 40,000-100,000 births worldwide.
What should parents do after diagnosis?
As the years go by, the prevalence of this disease decreases, thanks to genetic screening tests. Since this disease is incurable and causes great suffering to both the child and their immediate family, parents are usually recommended to terminate the pregnancy when the disease is diagnosed prenatally.
