Ataxia-Telangiectasia (A-T) is a very rare familial neurodegenerative disorder. Signs of the disorder usually become noticeable between one to four years although occasionally not until the teenage years. Affected children have problems of balance control (ataxia) and so unsteady walking is observed, as well as prominent blood vessels most commonly seen on the conjunctiva of the eyes in early childhood (telangiectasia). Speech problems occur but, after a period of deterioration, a stable state is reached and speech is always understandable. There is often a gradual loss of power as well as other co-ordination problems over the decades. Intelligence is normal. There is a lot of variation in how severely individuals are affected which can now be explained to some extent by recent developments in genetic understanding.

Other features of the disorder include: frequent infections due to a defect in the immune system; short stature and an increased risk of cancers. The diagnostic finding is an increased sensitivity to high doses of ionising radiation. Normal x-rays pose little risk to affected individuals as radiation doses are very low. However, unnecessary x-rays should be avoided where possible.

Due to the demonstration of increased levels of oxidative stress in AT cells, clinical trials are being planned with anti-oxidant therapy. Stem cell research may also lead to possible therapeutic strategies in the future.

Inheritance patterns
The mode of inheritance is autosomal recessive. In families with an affected child there would be a twenty-five per cent chance of recurrence in further pregnancies. Two genes have been found which can cause Ataxia Telangiectasia. The gene causing AT has been found. It is called ATM and is located on chromosome 11q23. Many different mutations in the ATM gene have been found. Some completely inactivate the gene causing a 'classical' picture and others may allow some function of the ATM protein and lead to a milder clinical picture. Many different mutations in the ATM gene have been found. A second gene, hMre11,has also been identified. People with hMre11 have symptoms which are less marked than A-T with a later onset of unsteadiness and jerky movements. Chromosome instability studies were also found to be less marked than in the usual cases of A-T. Both ATM and hMre11 were mapped to chromosome 11. Routine analysis for faults in this gene is not currently available on the NHS. Both genes are involved in the signalling pathway used by cells to indicate that DNA has been damaged and should be repaired.

Prenatal diagnosis
This is usually possible, but requires discussion before conception. The regional genetic centres will be able to co-ordinate this.

Medical text written November 1991 by Contact a Family. Approved November 1991 by Professor M Patton, Professor of Medical Genetics, St Georges Hospital Medical School, London, UK and Dr J E Wraith, Consultant Paediatrician, Royal Manchester Children's Hospital, Manchester, UK. Last updated July 2005 by Dr S Ritchie, Associate Specialist in Clinical Genetics, City Hospital, Nottingham, UK.

Further Online Resources
Medical texts in The Contact a Family Directory are designed to give a short, clear description of specific conditions and rare disorders. More extensive information on this condition can be found on a range of reliable, validated web sites and links to them are included in the CD-ROM version of this Directory. Further information on these resources can be found in our Medical Information on the Internet article.

ATAXIA-TELANGIECTASIA SOCIETY

A-T Society
IACR-Rothamsted
Harpenden
AL5 2JQ
Tel: 01582 760733
Tel: 0131 667 4065 A-T Counsellor
Fax: 01582 760162
e-mail: atcharity@aol.com
Web Site http://www.atsociety.org.uk

The Society is a National Registered Charity No. 1105528, established in 1989. It offers support for the newly diagnosed family, contact with other families, annual family days and youth meetings, specialist clinics at Nottingham City Hospital and Papworth Hospital and support grants for families. It publishes a twice yearly newsletter and has a wide range of information available, details on request. The society represents over 100 families and funds research into A-T.

Group details last updated June 2007.

As Ataxia-Telangiectasia is a metabolic disease, support and advice are also available from Climb (see entry, Metabolic diseases).