A-T Overview - Printer Friendly Version

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Summary

A-T is a rare, neurodegenerative, inherited disease which affects many parts of the body and causes severe disability. Ataxia means poor co-ordination and the Telangiectasia are extra blood vessels which can be seen, especially on the whites of the eyes.

A-T is progressive and affects the cerebellum (the body's motor control centre) and, in about 70% of cases, weakens the immune system as well, leading to respiratory disorders.

A-T first shows itself in early childhood, i.e. the toddler stage. The symptoms are lack of balance, slurred speech and perhaps a more than normal number of infections. All children at this age take a little while to develop good walking skills, coherent speech and an effective immune system so it may be some years before A-T is properly diagnosed.

A-T: An Overview

CLINICAL FEATURES

1. Introduction
The first indications of A-T usually occur during the toddler years. These first signs indicate difficulty with control of the body posture and body movement (truncal ataxia). The child may start to walk later than usual (after 18 months), may be reluctant to let go of supporting people or objects, may continue to walk unsteadily for longer than normal, may be unable to stand still without tottering back and forth and may fall frequently.

Prominent blood vessels in the whites of the eyes usually occur by the age of 5 years. These are the ocular telangiectasia of the condition and resemble those vessels seen in the eyes of much older people. They can occasionally be present at birth yet in others may not develop until the teenage years. Although potentially a cosmetic problem they do not bleed or itch. It is their constant nature, not changing with time, weather or emotion, which marks them as different from other eye blood vessels.

Initially it may be hard to be sure that anything is amiss and some children seem to improve from 3 to 5 years, but eventually it becomes obvious that balance control is abnormal.

Walking becomes more strenuous and appears awkward, doors and walls are frequently used for support. Running may, for a time, seem less affected; this is because less balance is needed for quick movements than slower graceful ones. At the beginning of the second decade of their lives most people with A-T begin to use a wheelchair.

Towards the end of the first decade and the start of the second other problems come to light; these can be as handicapping as the loss of body balance control.

Incidence: 3 Per Million.

2. Co-ordination of Limbs
Co-ordination of limbs becomes abnormal (peripheral ataxia), but much less so than that of the body. Involuntary movements may start in some but not all. These are:-

a) Little jerks of the hands and feet which look like fidgeting (chorea).
b) Slower, larger twisting movements of the neck, face and shoulders (athetosis).
c) The adoption of rather stiff and twisted postures (dystonia).
d) Occasional uncontrolled jerks of limbs (such as we all have sometimes when going to sleep).
e) Shaking episodes of a limb which are like shivering (tremors).

3. Slurred Speech (Dysarthria)
Slurring of speech may develop in the first decade, becoming worse for 5 to 10 years and then remaining a static problem. We know of no-one with A-T who cannot be understood, although conversation may be a slow process.

4. Eye Movements
Eye movements become restricted (vertical and horizontal sacchadic apraxia). Reading and following moving objects becomes difficult.

5. Intellect
Mental retardation is not seen in A-T. However, many children seem to have a slowing-down in their thinking speed. Some children remain in mainstream schools while others are in special schools; one young man graduated from university.

6. Immune Problems
About half the people with A-T have immune problems. These usually take the form of repeated colds and runny noses (sinopulmonary infections).

The immune system is complex and difficult to assess, but if the child is suffering more than his/her fair share of infections a physician should undertake this assessment. Some people with A-T need additional immunisations (DPT, Hib and Pneumovax), others need continued antibiotics to provide "background cover" and some need injections of immunoglobulins (proteins that the body makes to fight infections). Others are never troubled. The impression is that bacterial, rather than viral, infections are the most trouble.

7. Thin Build
Thinness, sometimes to an excessive degree, is a part of A-T. Some of this is due to a poor appetite, some to the energy expended with involuntary movements and some must be inherent in the disorder.

Some patients have a mild form of A-T, the disorder starting later and all the features being less marked.

Some people with A-T, both males and females, have a delayed puberty. This seems more common in those who are thin or are prone to infections.

DRUGS

No single drug, medicine, herbal remedy etc. can help all people with A-T. Most drugs which act on the nervous system can cause problems in A-T. Some people have found Benzhexol beneficial, but others have suffered reactions to it. Drug therapy requires specialised attention.

LABORATORY FINDINGS AND DIAGNOSIS

The four tests that are of use in the diagnosis of the disorder are shown in Table 1. The most useful test is to expose white cells from an individual to X-rays or gamma rays and assess the cells' response. This can only be carried out in specialist centres and takes much longer than the other tests. A-T is a clinical diagnosis. The laboratory findings are helpful, but not as important as the individual patient's symptoms and signs. Diagnosis is more difficult before the disorder has fully developed, when the child may be "a bit wobbly on his/her feet".

*Tests*	Results	Usefulness
Alpha-fetaprotein in blood	Increased	Good, but also raised in other conditions
Immunoglobulin levels (Iga, IgG, IgM)	Decreased	Not always low, also low in other conditions
Chromosome breaks and rearrangements	Increased	Good if increased, but of no help if normal
Ionising irradiation sensitivity	Increased	Very reliable, but only done in a few centres

GENETICS AND INCIDENCE

A-T is usually familiar, that is it runs in families. The mode of inheritance is autosomal recessive ("AR"). In AR families there is 1 chance in 4 that each child born to the parents will have the disorder. Prenatal diagnosis can be carried out in most families, but this is complex and must be arranged before conception. Further information can be obtained from the A-T Society

The incidence of A-T in Caucasians is about 3 per million so the disorder is very rare, with probably fewer than 200 affected people in the UK.

CANCER

People with A-T have an increased incidence (probably 1% risk per year) of tumours, particularly lymphomas and leukaemia. The treatment of these tumours may require the use of ionising radiation in large doses. As this can be dangerous, careful discussion with the relevant doctor is needed.

It has been reported that there is a small increased risk of breast cancer in mothers of children with A-T. This finding is the subject of much debate and research at present. Mammography before 50 years however is not recommended unless there is a strong family history of breast cancer.

RADIATION

It is important to put the radiation sensitivity into context. Although people with A-T have an increased sensitivity to ionising radiation (X-rays and gamma rays), they cope with other forms of radiation normally, i.e. obtaining a suntan from ultraviolet light. Also, the tumours seen in A-T are not thought to be radiation induced. Finally, normal X-rays of arms and chest and any necessary dental X-rays are not thought to produce enough radiation to be harmful.

TREATMENT

Presently there is no cure for A-T, but there are many things that can be done to help those with the disorder. Some of these are listed in Table 2. Contact the A-T Society for the most up-to-date information.

*Action*	*Benefit*
Exercise and physiotherapy	Makes best use of muscle control, should be fun - stretches muscles and ligaments
Antibiotics, immunoglobulins, vaccinations and chest physiotherapy	To treat chest infections and prevent permanent chest problems
Speech therapy	Of great help with diction, especially in the second decade
Orthopaedic referral/assessment	Corrective procedures can be helpful for joint or postural problems, particularly in the lower limbs or spine.

THE CAUSE OF A-T AND THE FUTURE

The neurological findings in A-T are of selective nervous system damage (of the cerebellum, brain stem, basal ganglia and spinal cord). The laboratory findings suggest a defect of DNA (genes and chromosomes) processing and an inability to repair some kinds of damage to DNA. No-one as yet knows how these parts add up to a whole, however, research is continuing.

RECENT RESEARCH

The A-T gene (known as ATM) was cloned in 1995. Work on this gene is underway and we can expect it to lead to a greater understanding of A-T, increased awareness, more genetic counselling, and hopefully better prospects for more effective treatments in the future.

A-T NATIONAL CLINIC

All families with a child who has A-T have the opportunity (via their GP, specialist or the A-T Society) to visit the specialist clinic in Nottingham where a multi-disciplinary team (involving a neurologist, a geneticist and therapists) has seen many families with A-T. This is intended to be complimentary to local care arrangements and allows all the concerns of the family to be addressed at a 'one stop shop' by interested experienced staff. There are close links with the A-T Society, the A-T Clinical Center in the U.S.A. and the various research groups (please visit Clinic section of the web-site).

The Overview Leaflet is available in several languages. To make enquiries please e-mail us at atsociety@btconnect.com