Some Information On Ataxia Telangiectasia

   Questions and Answers About Ataxia Telangiectasia

   1. What is ataxia telangiectasia?

   Ataxia telangiectasia (A-T) is a rare, recessive genetic disorder of
   childhood that occurs in 1/40,000 to 1/100,000 persons worldwide. The
   ailment is progressive. By their teens, patients with A-T are
   frequently wheelchair-bound.

   The disease is characterized by neurologic problems, particularly
   abnormalities of balance, recurrent serious sinus and respiratory
   infections, and dilated blood vessels in the eyes and on the surface
   of the skin. Patients usually have immune system abnormalities and are
   very sensitive to the effects of radiation treatments.

   In the United States, where recurrent infections typical of the
   disorder are usually controlled by antibiotics, patients are at high
   risk of developing and dying of cancer, particularly leukemias and
   lymphomas.

   2. Is the disorder curable?

   There is no cure for A-T at the present time. With the cloning and
   eventual sequencing of the gene (named ATM), several avenues of
   research to develop better treatment become possible, including: (1)
   gene therapy; (2) rational drug design; and (3) direct replacement of
   the functional protein.

   3. What does it mean that the disorder is recessive?

   A disease is recessive when a person inherits the predisposing gene
   from both parents, each of whom transmits one copy of the abnormal
   gene to his/her child.

   4. What is a carrier?

   A carrier is a person with one normal and one altered copy of a gene
   that is linked to a particular disease. These individuals usually do
   not realize they are carriers, because the disease is not present or
   its signs and symptoms are very mild.

   5. How many A-T carriers are there in the United States?

   An estimated one percent, or 2 1/2 million, of the U.S. population may
   be carriers for A-T.

   6. How do I know if I am a carrier?

   In the past, carriers have been identified chiefly because they are
   parents of a child with A-T. In a small number of cases, carriers have
   been identified through extensive laboratory and clinical studies of
   families in which A-T has occurred. With the cloning of the ATM gene,
   however, scientists will be able to devise a test to detect A-T
   carriers. To do this, they take advantage of what they know about
   alterations to the gene in a particular family. Because different
   carriers will have different mutations in the gene, devising a
   diagnostic gene test may be difficult.

   7. What cancers are increased in A-T patients?

   At least 10 percent of A-T patients develop cancer. Most of these are
   cancers of the lymphoid tissues (leukemias and lymphomas), but
   one-fifth of the cancers occur in the stomach, brain, ovary, skin,
   liver, larynx, parotid gland, and breast.

   8. What cancers are increased in A-T carriers?

   Definitive information does not yet exist to answer this question, and
   must await the development of a test to identify ATM gene carriers.
   Some studies of the families of A-T patients have reported a 3- to
   4-fold increased risk of cancer, including breast cancer; this finding
   is controversial. Current estimates of risk are based on studies of
   selected families of A-T patients. The cloning of the ATM gene now
   allows scientists worldwide to evaluate suggestions of increased risk
   for cancer.

   9. Are A-T patients sensitive to radiation?

   A-T patients have an increased sensitivity to ionizing radiation, the
   type found in x-rays. When cultured in the laboratory, the blood and
   skin cells of these patients have markedly reduced ability to
   replicate and form cell colonies after x-ray exposure. Scientists
   believe that the ATM gene is one of at least three genes, (ATM, p53,
   and GADD45) involved in this cell cycle arrest.

   10. Are ATM gene carriers also sensitive to the effects of radiation?

   This is a question needing further study, and the cloning of the ATM
   gene will make new studies of carriers possible. When cultured in the
   laboratory, the blood and skin cells of known ATM gene carriers are
   intermediate in their sensitivity to x-rays, compared to A-T patients
   and the general public.

   11. Does their increased sensitivity to radiation, compared to the
   general public, make it dangerous for carriers to have diagnostic
   x-rays?

   There is no evidence to support this. At the dosages of radiation
   delivered by today's technology, diagnostic tests are not considered
   harmful to carriers.

   12. Are x-rays harmful to A-T patients?

   A-T patients are sensitive to the effects of radiation and should be
   monitored for adverse effects. However, they do receive diagnostic
   x-rays when necessary.

   The information about radiation sensitivity in A-T comes largely from
   observations of A-T patients who undergo radiation treatments,
   especially for cancer, and also from laboratory studies on skin and
   blood cells. Physicians who treat A-T patients limit x-ray exposures
   by using the most modern equipment and techniques available, but they
   do recommend these diagnostic tests when they are needed.

   Now that the ATM gene has been isolated, scientists will be able to
   study the nature of the radiation sensitivity observed in cells from
   A-T patients, as well as any intermediate level of radiation
   sensitivity observed in cells from known carriers.

   13. Suppose I learn I am an A-T carrier. Will mammography increase my
   chances of getting breast cancer?

   There is no definitive evidence that A-T carriers of any age have
   increased sensitivity to x-rays from mammograms or other diagnostic
   tests. For women 50 and older, the benefits of mammography have been
   demonstrated clearly.

   14. Are there any alternatives to mammography on the horizon?

   Recent technological modifications to mammography result in delivery
   of lower radiation doses than 20 years ago.

   15. What about environmental sources of radiation, such as cellular
   phones. Should A-T carriers avoid these exposures?

   To date, there have been no definitive studies linking non- ionizing
   radiation, such as that from cellular phones, to cancer.