Role of Genetics in Ataxia Term Paper

  • Length: 10 pages
  • Subject: Disease
  • Type: Term Paper
  • Paper: #22182658

Excerpt from Term Paper :

The most frequent symptom is difficulty in walking or gait ataxia (Unicorn Self-Help Committee 2000), which spreads slowly to the arms and the trunk. Foot deformities, such as clubfoot, flexion of the toes or foot inversion are other early signs. In time, muscles weaken and waste, especially the muscles in the feet, lower legs and hands and, at this time, deformities s begin to show. Other symptoms are the loss of tendon reflexes especially in the knees and ankles, the gradual disappearance of sensation in the extremities, dysarthria or slowness of speech or slurring, easy fatigue, rapid and involuntary movements of the eyes, scoliosis, chest pain, shortness of breath, palpitations, heart enlargement, myocardial fibrosis, tachycardia, heart block and heart failure. Studies showed that about 20% of FA patients also develop carbohydrate intolerance and 10%, of diabetes mellitus, while others lose their hearing or eyesight.

In most cases, the patient gets strapped to a wheelchair within 15 to 20 years from the appearance of the first symptoms (Unicorn Self-Help Committee 2000). In the later stage of the disease, the patient becomes completely incapacitated and his or her life expectancy is reduced. Most FA sufferers die in early adulthood, often because of a serious and resulting heart condition, which also becomes the immediate cause of death. Patients with less than severe symptoms fortunately live longer (Unicorn).

Another serious type of ataxia is ataxia-telangiectasia or at, also called Louis-Bar syndrome, although a rare type (Barrett 1999). At patients mostly die in their early 20s. The abnormal effects of at on the nervous system are first observed or detected at age 2, during which muscle control progressively decreases. It is also at this age that immune system defects and blood cancers are not uncommon and the patient becomes most sensitive to radiation.

It was first discovered and written about in the mid-1920s but got recognized as a specific disorder and given a name only in 1957 (Barrett 1999). At is a combination of ataxia and telangiectasia, which is characterized by tiny red spots, but is more than a combination of these disorders. At is liked with immune system deficiencies, extreme sensitivity to radiation, and blood cancers. Medical experts first suspected that it was caused by multiple genes. In 1995, the discovery of a single gene behind at denied their suspicion and they named the gene ATM or at mutated. Further tests and discoveries revealed that ATM plays a role in cell division. Under normal conditions, a proofreading and repair mechanism is able to correct a damage on the DNA before cell replication continues. At cells seem to ignore this mechanism and continue to grow and divide.

AT is a rare condition. It affects only about 500 persons in the U.S. (Barrett 1999), but approximately.5 to 14% of the population or roughly 2.5 million are carriers of one copy of the mutated gene (Barrett 1999). Many or most of these carriers do not experience signs or symptoms, such as increased sensitivity to radiation or a higher rate of cancer.

The ATM gene is autosomal recessive or occurs only if inherited from both parents. A child of such parents first appears healthy, but develops the symptoms of at when he or she turns 2. The root cause is cell death in the brain, specifically the large ones in the middle layer of the cerebellum. The toddler suddenly turns clumsy and loses balance, his speech becomes slurred and more difficult and symptoms progressively get worse. Up to age 8, there appear tiny, red spider veins on the cheeks, ears and the eyes. Between 10 and 12, the child with at can no longer control their muscles. Their immune system is affected. They have lower-than-normal level of antibodies and white blood cells. Their thymus gland is either missing or abnormally developed. Although intelligence remains normal, their growth may be retarded on account of their disturbed immune system functioning. Some at patients are stricken with diabetes, premature graying of the hair, and have difficulty swallowing. As children with at grow older, their immune system turns weaker and so they become less capable of fighting disease. In the later stages of at, recurrent respiratory infections and blood cancers, like leukemia and lymphoma, are common.

The diagnosis of at depends on that of at progressive ataxia and telangiectasia (Barrett 1999). But because ataxia symptoms appear before those of telangiectasia for many years, diagnosis of the combination becomes difficult. Symptoms also vary among the affected persons. About 70% of them have a high incidence of respiratory infection and 30% do not. Only when the ATM is identified does screening or treatment becomes possible. Like FA, there is as yet no known cure for at. Individual symptoms can only be managed, such as by a physical therapist and a speech therapist, who can help the patient adjust to ataxia. Gamma globulin injections or extracts of human blood with antibodies have been used to strengthen a patient's weakened immune system along with high doses of vitamins.

AT, however, remains a fatal condition. At children become physically disabled in early teens and mostly die in their early 20s (Barrett 1995). In a few and rare cases, the progression may be slowed down and the life span extended to their 30s. At carriers are five times likelier to develop certain cancers, like breast cancer and bone cancer, than non-carriers. Medical experts continue to investigate and improve on screening methods to detect if a person carries the defective gene. Commercial tests have yet to be developed as a preventive measure.

The identification of the ATM should now help and direct geneticists in developing diagnostic those diagnostic tests, including prenatal diagnosis and carrier detection to at families, according to Yosef Shioh of the Sackler School of Medicine in Tel Aviv University and his colleagues (Adler 1995). Shiloh and his colleagues believed that 1 in 40,000 in a population of 100,000 develop at. They also said that certain groups, such as Italians and Turks, seem to have higher incidence of at than other races. At sufferers represent only 1% of the U.S. population (Adler).

Nevertheless, the discovery of the ATM gene is assumed to be helpful in detecting whether a male of female carrier is at an increased risk of developing cancer, according to David L. Nelson of the National Cancer Institute of Bethesda, Maryland (Adler 1995). The gene's protein resembles enzymes involved in immune function, cell death and cell division and will help researchers in their search for a treatment for at, said Nathaniel Heintz of the Howard Hughes Medical Institute (as qtd in Adler). Their study may just bring them to discover life-saving information on how the body controls cell division or brings about cell death. At patients suffer from rapid loss of brain cells and from tumors (Adler) and further discovery on cell division and cell death can break the mystery of such loss of brain cells, tumors and ataxia.


Adler, Tina. Single Gene Causes Ataxia, Cancer Risk - Ataxia-Telangiectasia Mutated Gene Causes Fetal Disorder or Increased Risk of Cancer. Science News: Science Service, Inc., 1995.

Barrett, Julia. Ataxia-Telangiectasia. Gale Encyclopedia of Medicine, Gale Research, 1999.

Bird, Thomas D. Hereditary Ataxia Overview. Gene Reviews: National Human Genome Research Institute, 2005.

Robinson, Richard. Friedreich's Ataxia. Gale Encyclopedia of…

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