Ataxia telangiectasia (Louis-Bar syndrome)

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Overview

Ataxia telangiectasia, also known as Louis-Bar syndrome, is a rare hereditary disorder that affects nervous system, immune system and other body systems.

The condition is characterized by progressive difficulty of a person to coordinate movements (ataxia) and begins in early childhood, usually before age of 5. In children affected by balance problems, gait, coordination of hands, abnormal involuntary movements (chorea), muscle twitching (myoclonus) and impaired nerve function (neuropathy).

Specific movement difficulties, often requires wheelchair use since adolescence. People who suffer from this disorder have trouble speaking but also about lateral eye movement. On the eye sclera and skin appear grouped small blood vessels called telangiectasia extended.


Contents

1. Overview
2. Ataxia telangiectasia and immune system
3. Incidence of ataxia telangiectasia
4. Genes that cause ataxia telangiectasia
5. How is ataxia telangiectasia inherited by people?
6. Signs of ataxia telangiectasia
7. Is ataxia telangiectasia treatable?
8. Predisposition to the development of certain cancers


Ataxia telangiectasia and immune system

In people affected will detect large amounts of protein in the blood called alpha-protein. The level of this protein is usually increased in the blood of pregnant women. Abnormal effect of elevated alpha-fetoprotein in people suffering from ataxia telangiectasia is unknown.

Patients who suffer from ataxia telangiectasia often have weakened immune systems and manifest many chronic lung infections. They have an increased risk of developing cancer, especially leukemia and cancers of immune system cells (lymphoma).

Affected people are very sensitive to the effects of exposure to radiation, including medical radiographs. Although people who suffer from ataxia telangiectasia reach adulthood, their life expectancy is quite low.


Incidence of ataxia telangiectasia

There is a case of ataxia telangiectasia in 40,000 people and there are approximately 100,000 people worldwide suffering from this disease.


Genes that cause ataxia telangiectasia

Ataxia is caused by mutations in the ATM gene (ataxia telangiectasia mutated). This is important in the production of a protein that helps control cell division and is involved in DNA repair. Protein plays an essential role in normal development and functioning of many body systems, including the nervous and immune system.

ATM gene mutations diminish or eliminate the function of ATM protein. Without this protein, the cells become unstable and die. Cells in the brain involved in movement coordination are particularly affected. The loss of these brain cells causes movement problems characteristic of ataxia telangiectasia.

ATM gene mutations determine the correct response of cells to DNA damage, which cause breaks in DNA strands and lead to the formation of cancerous tumors.


How is ataxia telangiectasia inherited by people?

Ataxia telangiectasia is inherited by autosomal recessive pattern, which means both copies of the ATM gene in each cell have mutated. Most often, parents suffering from autosomal recessive and each carry one copy of the mutated gene, but do not show signs and symptoms.

Although ATM mutation does not always cause ataxia-telangiectasia in some patients, there is a good chance to develop cancer, especially breast cancer, and heart disease or diabetes.


Signs of ataxia telangiectasia

The first symptoms of the disease occur in the first decade of life and include delayed development of motor skills, balance and unclear speech. Spider veins that appear in the corners of the eyes or ears and cheeks surface are characteristic but are not always a present condition (not shown in the first years of life).

About 20% of people diagnosed with ataxia telangiectasia develop acute lymphocytic leukemia or lymphoma. Many of them have a weakened immune system, which can make them susceptible to current respiratory infections.

Other features of the disease include light diabetes, premature graying of hair, difficulty swallowing, delayed physical and sexual development. Children suffering from ataxia telangiectasia have normal or above normal intelligence.


Is ataxia telangiectasia treatable?

Currently, the disease is not curable. Cloning and sequencing of the gene that trigger the disease was the base of the initiation of several avenues of research for finding effective treatment, including gene therapy, development of drugs for the correction of impaired protein function and direct replacement of functional proteins.

Can be initiated physical, occupational and speech therapy that are designed to help maintain flexibility and gamma-globulin injections to help support the immune system of patients with ataxia telangiectasia. High doses of vitamins are being researched, is some cases being moderate results.

Research has shown that protein kinase called ATM responds to DNA damage by chemical changes and triggers the accumulation of molecules or tumor suppressor gene called p53. In patients suffering from ataxia telangiectasia, ATM protein is missing or is abnormal. This delays the accumulation of p53, allowing cells to reproduce, increasing the risk of cancer.


Predisposition to the development of certain cancers

There is no clear information in order to confirm the fact that ataxia telangiectasia can predispose to some types of cancers, but some people find that the presence of this disease is a risk factor for developing certain cancers. The most common met are breast and gastric cancer.

Animal studies have not supported these theories, however, and those with human subjects have suggested the presence of a link between ATM gene and increased risk of breast cancer but the results were not conclusive.

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