Ataxia-telangiectasia; Louis-Bar Syndrome (Ataxia-telangiectasia syndrome) - Gen ATM
Ataxia-telangiectasia is a rare inherited process affecting the nervous system, the immune system and other body systems. It is characterized by progressive difficulty coordinating movements (ataxia), manifested usually before 5 years. Affected children have difficulty walking, problems with balance and coordination between hands, chorea, myoclonus and neuropathy. Movement problems usually cause people require a wheelchair in adolescence. In addition, affected individuals manifest difficulty speaking and oculomotor apraxia. In this condition it is characteristic of small clusters enlarged blood vessels called telangiectasia, which appear in the eyes and the skin surface.
People usually have high amounts of a protein called alpha-fetoprotein (AFP) levels. This protein concentrations tend to increase in the blood of pregnant women, but it is unknown why people with ataxia-telangiectasia have it high or how it impacts on these individuals. Likewise, individuals with ataxia-telangiectasia often have a weakened immune system, and many develop chronic lung infections. They also have an increased risk of developing malignancies, especially leukemias and lymphomas. Affected individuals are very sensitive to the effects of exposure to radiation, including X - rays The life expectancy of people with ataxia-telangiectasia is very variable but often live until early adulthood.
This process is due to mutations in the ATM gene, located on the short arm of chromosome 11 (11q22-q23). The ATM gene encodes a protein that helps control cell division and is involved in DNA repair. This protein plays an important role in normal development and the activity of various body systems, including the nervous system and the immune system. Protein helps cells recognize molecules damaged or broken DNA and coordinates DNA repair by activating enzymes that fix the broken DNA strands. This repair damaged DNA strands helps maintain the stability of the genetic information of the cells.
They have identified several hundreds of mutations in the ATM gene responsible for ataxia-telangiectasia. Mutations in the ATM gene reduce, or eliminate, the function of ATM protein. Without this protein, the cells become unstable and die. Instead of activating DNA repair, defective ATM protein allows mutations in other genes, which can cause the cells to grow and divide in an uncontrolled accumulate. Such regulated cell growth can not lead to the formation of cancerous tumors. The cells in the cerebellum are particularly affected by the loss of ATM protein, leading to some of the problems characteristic of motion ataxia telangiectasia.
Ataxia-telangiectasia is inherited as an autosomal recessive pattern, meaning that two copies of the ATM gene in every cell must have mutations for the process is revealed. Often, parents of a person with an autosomal recessive disorder each have a copy of the mutated gene, but do not show signs and symptoms of the disease. It has been found to have a mutation in one copy of the ATM gene in each cell, especially in people who have at least one family member with ataxia-telangiectasia, it is associated with an increased risk of developing breast cancer. Carriers of a mutation in the ATM gene may also have an increased risk of heart disease.
Tests in IVAMI: in IVAMI perform detection of mutations associated with syndrome ataxia-telangiectasia, by complete PCR amplification of the exons of the ATM gene and subsequent sequencing.
Samples recommended: EDTA blood collected for separation of blood leukocytes, or impregnated sample card with dried blood (IVAMI may mail the card to deposit the blood sample).