Ataxia Telangiectasia (A-T) is a rare, inherited childhood neurological disorder that causes degeneration in the part of the brain that controls motor movements and speech.
The gene responsible for A-T, known as ATM (ataxia-telangiectasia mutated) makes a protein that activates a number of other proteins that control cell cycle, DNA repair, and cell death. Without it, cells are unable to activate the cellular checkpoints that protect against the damage of ionizing radiation and other agents that can harm DNA.
The most unusual symptom of A-T is an acute sensitivity to ionizing radiation, such as X-rays or gamma-rays. The first signs of the disease, which include delayed development of motor skills, poor balance, and slurred speech, usually occur during the first decade of life. Telangiectasias (tiny, red "spider" veins), which appear in the corners of the eyes or on the surface of the ears and cheeks, are characteristic of the disease, but are not always present and generally do not appear in the first years of life.
About 20% of those with A-T develop cancer, most frequently acute lymphocytic leukemia or lymphoma. Many people with A-T have a weakened immune system, making them susceptible to recurrent respiratory infections.
Other features of the disease may include:
mild diabetes mellitus,
premature graying of the hair,
difficulty swallowing, and
delayed physical development.
Children with A-T usually have normal or above normal intelligence. A-T affects boys and girls equally.
TESTING, PHYSICAL FINDINGS, AND ICD-9-CM CODING
A physical exam revealing symptomology of the disease, laboratory testing including Alpha fetoprotein, B and t cell screen, carcinoembronic antigen, genetic testing for ATM gene, glucose tolerance testing, serum immunoglobulin levels, and x-rays of the thymus gland to determine the size of the gland.
ONSET AND PROGRESSION
The prognosis for people with A-T is poor. People with the disease usually die in their teens or early 20s.
Complications that can arise from A-T include:
lymphoma (cancerous tumors that are in the lymph nodes),
kyphosis (abnormal curvature of the spine) resulting in a progressive movement disorder that leads to wheelchair use,
severe, recurrent lung infections.
There is no cure for A-T and, currently, no way to slow the progression of the disease. Treatment is symptomatic and supportive. Physical and occupational therapy may help maintain flexibility. Speech therapy may also be needed. Gamma-globulin injections may be given to help supplement a weakened immune system. High-dose vitamin regimens may also be used.
Suggested MER for Evaluation: If sequence analysis of the ATM gene has identified mutations in both alleles in the proband, then the diagnosis of A-T is confirmed. If this is unavailable, then a complete review of the clinical course, findings, and the available laboratory studies on which the disorder is suspected will be needed. Once the diagnosis is confirmed, then a review of the current examination will be needed to establish severity as variability in this disorder, although rare, has been reported.