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ataxia-telangiectasia (AT)

Defects in ATM are the cause of ataxia telangiectasia (AT); also known as Louis-Bar syndrome, which includes four complementation groups: A, C, D and E. This rare recessive disorder is characterized by progressive cerebellar ataxia, dilation of the blood vessels in the conjunctiva and eyeballs, immunodeficiency, growth retardation and sexual immaturity. AT patients have a strong predisposition to cancer; about 30% of patients develop tumors, particularly lymphomas and leukemias. Cells from affected individuals are highly sensitive to damage by ionizing radiation and resistant to inhibition of DNA synthesis following irradiation.

A-T affects the cerebellum (the body's motor coordination control center) and also weakens the immune system in about 70% of the cases, leading to respiratory disorders and increased risk of cancer. It first appears in early childhood (the toddler stage) with symptoms such as lack of balance, slurred speech, and increased infections. Because all children at this age take time to develop good walking skills, coherent speech, and an effective immune system, it may be some years before A-T is properly diagnosed. AT is caused by a defect in the ATM gene, which is responsible for recognizing and correcting errors in duplicating DNA when cells divide, and in destroying the cells when the errors can't be corrected. The protein normally repairs double-stranded DNA breaks. These are sometimes classified into ‘types’ from I to IV. - Type I is the classic syndrome with all manifestations. - Type II lacks some of the typical findings but shows radiosensitivity. - Type III has the classic clinical findings but is not radiosensitive. - Type IV shows only some clinical features and is not radiosensitive.

OTHER NAME(S): Louis-Bar syndrome
Boder-Sedgwick syndrome


TYPE: neurodegenerative disease, blood cell cancer, psychomotor impairment, skeletal abnormalities, risk of malignant disease, chromosomal instability, immunodeficiency, sexual immaturity, sensitivity to radiation, CANCER, eye or vision problem

Related patway(s): DNA damage response (DDR)

DNAtraffic protein(s) related to disease: ATM

OMIM: 208900

Last modification date: Aug. 17, 2011