Ataxiatelangiectasia AT

AT is an autosomal recessive disorder characterized by:

♦ Development of telangiectasia (particularly on the bulbar conjunctiva).

♦ Progressive cerebellar ataxia.

♦ Premature ageing.

♦ Variable immunodeficiencies.

Patients develop cancer (usually lymphoma and leukaemia) at an early age and show a hypersensitive response to therapeutic treatment with ionising radiation.

The defective gene responsible, ATM (AT mutated), has been identified and cloned. It lies on chromosome 11q22.23, is approximately 150 kb in length and contains 66 exons. The gene encodes a 3056 amino acid protein with molecular weight of 350 kDa. The protein is thought to function in the detection of oxidative DNA damage and DNA damage signal transduction.

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