Cancer susceptibility in ataxia-telangiectasia

Ataxia-telanglectasia (A-T) is a syndrome that has an extremely high incidence of cancer. Patients with the disease are homozygous for a mutant gene, the A-T gene, located at 11q23. Of these individuals, 30-40% develop cancer. Of thede cancers, 80% are lymphoid. Those heterozygous for the A-T gene also have an increased frequency of cancer, the most notable being the 6.8-fold increase of breast cancer in females carriers. The syndrome is characterized cytogenetically by increased non-random chromosome breaks and rearrangements in lymphocytes involving the sites of the immunoglobulin and T-cell receptor genes