Gene instability associated with malignancy is seen in

Ataxia-telangiectasia (AT or A-T), also referred to as ataxia-telangiectasia syndrome or Louis-Bar syndrome, is a rare, neurodegenerative, autosomal recessive disease causing severe disability. Ataxia refers to poor coordination and telangiectasia to small dilated blood vessels, both of which are hallmarks of the disease. A-T affects many pas of the body: It impairs ceain areas of the brain including the cerebellum, causing difficulty with movement and coordination. It weakens the immune system, causing a predisposition to infection. It prevents repair of broken DNA, increasing the risk of cancer.A-T is caused by a defect in the ATM gene, which is responsible for managing the cell's response to multiple forms of stress including double-strand breaks in DNA. In simple terms, the protein produced by the ATM gene recognizes that there is a break in DNA, recruits other proteins to fix the break, and stops the cell from making new DNA until the repair is complete.