Germline inactivation of both copies of the ATM gene causes Ataxia-Telangiectasia (A–T), an autosomal recessive disorder characterized by progressive cerebellar degeneration, oculocutaneous telangiectasias, immunodeficiency, and susceptibility to cancer, mainly leukemias and lymphomas [2]. This evidence concerns the gene ATM and ataxia telangiectasia.