ATM and Immunodeficiency: Ataxia telangiectasia (AT, MIM#208900), due to mutations in the ataxia telangiectasia mutated gene (ATM, MIM*600118), is an autosomal recessive disease characterized by progressive cerebellar ataxia, oculocutaneous telangiectasia and immunodeficiency, as well as elevated α-fetoprotein (AFP) serum levels, immunoglobulin deficiency and predisposition to cancers[1–4].