Biallelic germline mutations of the ATM gene are associated with the autosomal recessive ataxia-telangiectasia syndrome, characterized by cerebellar degeneration, telangiectasia, immunodeficiency, cancer susceptibility, and radiation sensitivity (25). Carriers of monoallelic pathogenic germline mutations of the ATM gene have also been related with varied tumor predisposition, particularly lymphomas and leukemia (26,27). The gene discussed is ATM; the disease is Immunodeficiency.