ATM and immunodeficiency disease: Mutationsin ATM are responsible for a rare autosomal recessive disorder known as ataxia-telangiectasia (A-T) [115].It is exemplified by immunodeficiency, susceptibility to ionizing radiation, neuro-degeneration and an increased likelihood of BC.Individuals with BC who received radiation treatment and possessed mutated ATM experienced secondary malignancies earlier than those whodid not undergo radiation therapy and did not have mutated ATM [116, 117].CHEK2 encodes protein checkpoint kinase 2, which is a regulator of DNA repair that maintains genomic stability.