Germline variants of homologous recombination deficiency (HRD) genes, such as BRCA1, BRCA2, ATM, BARD1, BRIP1, CHEK2, NBS1, PALB2, RAD51C, and RAD51D, led to inherited susceptibility to specific types of cancer including breast cancer. The gene discussed is ATM; the disease is breast carcinoma.