Protein-truncating mutations in ataxia telangiectasia mutated (ATM), breast cancer type 1 susceptibility protein (BRCA1)-interacting protein 1 (BRIP1) and partner and localizer of the breast cancer 2 early onset protein (BRCA2) (PALB2), as well as CHK2 checkpoint homolog (CHEK2), have been observed to be nearly 10 times more likely in patients with strong breast cancer family histories than in unaffected controls [2-4]. The gene discussed is ATM; the disease is breast carcinoma.