Varying degrees of antibody deficiency have also been noted in chromosomal instability syndromes such as ataxia-telangiectasia (A-T, ATM mutations), Nijmegen breakage syndrome (NBS, NBS1 mutations), and ataxia-telangiectasia-like disorder (ATLD, MRE11 mutations) [24]–[30]. The gene discussed is ATM; the disease is ataxia-telangiectasia-like disorder.