ATR and microcephalic primordial dwarfism: These disorders include ataxia-telangiectasia (A-T, mutation in the ATM gene encoding ataxia-telangiectasia mutated) [18], ataxia-telangiectasia-like disorder (A-TLD, mutation in meiotic recombinant 11 homolog; MRE11) [19], Seckel syndrome (mutation in ataxia telangiectasia and Rad3 related; ATR) [20], and Nijmegen breakage syndrome (NBS, mutation in nibrin NBS1) [21].