NKX2-5 and thanatophoric dysplasia: Furthermore, given the lack of clear evidence of pathogenicity of the reported NKX2-5 mutations, the high amounts of patients with TD without an NKX2-5 mutation and the absence of TD in NKX2-5 mutation carriers, we suggest that NKX2-5 mutations do not play a major pathogenic role in thyroid dysgenesis and that genetic testing for NKX2-5 in TD is not warranted.