SOX9 and Hirschsprung disease: The genes responsible for neurocristopathies have been identified in the cases of several clinical abnormalities, as follows: tfap2a (Branchio‐oculo‐facial syndrome), zic2a1 (holoprosencephaly), pax3, sox10, and snail2 (Waardenburg syndrome and Hirschsprung's disease), and sox9 (Pierre Robin sequence).74, 75, 80, 81, 83, 105