Several susceptibility genes have been identified for HSCR, namely the RET proto-oncogene [6]–[8], endothelin receptor B gene (EDNRB) [9]–[16], endothelin-3 gene (EDN3) [17], [18], GDNF gene [19]–[21], and SOX10 gene [22], [23], which play important roles in the formation of the enteric nervous system (ENS). The gene discussed is EDNRB; the disease is Hirschsprung disease.