EDNRB and Waardenburg-Shah syndrome: Three causative genes have been identified for WS4, WS 4A, and WS 4B, including mutation of EDNRB and EDN3, respectively, while WS 4C is caused by heterogeneous mutation in the SOX10 gene, which plays a major role in the development and migration of neural crest cells [25, 36, 37].