WS, type 4C (WS4C, OMIM#613266) is caused by heterozygous mutation in the SOX10 gene, whereas WS, type 4A (WS4A, OMIM#277580) and WS, type 4B (WS4B, OMIM#613265) are caused by mutation of EDNRB and EDN3, respectively. This evidence concerns the gene SOX10 and Werner syndrome.