“…Autosomal dominant forms are caused by mutations in the heterozygous state in EDN3, EDNRB, or SOX10 [Pingault et al, 1998[Pingault et al, , 2001[Pingault et al, , 2002Southard-Smith et al, 1999;Syrris et al, 1999;Sham et al, 2001;Mor ın et al, 2008]. Mutations affecting SOX10 result in a great phenotypic variability, including not only the canonical WS4, but ranging from the more severe PCWH phenotype (Peripheral demyelinating neuropathy, Central dysmyelinating leukodystrophy, and Waardenburg-Hirschsprung features, OMIM 609136) [Inoue et al, 1999[Inoue et al, , 2002[Inoue et al, , 2004Pingault et al, 2000;Touraine et al, 2000;Verheij et al, 2006] to milder forms with only pigmentary abnormalities and sensorineural hearing impairment, but no Hirschsprung disease [Bondurand et al, 1999[Bondurand et al, , 2007Iso et al, 2008]. Here we report on two Spanish cases of WS4, with novel mutations in the EDN3 and SOX10 genes, respectively, further illustrating the genetic and phenotypic heterogeneity of this syndrome.…”