EDNRB and Waardenburg syndrome type 4A: Homozygous (and very rarely heterozygous) loss of function mutations in EDNRB have previously been associated with Waardenburg syndrome type 4A (WS4A) whereas heterozygous mutations have been described in association with isolated Hirschsprung disease, and suggestively with Waardenburg syndrome type 2 (WS2) (Issa et al., 2017).