The endothelin receptor B (EDNRB) is a non-specific receptor for endothelin 1, 2 and 3. EDNRB mediates its action by association with G-proteins that activate a phosphatidylinositol-calcium second messenger system. Defects in the endothelin receptor B are a cause of Waardenburg syndrome type 4A (WS4A), also known as Waardenburg-Shah syndrome. WS4A is characterized by the association of Waardenburg features (depigmentation and deafness) and the absence of enteric ganglia in the distal part of the intestine (Hirschprung disease).