Type IV or Waardenburg-Shah syndrome is associated with mutations in either Sry BOXIO transcription factor (SOX10), at 22q13.1, Endothelin 3 (EDN3), at 20q13, or Endothelin Receptor Type B (EDNRB) on chromosome 13q22.321,22. The gene discussed is EDNRB; the disease is Waardenburg-Shah syndrome.