ACVRL1 and hereditary hemorrhagic telangiectasia: AVM is also a component of several hereditary disorders, like hereditary hemorrhagic telangiectasia (HHT, also known as Osler–Weber–Rendu disease), Wyburn–Mason syndrome, and Sturge–Weber syndrome characterized by mutations of endoglin (ENG) or Alk1 (ACVRL1) [7, 8].