SMAD4 and hereditary hemorrhagic telangiectasia: Although the majority of BAVMs arise sporadically, they also occur in patients with Hereditary Hemorrhagic Telangiectasia (HHT), a Mendelian disorder inherited in an autosomal dominant fashion and caused by mutations in one of three genes (ACVRL1, ENG and SMAD4) in the TGFβ signaling pathway [1], [2], [3], [4], [5].