Germline variants in COL3A1 are associated with vascular Ehlers-Danlos and vessel aneurysms [12], while pathogenic variants in SMAD4 cause hereditary hemorrhagic telangiectasia (HHT), an autosomal dominant condition characterized by visceral arteriovenous malformation with intestinal, lung, and central nervous system localization. Here, SMAD4 is linked to hereditary hemorrhagic telangiectasia.