Characterized by subcutaneous telangiectasias and AVMs in various organs, HHT is primarily caused by mutations in TGF-β/BMP signaling pathway genes, including ENG (HHT1), ACVRL1 (ALK1; HHT2), SMAD4 (juvenile polyposis and HHT syndrome), and GDF2 (HHT5). Here, ACVRL1 is linked to hereditary hemorrhagic telangiectasia.