The endogolin (ENG)g (*131195), activin A receptor type 1 (AVCRL1) (*601284), SMAD4 (SMAD family member 4) (*600993), and growth differentiation factor 2 (GDF2) (*605120) genes have been identified as the underlying cause of hereditary hemorrhagic telangiectasia (4). Here, SMAD4 is linked to hereditary hemorrhagic telangiectasia.