SMAD4 and hereditary hemorrhagic telangiectasia: Although many mutated genes in HHT encode components of the TGF-β signaling pathway (e. g., ENG, ALK1, SMAD4, and GDF2), a recent study identified other genes (INHA, HIFA, DNM2, POSTN, and ANGPTL4) as potential drivers of HHT [44].