The two common genes implicated in HHT are the endoglin gene (ENG or HHT1) and the activin A receptor type II-like 1 gene (ALK-1 or HHT2), both encoding endothelial cell surface proteins of the TGF-β/BMP-9 signaling pathway [[8]–[10]]. This evidence concerns the gene ENG and hereditary hemorrhagic telangiectasia.