Genes involved in the TGF-β signaling pathway related to aneurysm formation include TGFBR1 (LDS1), TGFBR2 (LDS2), SMAD3 (LDS3), TGFB2 (LDS4), TGFB3 (LDS5), SMAD2 (LDS6), SMAD4 (juvenile polyposis/hereditary hemorrhagic telangiectasia), SMAD6 (bicuspid aortic valve/thoracic aortic aneurysm) and SKI (Shprintzen-Goldberg syndrome) [4–14]. The gene discussed is SMAD2; the disease is juvenile polyposis/hereditary hemorrhagic telangiectasia syndrome.