SMAD3 and Loeys-Dietz syndrome: Mutations in SMAD3, have been identified in up to 2% of patients with familial thoracic aneurysms leading to acute aortic dissection (Regalado et al., 2011) Patients with the Loeys-Dietz syndrome have mutations in receptors for TGF-β (TGFBR1 and TGFBR2) (Loeys et al., 2006).