Aortic aneurysm/dissection is a common cause of cardiovascular morbidity and mortality in the Western world. In general, two forms have been recognised: abdominal aortic aneurysm/dissection (AAAD) and thoracic aortic aneurysm/dissection (TAAD). Although some genetic predisposition for abdominal aneurysm has been recognised, major risk factors include male sex, age, smoking, hypercholesterolaemia and hypertension. Variants in several genes, including DAB2IP, LRP1, CDKN2B-AS1, CNTN3, LPA and IL6R, and the sortilin-1 (SORT1) locus1–10 have been associated with AAA. In contrast to abdominal aneurysms, TAA can occur at young age without significant cardiovascular risk factors. These aneurysms have a strong monogenic contribution. A positive family history for TAA is identified in about one out of five patients. Over the last two decades, several genes causing TAA have been identified.11 These genetic forms of TAA can be grouped into syndromic and non-syndromic forms. Within the syndromic forms, Marfan syndrome, which is characterised by aortic root dilatation among other symptoms, has served for a long time as the paradigm for the study of the pathogenesis of TAA. Through the study of Marfan mouse models, Marfan syndrome has evolved from a disease thought to be the consequence of a pure structural failure of the microfibrils due to a deficiency of fibrillin-1 to a disease in which dysregulation of the transforming growth factor (TGF)-β signalling pathway plays a critical role.12 The key role of this pathway has been further supported by the identification of the molecular basis of Marfan-related disorders: Loeys–Dietz syndrome (caused by mutations in TGFBR1, TGFBR2, …