SMAD3 and aneurysm: AOS is a recently delineated autosomal dominant disorder characterized by aneurysms, dissections, and tortuosity throughout the arterial tree in association with early onset osteoarthritis, mild craniofacial features, and skeletal and cutaneous anomalies [2]. SMAD3 is the causative gene of AOS and may account for up to 2% of familial and nonfamilial thoracic aortic aneurysms and dissections (TAAD) [1].