Almost one-quarter of patients presenting with thoracic aortic aneurysms (TAAs) or acute aortic dissections (TAADs) have an underlying mutation in a specific gene. A subset of these patients will have systemic syndromic features, for example, skeletal features in patients with Marfan Syndrome. It is important to note that the majority of patients with thoracic aortic disease will not have these syndromic features but many will have a family history of the disease. The genes predisposing to these thoracic aortic diseases are inherited in an autosomal dominant manner, and thirteen genes have been identified to date. As the clinical phenotype associated with each specific gene is defined, the data indicate that the underlying gene dictates associated syndromic features. More importantly, the underlying gene also dictates the aortic disease presentation, the risk for dissection at a given range of aortic diameters, the risk for additional vascular diseases and what specific vascular diseases occur associated with the gene. These results lead to the recommendation that the medical and surgical management of these patients be dictated by the underlying gene, and for patients with mutations in ACTA2, the specific mutation in the gene.