 Cardiovascular malformations (typically bicuspid aortic valve, coarctation of the aorta, and some other left-sided cardiac malformations) and hypertension predispose to aortic dilatation and dissection in the general population.Indeed, these same risk factors are found in more than 90% of patients with Turner syndrome who develop aortic dilatation.Only a small number of patients (around 10%) have no apparent predisposing risk factors.