Aortic size index (ASI) has been proposed as a reliable criterion to predict risk for aortic dissection in Turner syndrome with significant thresholds of 20-25 mm/m(2). We report a case of aortic arch dissection in a patient with Turner syndrome who, from the ASI thresholds proposed, was deemed to be at low risk of aortic dissection or rupture and was not eligible for prophylactic surgery. This case report strongly supports careful monitoring and surgical evaluation even when the ASI is < 20 mm/m(2) if other significant risk factors are present.

Aortic disease is a significant cause of death in developed countries. The most common forms of aortic disease are aneurysm, dissection, atherosclerotic occlusion and ageing-induced stiffening. The microstructure of the aortic tissue has been studied with great interest, because alteration of the quantity and/or architecture of the connective fibres (elastin and collagen) within the aortic wall, which directly imparts elasticity and strength, can lead to the mechanical and functional changes associated with these conditions. This review article summarizes the state of the art with respect to characterization of connective fibre microstructure in the wall of the human aorta in ageing and disease, with emphasis on the ascending thoracic aorta and abdominal aorta where the most common forms of aortic disease tend to occur.