Marfan's syndrome: structural, biochemical, and mechanical studies of the aortic media.

An intrinsic defect in the aortic media in six patients with Marfan's syndrome, who died of cardiovascular complications of the disease at an average age of 32 years, has been delineated by correlated morphologic, biochemical, and mechanical studies. The findings in the Marfan aortas have been compared with those in age- and sex-matched controls, who died of unrelated diseases without significant aortic lesions, and in three patients with dissecting aneurysms of non-Marfan origin. The results showed that there was a significant reduction in the tensile strength of the aorta in Marfan's syndrome. This finding was correlated by scanning electron microscopy with structural alterations of the medial elastic fibers, including enlarged interlaminar spaces and loss of interlaminar elastic fibrils. No structural alterations were identified in collagen fibers. Biochemical analyses of the aortic media revealed a substantial reduction in aortic elastin content. Furthermore, the desmosine content of the isolated elastin was reduced by approximately 50%. No changes were detected in the composition or solubility of the medial collagen. In contrast to Marfan aortas, the elastin and collagen contents of the dissecting aneurysms of non-Marfan origin were similar to those of the controls. These findings suggest that the vascular complications in Marfan's syndrome may be based on a genetic abnormality affecting elastin fibrillogenesis.