[Pathology of aortic dissection].

Aortic dissection is not a popular disease but it should be listed in the disease to be excluded especially in acute emergent cases, because of its serious and protean clinical manifestations. While DeBakey classification was used over 30 years. Stanford classification is now widely accepted for its clinical availabilities. The features of the aortic dissection are 1) presence of the intimal tear at the proximal end in almost all cases, 2) its frequent location in the ascending aorta and aortic segment just distal to the left subclavian artery, and 3) the dissected plane at the outer media or medial-adventitial border. Systemic hypertension is frequently noticed in cases with aortic dissection. These features suggest hemodynamic effect as a pathogenic factor in addition to mural fragility of the aorta. Aortic dissection is frequently encountered in Marfan syndrome and other heritable diseases of connective tissue. Concerning Marfan syndrome, mutation of fibrillin gene was confirmed. Fibrillin is a microfibril consisting of glycoprotein closely bound to elastin. Therefore, traditional "cystic medial necrosis" which was referred as a principal morphological change corresponding to aortic dissection is now thought to be a secondary change to the aortic injuries occurred in the aortic wall.