Objective：To study the clinical features, diagnosis and treatment outcome of aortic dissection in under 50 years old patients.

Methods： From March 2002 to February 2010, a total of 61 cases of aortic dissection were treated in our hospital. Among them, 23 patients were less than 50 years of age. Their clinical characteristics were analyzed and compared with 38 cases of aortic dissection in ≥50 years of age.
Results：Hypertension, hyperlipidemia and diabetes were  less present in younger-aged patients than in older-aged patients. But in younger aged group there were more patients with aortic rupture at time of admission. Also, more younger-aged patients required surgical reconstruction wiht right subclavian artery (RSA)- left subclavian artery(LSA)bypass, and more younger-aged patients had temporary ischemic complications of left upper extremity when LSA was not reconstructed. Mortality rate was higher in the young-aged patients than in older patients.
Conclusions：The etiology of aortic dissection in young-aged patients is complex. Arteriosclerosis is not the main cause of aortic dissection, while activated T cells and macrophages in the media of aorta may contribute to the elimination of smooth muscle cells and degradation of the matrix associated with aortic dissections. Aortic dissection in younger-aged patients progresses more rapidly and perioperational mortality is higher than in older patients. Etiological prevention, early diagnosis and timely therapy can improve the outcome of aortic dissection in younger-aged patients.