Aortic Aneurysm-Cause Abdominal and thoracic aortic aneurysms have a number of causes, including:

• Hardening of the arteries (atherosclerosis). Exactly how atherosclerosis leads to abdominal aortic aneurysms is unclear. It is thought that atherosclerosis causes changes in the lining of the artery wall that may affect oxygen and nutrient flow to the aortic wall tissues. The resulting tissue damage and breakdown may lead to the development of an aneurysm.
• Genetics. In some people who have Marfan's syndrome, Ehlers-Danlos syndrome, or other inherited conditions, the walls of the major arteries, including the aorta, are weakened. Aortic aneurysms run in families.
• Aging. The aorta naturally becomes less elastic and stiffer with age, increasing the risk for an abdominal aortic aneurysm.
• Infections. Infections such as syphilis and endocarditis, an infection of the lining of the heart, can cause aneurysms.
• Injury. A sudden, intense blow to the chest or abdomen, such as hitting the steering wheel in a car accident, can damage the aorta.
• Inflammation.Inflammation of the aorta can weaken the aortic wall. What causes the aorta to become inflamed is not clear.

Thoracic aortic aneurysms are much less common than abdominal aortic aneurysms. They are often caused by an abnormal breakdown of the elastic fibers in the aortic wall.

A pseudoaneurysm happens when a bulge occurs in the wall of the aorta. But the bulge doesn't affect all three layers of tissue in the wall of the aorta. This type of aneurysm might be caused by an injury.

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