Causes

Factors that can contribute to an aneurysm's development include:

• Hardening of the arteries (atherosclerosis). As plaque builds up on your artery walls, they become less flexible, and the additional pressure can cause them to weaken and bulge. High blood pressure and high cholesterol are risk factors for hardening of the arteries. This is more common in older people.

• Genetic conditions. Aortic aneurysms in younger people often have a genetic cause. People who are born with Marfan syndrome, a genetic condition that affects the connective tissue in the body, are particularly at risk of a thoracic aortic aneurysm because they may have weakness in the aortic wall.

  Marfan syndrome generally causes distinct physical traits, including tall stature, very long arms, a deformed breastbone and eye problems.

  Other family-related disorders can cause an aortic aneurysm, including vascular Ehlers-Danlos, Loeys-Dietz and Turner syndromes. Vascular Ehlers-Danlos syndrome causes your skin, joints and connective tissue to be fragile and makes your skin stretch easily.

• Other medical conditions. Inflammatory conditions, such as giant cell arteritis and Takayasu arteritis, are associated with thoracic aortic aneurysms.
• Problems with your heart's aortic valve. Sometimes people who have problems with the valve that blood flows through as it leaves the heart (aortic valve) have an increased risk of thoracic aortic aneurysm. This is mainly true for people who were born with an aortic valve that has only two flaps instead of three (bicuspid aortic valve).
• Untreated infection. Though rare, it's possible to develop a thoracic aortic aneurysm if you've had an untreated infection, such as syphilis or salmonella.
• Traumatic injury. Rarely, some people who are injured in falls or motor vehicle crashes develop thoracic aortic aneurysms.

Aortic emergencies

In aortic dissection, a tear occurs in the wall of the aorta. This causes bleeding into and along the aortic wall and, in some cases, completely outside the aorta (rupture).

An aortic dissection is a potential life-threatening emergency, depending on where in the aorta it occurs. It's important to treat an aortic aneurysm to try to prevent dissection. If dissection occurs, people can still be treated with surgery, but they will have a higher risk of complications.