An aortic aneurysm is a balloon-like bulge in the aorta, the large artery that carries blood from the heart through the chest and torso.
What could be the possible causes of aneurism?
Source: http://www.nhlbi.nih.gov/health/health-topics/topics/arm/types - Public Domain
In order for an aneurysm to occur, conditions must be present that cause degradation or abnormal development of the structural components of the blood vessel wall.
We can list out common causes into those two categories:
The usual suspects.
These factors all contribute to inflammation, oxidative stress, and biomechanical wall stress in blood vessels like the aorta. This damage to the structural integrity of the aortic wall can lead to an aneurysm.
These factors can lead to a weakened and vulnerable aortic wall:
Other causes can include infections or chest trauma.
Primary source: Harrison's Principles of Internal Medicine; 19th Ed. (pp 1637-1638)