Familial thoracic aortic aneurysm is an autosomal dominant^[1] disorder of large arteries.

There is an association between familial thoracic aortic aneurysm and Marfan syndrome as well as other hereditary connective tissue disorders.

A degenerative breakdown of collagen, elastin, and smooth muscle caused by aging contributes to weakening of the wall of the artery.^[2]

In the aorta, this can result in the formation of a fusiform aneurysm. There is also increased risk of aortic dissection.^{[citation needed]}

Types include:

It is sometimes called "Erdheim cystic medial necrosis of aorta", after Jakob Erdheim.^[3][4]

The term "cystic medial degeneration" is sometimes used instead of "cystic medial necrosis", because necrosis is not always found.^{[citation needed]}