Familial thoracic aortic aneurysm is an autosomal dominant disorder of large arteries. Familial thoracic aortic aneurysm is an autosomal dominant 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. In the aorta, this can result in the formation of a fusiform aneurysm. There is also increased risk of aortic dissection.