familial thoracic aortic aneurysm familial thoracic aortic aneurysm familial thoracic aortic aneurysm is an autosomal dominant disorder of large arteries. familial thoracic aortic aneurysmother namesfamilial aortic dissection, cystic medial necrosis of aortamicrograph showing cystic medial degeneration, the histologic correlate of familial thoracic aortic aneurysms. the image shows abundant basophilic ground substance in the tunica media (blue at top of image) and disruption of the elastic fibers. the tunica adventitia (yellow at bottom of image) with vaso vasorum is also seen. movat's stain. there is an association between familial thoracic aortic aneurysm and marfan syndrome as well as other hereditary connective tissue disorders. signs and symptoms 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. genetics types include: type omim gene locus aat1 607086 11q23.3-q24 aat4 132900 myh11 16p aat6 611788 acta2 10q diagnosis terminology it is sometimes called "erdheim cystic medial necrosis of aorta", after jakob erdheim. the term "cystic medial degeneration" is sometimes used instead of "cystic medial necrosis", because necrosis is not always found.