Cystic medial necrosis and internal carotid artery dissection in a marfan sibling: Partial expression of marfan syndrome.

Only rare cases of primary extra-aortic cystic medial necrosis and cervicocephalic arterial dissections have been reported in Marfan syndrome. We report an apparently traumatic dissection of the internal carotid artery in a woman whose brother had classic Marfan syndrome. The patient herself had no apparent manifestations of the syndrome, but she had cystic medial necrosis and significant loss of elastic fibers of the media. In Marfan syndrome, the penetrance of the gene can be quite variable, such that some members of the same family may show the full syndrome, whereas others reveal only the rudiments of the syndrome or, perhaps as exemplified by the case reported here, only manifest microscopic arterial abnormalities.