FBN1 and Marfan syndrome: Previous studies have shown that more than 20% of individuals with thoracic aortic aneurysms and dissections have a family history of disease that may be caused by a genetic syndrome, resulting from a single-gene mutation such as Marfan syndrome (MFS [MIM:154700]) arising from a fibrillin-1 (FBN1 [MIM:134797]) mutation (Biddinger et al., 1997).