Genetic syndromes are genetic diseases that affect more than one system, and some of these syndromes increase the risk for thoracic aortic aneurysm and dissection. Disorders that confer this increased risk for TAAD include: Marfan syndrome, Loeys-Dietz syndrome, Ehlers-Danlos syndrome- vascular type, and Turner syndrome. To learn more about these genetic conditions, please visit the following:
Marfan syndrome: National Marfan Foundation
Loeys-Dietz syndrome: Loeys-Dietz Syndrome Foundation
Ehlers-Danlos syndrome, vascular type: Ehlers-Danlos National Foundation
Turner syndrome: Turner Syndrome Society of the United States
Familial Thoracic Aortic Aneurysm and/or Dissection (FTAAD)
Thoracic aortic aneurysm and/or dissection (abbreviated TAAD) can “run in families” even when no genetic syndrome like Marfan syndrome is present in affected family members. In these families, multiple people develop TAAD due to an underlying genetic change or mutation. These families have Familial Thoracic Aortic Aneurysm and/or Dissection (FTAAD). In families with FTAAD:
- Both men and women can be affected
- The genetic predisposition is typically passed from generation to generation in what is termed an autosomal dominant pattern of inheritance.
- Children of an parent with FTAAD have up to a 50% chance to develop a thoracic aneurysm and/or dissection or other vascular disease
- FTAAD is only a genetic predisposition, or tendency, to develop a TAAD, not a genetic certainty. A subset of people who inherit the genetic change may NOT develop an aneurysm or dissection (termed decreased penetrance of the disease).
- In a family there can be a wide range of age of onset of the thoracic aortic disease.
- Sometimes there are other heart or artery features that can be inherited with the thoracic aortic disease, such as a bicuspid aortic valve.
Unlike syndromes such as Marfan syndrome, there typically are no outward features to suggest that people with FTAAD have inherited a predisposition for thoracic aortic disease. Generally, the only disease manifestation is the aortic disease, which is often asymptomatic until there is an aortic rupture or dissection. This is why family history and aortic imaging are so important to help identify people who are at risk for aortic disease.
There are five genes that are known to cause FTAAD: ACTA2, responsible for 10-15% of FTAAD, MYH11 (1%), FBN1 (rare), TGFBR1 (1%), and TGFBR2 (2.5%). Mutations in any one of these genes cause a predisposition to develop TAAD to be inherited in a family.
Note: Changes in these five genes only explain the family history of FTAAD in one-fifth, or 20%, of families affected with FTAAD. We cannot identify the underlying genetic cause of FTAAD in 80% of families. We need to continue ongoing research to find more genes and provide information to these families.
Clinical genetic testing of these genes is available through a clinical DNA diagnostic lab. It is important that genetic testing be done with the guidance of a genetics professional (clinical geneticist or genetic counselor) so that families understand what the results mean (either positive or negative) for a change or mutation in one of these genes. To find a local genetics provider in your area, visit the National Society of Genetic Counselors.