Study reveals common gene variant associated with aortic dissection

Posted on Friday, February 24th, 2012

Richard Holbrooke, John Ritter, Lucille Ball, and Great Britain’s King George II were all taken by the same silent killer: an acute aortic dissection.

Now, scientists led by researchers at The University of Texas Medical School, associated with UT Physicians, and Baylor College of Medicine have found an association with a common genetic variant in the population that predisposes people to acute dissections and can approximately double a person’s chances of having the disease.

An aortic aneurysm is an enlargement or ballooning of the aorta in the segment where it comes out of the heart (thoracic aortic aneurysm). The natural history of a thoracic aortic aneurysm is to enlarge without symptoms over time, leading to instability of the aorta and ultimately an acute aortic dissection. The dissection is a tear in the aorta that allows blood to flow within its layers. It is a life-threatening event, with up to 40 percent of patients dying suddenly.

Although the average age of a person who suffers an aortic dissection is early 60s, the disease can strike at any age. Since the majority of individuals have an aortic aneurysm prior to dissection, identification of these aneurysms is critical since the aneurysm can be surgically repaired to prevent the aortic dissection, which typically occurs when the diameter of the aneurysm reaches twice that of the normal aorta. Therefore it is important to know who is at risk for this disorder.

The results of the research were published in the Sept. 11, 2011, advance online issue of Nature Genetics. Senior author is Dianna Milewicz, M.D., Ph.D., UT Physicians cardiologist and holder of the the President George H.W. Bush Chair in Cardiovascular Research.

“This is the first time we’ve found an association with a common genetic variant in the population that predisposes people to thoracic aortic aneurysms that cause acute aortic dissections. This variant in the DNA is on chromosome 15 (15q21.1) and involves a gene called FBN1. We already know that mutations in this gene cause Marfan syndrome, which is a genetic syndrome that strongly predisposes individuals to aortic dissections but also causes people to grow tall and have weak eyes,” said Dr. Milewicz, who is also director of the Division of Medical Genetics and heads the John Ritter Research Program in Aortic and Vascular Diseases. “Although patients with aortic dissection in our study did not have Marfan syndrome, this study suggests that the same pathways are involved in causing aortic dissections in patients with and without Marfan syndrome.”

Dr. Milewicz said the research has implications for using drugs to treat patients to prevent aortic aneurysms from even forming, such as losartan, which is now being tested in clinical trials for people with Marfan syndrome. “Whether they have Marfan or the common variant in FBN1, it may be the same pathway and we may be able to treat these patients the same way. That means that what we learn in treating patients with Marfan syndrome has implications for this larger group of individuals with thoracic aortic disease,” she said.

The study examined more than 1,300 patients who had sporadic thoracic aortic disease, meaning they did not have a known family genetic history or genetic syndrome associated with the disease. The patients came from the Memorial Hermann Heart & Vascular Institute, the Texas Heart Institute, and Harvard Medical School, as well as from the National Institutes of Health GenTAC program, which includes the Perelman School of Medicine at the University of Pennsylvania, Johns Hopkins University School of Medicine, Weill Cornell Medical College of Cornell University, and Oregon Health and Science University.

The discovery was made possible by a grant from the NIH that funded the Specialized Center for Clinically Oriented Research in Aortic Diseases, a multi-institutional collaboration in the Texas Medical Center. The title of the article is “Genome-wide association study identifies a susceptibility locus for thoracic aortic aneurysms and aortic dissections spanning FBN1 at 15q21.1.”

— Deborah Mann Lake, Office of Advancement, Media Relations

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