Texas Researchers Identify New Genomic Site Associated With Fatal Cardiac Disorder
Researchers have mapped a new location for the genetic mutation that causes familial thoracic aortic aneurysm and dissection, or TAAD.
The finding was published in last week’s issue of Circulation: Journal of the American Heart Association.
TAAD, in which the aorta enlarges until it eventually bursts, is found in some people with the inherited single-gene disorder Marfan syndrome. It is also linked to Turner syndrome, which results from a missing X chromosome. TAAD can also run in families independently of the two syndromes. “Because it is difficult to diagnose, victims often die young,” according to researchers at University of Texas Medical School at Houston, where the mutation was discovered.
Today, people with TAAD are unaware of the risk they face because the slowly enlarging aorta does not cause any symptoms until it has reached a critical diameter, according to lead researcher Dianna Milewicz, professor and vice chair in the department of internal medicine at the University of Texas. At that point, Milewicz said, the aorta dissects or ruptures, both events being life-threatening. The patient develops chest pain and usually goes to an emergency department to seek treatment.
“Usually emergency room physicians will run a series of tests designed to detect heart attack and those tests will be negative,” she said in a statement. “So the patient frequently is sent home with a diagnosis of heart burn or anxiety. If these patients are sent back out, they will die.”
Milewicz and colleagues had already identified two chromosome sites linked to TAAD: 5q13-15, known as TAAD1, and 11q23.2-q24, called FAA1. However, some families known to have the disease could not be linked to these sites, Milewicz said.
In her study, Milewicz examined four generations of one family of Swiss-German heritage that had a history of TAAD unlinked to the previously identified chromosome locations. The team collected and analyzed DNA samples from 52 family members and identified a new location for familial TAAD at 3p24-25 and named it TAAD2.
Other TAAD families “don’t have the link to any of these three chromosome locations, so there is at least one more unmapped location for familial TAAD,” she said.
As Milewicz and her team continue looking for other sites, they are also hunting the exact mutant gene. If found, the mutation may help researchers develop tests to identify people at risk for familial TAAD.