The discovery of a defective gene that causes a common vascular aneurysm -- a balloonlike swelling in the aorta, the largest artery of the body -- was reported today by researchers at Thomas Jefferson University in Philadelphia.
"Our study proves for the first time there is a genetic cause for aortic aneurysms in people who do not have any other signs of a genetic disease," says Dr. Darwin J. Prockop, a physician who led the research team.
More than 15,000 Americans die annually from ruptured aortic aneurysms and it is estimated that about 2 million people are at risk for developing the disease.
"Our discovery means that we can identify people with anuerysms before they burst," said Prockop, who is also the director of the Jefferson Institute of Molecular Medicine. "Some of the people can be saved by surgery in which the defective part of the aorta is replaced by a synthetic aorta."
The findings are published in today's edition of the Journal of Clinical Investigation.
The scientists discovered the defective gene while studying the genetic makeup of Michele Hegler, 37, of Houston, a former Air Force captain who was in excellent health but had a strong family history of the disease.
Five relatives, including her mother and a cousin, 15, died suddenly from ruptured aortic aneurysms.
The discovery has led to the development of a saliva test, which has identified that Hegler's two children, her brother and half-aunt also carry the defective gene.
"I've always been concerned about my family's history of aneurysms because so many died," said Hegler. "I've often wondered if the same thing could happen to me. Now that I know, my family and I can take precautions."
In a study of cultured skin cells from Hegler, the researchers found an alteration in the gene responsible for collagen, a protein that provides the structural foundation for many body tissues, including blood vessels and skin.
While the long chain of amino acids making up Hegler's defective protein differs from the normal protein by only one amino acid, this single substitution is sufficient to weaken the strength of the protein, the scientists said.
The researchers linked this gene alteration or mutation to aortic aneurysms by studying small amounts of DNA found in microscopic slides and preserved tissue slices from Hegler's mother and aunt. Hegler's mother died of an aneurysm in 1960 and an aunt, who had several aneurysms, died in 1986.
These studies proved, according to the report, that Hegler's relatives also had the same mutated gene that is responsible for the weakened collagen.