Scientists have discovered a genetic defect that seems to predispose people to one type of aneurysm, a step that may help identify those prone to deadly artery ruptures, it was reported Thursday.

Researchers at Philadelphia's Thomas Jefferson University found a genetic defect that appears to cause aneurysms on a major artery in at least one family and devised a simple saliva test for the defect in that family."I think it's a very important discovery," said Dr. M. David Tilson, a professor of surgery at Columbia University in New York. "It's a milestone in the understanding of this problem."

Aneurysms are a weakening and ballooning of the side of an artery wall that can eventually burst. There are many kinds of aneurysms that occur in various parts of the body, including the brain, the chest and the abdomen.

Doctors had long suspected aneurysms ran in families, but the new research is the first direct evidence of a genetic link.

"It's the first definitive identification of a gene that's probably involved in aneurysm disease in a family," Tilson said.