Abraham Lincoln's appearance and historical documents that note his especially clumsy gait have long caused researchers to puzzle over whether he may have had a genetic disorder called Marfan syndrome. Now, members of the president's family tree are wondering if Lincoln had a different, incurable hereditary disease called ataxia that affects the coordination it takes to walk, write, speak and swallow.

Researchers at the University of Minnesota have discovered a gene mutation in 11 generations of relatives who descended from Lincoln's grandparents. There's a 25 percent chance that Lincoln also inherited the gene, said Laura Ranum, a genetics professor who led the research.

"Because the historical literature talks about his clumsy gait ... it raises the possibility that that was caused by a mutation in this gene," Ranum said.

But since Lincoln has no living direct descendants, confirming whether the nation's 16th president had the defective gene would require that his DNA be taken from historical artifacts and tested _ an issue that has been debated over the years.

"What historical purpose would it serve? It (wouldn't) change the facts of how he became a great president," said Kim Bauer, Lincoln curator at the Abraham Lincoln Presidential Library and Museum in Springfield, Ill. "I would fall on the side of leaving President Lincoln alone."

The new findings on the ataxia gene were reported this week in the online edition of the journal Nature Genetics. Since 1992, the Minnesota researchers have studied more than 300 members of the Lincoln family. About one-third of them have ataxia.

Terry Smith and Laurie Crary _ both ataxia sufferers and descendants of Abraham Lincoln's uncle Josiah Lincoln _ said they would like to know if the president had their disease.

"If a president had it, and he was disabled but still running the country, maybe people would lighten up on disabled people a little bit," said Smith, 57, of Manteca, Calif., who said he was once arrested for drunken driving because of the disease's symptoms.