Scientists have linked certain genes to restless legs syndrome, suggesting that the twitching condition that was described as “jimmy legs” in an episode of “Seinfeld” is biologically based and not an imaginary disorder.
New studies published this week in two top medical journals are being called the first to identify specific genes responsible for the irritating symptoms of restless legs syndrome.
The New England Journal of Medicine published new research linking a common gene variation to nighttime leg-twitching. The study involved people in Iceland and the United States.
A second study in Nature Genetics also identified the same gene variation and two others in Germans and Canadians who suffered with restless legs syndrome.
“This discovery highlights the power of genetics, not only for uncovering the biological causes of disease, but also for defining diseases such as RLS and establishing them as medical conditions,” said Dr. Kari Stefansson.
What Is Restless Legs Syndrome?
Restless legs syndrome is a neurological condition that is characterized by an irresistible urge to move the legs. Sufferers say it often hits at night as they become tired, preventing them from sleeping.
“It feels just like something crawling inside your legs, biting on you,” said Betty Shaw, a 68-year-old florist in Covington, Ga., who was diagnosed with it. Her 43-year-old daughter has also been diagnosed with the condition.
The condition gained cultural status through an episode of the sitcom “Seinfeld,” in which the character Kramer is disturbed that his girlfriend has “the jimmy legs” and kicks in bed.
It is commonly treated with two government-approved drugs, including the heavily advertised Requip, made by GlaxoSmithKline PLC. Sales of Requip hit about $500 million last year. Shaw takes the aqua-colored pill and says it’s the only thing that’s helped to relieve her symptoms.
The initial study took blood samples from more than 1,000 Icelanders and Americans, comparing the DNA of leg twitchers to the DNA of people without the condition. Scientists found a certain variation in the human genome that, they say, most probably accounts for 50 percent of restless legs cases.
They also found that the variation was associated with lower iron levels, echoing results noted in earlier research.
The second study compared the DNA of 400 people who had a family history of the syndrome with the DNA of 1,600 who did not. It found variations in three areas of the genome that each were responsible for a 50 percent increase in the risk for the syndrome.
More research is needed to develop a full explanation of the causes of restless legs syndrome and how it might be better treated. The New England Journal study indicates as many as 65 percent of adults carry the gene variation that can lead to symptoms, said Dr. David Rye, an Emory University neurologist who was another co-author of the studies.
“People who make the argument that this can’t be very common – that’s just gone,” said Rye, who himself suffers from restless legs.
The syndrome is diagnosed through symptoms like periodic limb movements during sleep, but lots of people may have limb movements without having the condition, noted Dr. Steven Woloshin, a Dartmouth Medical School researcher who has argued the diagnosis is overhyped.
He argues that the best evidence puts the U.S. prevalence of restless legs at under 3 percent, less than common estimates of 10 percent.
The new research doesn’t pin down what the condition is, who has it, or what medication is needed, he also wrote in an e-mail.