MCM001:  Studies

Studies find gene linked to night leg movement: Scientific American

July 18, 2007

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July 18, 2007

Studies find gene linked to night leg movement

By Gene Emery

BOSTON (Reuters) - Two studies released on Wednesday offer
new evidence that inheritance plays a role in restless leg
syndrome, an uncomfortable and sometimes painful feeling in the
legs that can wreak havoc with sleep.

Researchers reporting in the journal Nature Genetics say
they have found three pieces of the human genetic code that are
linked to RLS, giving more scientific backing to a condition
sometimes derided as normal restlessness.

About 3 percent of the population is affected with RLS so
badly that they have trouble sleeping. About 10 percent
reportedly experience some degree of symptoms, which usually
appear when a person is in bed or sitting quietly and can
sometimes temporarily relieved by moving the legs or getting up
and walking.

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Julianne Winkelman of the Max Planck Institute of
Psychiatry in Munich, and her colleagues, said three genes seem
to account for up to 74 percent of the cases, based on studies
of people in Germany and Canada.

In a related study, published online by the New England
Journal of Medicine, a team led by Hreinn Stefansson of deCODE
Genetics Inc. in Reykjavik, Iceland, found that the periodic
leg movements that occur during the night in most patients with
RLS seems to be linked one of the three identified in the
Nature Genetics article.

Both research teams pinpointed the same gene independently.

The Stefansson team found from genetic testing of people in
Iceland and North America that the gene accounts for about half
of the cases of people whose legs move two or three times per
minute during sleep and complain of RLS.

"And that's a conservative estimate," said David Rye of
Emory University School of Medicine in Atlanta, who worked on
the Stefansson study.

However many doctors believe that most people who
experience periodic limb movements during sleep do not have
RLS. Growing older, antidepressant medicines and other sleep
disorders can cause the movements as well.

BIOLOGICAL BASIS

RLS has been the subject of skepticism from people who
regard it as little more than a modern-day diagnosis for old
fashioned "ants in the pants" restlessness. This attitude has
gained some popularity after the condition was heavily promoted
in "talk to your doctor" advertisements by GlaxoSmithKline,
which is marketing the Parkinson's disease drug Requip as an
RLS treatment.

"We now have concrete evidence that RLS is an authentic
disorder with recognizable features and an underlying
biological basis," said Rye.

He said the new finding was derived from genetic studies
from French Canadians, Germans, Central Europeans, Icelanders
and Americans. "So I don't think it's a frivolous result."

In a Journal commentary, Dr. John Winkelman of Brigham and
Women's Hospital in Boston said the gene may not be one for RLS
per se, but for its worst symptom -- the leg movements that
disturb sleep. Winkelman said the findings offer hope for a
durable treatment for the condition.

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