Multiple Sclerosis Gene Cluster Pinpointed

The most comprehensive genetic study to date of multiple sclerosis has pinpointed a cluster of genes on chromosome 6 as playing the major role in causing the disorder.

The findings will ultimately help doctors to develop better treatments for MS, researchers say.

Researcher Margaret Pericak-Vance, MD, director of the Center for Human Genetics at Duke University in Durham, N.C., says previous studies had already pointed to this area on chromosome 6 as playing a role in MS.

“What’s different here is that we now know that it is the major effect -- that is, no other genes have an effect as large on causing MS,” she tells WebMD.

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Having the Genes Doesn’t Equal MS

A person who harbors the genetic defect will not definitely develop MS, Pericak-Vance adds. “It does, however, make them more susceptible.”

As a result, she says she does not recommend people be tested for the genes.

Nearly 400,000 Americans have MS, according to the National Multiple Sclerosis Society.

Worldwide, up to 2.5 million may be affected by the chronic disease of the brain and spinal cord.

In healthy people, nerve fibers are wrapped in a protective coating called myelin. But MS inflames or destroys myelin, disrupting the flow of nerve impulses. That can prompt problems with muscle control and strength, vision, balance, sensation, and mental function.

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Genes and Environment Play Role in Causing MS

Pericak-Vance says no one knows exactly what causes MS, but it is thought to be a complex interaction of genetic and environmental factors.

The genes pinpointed on chromosome 6 are known as major histocompatibility complex genes.

“These are genes that play a critical role in helping the body to distinguish its own cells from outside invaders such as bacteria or other microbes,” Pericak-Vance says. “If the system breaks down, the immune system may attack your body’s own cells, as happens in MS.”

For the study, presented here at the annual meeting of the American Neurological Association, the researchers used the latest genetic techniques to analyze data on 730 families in which more than one family member was affected by the disorder.

The next step, Pericak-Vance says, will be to hone in on other genes that may play smaller roles in causing the disease.

Henry McFarland, MD, chief of the neuroimmunology branch at the National Institute of Neurological Disorders and Stroke in Bethesda, Md., says the findings are “significant.”

“Identifying these genes starts to give us new clues into the causes of MS as well as how to treat it,” he tells WebMD.

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By Charlene Laino, reviewed by Michael W. Smith, MD

SOURCES: American Neurological Association 130th Annual Meeting, San Diego, Sept. 25-28, 2005. Margaret Pericak-Vance, MD, director, Center for Human Genetics, Duke University. Durham, N.C. Henry McFarland, MD, chief, neuroimmunology branch, National Institutes of Neurological Disorders and Stroke, Bethesda, Md.