Jan. 27, 2005 -- Genetic differences between men and women could be the reason why multiple sclerosis strikes more women than men.
About 400,000 people in the U.S. say they 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, spinal cord, and optic nerve.
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.
MS is twice as common among women as it is in men. The reasons for the gap aren't known.
Genetics seemed like a possible influence to Brian Weinshenker, MD, and colleagues. Genes and environment are probably both involved in the development of MS, they write in the online edition of Genes & Immunity.
Weinshenker and his Mayo Clinic co-workers searched for clues about the MS gender gap. They also enlisted help from experts in Northern Ireland, Belgium, and Italy.
The international team studied the genes of MS patients in the U.S. They also looked at gene patterns in people from Northern Ireland and Belgium, some of whom had MS.
Women with MS were more likely to have a variation of a gene that produces high levels of a protein called interferon gamma. Interferon gamma can aggravate MS by promoting inflammation and tissue damage.
In the U.S. and Northern Ireland, men with the gene variation were more susceptible to MS. That was also true for Belgian men, but the effect wasn't significant there.
The gene variation was less common among men. "That might explain why men are generally protected more from MS," says Weinshenker in a news release. Similar findings were reported by Italian researchers.
"Our finding isn't the whole genetic cause, but it's a helpful step that could lead us to a more complete understanding of MS -- and ultimately, effective treatment. It's also a very promising lead about gender differences that may pertain to susceptibility of other diseases, too, such as rheumatoid arthritis."