WASHINGTON, June 27 (Reuters) - Mothers and fathers with multiple sclerosis are equally likely to pass genetic risk for it on to their children, according to a study countering a previous finding that fathers were twice as likely to do so.
Writing on Wednesday in the journal Neurology, researchers said they looked at 3,088 Canadian families with one parent with the disease.
They found that 9.41 percent of children of fathers with MS got the disease, compared to the nearly identical figure of 9.76 percent of children of mothers with MS.
"We found that it's absolutely bang-on random," Dr. George Ebers of Britain's University of Oxford said in a telephone interview.
"That is to say that the offspring risk from the female side is no different than the offspring risk from the male side," when a parent has MS.
MS is an incurable and sometimes disabling disease of the central nervous system in which communication between the brain and other parts of the body is disrupted. It is thought to be an autoimmune disease in which the body mistakenly attacks its own tissues.
The exact cause of MS is unknown, but experts believe genetic and environmental factors are at play. Ebers said the new findings do not support the notion that a whole bunch of genes determine MS susceptibility.
Of the 8,401 children in these families, 798 had MS. The study also found that genetic risk was no more likely to be transmitted to daughters or sons from a parent with MS.
PATERNAL TRANSMISSION
The findings run counter to a smaller study published in July 2006 in the same journal led by Mayo Clinic researchers. That study, which looked at 444 U.S. children of a parent with MS, concluded that fathers with the disease transmitted it to their children 2.2 times more often than mothers.
MS is far more common in women than men. These researchers hypothesized that because men are more resistant to MS, they need stronger or a larger number of genes in order to develop it, and then pass those genes to their children.
Mayo Clinic neurologist Dr. Orhun Kantarci, who led last year's study, said of the new findings: "This is a very important study involving a much larger sample of patients than previous studies and, therefore, the results are valid."
But Kantarci added that he did not think the new study necessarily negated the earlier finding that fathers were more likely to pass on MS to children than mothers, saying the differing results may be because the two studies examined different populations.
"This is just one of those studies, as is the case with our study, that adds to the pool of interesting results in this field," Kantarci said, adding that more research was needed to clarify parental genetic transmission of MS risk.
Multiple sclerosis can be mild in some people while causing permanent disability in others. Symptoms may include numbness or weakness in the limbs, partial or complete loss of vision, tingling or pain, electric-shock sensations with certain head movements, tremors and an unsteady gait.
About 2.5 million people worldwide, including about 400,000 Americans, have MS, according to the National Multiple Sclerosis Society.
