Transmission of MS to children: Study finds men transmit MS more often to their children than do women
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Medical Update Memo
September 6, 2006
Summary
A new study shows that, in a group of 441 children with a parent with multiple sclerosis, fathers with MS were more likely to pass on the disease to children than mothers with MS. Since women are twice as likely to develop MS as men, the researchers at the Mayo Clinic suggest men who develop MS may have more susceptibility genes than women to overcome this resistance.
Details
A new study shows that, in a group of 441 children with a parent with multiple sclerosis, fathers with MS were more likely to pass on the disease to children than mothers with MS. Orhun H. Kantarci, MD, Brian G. Weinshenker, MD (Mayo Clinic, Rochester, MN) and colleagues report their findings in the July 25 issue of Neurology (2006;67:305-310).
Although MS is not directly hereditary, a person who has a first-degree relative (such as a parent or sibling) with MS has a greater risk of developing MS than a person with no MS in the family. Researchers believe that MS occurs in individuals who have genes that make them susceptible to an unknown environmental trigger or triggers. In addition, women are twice as likely as men to develop MS. The reason for this difference is unknown. Dr. Kantarci’s group examined the possibility that if men are more resistant to MS, then those men who actually develop the disease must have more susceptibility genes in order to overcome that resistance. Therefore they might be expected to pass on a larger number or stronger susceptibility genes to their children. This phenomenon is known as the Carter effect, which has been observed in other diseases. This is the first time the Carter effect has been demonstrated in MS.
To investigate this idea, Dr. Kantarci’s team collected information on 3,598 people from multiplex families with MS (those with more than one person with the disease) from the MS DNA Bank at University of California at San Francisco, which is established and maintained with funding from the National MS Society. They studied 441 children who had a father or mother with MS, 45 of whom had definite MS. Fathers with MS transmitted the disease to 18 children, and did not transmit it to 99 children. Mothers with MS transmitted it to 27 children, and did not transmit it to 296 children. Therefore, in this study men were more than twice as likely to transmit MS to their children as women.
The Mayo Clinic researchers’ findings are supported by a previous Canadian study (Neurology, 1998:50) which found that people with MS who have affected fathers will have affected siblings more often than those with affected mothers. In that study headed by Drs. A. Dessa Sadovnick (University of British Columbia), Dr. George Ebers (University of Oxford) and with colleagues across Canada, 12.2 percent of people with MS who had a father with MS also had an affected sibling, while just 3.3 percent of people with MS who had a mother with MS had an affected sibling. The world’s largest study of genetic susceptibility is taking place in Canada and is supported by the MS Scientific Research Foundation, which is related to the Multiple Sclerosis Society of Canada.
In terms of genetic counselling, while the average person has about one chance in 750 of developing MS, the risk for a person who has a parent with MS increases to about one in 40. Thus, the risk increases significantly for a person whose parent has MS, but still remains relatively low.
[With information from the National MS Society (USA)]
ASK MS Information System Code: 2.6.2.y
National Research Department
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The Multiple Sclerosis Society of Canada is an independent,
voluntary health agency and does not approve, endorse or
recommend any specific product or therapy but provides
information to assist individuals in making their own decisions.
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