http://www-gene.cimr.cam.ac.uk/MSgenetics/newsletter.shtmlTwins are important for research because they can be used in a variety of comparative ways: they have usually shared the same environment and been exposed to the same viruses and infections in childhood. In general if it were the case that identical twins are both affected with a disease (100%), this indicates a large genetic component; if however, only one is affected, then correspondingly the genetic component must be small. In our study of MS only 25% of identical twin pairs were both found to be affected.
We also looked at non-identical twins and found in 97% of pairs that the co-twin was not affected.
This and other similar studies demonstrate a genetic contribution to MS, but it is by no means the whole story. We think that having a particular combination of several genes means some people are more susceptible to getting MS; however, other trigger factors have to be encountered over a number of years before the symptoms develop and this is where the importance of enviromental factors including viral infections come into the story.
Which tells us what? Just that nearly all the people in that study were between 10 and 58. From wich we can conclude what? Perhaps not much more than people are middle-aged at 34!Age at diagnosis, mean ± SD (years), 31 ± 11, 34 ± 12
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