MS transmission more likely from affected fathers

A recent study shows that fathers with MS are more than twice as likely to transmit MS to their children as mothers, consistent with what's known as the Carter effect.The study compared transmission of MS from men with transmission from women in 441 children (45 with definite MS) of an affected mother or father in 197 families from 3,598 individuals in 206 multiplex families. Men were found to be 2.2 times more likely than women to transmit MS to their children (p = 0.036), independent of the sex of the offspring.The authors say that the apparent excess of MS susceptibility in women may be due to men requiring a greater number of risk factors to overcome their relative resistance to MS. They explain, "If this difference were due to genetic rather than environmental factors, men would need a greater number of or more potent susceptibility genes than women and would be predicted to transmit the disease more often to their children. This phenomenon is known as the Carter effect." The original description of the Carter effect was in pyloric stenosis, where a 2.2-fold excess of transmission from mothers has been shown, independent of the sex of the child."Another testable prediction of the Carter effect is that patients who have affected fathers will have affected siblings more often than those with affected mothers," the authors say. They note that a Canadian study supports this prediction, finding that 12.2% of patients who had a father with MS also had an affected sibling, whereas only 3.3% of patients who had a mother with MS had an affected sibling.The authors suggest that studies analysing linkage and family-based associations should separately analyse families with affected fathers, as they have a higher likelihood of transmitting MS to their children. Reference...