Size and ascertainment constraints often limit twin studies to concordance comparisons between identical and fraternal twins. Here we report the final results of a longitudinal, population-based study of twins with multiple sclerosis (MS) in Canada. Bias was demonstrably minimized, and an estimated 75% of all Canadian MS twin pairs were ascertained, giving a sample sufficiently large (n = 370) to permit additional informative comparisons. Twinning was not found to affect prevalence, and twins with MS did not differ from nontwins for DR15 allele frequency nor for MS risk to their siblings. Probandwise concordance rates of 25.3% (SE +/- 4.4) for monozygotic (MZ), 5.4% (+/-2.8) for dizygotic (DZ), and 2.9% (+/-0.6) for their nontwin siblings were found. MZ twin concordance was in excess of DZ twin concordance. The excess concordance in MZ was derived primarily from like-sexed female pairs with a probandwise concordance rate of 34 of 100 (34 +/- 5.7%) compared with 3 of 79 (3.8 +/- 2.8%) for female DZ pairs. We did not demonstrate an MZ/DZ difference in males, although the sample size was small. We observed a 2-fold increase in risk to DZ twins over nontwin siblings of twins, but the difference was not significant.
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Cites: Brain. 2000 Mar;123 Pt 3:641-910686184
Cites: Can J Neurol Sci. 1998 Aug;25(3):216-219706723
Cites: Arch Neurol. 1966 Nov;15(5):449-625955946
Cites: J Med Genet. 1968 Dec;5(4):266-85713636
Cites: J Neurol Sci. 1975 Nov;26(3):361-751237538
Cites: Neurology. 1978 Oct;28(10):978-87570667
Cites: Ann Hum Genet. 1979 May;42(4):507-12475337
Cites: Neurology. 1980 Nov;30(11):1139-477191511
Cites: Arch Neurol. 1982 Mar;39(3):140-47199899
Cites: Can Med Assoc J. 1982 Aug 15;127(4):295-77093869
Cites: Can Med Assoc J. 1982 Dec 15;127(12):11707139466
Cites: Ann Neurol. 1983 Mar;13(3):227-316847134
Cites: N Engl J Med. 1986 Dec 25;315(26):1638-423785335