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. 2001 Nov;69(5):1062-7.
doi: 10.1086/324191. Epub 2001 Oct 2.

Excess of twins among affected sibling pairs with autism: implications for the etiology of autism

D A Greenberg  1 , S E Hodge, J Sowinski, D Nicoll
Affiliations

Excess of twins among affected sibling pairs with autism: implications for the etiology of autism

D A Greenberg et al. Am J Hum Genet. 2001 Nov.

Abstract

It is widely accepted that genes play a role in the etiology of autism. Evidence for this derives, in part, from twin data. However, despite converging evidence from gene-mapping studies, aspects of the genetic contribution remain obscure. In a sample of families selected because each had exactly two affected sibs, we observed a remarkably high proportion of affected twin pairs, both MZ and DZ. Of 166 affected sib pairs, 30 (12 MZ, 17 DZ, and 1 of unknown zygosity) were twin pairs. Deviation from expected values was statistically significant (P<10(-6) for all twins); in a similarly ascertained sample of individuals with type I diabetes, there was no deviation from expected values. We demonstrate that to ascribe the excess of twins with autism solely to ascertainment bias would require very large ascertainment factors; for example, affected twin pairs would need to be, on average, approximately 10 times more likely to be ascertained than affected non-twin sib pairs (or 7 times more likely if "stoppage" plays a role). Either risk factors (related to twinning or to fetal development) or other factors (genetic or nongenetic) in the parents may contribute to autism.

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References

Electronic-Database Information

    1. Online Mendelian Inheritance in Man (OMIM), http://www.ncbi.nlm.nih.gov/Omim (for autism [MIM 209850])

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