Craniosynostosis anomalies in twins.

This report discusses the incidence of twinning in nonsyndromic and syndromic craniosynostosis. Nonsyndromic craniosynostosis occurs in approximately 1 in 2,100 live births; the incidence of twinning in patients with nonsyndromic craniosynostosis has been reported to be higher than the rate of 2.5% of live births in the general population. No definitive explanation for this increased risk is known. The incidence of twinning in patients with nonsyndromic craniosynostosis may range between 2.5 and 19 in 210,000 live births. Syndromic craniosynostosis occurs in between 1 per 10,000 live births (Muenke's syndrome) to 1 per 80,000 live births (Apert's syndrome). Because of the these low occurrences, the actual incidence of twinning in syndromic craniosynostosis is difficult to predict. A theoretical incidence between 2.5 per million live births in Muenke's syndrome and 2.5 per 8 million live births in Apert's syndrome can be estimated.