Familial incidence of congenital anorectal anomalies.

We describe two families with pedigrees over three and two generations with nine members affected with anorectal malformations. Both pedigrees are compatible with autosomal dominant inheritance with variable penetrance and expression or with multifactorial inheritance with a high genetic load. The recurrence risk is thought to be in the range of 10% to 20% for first degree relatives of affected members.