Bilateral choanal atresia in two members of one family.

Two children are presented with bilateral choanal atresia: a girl with the typical features of the Treacher Collins syndrome, and a boy, a third cousin of the girl, without mandibulo-facial dysostosis. Simultaneous occurrence of choanal atresia and the Treacher Collins syndrome may be based on a defective ossification of the mesenchyme of the first visceral arch. Choanal atresia may be due to nonabsorption of the bucconasal membrane and/or extension of the sphenoid or palate bone.