Inheritance of Treacher Collins syndrome is autosomal dominant, with complete penetrance and variable expressivity. Nonpenetrance is rare. Approximately 60% of cases represent fresh mutations. Administration of a teratogenic dose of vitamin A or isotretinoin in mice, rats, and hamsters produced malformations of the craniofacial skeleton that resembled features of mandibulofacial dysostosis.[8, 9, 10]