Treacher-Collins syndrome, also called mandibulofacial dysostosis, is a rare congenital condition characterized by distinct facial features, craniofacial hypoplasia, and ear defects. In severe cases, craniofacial malformations may cause life-threatening respiratory distress. However, severity is widely variable; mild cases present with slight abnormalities. Characteristic findings include underdeveloped or absent zygomas, micrognathia, cleft palate, downward-slanted eyes, coloboma, eyelash madarosis, macrostomia, malocclusion, small or absent ears, and inner ear abnormalities. Case-dependent complications include dysphonia, dyspnea, dysphagia, vision impairment, and commonly, hearing impairment. Surgery to correct deformities may be required.

Treacher-Collins syndrome is commonly caused by a mutation in the TCOF1 gene, although in rare cases due to mutations in the POLR1C or POLR1D genes. Most cases are the result of a new mutation, and about 40% are the result of autosomal dominant inheritance.