A syndrome with variable expressivity, largely involving structures derived from the first pharyngeal arch, groove or pouch. It is characterized mainly by fishlike facies with receding chin, downward sloping palpebral fissures, colobomas of the eyelids, macrostomia, dysplastic ears, and other anomalies. Ear malformation are usually associated with hearing loss. Orofacial defects are symmetrical and differ from those in oculo-auriculovertebral dysplasia which generally affect one side of the body. Mental retardation occurs in some cases. The name Treacher Collins is sometimes erroneously hyphenated.