Webbing or fusion of the toes, involving soft parts only or including bone structure. Bony fusions are referred to as "bony" Syndactyly if the fusion occurs in a radio-ulnar axis. Fusions of bones of the toes in a proximo-distal axis are referred to as "Symphalangism".

A condition in which middle parts of the foot (toes and metatarsals) are missing giving a cleft appearance. The severity is very variable ranging from slightly hypoplastic 3rd toe over absent 2nd or 3rd toes as far as oligo- or monodactyl feet.

A condition in which middle parts of the hand (fingers and metacarpals) are missing giving a cleft appearance. The severity is very variable ranging from slightly hypoplastic middle fingers over absent middle fingers as far as oligo- or monodactyl hands.

An abnormality of the ear.

Developmental hypoplasia of the mandible.

Underdevelopment of the malar prominence of the jugal bone (zygomatic bone in mammals), appreciated in profile, frontal view, and/or by palpation.

Treacher Collins syndrome (TCS) is a disorder of craniofacial development. The features include downslanting palpebral fissures, coloboma of the eyelid, micrognathia, microtia and other deformity of the ears, hypoplastic zygomatic arches, and macrostomia. Conductive hearing loss and cleft palate are often present (summary by Dixon, 1996). Genetic Heterogeneity of Treacher Collins Syndrome Treacher Collins syndrome-2 (TCS2; 613717) is caused by mutation in the POLR1D gene (613715) on chromosome 13q12. Treacher Collins syndrome-3 (TCS3; 248390) is caused by mutation in the POLR1C gene (610060) on chromosome 6p21. Treacher Collins syndrome-4 (TCS4; 618939) is caused by mutation in the POLR1B gene (602000) on chromosome 2q14.

Cleft palate is a developmental defect of the palate resulting from a failure of fusion of the palatine processes and manifesting as a separation of the roof of the mouth (soft and hard palate).