The Treacher Collins Syndrome (named for E. Treacher Collins) involves defects in craniofacial development. Severity of involvement may range from clinically inapparent to severe with intrauterine fetal demise. The affected genetic locus has been identified and can be used to confirm the diagnosis.
Frequency: 1 in 50,000 live births
Occurrence:
(1) about 40% have a family history with autosomal dominant inheritance
(2) about 60% have a de novo mutation
Phenotype:
(1) midface hypoplasia showing bilateral symmetry, due to involvement of the zygomatic complex
(2) downward slanting of the palpebral fissures
(3) colobomas (notching) of the lower eyelids with sparse eyelashes
(4) cleft palate
(5) micrognathia
(6) microtia (hypoplasia or aplasia of the pinna)
(7) other external deformities of the external ears
(8) conductive hearing loss
The disorder appears to be caused by a defect in the protein treacle which is encoded by TCOF1 which maps to chromosome 5q32-q33.1
