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Treacher Collins syndrome

Treacher Collins syndrome is a genetic condition with characteristic facial features. It is mainly caused by mutations in the TCOF1 gene which makes a protein called treacle.

Characteristics of Treacher Collins syndrome
Treacher Collins syndrome (TCS) is a genetic condition that affects the development of the bones of the face, in particular the cheek (i.e., zygomata) and jaw (i.e., mandible) bones. In individuals with TCS, these bones are smaller than typical and sometimes absent. People with TCS have characteristic facial features involving their eyes, ears, and mouth. The eyes are typically downslanting with small notches missing from the lower eyelid, called colobomas. Some individuals with TCS have poor vision which can affect one or both eyes. The outer ears are usually small and sometimes absent, and the ear canal may be absent or underdeveloped. Because of these features, some people with TCS have hearing loss. The jaw is typically very small, which causes the teeth to be crowded inside the mouth. Babies with TCS are often born with a cleft palate (split in the roof of the mouth). Because of the structure of the mouth, feeding can be very difficult for individuals with TCS, particularly in infancy. People with this condition have normal intellect and cognitive functioning.

Diagnosis/Testing
TCS can be diagnosed either by meeting certain clinical criteria or by genetic testing. Most individuals with TCS have a change or mutation in a gene called TCOF1. This gene makes a protein called treacle, which plays an important role in facial structure during early development. Some individuals with TCS have a mutation in the POLR1D or POLR1C genes. Like TCOF1, it is thought that these genes also play an important role in facial structure during early development.
The characteristic facial shape may be seen before birth on an ultrasound evaluation. If a pregnancy is known to be at risk for TCS, amniocentesis can be used for prenatal diagnosis.

Management/Surveillance
For infants with TCS, management is often focused around making sure that the baby can breathe and eat. If breathing is a problem, positioning devices, tubes, and surgical jaw procedures may be offered to improve airflow to the lungs. Meeting with a nutritionist and/or occupational therapist can be helpful to review feeding practices and ensure that the baby is growing appropriately. For babies with a cleft palate, corrective surgery is typically performed in the first year of life. In childhood, orthodontic management is typically required due to the small size of the mouth. Surgery may be required to lengthen the jaw and otherwise increase space in the mouth to reduce dental crowding.
For children with hearing loss, regular hearing evaluations are done to determine if/when interventions, such as hearing aids, are needed. Children with very small or absent ears may be given prosthetics.
Other surgeries are sometimes performed for cosmetic purposes, such as facial reconstruction procedures and bone grafts. Psychological counseling and support are also very important aspects of management.

Mode of inheritance
TCS is inherited in an autosomal dominant pattern. This means inheriting one gene mutation is enough for an individual to be affected and show signs of TCS. The mutation can be inherited from an affected parent or it can occur brand new (de novo) in an affected child. Most of the time (approximately 60%), the condition occurs de novo in an affected child.

Risk to family members
The risk to family members depends on whether or not the individual with TCS also has a parent affected with TCS. If a parent also has TCS, the risk of having a child with TCS is 50% with each pregnancy. If a parent does not have TCS, the risk of other siblings being affected is very low.

Special considerations
None

Resources
Children’s Craniofacial Association
Seattle Children’s Hospital: Treacher Collins Syndrome
Genetics Home Reference: Treacher Collins syndrome

References
Chang, CC. et al. (2012).Treacher Collins syndrome”. Seminars in Plastic Surgery 26(2): 83-90.
Hylton, JB. et al. (2012).Multidisciplinary Treatment Approach in Treacher Collins syndrome.” Journal of Dentistry for Children 79(1): 15-21.
Katsanis SH, Jabs EW. (Updated 30 April 2012). Treacher Collins Syndrome. In: GeneReviews at GeneTests Medical Genetics Information Resource (database online). Copyright, University of Washington, Seattle. 1997-2013. Available at http://www.ncbi.nlm.nih.gov/books/NBK1532/. Accessed [07/10/2013].
The National Organization for Rare Disorders"The Physicians's Guide to Treacher Collins Syndrome"

Created:07/2013

Updated:mm/yyyy

Created by:Katie Golden-Grant, MS, LCGC

Edited by:Seema Jamal, MSc, LCGC



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