Treacher Collins Syndrome

Mar 14, 2021 4 min read
Treacher Collins Syndrome

Treacher Collins Syndrome is a genetic craniofacial syndrome characterised by hypoplasia, external ear and eyelid malformations and visual disturbance.

5 Key Points

  1. A rare genetic craniofacial syndrome first described in the late 1800s, which affects approximately 1 in 50,000 people.
  2. Inheritance is either sporadic (60%) or autosomal dominant with variable penetrance (40%)
  3. TCOF1 is the most common gene mutation. Others include PLORIC and POLR1D.
  4. Classic clinical picture of hypoplasia of the mandible and zygoma, external ear and eyelid malformations, and visual disturbance.
  5. Other names for Treacher Collins Syndrome include mandibulofacial dysotosis or first and second branchial arch syndrome.

Definition

Treacher Collins Syndrome, also known as mandibulofacial dysotosis or first and second branchial arch syndrome, is a genetic craniofacial syndrome characterised by hypoplasia, external ear and eyelid malformations and visual disturbance.

History

First described by Berry in 1889 and later by Treacher Collins in 1900, who was a British Opthalmogist​1​. It can also be referred to as Franceshetti-Klein Syndrome​2​.


Genetics

The incidence of Treacher Collins syndrome is approximately 1/50,000 live births.

The inheritance pattern is:

  • Autosomal dominant inheritance in 40% with variable penetrance,
  • Sporadic inheritence in 60%

Genetically, it has been linked to a mutation on the following genes:

  • TCOF1​3​ – most common and is associated with an underproduction of treacle protein, a neural crest precursor.
  • PLORIC​4​
  • POLR1D​4​

Pathophysiology

There is no general consensus on the pathophysiology of Treacher Collins Syndrome.

There are two main theories:

  1. Failure of the facial and mandibular facial processes to fuse​5​.
  2. Manifestation of a combined Tessier 6, 7, 8 facial clefts​6​.

Clinical Picture

Treacher Collins Syndrome (anterior and lateral views)

Hypoplasia

  • Bilateral Zygomatic Hypoplasia
  • Malar Hypoplasia
  • Mandibular Hypoplastic (microgenia or retrogenia)

As a result, patients often present as a Pierre-Robin Sequence​2​. Also, the combined effect of mandibularand maxillary hypoplasia often leads to significant ankylosis of the tempormandibular joint.

External Ear Malformations​2,7​

  • Small and malformed
  • Atretic or stenotic external auditory canals
  • Accessory auricle (30-40% incidence)​8​
  • These issues associated with conductive hearing loss and speech delay.

Lower eyelid abnormalities​2​

  • Anti-mongolian (downward slanting) palpebral fissures due to absence of the lateral orbital walls.
  • Lower eyelid colobomas
  • Absence of eyelash in the medial aspect.

Visual Disturbance​9​

  • Strabismus
  • Vision Loss
  • Amblyopia
  • Lateral canthal vertical dystopia

Other issues include secondary cleft palate (36%) and velopharyngeal insufficiency ​7,10​.




References

  1. 1. Collins ET. Cases of symmetrical congenital notches in the outer part of each lower lid and defective develop- ment of the malar bones. Trans Ophthalmol Soc . 1900:20: 190–192.
  2. 2. FRANCESCHETTI A, KLEIN D. The mandibulofacial dysostosis; a new hereditary syndrome. Acta Ophthalmol (Copenh). 1949;27(2):143-224. https://www.ncbi.nlm.nih.gov/pubmed/18142195.
  3. 3. Posnick J, Ruiz R. Treacher Collins syndrome: current evaluation, treatment, and future directions. Cleft Palate Craniofac J. 2000;37(5):434. doi:10.1597/1545-1569(2000)037<0434:TCSCET>2.0.CO;2
  4. 4. Fisher E. Exploring the genetic origins of Treacher Collins syndrome. Clin Genet. 2011;79(4):330-332. doi:10.1111/j.1399-0004.2011.01632.x
  5. 5. van der, Mazzola R, Vermey-Keers C, Stricker M, Raphael B. A morphogenetic classification of craniofacial malformations. Plast Reconstr Surg. 1983;71(4):560-572. doi:10.1097/00006534-198304000-00022
  6. 6. Hunt J, Hobar P. Common craniofacial anomalies: the facial dysostoses. Plast Reconstr Surg. 2002;110(7):1714-1725; quiz 1726; discussion 1727-8. doi:10.1097/01.PRS.0000033869.10382.91
  7. 7. Poswillo D. The pathogenesis of the first and second branchial arch syndrome. Oral Surg Oral Med Oral Pathol. 1973;35(3):302-328. doi:10.1016/0030-4220(73)90070-4
  8. 8. Amirhassankhani S, Lloyd M. Accessory Auricles: Systematic Review of Definition, Associated Conditions, and Recommendations for Clinical Practice. J Craniofac Surg. 2018;29(2):372-375. doi:10.1097/SCS.0000000000004201
  9. 9. Hertle RW, Ziylan S, Katowitz JA. Ophthalmic features and visual prognosis in the Treacher-Collins syndrome. British Journal of Ophthalmology. October 1993:642-645. doi:10.1136/bjo.77.10.642
  10. 10. Marsh J, Celin S, Vannier M, Gado M. The skeletal anatomy of mandibulofacial dysostosis (Treacher Collins syndrome). Plast Reconstr Surg. 1986;78(4):460-470. doi:10.1097/00006534-198610000-00003
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