Treacher Collins syndrome

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Treacher Collins syndrome
Classification and external resources
Specialty Medical genetics
ICD-10 Q75.4
ICD-9-CM 756.0
OMIM 154500
DiseasesDB 13267
MedlinePlus 001659
eMedicine plastic/183
Patient UK Treacher Collins syndrome
MeSH D008342
[[[d:Lua error in Module:Wikidata at line 863: attempt to index field 'wikibase' (a nil value).|edit on Wikidata]]]

Treacher Collins syndrome (TCS), also known as Treacher Collins–Franceschetti syndrome,[1] or mandibulofacial dysostosis,[2] is a rare autosomal dominant congenital disorder characterized by craniofacial deformities, such as absent cheekbones.[3]:577 Treacher Collins syndrome is found in about one in 50,000[4] births. The typical physical features include downward-slanting eyes, micrognathia (a small lower jaw), conductive hearing loss, underdeveloped zygoma, drooping part of the lateral lower eyelids, and malformed or absent ears.

Signs and symptoms

The presentation of symptoms in people with Treacher Collins syndrome varies. Some individuals may be so mildly affected, they remain undiagnosed; others can have severe facial involvement and life-threatening airway compromise.[5] Most of the features of TCS are bilateral and are already recognisable at birth.

Patients are mostly characterized by these abnormalities:

  • Hypoplasia of the facial bones: Most described is an underdeveloped mandibular and zygomatic bone. This leads to a small and malformed jaw. Mandible hypoplasia can result in a malocclusion.[6]
  • Ear anomalies: The external ear anomalies consist of small, rotated, or even absent auricles. Also symmetric, bilateral stenosis or atresia of the external auditory canals is described.[7] In most cases, the ossicles and the middle ear cavity were dysmorphic. Inner ear malformations are rarely described. As a result of these abnormalities, a majority of the individuals with TCS have conductive hearing loss.[8]
  • Most patients experience eye problems, varying from colobomata of the lower eyelids and aplasia of lid lashes to short, down-slanting palpebral fissures, and missing eyelashes. Vision loss can occur and is associated with strabismus, refractive errors, and anisometropia.[7][9]
  • Cleft palate [6]
  • Airway problems, which are often a result of mandibular hypoplasia, can occur.[6]

The presence of an abnormally shaped skull is not distinctive for Treacher Collins syndrome, but brachycephaly with bitemporal narrowing is sometimes observed.[7]

Dental anomalies are seen in 60% of TCS patients. These anomalies consist in tooth agenesis (33%), enamel disformaties (20%), and malplacement of the maxillary first molars (13%). In some cases, dental anomalies in combination with mandible hypoplasia result in a malocclusion. This can lead to problems with food intake and the ability to close the mouth.

Some features related to TCS are seen less frequently:[6]

Facial deformity is still associated by the general public with developmental delay, and lesser intelligence, but intelligence of patients with TCS is usually normal. The psychological and social problems associated with facial deformity may affect quality of life in a number of patients.

Cause

Mutations in TCOF1, POLR1C, or POLR1D genes can cause Treacher Collins syndrome. TCOF1 gene mutations are the most common cause of the disorder, accounting for 81 to 93% of all cases. POLR1C and POLR1D gene mutations cause an additional 2% of cases. In individuals without an identified mutation in one of these genes, the genetic cause of the condition is unknown. The proteins produced from the TCOF1, POLR1C, and POLR1D genes all appear to play important roles in the early development of bones and other tissues of the face. These proteins are involved in the production of ribosomal RNA (rRNA), which helps assemble protein building blocks (amino acids) into new proteins, which are essential for the normal functioning and survival of cells. Mutations in the TCOF1, POLR1C, or POLR1D genes reduce the production of rRNA. A decrease in the amount of rRNA may trigger the self-destruction (apoptosis) of certain cells involved in the development of facial bones and tissues. The abnormal cell death could lead to the specific problems with facial development found in Treacher Collins syndrome. However, it is unclear why the effects of a reduction in rRNA are limited to facial development.

Genetic mutation

TCOF1 is the only gene currently known to be associated with TCS, a mutation in this gene being found in 90-95% of the individuals with TCS.[6][11] However, in some individuals with typical symptoms of TCS, mutations in TCOF1 have not been found.[12] Investigation of the DNA has resulted in the identification of the kind of mutations found in TCOF1. The majority of mutations are small deletions or insertions, though splice site and missense mutations also have been identified.[6][13][14][15] Mutation analysis has unveiled more than 100 disease-causing mutations in TCOF1, which are mostly family-specific mutations. The only recurrent mutation accounts for about 17% of the cases.[16]

Treacher Collins syndrome is inherited in an autosomal-dominant pattern.

Function of the TCOF1 gene

TCOF1 codes for a relatively simple, nucleolar protein called treacle.[11] Mutations in TCOF1 lead to haploinsufficiency of the treacle protein.[17] Haploinsufficiency occurs when a diploid organism has only one functional copy of a gene, because the other copy is inactivated by a mutation. Thereby, the other functional gene does not produce enough of a gene-product to have the expected function, resulting in an abnormal disease state. Haploinsufficiency of the treacle protein leads to a depletion of the neural crest cell precursor, which leads to a reduced number of crest cells migrating to the first and second pharyngeal arches. These crest cells play an important role in the development of the craniofacial appearance.[13][18] So down regulation of treacle expression results in craniofacial defects and growth retardation.

Genetic counselling

TCS is inherited in an autosomal dominant manner and the penetrance of the affected gene is almost complete.[19] Some recent investigations, though, described some rare cases in which the penetrance in TCS was not complete. Causes may be a variable expressivity, an incomplete penetrance [20] or germline mosaicism.[21] Only 40% of the mutations are inherited. The remaining 60% are a result of a de novo mutation.[22] In the outcome of the disease, inter- and intrafamilial variability occurs. This suggests, when an affected child is born, it is important to investigate the parents to determine whether the affected gene is present. A parent could have a mild and undiagnosed TCS. In this case, the risk of having another affected child is 50%. If the parents do not have the affected gene, the recurrence risk appears to be low.[19] In following generations, the severity of the clinical symptoms increases.[14]

Diagnosis

The diagnosis of Treacher Collins syndrome relies upon clinical and radiographic findings.

Clinical findings

A set of typical symptoms occurs within Treacher Collins syndrome, which can be detected by a critical clinical view. The wide spectrum of diseases which have similar characteristics make it sometimes difficult to diagnose TCS.[23] The OMENS classification was developed as a comprehensive and stage-based approach to differentiate the diseases. This acronym describes five distinct dysmorphic manifestations, namely orbital asymmetry, mandibular hypoplasia, auricular deformity, nerve development, and soft-tissue disease. The table below shows the OMENS classification in more detail.[24]

Orbit

  • O0: normal orbital size, position
  • O1: abnormal orbital size
  • O2: abnormal orbital position
  • O3: abnormal orbital size and position

Mandible

  • M0: normal mandible
  • M1: small mandible and glenoid fossa with short ramus
  • M2: ramus short and abnormally shaped
  1. 2A: glenoid fossa in anatomical acceptable position
  2. 2B: Temperomandibular joint inferiorly (TMJ), medially, anteriorly displaced, with severely hypoplastic condyle
  • M3: Complete absence of ramus, glenoid fossa, and TMJ

Ear

  • E0: normal ear
  • E1: Minor hypoplasia and cupping with all structures present
  • E2: Absence of external auditory cannel with variable hypoplasia of the auricle
  • E3: Malposition of the lobule with absent auricle, lobular remnant usually inferior anteriorly displaced

Facial nerve

  • N0: No facial nerve involvement
  • N1: Upper facial nerve involvement (temporal or zygomatic branches)
  • N2: Lower facial nerve involvement (buccal, mandibular or cervical)
  • N3: All branches affected

Soft tissue

  • S0: No soft tissue or muscle deficiency
  • S1: Minimal tissue or muscle deficiency
  • S2: Moderate tissue or muscle deficiency
  • S3: Severe tissue or muscle deficiency

Radiological findings

Radiologic manifestations can be used to confirm the diagnosis. Imaging evaluation consists of X-rays (radiographs), CT scans, MRI, and/or ultrasound.

Radiographs

A few techniques are used to confirm the diagnosis in TCS. An orthopantomogram (OPG) is a panoramic dental X-ray of the upper and lower jaw. It shows a two-dimensional image from ear to ear. Particularly, OPG facilitates an accurate postoperative follow-up and monitoring of bone growth under a mono- or double-distractor treatment. Thereby, some TCS features could be seen on OPG, but better techniques are used to include the whole spectrum of TCS abnormalities instead of showing only the jaw abnormalities.[23] Another method of radiographic evaluation is taking a X-ray image of the whole head. The lateral cephalometric radiograph in TCS shows hypoplasia of the facial bones, like the malar bone, mandible, and the mastoid.[23] Finally, occipitomental radiographs are used to detect hypoplasia or discontinuity of the zygomatic arch.[25]

CT scan

A temporal-bone CT using thin slices makes it possible to diagnose the degree of stenosis and atresia of the external auditory channel, the status of the middle ear cavity, the absent or dysplastic and rudimentary ossicles, or the inner ear abnormalities such as a deficient cochlea. Two- and three-dimensional CT reconstructions with VRT and bone and skin-surfacing are helpful for more accurate staging and the three-dimensional planning of mandibular and external ear reconstructive surgery.

Differential diagnosis

Other diseases have similar characteristics to Treacher Collins syndrome. In the differential diagnosis, one should consider the acrofacial dysostoses. The facial appearance resembles that of Treacher Collins syndrome, but additional limb abnormalities occur in those patients. Examples of these diseases are Nager syndrome and Miller syndrome. The oculoauriculovertebral spectrum should also be considered in the differential diagnosis. An example is hemifacial microsomia, which primarily affects development of the ear, mouth, and mandible. This anomaly may occur bilaterally. Another disease which belongs to this spectrum is Goldenhar syndrome, which includes vertebral abnormalities, epibulbar dermoids and facial deformities.[26]

Treatment

The treatment of individuals affected by TCS needs a multidisciplinary approach and may involve the intervention of different professionals. The primary concerns in individuals with TCS are breathing and feeding problems, which are a consequence of the hypoplasia of the mandibula and the obstruction of the hypopharynx by the tongue. Sometimes, even a tracheostomy is necessary to maintain an adequate airway.[27] Also, a gastrostomy could be necessary to assure an adequate caloric intake while protecting the airway. Surgery to restore a normal structure of the face is normally performed at defined ages, depending on the development state.[28]

An overview of the present guidelines:

  • If a cleft palate is present, the repair normally takes place at 9–12 months old. Before surgery, a polysomnography with a palatal plate in place is needed; this may predict the postoperative situation and gives insight on the chance of the presence of sleep apnea (OSAS) after the operation.[6][29][30]
  • Hearing loss is treated by bone conduction amplification, speech therapy, and educational intervention to avoid language/speech problems. The bone-anchored hearing aid is an alternative for individuals with ear anomalies[31]
  • Zygomatic and orbital reconstruction is performed when the cranio-orbitozygomatic bone is completely developed, usually at the age of 5–7 years. In children, an autologous bone graft is mostly used. In combination with this transplantation, lipofilling can be used in the periorbital area to get an optimal result of the reconstruction.
  • Reconstruction of the lower eyelid coloboma includes the use of a myocutaneous flap, which is elevated and in this manner closes the eyelid defect.[32]
  • External ear reconstruction is usually done when the individual is at least eight years old. Sometimes, the external auditory canal or middle ear can also be treated.
  • The optimal age for the maxillomandibular reconstruction is still a major point of discussion; at present, this classification is generally used:[6]
  1. Type I (mild) and Type IIa (moderate) 13–16 years
  2. Type IIb (moderate to severe malformation) at skeletal maturity
  3. Type III (severe) 6–10 years
  • When the teeth are cutting, the teeth should be under supervision of an orthodontist to make sure no abnormalities occur. If abnormalities like dislocation or an overgrowth of teeth are seen, appropriate action can be undertaken as soon as possible.[13]
  • Orthognatic treatments usually take place after the age of 16 years; at this point, all teeth are cut and the jaw and dentures are mature. Whenever OSAS is detected, the level of obstruction is determined through endoscopy of the upper airways. Mandibular advancement can be an effective way to improve both breathing and æsthetics, while a chinplasty only restores the profile.[6]
  • If a nose reconstruction is necessary, it is usually performed after the orthognatic surgery and after the age of 18 years.[6]
  • The contour of the facial soft tissues generally requires correction at a later age, because of the facial skeletal maturity. The use of microsurgical methods, like the free flap transfer, has improved the correction of facial soft tissue contours.[33] Another technique to improve the facial soft tissue contours is lipofilling. For instance, lipofilling is used to reconstruct the eyelids.[32]

Hearing loss

Hearing loss in Treacher Collins syndrome is caused by deformed structures in the outer and middle ear. The hearing loss is generally bilateral with a conductive loss of about 50-70 dB. Even in cases with normal auricles and open external auditory canals, the ossicular chain is often malformed.[34]

Attempts to surgically reconstruct the external auditory canal and improve hearing in children with TCS have not yielded positive results.[35] Auditory rehabilitation with bone-anchored hearing aids (BAHAs) or a conventional bone conduction aid has proven preferable to surgical reconstruction.[31]

For patients with Treacher Collins syndrome, BAHAs provide several advantages:

  • As early aiding is of the utmost importance for this patient group, the BAHA facilitates normal language development.[36]
  • Pure tone audiometry (PTA) threshold improvements in the speech spectrum of >40 dB have been reported using the BAHA in pediatric users with craniofacial anomalies.[37]
  • Compared to a conventional bone conduction aid, BAHA provides better outcomes both audiologically and esthetically[38]
  • Compared to surgical reconstruction, BAHA provides more reliable outcomes and superior audiological results.[35]
  • Spontaneous improvement in the quality, pitch, and intensity of a patient’s own voice may be seen after BAHA aiding.[39]

Epidemiology

The syndrome occurs in one in 50,000 live births.

Eponym

It is named after Edward Treacher Collins (1862–1932), the English surgeon and ophthalmologist who described its essential traits in 1900.[40] In 1949, Adolphe Franceschetti and David Klein described the same condition on their own observations as mandibulofacial dysostosis. The term mandibulofacial dysostosis is used to describe the clinical features.[41]

Media portrayals

A July 1977 New York Times article[42] that was reprinted in numerous newspapers nationwide over the ensuing weeks, brought this malady to many people's attention for the first time.

While a student at Temple University, Bob Saget directed an 11-minute documentary about his seven-year-old nephew Adam who was undergoing cranial surgery to correct his symptoms of Treacher Collins syndrome. The documentary, Through Adam's Eyes, went on to win a 1978 Student Academy Award.

Treacher Collins syndrome was featured in the 2005 Discovery Channel documentary, Unmasked: Treacher Collins Syndrome. As of 2008, it was still being shown on Discovery Health and the TLC channels.

The disorder was featured on the show Nip/Tuck, in the episode "Blu Mondae".[43]

TLC's Born Without a Face[44] features Juliana Wetmore, who was born with the most severe case in medical history of this syndrome and is missing 30%–40% of the bones in her face.[44]

In 2010, BBC Three documentary Love Me, Love My Face[45] covered the case of a man, Jono Lancaster, with the condition. In 2011, BBC Three returned to Jono to cover his and his partner Laura's quest to start a family,[2] in So What If My Baby Is Born Like Me?,[46] which first aired as part of a BBC Three season of programmes on parenting.[47] The first film was replayed on BBC One shortly ahead of the second film's initial BBC Three broadcast. Lancaster's third BBC Three film, Finding My Family on Facebook,[48] which looked at adoption, aired in 2011.

A young man with TCS was one of a number of people with various face/body-altering medical conditions or injuries to take part in Katie Piper's 2011 Channel 4 television series Katie: My Beautiful Friends.

A boy, Nathaniel Newman, with TCS was one of the subjects on National Geographic Channel series Taboo, in the episode, "Ugly".

Wonder, written by R. J. Palacio and published by Knopf in February 2012, is a children's novel that features a boy with the disorder.

An episode of Grey's Anatomy, season 7 episode 12, features a character who has Treacher Collins syndrome.

See also

References

  1. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ 2.0 2.1 Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ James, William; Berger, Timothy; Elston, Dirk (2005). Andrews' Diseases of the Skin: Clinical Dermatology. (10th ed.). Saunders. ISBN 0-7216-2921-0.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 Katsanis SH, et al., Treacher Collins syndrome, 2004, GeneReviews
  7. ↑ 7.0 7.1 7.2 Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ 10.0 10.1 Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ 11.0 11.1 Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ 13.0 13.1 13.2 Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ 14.0 14.1 Lua error in package.lua at line 80: module 'strict' not found.
  15. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  17. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  18. ↑ Gorlin RJ, Syndromes of the Head and Neck, 2001, Oxford University Press, 4th edition
  19. ↑ 19.0 19.1 Lua error in package.lua at line 80: module 'strict' not found.
  20. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  21. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  22. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  23. ↑ 23.0 23.1 23.2 Lua error in package.lua at line 80: module 'strict' not found.
  24. ↑ Vento AR, et al., The O.M.E.N.S classification of hemifacial microsomia, 1991, Cleft Palate Craniofac, J 28,p. 68-76
  25. ↑ Posnick JC, et al., Treacher Collins syndrome: current evaluation, treatment, and future directions, 2000, Cleft Palate Craniofac J., 55, p. 1120-1133
  26. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  27. ↑ Goel L, et al., Treacher Collins syndrome-a challenge for anaesthesiologists, 2009, Indian J Anaesth, 53, p. 642-645
  28. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  29. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  30. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  31. ↑ 31.0 31.1 Lua error in package.lua at line 80: module 'strict' not found.
  32. ↑ 32.0 32.1 Lua error in package.lua at line 80: module 'strict' not found.
  33. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  34. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  35. ↑ 35.0 35.1 Lua error in package.lua at line 80: module 'strict' not found.
  36. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  37. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  38. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  39. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  40. ↑ Treacher Collin E, Cases with symmetrical congenital notches in the outer part of each lid and defective development of the malar bones, 1900, Trans Ophthalmol Soc UK, 20, p. 190-192
  41. ↑ Franceschetti A, Klein D, Mandibulo-facial dysostosis: new hereditary syndrome, 1949, Acta Ophtalmol, 27, p. 143-224
  42. ↑ "Surgical Teamwork Gives Disease Victims a New Life", Donald G. McNeil, Jr., July 26, 1977, page L31.
  43. ↑ Nip/Tuck: Blu Mondae - TV.com
  44. ↑ 44.0 44.1 First Coast News: Local Family Has Daughter Born Without a Face
  45. ↑ BBC programme page for Love Me, Love My Face
  46. ↑ BBC programme page for So What If My Baby...
  47. ↑ BBC Three Bringing Up Britain season
  48. ↑ BBC Programmes: 'Finding My Family on Facebook'

External links

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