Treacher Collins Syndrome 1

Alternative Names

  • TCS1
  • Treacher Collins-Franceschetti Syndrome
  • TCOF
  • Treacher Collins Syndrome
  • TCS
  • Mandibulofacial Dysostosis
  • MFD1
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WHO-ICD-10 version:2010

Congenital malformations, deformations and chromosomal abnormalities

Congenital malformations and deformations of the musculoskeletal system

OMIM Number

154500

Mode of Inheritance

Autosomal dominant

Gene Map Locus

5q32-q33.1

Description

Treacher Collins syndrome (TCS) is a genetic defect characterized by congenital craniofacial abnormalities. The condition is also known as mandibulofacial dysostosis, since the cheek and jaw bones are primarily affected. Major characteristics of the condition are downward slanting eyes, small lower jaw and chin, notched lower eyelids (coloboma), and malformed or missing ears. Some patients may also present with a cleft palate, receding chin, scalp hair extending onto cheeks, breathing problems, including sleep apnea, and/or eating difficulties. Malformations in the outer and middle ear may lead to hearing difficulties. However, not all affected patients suffer in the same way. The severity of the disease presentation varies greatly, with some patients showing the entire range of disease features, and some others hardly showing any symptoms at all. One in every 50,000 children is estimated to be born with this genetic defect. Diagnosis is principally based on the clinical features. Differential diagnoses to be considered include Goldenhar syndrome, Nager syndrome, Miller syndrome, Pierre Robin Sequence, and Nonsyndromic Mandibular Hypoplasia.

Mutations in the TCOF1 gene are responsible for TCS. This gene codes for a protein called treacle, which is expected to play an important role in the embryonal development of facial bones. Mutations in the TOCF1 gene result in defective or lowered levels of treacle, which causes the facial bone cells to undergo apoptosis. About 90-95% of patients with TCS, in whom the TCOF1 gene has been studied, have shown mutations in the coding and flanking intronic regions of the gene. TCS, although transmitted in an autosomal recessive manner, shows variable penetrance and marked variability in expressivity, sometimes, even within the same family.

Epidemiology in the Arab World

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Subject IDCountrySexFamily HistoryParental ConsanguinityHPO TermsVariantZygosityMode of InheritanceReferenceRemarks
154500.1Saudi ArabiaFemaleYes Maxillozygomatic hypoplasia; Choanal atr...NM_001371623.1:c.2656C>THomozygousAutosomal, RecessiveMaddirevula et al. 2018

Other Reports

Oman

Shah et al. (2000) reported the rare association of acute airway obstruction with Treacher Collins syndrome in an Omani female child born to consanguineous parents. The patient was dysmorphic with features of Treacher Collins syndrome which included pre-auricular tags, microtia and a malformed externary auditory meatus in the right ear, while the left ear had atretic external auditory meatus with a tuft of hair on the pre-auricular area. Other features were a receding chin and cleft palate with no ocular abnormalities. She was noticed to have stridor, but no cyanosis, which was initially conservatively managed at the age of 13 days. But by the age of 20 days, her condition deteriorated with increase in respiratory distress with dropping in her oxygen saturation. She was managed by immediate tracheostomy and antibiotics after failure of endotracheal intubation. As a cranio-facial surgeon had advised on postponing cleft palate repair or any reconstructive surgery until she was older, she was discharged home after teaching the parents about tracheostomy care. At the age of two years, laryngoscopy and bronchoscopy were normal, but brainstem auditory thresholds at 115 dB in the right ear and 120dB in the left ear revealed bilateral profound mixed hearing loss. The child was waiting surgical intervention for her cranio-facial anomalies after which she would be decanulated. Shah et al. (2000) attributed the respiratory obstruction in this patient to factors which caused the tongue to fall back which included the receding chin, hypoplastic mandible, cleft palate and anteriorly placed larynx.

Sawardekar (2005) conducted a study to establish the prevalence of major congenital malformations in children born during a 10-year period in Nizwa Hospital. Of the 21,988 total births in the hospital, one child was born with Treacher Collins Syndrome. Sawardekar (2005) hinted for a possible genetic contribution in this child.

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