Treacher Collins syndrome


Treacher Collins syndrome

Description, Causes and Risk Factors:

ICD-10: Q75.4

Alternative Name: Mandibular dysostosis.

Treacher Collins syndrome is a well-characterized autosomal dominant disorder affecting craniofacial development. Great phenotypic variability is observed within and between families, but the most common clinical findings are: a) downward slanting of palpebral fissures, sometimes associated with lower lid coloboma; b) hypoplasia of malar bones and micrognathia; c) dysmorphic or hypoplastic external ears; d) atresia of middle-ear ossicles, sometimes resulting in conductive hearing loss.

The exact cause of this change is not known. If one parent is affected, the abnormal gene is then known to have been contributed by that parent. The gene associated with the syndrome, TCOF1, maps to chromosome 5q31.3-32, was cloned in 1996 by researchers. TCOF1 gene codes for the protein treacle, needed for migration of neural crest cells in the branchial arches. Effected structures are those derived from the first and second branchial arches.

The gene comprises 25 coding exons and encodes a low-complexity protein named treacle. Based on its amino acid sequence, it is proposed that treacle could be a nucleolar trafficking protein, as it displays repeated motifs (exons 7-16) that represent potential phosphorylation sites and a nucleolus targeting signal on its C-terminus. Immunocytochemical in-situ studies confirmed that the C-terminus of the protein is essential for its correct localization to the nucleolus and, more recently, it has been demonstrated that exons 7-16 are indeed subtract for casein kinase II (CKII) phosphorylation.

It is estimated that Treacher Collins syndrome occurs in one of 10,000 births. For unaffected parents with one child with Treacher Collins, the chances of giving birth to a second child with the condition is negligible. Adults with Treacher Collins syndrome have a 50% chances of passing the condition to their offspring.

Symptoms:

General Signs & Symptoms:

    “Fishlike” facialappearance.

  • Dolichofacial pattern.

  • Hypoplasticsupraorbital rims.

  • Hypoplastic zygomas.

  • Down turned corners ofmouth.

  • Process of hair thatextends toward thecheek-25%.

  • Retrusivemandible andmaxilla.

  • High mandibularplane angle.

  • Deficient malarprojection.

  • Antegonialnotching.

  • Dorsal nasal hump.

  • Cleft palate - 35%.

  • Cleft lip-palate - rare.

  • Macrostomia - 15%.

  • Abnormal molar morphology.

  • Abnormal condylar andcoronoid process.

  • Absent or hypoplasticparotid glands

  • Eyes:Hypertelorism, down slanted palpebralfissures, Coloboma of lower eyelid, decrease or absence ofcilia on lower eyelid, hypoplastic lacrimal glands.

  • Ears:Symmetric external earmalformations, middle ear abnormalities, hypoplastic or absent cavitiesand ossicles, most patients have moderate-to-severe conductive hearingloss.

  • Airway may becompromised insignificantlyretrognathic patients, tracheotomy and sleep apnea.

  • Glossoptosis.

  • Palatopharyngealincompetence.

  • Intelligence is usually normal.

  • Mild mental retardation is present in fewcases.

Diagnosis:

Diagnosis is usually based on clinical signs and findings. Genetic tests can help identify gene changes linked to this condition.The earliest possible diagnosis is by chorionic villus sampling (if there is a family history).Diagnosis may also be made at midtrimester antenatal ultrasound.Postnatally, diagnosis is essentially made on clinical features. A thorough assessment must be made for all associated features, especially those affecting breathing, and complications, e.g. conductive hearing loss.

Treatment:

Your child should be treated by a qualified craniofacial team. Treacher Collins syndrome is a complex problem. It requires the expert skill of many different specialists working together. These problems are best treated at a craniofacial center.

    First, your child may need a hearing aid and this can be determined in the first few months of life.

  • Second, an early childhood program for speech and language stimulation may be recommended.

  • Third, if a cleft palate is present, the craniofacial team will advise you on the optimum timing for surgical closure of the cleft.

  • Fourth, reconstructive surgery is available to improve the appearance of the face. The craniofacial center will advise you on what to expect from such surgery and on optimum timing. Since not all children are affected to the same degree, both the necessity and the outcome of reconstructive surgery vary from child to child. Surgical procedures vary among surgical treatment centers and according to the severity of the conditions. Surgery to rebuild the cheek bones usually begins before the child reaches the age of five. It is believed that the best approach is to use the child's own bone and to avoid placing artificial material beneath the skin. At the time of this surgery, the outer corners of the eyes are usually raised to tighter the lower eyelids.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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