Treacher Collins syndrome

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Treacher Collins syndrome is a condition that affects the development of bones and other tissues of the face. The signs and symptoms of this disorder vary greatly, ranging from almost unnoticeable to severe. Most affected individuals have underdeveloped facial bones, particularly the cheek bones, and a very small jaw and chin (micrognathia). Some people with this condition are also born with an opening in the roof of the mouth called a cleft palate. In severe cases, underdevelopment of the facial bones may restrict an affected infant's airway, causing potentially life-threatening respiratory problems.

People with Treacher Collins syndrome often have eyes that slant downward, sparse eyelashes, and a notch in the lower eyelids called an eyelid coloboma. Some affected individuals have additional eye abnormalities that can lead to vision loss. This condition is also characterized by absent, small, or unusually formed ears. Hearing loss occurs in about half of all affected individuals; hearing loss is caused by defects of the three small bones in the middle ear, which transmit sound, or by underdevelopment of the ear canal. People with Treacher Collins syndrome usually have normal intelligence.

ORPHANET DEFINITION A rare genetic mandibulofacial dysostosis characterized by bilateral symmetrical oto-mandibular dysplasia including underdeveloped cheekbones (malar hypoplasia), a very small low jaw (micrognathia) and downward-slanting palpebral fissures, coloboma of the lower eyelids, microtia, hearing loss and without abnormalities of the extremities. Intelligence is normal.

Inheritance

From: MedlinePlus Genetics, National Library of Medicine

Autosomal dominant

Frequency in the source

From: MedlinePlus Genetics, National Library of Medicine

Prevalence at birth: 1-9 / 1 000 000; France; Value and class. Point prevalence: 1-9 / 1 000 000; France; Class only. Prevalence at birth: 1-9 / 100 000; Japan; Value and class. Prevalence at birth: 1-9 / 100 000; Europe; Value and class.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Abnormal facial shape · Very frequent (99-80%)

An abnormal morphology (form) of the face or its components.

Abnormality of bone mineral density · Very frequent (99-80%)

This term applies to all changes in bone mineral density which (depending on severity) can be seen on x-rays as a change in density and or structure of the bone. Changes may affect all bones of the organism, just certain bones or only parts of bones and include decreased mineralisation as may be seen in osteoporosis or increased mineralisation and or ossification as in osteopetrosis, exostoses or any kind of atopic calicfications of different origin and distribution. The overall amount of mineralization of the bone-organ can be measured as the amount of matter per cubic centimeter of bones, usually measured by densitometry of the lumbar spine or hip. The measurements are usually reported as g/cm3 or as a Z-score (the number of standard deviations above or below the mean for the patient's age and sex). Note that measurement with this method does not reflect local changes in other bones, and as such might not be correct with regard the hole bone-organ.

Downslanted palpebral fissures · Very frequent (99-80%)

The palpebral fissure inclination is more than two standard deviations below the mean.

Hypoplasia of the maxilla · Very frequent (99-80%)

Abnormally small dimension of the Maxilla. Usually creating a malocclusion or malalignment between the upper and lower teeth or resulting in a deficient amount of projection of the base of the nose and lower midface region.

Hypoplasia of the zygomatic bone · Very frequent (99-80%)

Underdevelopment of the zygomatic bone. That is, a reduction in size of the zygomatic bone, including the zygomatic process of the temporal bone of the skull, which forms part of the zygomatic arch.

Malar flattening · Very frequent (99-80%)

Underdevelopment of the malar prominence of the jugal bone (zygomatic bone in mammals), appreciated in profile, frontal view, and/or by palpation.

Micrognathia · Very frequent (99-80%)

Developmental hypoplasia of the mandible.

Midface retrusion · Very frequent (99-80%)

Posterior positions and/or vertical shortening of the infraorbital and perialar regions, or increased concavity of the face and/or reduced nasolabial angle.

Open bite · Very frequent (99-80%)

Visible space between the dental arches in occlusion.

Retrognathia · Very frequent (99-80%)

An abnormality in which the mandible is mislocalised posteriorly.

Short face · Very frequent (99-80%)

Facial height (length) is more than two standard deviations below the mean (objective); or an apparent decrease in the height (length) of the face (subjective).

Skeletal dysplasia · Very frequent (99-80%)

A general term describing features characterized by abnormal development of bones and connective tissues.

Abnormality of the dentition · Frequent (79-30%)

Any abnormality of the teeth.

Abnormality of the middle ear · Frequent (79-30%)

An abnormality of the middle ear.

Other findings in the same source

From: Orphanet

Additional reported features include Abnormality of the outer ear (Frequent (79-30%)); Absent eyelashes (Frequent (79-30%)); Atresia of the external auditory canal (Frequent (79-30%)); Conductive hearing impairment (Frequent (79-30%)); Delayed speech and language development (Frequent (79-30%)); Dental malocclusion (Frequent (79-30%)); Eyelid coloboma (Frequent (79-30%)); Frontal bossing (Frequent (79-30%)); Iris coloboma (Frequent (79-30%)); Low anterior hairline (Frequent (79-30%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: MedlinePlus Genetics, National Library of Medicine

Antenatal; Neonatal

Inheritance in the source

From: MedlinePlus Genetics, National Library of Medicine

Autosomal dominant

Frequency and the population described

From: MedlinePlus Genetics, National Library of Medicine

Prevalence at birth: 1-9 / 1 000 000; France; Value and class. Point prevalence: 1-9 / 1 000 000; France; Class only. Prevalence at birth: 1-9 / 100 000; Japan; Value and class. Prevalence at birth: 1-9 / 100 000; Europe; Value and class.

Understanding the inheritance label

From: MedlinePlus Genetics

An autosomal dominant pattern means that one altered copy of a relevant gene can be sufficient for the condition. Some affected people inherit the change; others have a new change without an affected parent. The precise finding, family history and condition determine what this means for relatives.

Which doctor should you see?

The suggested department for discussing Treacher Collins syndrome is Clinical Genetics, with a clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with clinical geneticist referral.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Does the exact genetic or chromosome finding explain the observed features?
• Would a genetic counsellor help the family understand the result?
• Which organ-specific assessments are appropriate for this particular diagnosis?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Treacher Collins syndrome. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.