Bones / Orthopedics Genetics

What is Treacher Collins syndrome?

Treacher Collins syndrome is a rare medical condition caused by a genetic mutation. It affects the development of bones and other tissues of the face and results in abnormalities in the head, face, and ears.

Other names for this syndrome are mandibulofacial dysostosis, Treacher Collins-Franceschetti syndrome, Franceschetti-Zwahlen-Klein syndrome, and zygoauromandibular dysplasia.

Treacher Collins syndrome (TCS) affects approximately 1 in 50,000 live births.

In this article, we examine the symptoms, causes, and treatments available for TCS. We also take a look at living with TCS and what the outlook is for people with the condition.

Signs and symptoms

Doctor pointing at model of a human skull to explain symptoms of Treacher Collins syndrome.
Treacher Collins syndrome affects the facial bones and tissue, causing symptoms such as an underdeveloped jaw and chin.

The signs and symptoms of TCS vary and range from almost unnoticeable to severe.

While some individuals may experience very mild symptoms, others have extremely severe symptoms that may have serious consequences, such as life-threatening airway problems.

Signs and symptoms of TCS include some parts of the body developing in an abnormally or incompletely: These body areas include:

  • eyes, including lazy eye, an inability to focus, and vision loss
  • lower eyelids, which may include notching and sparse or absent eyelashes
  • cheekbones and jaw
  • chin
  • ears, which may include absent, small, malformed, or rotated ears
  • hair displacement, in which hair grows in front of the ears and to the lateral cheekbones
  • an opening in the roof of the mouth called a cleft palate, with or without a cleft lip
  • airways
  • skull
  • nose
  • teeth

Hearing loss may occur due to abnormal development of the facial bones and incomplete or abnormal development of the ears.

TCS may also cause a delay in motor and speech development.


Causes

Model of strands of DNA illustrating genetics.
Treacher Collins syndrome is a genetic condition caused by mutations of certain genes.

TCS is caused by mutations in one of three genes:

  • TCOF1
  • POLR1C
  • POLR1D

A mutation in the TCOF1 gene causes the syndrome in 90–95 percent of people with TCS. A mutation in the POLR1C or POLR1D gene accounts for around 8 percent of people with TCS.

All these genes play vital roles in the early development of facial bones and tissues. When they are mutated, certain cells involved in the development of bones and tissues of the face self-destruct.

Approximately 40 percent of people with TCS have a parent, or, rarely, two parents who carry affected genes. In these cases, the gene abnormality causing TCS is inherited.

The remaining 60 percent of people develop TCS as the result of a new mutation — a mutation occurring for the first time.

If the mutation has been detected within a family, there is an increased risk of a new baby getting it and having TCS. Therefore, a prenatal consultation is recommended in case of pregnancy.

Diagnosis

A diagnosis of TCS is made based on the following:

  • medical history
  • genetic testing
  • physical and radiographic exams

Radiographic exams may include different types of X-rays, or computed tomography (CT) scans to detect if the cheekbones and jawbone (mandible) have developed abnormally or incompletely way.

A craniofacial CT scan can be performed to analyze the anatomy of the head, neck, ears, and ear canal. Doctors use this scan where there is hearing loss during the first 6 months of a child’s life.

An examination of the teeth, to look for dental abnormalities, can also be performed when teeth first appear.

Genetic tests aim to detect mutations in the three genes that are known to cause TCS. Most of the time, genetic tests are not necessary to diagnose TCS, as a doctor can easily make a diagnosis by observing a person’s symptoms. Genetic testing is helpful for further family planning.

After the initial diagnosis, other tests can help determine the severity of TCS. Doctors may examine the following:

  • the airway to investigate predisposition to obstruction of the oropharynx
  • the roof of the mouth for clefts
  • the ability to swallow
  • hearing ability
  • the eyes


Treatment and living with TCS

Two surgeons at work in operating theatre, performing facial surgery.
Surgery is often required in infancy or childhood, to correct or rebuild certain areas such as the jaw or eye socket.

Treatment of TCS varies according to each person’s needs. Care will usually involve several different health professionals, such as:

  • a paediatrician
  • an orthodontist
  • a dentist
  • a skull and face surgeon
  • a speech therapist
  • a geneticist
  • nurses
  • an eye doctor
  • a hearing specialist
  • an ear, nose, and throat specialist.

For newborn infants with TCS, treatment will include procedures for improving breathing and how the airway works. Methods include special positioning of the infant and making an opening in the windpipe.

Doctors can treat hearing loss caused by TCS with hearing aids, speech therapy, and integration into the education system.

Surgeons can correct or rebuild the following areas if they are affected by abnormal or incomplete development:

  • the skull and face
  • the roof of the mouth
  • cheekbones, jaw, and eye sockets
  • the outer part of the ears
  • nose
  • teeth
  • lower eyelid

The age of the person will affect what surgery a doctor will recommend.

Repairs of the roof of the mouth are often carried out at 1–2 years of age. Cheek, jaw, and eye socket rebuilding is often done at 5–7 years of age. Ear corrections are usually made after 6 years of age. Jaw repositioning is typically done before 16 years of age.

Other potential treatments are still under investigation, and no scientific results have yet been confirmed. They include:

  • Adding stem cells to bone and cartilage to improve surgical outcomes when treating abnormalities of the skull and face.
  • Treating TCS in the womb, when the embryo is still developing, by genetically manipulating a gene called p53 and blocking what it does.

Genetic counseling may also be suggested for individual people with TCS or the whole family if the syndrome was inherited. At these meetings, people will learn about the outlook for a genetic disorder, and experts will advise them about what the chances are of passing the condition on.

Life expectancy and outlook

Most children with TCS have normal development and intelligence.

The outlook for each person depends on their specific symptoms and the severity of the syndrome. Unless there is a severe abnormality in the jaw that affects breathing, life expectancy for people with TCS tends to be similar to people without the condition.

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