Treacher Collins Syndrome and Its Causes

Treacher Collins syndrome is a rare genetic condition that affects facial bone development, causing major facial deformities. Children with the syndrome can have a very unusual facial appearance. Also known as mandibulofacial dysostosis, Treacher Collins affects approximately one in 50,000 people worldwide.

Because it is so uncommon, Treacher Collins is not well known outside the medical community. A central character in a 2017 Hollywood movie, Wonder, was afflicted with Treacher Collins syndrome, which helped increase awareness and interest in the condition. 

This article discusses Treacher Collins syndrome and its symptoms and causes.

What Are the Symptoms of Treacher Collins Syndrome?

There can be some variability in the severity of Treacher Collins syndrome. The most prominent feature of the condition is its effect on facial appearance. The bone deformities can also cause impaired hearing, and facial bone malformations can result in vision deficiencies. The condition can also impact the sense of smell, and problems with airway structure may interfere with breathing. 

Other symptoms, such as hearing, vision, and smell deficits, may be less noticeable during infancy. Breathing difficulties can begin during infancy or may develop later in life. Treacher Collins syndrome does not typically affect intelligence, but the severe facial deformities can interfere with normal socializing and peer interactions, which can affect school attendance. 

The symptoms of Treacher Collins Syndrome include:

• Changes in facial appearance: Treacher Collins syndrome is characterized by a small jaw and chin (micrognathia), a very thin and elongated face, and small, sunken cheekbones. The facial features are usually almost symmetrical.
• Abnormal eye appearance: The small cheekbones result in a downward slant of the eyes, which can appear to be set back into the face. A characteristic notch that appears like a missing piece of skin on the eyelids is called an eyelid coloboma. If the shape of the eyes and the bone structure around eyes is severely affected, it may result in a visual deficit. Eyelashes are thin, often causing dry eyes.
• Cleft palate: A cleft palate may be present as well. This is a defect in the bone that normally separates the roof of the mouth from the nasal passages above it. Children with a cleft palate have an open space between the roof of the mouth and the nose. This defect can allow food to enter into the nose, and potentially into the lungs, causing an infection. It may also allow mucus to enter into the mouth. 
• Ear and hearing problems: Among the obvious changes in appearance, the ears can be small or unusually shaped. The bones of the ear canal, which cannot be seen easily without an ear examination, can be underdeveloped as well. This results in auditory (hearing) deficits. Rarely, the ears may be completely undeveloped, resulting in complete deafness. 
• Respiratory problems: As a child’s face grows and develops, the facial bones may block the airway. At any point during life, respiratory problems may develop and can even be life-threatening if left untreated.
• Problems with the sense of smell: Abnormalities in the development of the nasal passages and bone structure of the nose can affect smell sensation. 
• Hand deformities: Some children who have Treacher Collins syndrome have minor deformities of the hands or fingers.

What Is the Main Cause of Treacher Collins Syndrome?

Treacher Collins syndrome is caused by underdevelopment of a child’s facial bones, beginning before birth.

It is unclear why this deficiency in treacle protein specifically affects the bone structure of the face so severely. 

Genetic Mutation

Several different genetic mutations can cause the treacle defect. A mutation is an error in a person’s DNA code. In Treacher Collins, the mutation results in a problem with physical features.

The most common mutation associated with Treacher-Collins syndrome is a defect in the TCOF1 gene, located on chromosome 5 in the 5q32 region. At least 200 different defects have been known to occur on this chromosome.

Other genetic abnormalities can also cause Treacher Collins syndrome, although the TCOF1 abnormality is the most common. 

The POLR1C gene, which is on chromosome 6 in the 6q21.2 region, and the POLR1D gene, which is on chromosome 13 in the 13q12.2 region, both code for molecules called polymerase that help in the production of ribosomes. Defects in either of these genes can cause Treacher Collins syndrome. 

Inheritance Pattern

Fewer than half of children with Treacher Collins syndrome inherit it from their parents. It is a hereditary autosomal dominant condition, which means a person who inherits the genetic defect from one parent will develop the condition. Parents who have the condition will pass on the genetic defect to half of their children.

Every person has two chromosomes that code for treacle production, and if a person has only one defective chromosome, the body still produces some of the treacle product. However, this not is enough to support the normal formation of the bones and tissues of the face. 

Approximately 60% the time, Treacher Collins syndrome develops as a de novo genetic condition, meaning that it is caused by a new mutation that was not inherited. Some suspect that de novo mutations causing Treacher Collins syndrome may be caused by some type of environmental factor, although no specific environmental factor has yet been identified. 

How Treacher Collins Is Diagnosed

The diagnosis of Treacher Collins syndrome is based on the unique facial appearance characteristic of the condition. It can be diagnosed based on ultrasound features prior to a child’s birth or by the baby’s physical features immediately after birth. 

The condition is usually associated with genetic defects, and genetic testing of an affected child can confirm the diagnosis. Genetic testing of the parents can be helpful in assessing the risk that a couple may have more children with the disorder.

Specialized diagnostic tests are necessary to assess hearing and vision. Diagnosis of respiratory impairment may require a multidisciplinary approach, including:

• Bone X-rays
• Evaluation of respiratory function,
• Interventional diagnostic testing using a bronchoscope—a camera-equipped device that can be placed into the nose and threaded down the nasal passage to evaluate the structure of the respiratory system.

Treatment 

There is no treatment to cure Treacher Collins syndrome, but surgery can repair many of the bone deformities. Supportive care for the treatment of hearing loss, visual defects, and impaired smell may improve your child’s symptoms.

Surgery 

Children may need to have many surgeries, and the optional timing may require surgery to be spaced out over a period of several years. 

Surgical planning is based on a number of factors, including:

• Waiting for a child to reach an age at which surgery can be well tolerated
• Early reconstruction of auditory bones to permit proper development of hearing function
• Early correction of cleft palate to avoid the associated complications
• Correcting cosmetic problems to maximize a child’s ability to interact with peers, while minimizing the psychological effects of social ostracism
• Waiting for the development of the facial structure to be able to plan out corrective surgery with the best long-term outcome
• Preventing life-threatening respiratory problems

Because the facial deformities of Treacher Collins syndrome can be quite extensive, surgical interventions generally do not result in a completely normal facial appearance. 

Supportive Care 

In most instances, hearing loss is treated with surgery, hearing aids, or rehabilitation. Vision may improve with surgical correction of anatomical structural abnormalities or with visual aids.

In some instances, respiratory support with a mechanical respiratory device may be necessary. 

Coping With Treacher Collins Syndrome

There are many serious concerns that you may have if your child has Treacher Collins syndrome. 

The social and psychological issues associated with such a severe facial deformity can be excruciatingly difficult throughout the lifetime of a person who is afflicted with the condition. It can be painful for parents, siblings, and other family members to watch. Psychological counseling, family counseling, and support groups may be helpful. 

Strategies that may help in the school and work setting may involve sharing details about the condition with peers through a school assembly or a workshop. Suitable approaches for interacting with peers have to be based on your individual family’s circumstances, your child, and the receptiveness of your community. 

Summary

Treacher Collins syndrome is a rare genetic condition that affects the way the face develops. People with Treacher Collins have an unusual appearance including a small jaw and chin, a thin face, and small, sunken cheekbones. 

People with Treacher Collins may also have other symptoms like problems with hearing, vision, and sense of smell. Breathing difficulties may be present at birth or may develop later on.

Treacher Collins can affect a person's social experiences and self-esteem. People with the condition and their families can benefit from support groups, counseling, and other services.