What is Treacher-Collins syndrome?

Rare genetic disease

Treacher Collins syndrome or Franceschetti-Zwahlen-Klein syndrome

The Treacher Collins or Franceschetti-Zwahlen-Klein syndrome, also called facial jaw dysostosis, is a rare genetic condition that causes facial deformity and abnormalities. The condition may be inherited or acquired during embryonic development. Approximately one in 50,000 children is affected, and this pathology is named after the English surgeon and ophthalmologist Edward Treacher Collins, who first described it in 1900.

What causes Treacher Collins syndrome?

The disease is caused by mutations of DNA genes known as TCOF1, POLR1C, and POLR1D. These genes appear on chromosomes 5, 6, and 13 and are required for the proper development of the bones and soft tissues of the face in the absence of mutations. To produce this anomaly, either parent must carry out a hereditary mutation or the condition must be acquired during embryonic development. In terms of statistics, there are more cases of the second type of mutation (i.e., mutations acquired during embryogenesis) than the first type (i.e., hereditary mutations) at 60% against 40%.

Signs and problems

Starting with abnormalities of the face (hypoplasia), it can progress to problems with the ear bones and jawbones (micrognathia). The symptoms of the disorder generally vary from patient to patient and according to the severity of the disease: there may be severe manifestations and, in other cases, less severe consequences. The severity is largely determined by the level of development of the facial bones.

Face

In particular, the syndrome affects the face in the following ways:

  • Micrognathy, which means the mandible and chin are smaller than average;
  • An abnormal or missed development of the cheekbones;
  • Anomalies of the eye (eyes oriented downwards, coloboma of the lower eyelid, eyelid ptosis consisting of the lowering of the eyelids, and narrowing of the tear ducts).

Ears

77% of patients with this syndrome have abnormalities of the external ear including incomplete or absent auricles. Specifically, in 36% of external ear anomalies, the external auditory canal does not develop sufficiently (stenosis). Approximately 40-50% of cases are associated with conductive hearing loss (causing hearing loss or reduction) as a result of the ossicular chain and middle ear development abnormalities; however, in this case, the inner ear tends to be preserved.

Other

Severe cases of the syndrome can result in:

  • brachycephaly (cranial abnormality characterized by the posterior flattening of the head);
  • deformation of the teeth (lack of tooth formation or dental diastema, i.e. excessive spacing between one tooth and another);
  • macrostomy (enlargement of the mouth opening);
  • cleft palate (palate malformation);
  • heart defects;
  • nasal deformities.

However, in even more serious cases, the patient also suffers a host of further consequences, including deficits in breathing and chewing due to abnormalities of the cheekbones, jaw, chin, and teeth, hearing problems caused by abnormal ear development, as well as a loss of vision.

The patient is generally intelligent and does not have a modification of his intellectual qualities; however, psychologically, patients suffer from depression and social phobia as a result of living with facial deformities, and this affects their quality of life. 

How is Treacher Collins syndrome diagnosed?

A doctor can make a diagnosis in various ways: first, they begin by examining the patient's medical history and performing a physical exam; they may also conduct a genetic test, which searches for mutations in critical genes and can be used to highlight any mutations. Following the diagnosis of the syndrome, other diagnostic tests such as CT and X-rays will be ordered to clarify the patient's clinical picture. Additionally, amniocentesis and CVS can be used to diagnose prenatally.

How to treat Treacher Collins syndrome?

The disease is neither curable nor preventable but, once diagnosed, it is possible to intervene with facial surgical treatment and other tools capable of managing its symptoms. Based on the severity of the disease, deformities of the palate, cheekbones, nose, ears, and teeth may require a series of maxillofacial surgeries. As with corrective glasses in the case of vision problems, and hearing aids in the case of hearing loss, it is essential to use psychological therapy to overcome the depressive and phobic effects of deformities.

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