Treacher Collins syndrome (TCS) is a genetic disorder characterized by deformities of the ears, eyes, cheekbones, and chin. The degree to which a person is affected, however, may vary from mild to severe. Complications may include breathing problems, problems seeing, cleft palate, and hearing loss. Those affected generally have normal intelligence.TCS is usually autosomal dominant. More than half the time it occurs as a result of a new mutation rather than being inherited from a persons parents. The involved genes may include TCOF1, POLR1C, or POLR1D. Diagnosis is generally suspected based on symptoms and X-rays, and potentially confirmation by genetic testing.Treacher Collins syndrome is not curable. Symptoms may be managed with reconstructive surgery, hearing aids, speech therapy, and other assistive devices. Life expectancy is generally normal. TCS occurs in about one in 50,000 people. The syndrome is named after Edward Treacher Collins, an English surgeon and ophthalmologist, who described its essential traits in 1900. Signs and symptoms
Symptoms in people with Treacher Collins syndrome vary. Some individuals are so mildly affected that they remain undiagnosed, while others have moderate to severe facial involvement and life-threatening airway compromise. Most of the features of TCS are symmetrical and are already recognizable at birth.The most common symptom of Treacher Collins syndrome is underdevelopment of the lower jaw and underdevelopment of the zygomatic bone. This can be accompanied by the tongue being retracted. The small mandible can result in a poor occlusion of the teeth or in more severe cases, trouble breathing or swallowing.
This can lead to problems with food intake and the ability to close the mouth.Less common features of TCS may add to an affected persons breathing problems, including sleep apnea. Choanal atresia or stenosis is a narrowing or absence of the choanae, the internal opening of the nasal passages, which may also be observed. Underdevelopment of the pharynx can also narrow the airway.Features related to TCS that are seen less frequently include nasal deformities, high-arched palate, macrostomia, preauricular hair displacement, cleft palate, hypertelorism, notched upper eyelid, and congenital heart defects.Although facial deformity is often associated with developmental delay and intellectual disability, more than 95% of people affected with TCS have normal intelligence. The psychological and social problems associated with facial deformity can affect quality of life in individuals with TCS. Genetics
Mutations in TCOF1, POLR1C, or POLR1D genes can cause Treacher Collins syndrome. TCOF1 gene mutations are the most common cause of the disorder, with POLR1C and POLR1D gene mutations causing an additional 2% of cases. In individuals without an identified mutation in one of these genes, the genetic cause of the condition is unknown. The TCOF1, POLR1C, and POLR1D genes code for proteins which play important roles in the early development of bones and other tissues of the face. Mutations in these genes  reduce the production of rRNA, which may trigger the self-destruction (apoptosis) of certain cells involved in the development of facial bones and tissues. It is unclear why the effects of a reduction in rRNA are limited to facial development.