Treacher Collins Syndrome (cont.)

People with Treacher Collins syndrome often have eyes that slant downward, sparse eyelashes, and a notch in the lower eyelids called a 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. Defects in the middle ear (which contains three small bones that transmit sound) cause hearing loss in about half of cases. People with Treacher Collins syndrome usually have normal intelligence.

This condition affects an estimated 1 in 50,000 people.

Mutations in the TCOF1 gene cause Treacher Collins syndrome.

The TCOF1 gene provides instructions for making a protein called treacle. Although researchers have not determined the precise function of this protein, they believe that it plays a critical role before birth in the development of bones and other tissues in the face. Mutations in the TCOF1 gene reduce the amount of treacle that is produced in cells. Researchers believe that a loss of this protein signals cells that are important for the development of facial bones to self-destruct (undergo apoptosis). This abnormal cell death may lead to the specific problems with facial development found in Treacher Collins syndrome.

This condition has an autosomal dominant pattern of inheritance, which means one copy of the altered gene in each cell is sufficient to cause the disorder. About 60 percent of cases result from new mutations in the TCOF1 gene. These cases occur in people with no history of the disorder in their family. In the remaining cases, a person with Treacher Collins syndrome inherits the altered gene from an affected parent.

Source: MedicineNet.com
http://www.medicinenet.com/treacher_collins_syndrome/article.htm