Treacher Collins Syndrome (TCS)

What is Treacher Collins Syndrome (TCS)?

Treacher Collins syndrome (TCS) is a rare disorder characterized by distinct abnormalities of the head and face. It affects the development of bones and tissues in the face, which leads to underdevelopment in the cheek bones, and a very small chin and jaw. Abnormalities are usually present at birth. TCS affects males and females equally and is estimated to occur in about 1 in 50,000 people. However, since some cases are very mild, they may go undiagnosed.

What are the symptoms of TCS?

The signs in TCS can vary greatly, meaning that not every person will have all the symptoms listed below. They include:

Underdeveloped cheek bones
Small jaw and chin
Cleft palate
Downward slanting eyes
Sparse eyelashes
Notches in the lower eyelids
Small, unusually developed, or completely absent ears
Hearing loss
Respiratory problems
Feeding problems
Vision impairment

What causes TCS?

When a gene mutates, it can lead to diseases. TCS can be inherited in different ways depending on which gene has mutated to cause the disease. In about sixty percent of cases, TCS is caused by a spontaneous mutation, meaning that it occurs in people with no family history of the disease. In other cases, TCS is inherited. Human traits are inherited from a person’s father and mother; each one contributes a copy of a gene, which interacts with the other copy. When the TCOF1 or POLR1D genes are affected, TCS is inherited in an autosomal dominant pattern, which means that only one parent needs to pass down a copy of the gene for the condition to occur. However, when the mutation occurs in the POLR1C gene, TCS is inherited in an autosomal recessive pattern. This means that both parents need to pass down a copy of the defective gene for the condition to occur. These genes affect early development of the face, before birth. Their mutations are what lead to the defects in facial structure. TCS can occur from mutations in other genes, but the specific genes have yet to be identified.