what causes treacher collins syndrome

Treacher Collins syndrome is a genetic disorder that affects the development of bones and other tissues of the face, causing facial anomalies and hearing loss. The condition is caused by mutations in one of three genes that control bone growth in and around the face: TCOF1, POLR1C, or POLR1D. TCOF1 gene variants are the most common cause of the disorder, accounting for 81 to 93 percent of all cases, while POLR1C and POLR1D gene variants cause an additional 2 percent of cases. In individuals without an identified variant in one of these genes, the genetic cause of the condition is unknown. The mutation occurs spontaneously in most cases, meaning neither parent has the TCS gene or TCS symptoms. However, if one parent has Treacher Collins syndrome, the child may also have it, depending on which gene is affected.