Treacher Collins syndrome (TCS) affects roughly 1 in 50,000 live births worldwide, making it a rare genetic condition. To put that in perspective, in a country with 4 million births per year, about 80 babies would be born with it. The condition primarily affects the bones and tissues of the face, and its severity varies widely from person to person.
What Causes It
TCS results from mutations in genes that help guide early facial development during pregnancy. The most commonly affected gene, TCOF1, accounts for 81 to 93 percent of all cases. Two other genes, POLR1C and POLR1D, cause about 2 percent of cases. A fourth gene, POLR1B, was identified more recently and is responsible for an even smaller fraction.
About 60 percent of cases arise from spontaneous, new mutations, meaning neither parent carries the gene variant. The remaining 40 percent involve a family history. When a parent does carry the mutation, each pregnancy has a 50 percent chance of passing it on, since TCS follows an autosomal dominant inheritance pattern. However, a parent with a very mild case may not realize they carry the gene until a child is born with more noticeable features.
How It Affects the Face and Body
The hallmark of TCS is underdevelopment of the cheekbones (the zygomatic complex), which occurs in 81 to 97 percent of affected individuals. This gives the midface a flattened or sunken appearance and causes the outer corners of the eyes to slant downward. Notching of the lower eyelids is present in 54 to 69 percent of cases, and eyelashes along the lower lid may be sparse or absent.
Ear abnormalities are common and range widely in severity. Ears may be small, unusually shaped, or missing entirely, and the ear canals can be narrowed or absent. About 50 percent of people with TCS have conductive hearing loss, meaning sound doesn’t travel efficiently from the outer ear to the inner ear. The inner ear itself typically works fine, so hearing aids or bone-anchored hearing devices can make a significant difference.
A small or recessed jaw is another frequent feature. In severe cases, this can narrow the airway enough to cause breathing difficulties, particularly in newborns. Obstructive sleep apnea affects roughly 46 percent of people with TCS overall, and the rate is even higher in children, at about 54 percent. Some infants with severely compromised airways need interventions like positive airway pressure devices or, in the most serious situations, a temporary tracheostomy to breathe safely.
Severity Varies Enormously
One of the most important things to understand about TCS is that it exists on a wide spectrum. Some people have features so subtle they go undiagnosed for years. Others are born with significant facial differences that affect breathing, hearing, and feeding from the start. There is no reliable way to predict severity based on the specific gene mutation alone, which is why even within the same family, one person may be mildly affected while another is more severely impacted.
How It’s Diagnosed
TCS is usually identified at birth based on its characteristic facial features. In families with a known history, prenatal diagnosis is possible. Genetic testing during the first trimester can determine whether the fetus carries the mutation, and detailed ultrasound imaging later in pregnancy can help assess how severely the condition may present. For cases without a family history, ultrasound findings such as an unusually small jaw or absent cheekbones may prompt genetic testing before delivery.
Genetic testing after birth confirms the diagnosis by identifying mutations in TCOF1, POLR1C, POLR1D, or POLR1B. In about 5 to 17 percent of clinically diagnosed cases, no mutation is found in any of these known genes, suggesting other genetic factors may be involved.
Treatment and Long-Term Outlook
TCS does not affect intelligence or cognitive development. Life expectancy is normal in the vast majority of cases, provided any airway issues in infancy are managed effectively. The primary challenges are functional (breathing, hearing, eating) and structural (facial bone development), and treatment focuses on addressing these over time.
Most children with TCS undergo a staged series of reconstructive procedures as they grow. Cheekbone and eye socket reconstruction typically happens around age five to seven, when the facial bones have grown enough to work with. Ear reconstruction, for children born with very small or absent ears, generally begins after age six. Lower eyelid repair to correct notching can involve minor procedures and is timed based on the child’s specific needs.
Hearing support often starts early. Bone-conduction hearing devices can be fitted in infancy, which is critical for speech and language development. Children with sleep apnea may use positive airway pressure machines at night, and some benefit from jaw advancement surgery as they get older, which both improves breathing and addresses facial symmetry.
Because TCS involves multiple systems, care is best coordinated by a craniofacial team that includes surgeons, audiologists, speech therapists, and other specialists. Many children undergo several surgeries throughout childhood and adolescence, with the goal of optimizing both function and appearance by the time they reach adulthood.