What is Treacher Collins syndrome

Treacher Collins syndrome is a rare genetic disorder characterized by distinctive craniofacial abnormalities, primarily affecting the development of the bones and tissues of the face. It typically impacts the cheekbones, jaw, and ears, often resulting in hearing loss and breathing difficulties, though intelligence is usually within the normal range.

What are the primary physical characteristics of Treacher Collins syndrome?

Treacher Collins syndrome manifests through a specific pattern of facial features caused by the abnormal development of the first and second pharyngeal arches during embryonic growth. While the severity varies significantly even among family members, the most common clinical features include underdeveloped cheekbones (zygomatic hypoplasia), a small lower jaw (micrognathia), and downward-slanting eyes with notches in the lower eyelids (colobomas). In many individuals with Treacher Collins syndrome, the external ears are small or malformed, and the middle ear bones may be affected, leading to conductive hearing loss in approximately 40% to 50% of cases.

What causes Treacher Collins syndrome and is it hereditary?

The underlying mechanism of Treacher Collins syndrome involves mutations in specific genes that govern the production of proteins essential for early facial bone and tissue development. The condition is most commonly associated with mutations in the TCOF1 gene, which accounts for about 80-95% of cases, though POLR1C and POLR1D mutations are also implicated. Inheritance is typically autosomal dominant, meaning one copy of the altered gene is sufficient to cause the condition, though many cases result from a new (de novo) mutation in an individual with no family history.

How common is Treacher Collins syndrome?

Treacher Collins syndrome is considered a rare condition with an estimated prevalence of approximately 1 in 50,000 live births globally. Because the condition affects development during gestation, it is present at birth (congenital). It affects males and females equally and occurs across all ethnic and geographic populations. Within the DiseaseMaps.org community, 78 people with Treacher Collins syndrome have already joined to share their lived experiences and connect with others navigating similar clinical journeys.

How is this condition differentiated from other craniofacial disorders?

While several syndromes affect facial development, Treacher Collins syndrome is distinct due to its specific combination of bilateral (two-sided) symmetry and the absence of limb or systemic organ abnormalities often found in other conditions like Nager syndrome or Miller syndrome. Key diagnostic markers include:

• Down-slanting palpebral fissures (eyes) with lower lid colobomas.


• Hypoplasia of the zygomatic complex (cheekbones).


• Mandibular retrognathia (recessed jaw).


• External ear abnormalities with associated conductive hearing loss.


• Normal cognitive development, which distinguishes it from many other complex genetic syndromes.

Next steps

• Consult with a clinical geneticist to confirm a diagnosis through molecular genetic testing.


• Schedule an evaluation with a multidisciplinary craniofacial team, including pediatric otolaryngologists, plastic surgeons, and speech therapists.


• Connect with the DiseaseMaps.org community to share experiences with others who have Treacher Collins syndrome.


• Review resources from organizations like the Children’s Craniofacial Association for specialized support and advocacy.

Medical Disclaimer: This content is for educational purposes only and does not constitute medical advice, diagnosis, or treatment; always seek the guidance of a qualified physician with any questions regarding a medical condition.

References

• NIH Genetic and Rare Diseases Information Center (GARD): Treacher Collins syndrome overview.


• Orphanet: Rare disease database entry for Treacher Collins syndrome.


• Online Mendelian Inheritance in Man (OMIM): Clinical synopsis for TCOF1-related disorders.


• Children's Craniofacial Association: Patient education and support resources.