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Treacher Collins syndrome is a rare autosomal dominant genetic disorder characterized by bilateral craniofacial malformations affecting structures derived from the first and second pharyngeal arches. The condition presents with distinctive facial features including downward-slanting eyes, micrognathia, malar hypoplasia, and conductive hearing loss due to external auditory canal atresia or middle ear malformations.
The syndrome results from mutations in genes involved in ribosomal biogenesis, primarily TCOF1 (90% of cases), POLR1C, or POLR1D, leading to defective ribosome assembly and increased apoptosis of neural crest cells. This disrupted neural crest cell migration and proliferation during embryogenesis specifically affects the development of facial bones, ears, and associated structures derived from the first and second pharyngeal arches.
Diagnosis is primarily clinical, based on characteristic facial dysmorphism including antimongoloid slant of palpebral fissures, colobomas of the lower eyelids, hypoplastic zygomatic arches, and micrognathia with potential airway compromise. The severity varies widely even within families due to variable expressivity, requiring multidisciplinary management including otolaryngology for hearing assessment, plastic surgery for reconstruction, and careful airway evaluation in neonates.