Mode of inheritance:
Autosomal dominant; genetic homogeneity; almost complete penetrance and wide variability in expression.
· Prevalence of Treacher Collins syndrome is in the range 1 per 25,000 to 1 in 50,000 live births.
Clinical manifestations: Abnormalities in the structures derived from the first and second pharyngeal pouch, groove, and arch.
· Facial hypoplasia with sunken cheek bones and malformed ears
· Macrostomia
· Cleft palate and/or cleft lip with palatopharyngeal incompetence
· Obliteration of the nasal frontal angle with narrow nares and hypoplasia of the alar cartilages
· Down slanting of the palpebral fissure and coloboma in the outer portion of the lower lid
· Conductive deafness
· Dental anomalies
· Projection of scalp hair onto the lateral aspect of the cheek
· Some association with congenital heart disease, tracheoesophageal fistula, and anal atresia
Radiologic manifestations:
· Hypoplasia of the malar bones
· Concave curvature of the horizontal ramus of the mandible is pathognomonic
o Hypoplasia or aplasia of the condylar and coronoid processes of the mandible
· Underdeveloped paranasal sinuses
· Various ear anomalies
o Hypoplasia or aplasia of the external auditory canal (EAC)
o Hypoplasia or aplasia of the tympanic cavity
o Closed middle ear cavity by a thick, osseous atretic plate
o Closed oval window
· Hypoplasia or aplasia of the mastoid air cells
· Progressive cranial basilar kyphosis associated with narrowing of the anteroposterior pharyngeal diameter and pharyngeal hypoplasia
· Vertebral anomalies
References
1. Posnick JC, Ruiz RL. Treacher Collins syndrome: Current evaluation, treatment, and future directions. Cleft Palate Craniofac J. 2000;37(5):434.
2. Sulik KK, Johnston MC, Smiley SJ, et al. Mandibulofacial dysostosis (Treacher Collins syndrome): A new proposal for its pathogenesis. Am J Med Genet. 1987;27(2):359-372.
