Mandibulofacial dysostosis (Treacher-Collins syndrome)

Findings

The lateral plain radiograph of the skull demonstrates the typical facial features of the abnormality. There is marked bowing of lower border of the mandible. The mastoids are acellular with absent external auditory canals. Note the constriction of the air-outlined pharynx, particularly at the level of the oropharynx. There is aplasia of the zygomatic arches.
Axial CT images through the level of the ear structures demonstrate microtia and aplasia of the external auditory canals. Congenitally small and abnormal middle ear cavities with absent ossicles. There is thickening of the bone at the oval window and dehiscence of the bilateral posterior semicircular canals.

Differential diagnosis:
- Maxillofacial dysostosis
- Mandibulofacial dysostosis (Treacher-Collins syndrome)
- Nager syndrome
- Oculoauriculovertebral sequence
- Toriello type mandibulofacial dysostosis


Diagnosis: Mandibulofacial dysostosis (Treacher-Collins syndrome)


Key points

Mode of inheritance: Autosomal dominant; genetic homogeneity; almost complete penetrance and wide variability in expression.
Gene maps to chromosome 5q32-33.1.
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, TEF, and anal atresia.


Radiologic manifestations

Hypoplasia of the malar bones.
Concave curvature of the horizontal ramus of the mandible is pathognomonic.
+ Hypoplasia or aplasia of the condylar and coronoid processes of the mandible.
Underdeveloped paranasal sinuses.
Various ear anomalies.
+ Hypoplasia or aplasia of the EAC.
+ Hypoplasia or aplasia of the tympanic cavity.
+ Closed middle ear cavity by a thick, osseous atretic plate.
+ 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.