13 Lateral Facial Dysplasias: Treacher Collins Syndrome

Clinical Presentation

A 2-week-old infant presents with facial deformity.

Figure 13A

Radiologic Findings

Three-dimensional CT demonstrates bilateral midfacial hypoplasia. There is hypoplasia of the malar bone, with absence of the zygomatic arch and hypoplasia of the mandibular ramus and condyle. The temporomandibular joint is absent (Fig. 13A1). The temporal bone is not fully developed, and the external auditory canal is abnormally located inferiorly. Soft tissue imaging demonstrates an abnormal pinna (Fig. 13A2). These abnormalities were essentially symmetrical.

Diagnosis

Lateral facial dysplasias: Treacher Collins syndrome (TCS), also called mandibulofacial dysostosis (MFD1) or Treacher Collins-Franceschetti syndrome (TCOF)

Differential Diagnosis

Hemifacial microsomia (HFM) is also called oculoauriculovertebral dysplasia and Goldenhar’s syndrome: coloboma of the upper eyelid, hemifacial microsomia (may be bilateral but asymmetrical), and vertebral defects.
Acrofacial dysostosis 1 or Nager’s syndrome: severe malar hypoplasia and micrognathia, associated with absence of radius, radio-ulnar synostosis, hypoplasia. or absence of the thumb. Gene defect located on 9q32
Ablepharon macrostomia syndrome (AMS): absent eyelid, eyebrows, eyelashes, fusion defect of the mouth, rudimentary external ears, ambiguous genitalia, rudimentary nipples, and coarse, dry skin

Discussion

Background

TCS is a disorder of craniofacial development. An autosomal dominant syndrome, it is found in 1 per 50,000 live births. The TCOF1 mutation is found in 78% of patients. Familial in 40% of cases, it arises as new spontaneous mutation in 60%. The obligatory features of TCOF are marked hypoplasia of the malar bone, hypoplasia of the mandibular ramus and condyle, obliteration of the frontonasal angle, colobomas of the lower eyelids, and malformation of the eyelashes.

Etiology

Various explanations have been offered regarding the pathogenesis of TCS: problems of differentiation of the branchial arch mesoderm preventing normal facial bone development, abnormal ossification of the viscerocranium, even ischemia from stapedial artery hypoplasia or defect of ectomesenchymal cells within the developing trigeminal ganglia.