ABC of clinical genetics. Dysmorphology and teratogenesis.

Treacher Collins syndrome: abnormal first branchial arch development giving rise to malar and mandibular hypoplasia with external ear malformations. Dysmorphology is the study of malformations arising from abnormal embryogenesis. Recognition of patterns of multiple congenital malformations may allow inferences to be made about the timing, mechanism, and aetiology of structural defects. Animal research is providing information about cellular interactions, migration, and differentiation processes and gives insight into the possible mechanisms underlying human malformations. Diagnosing multiple congenital abnormalities in children can be difficult but is important to give correct advice about management, prognosis, and risk of recurrence.