Hemifacial microsomia.

Hemifacial microsomia is the second most common congenital facial anomaly, second only to cleft lip and palate. While its precise etiology is not yet known, it is likely caused by a disruption in the development of the first two branchial arches early in embryologic development. The resulting phenotype is one of varying degrees of unilateral hypoplasia of the mandible, ear deformity, and macrostomia. Early diagnosis of hemifacial microsomia is important not only to plan for surgical reconstruction of affected features, but also to lead the physician in further evaluation for associated abnormalities or disabilities. This article will introduce the reader to the most common variants seen in hemifacial microsomia, discuss the possible etiologies of the anomalies, and will highlight the importance of evaluating these patients early in life for such potentially disabling but correctable problems such as hearing loss, feeding disabilities, and neurological deformities.