Hemifacial microsomia

Hemifacial microsomia is a congenital disorder that affects the development of the lower half of the face, most commonly the ears, the mouth and the mandible. It can occur on one side of the face or both. If severe it can lead to difficulties in breathing, obstructing the trachea and requiring a tracheotomy. It is the second most common facial birth defect after clefts, with an incidence in the range of 1 in 3500 to 4500. Hemifacial microsomia shares many similarities with Treacher Collins syndrome.