Hemifacial myohyperplasia: description of a new syndrome.

Hemifacial hypertrophy is a rare condition characterized by unilateral enlargement of all tissues of the face. We describe three patients who exhibit hemifacial hyperplasia of the muscles of facial expression with no other organ system involvement. These three cases, in addition to six other cases identified in the literature, describe a unique constellation of characteristics that place these patients into a distinct syndrome. We suggest that the term "hemifacial myohyperplasia" be used to describe this specific and unique condition.