We reported a case of first and second branchial arch syndrome in a patient who had jaw deformity with bilateral hyperplasia of the mandibular coronoid process. The patient was a 16-year-old girl. She visited our maxillofacial orthognathic department because of masticatory insufficiency and muscular contracture in 1989 (when she was 6 years old). She had an asymmetric face, deformed ears, and a small mandible. Panoramic X-ray examination revealedbilateral hyperplasia of the mandibular coronoid process. Orthodontic treatment was started in the same year. In 1999, the patient visited our dental surgery department to undergo orthgnathic surgery. Excision of the mandibular coronoid processes was performed to relieve the muscular contracture in the same year, and sagittal split ramus osteotomy was performed to improve the mandibular deformity in 2000. Both the muscular contracture and dental occlusion improved thereafter. The patient has been under long-term observation by the two departments.
