Abstract: Objective: To analyze the clinical materials of the patient with the first branchial arch syndrome complicated with dermoid cyst and clarify its pathogenesis, and to improve the understanding of the clinicians on this disease. Methods: The clinical materials of one patient with the first branchial arch syndrome complicated with dermoid cyst were collected. Combined with the relevant literatures, the clinical features, radiological appearance, and diagnosis and operation methods were discussed. Results: A 9-year-old girl was hospitalized because the right facial area had swollen with no obvious incentives for a week, the anti-inflammatory treatment was ineffective, and the swelling was slowly aggravated. The special examination showed that the face was asymmetrical, the right face was swollen, and the sinus was visible and yellow-white liquid could be squeezed out. The preauricular appendages from both sides of the parotideomasseteric region could be seen, and the right external ear canal was abnormal. The left external auditory canal and tragus of patient's father was deformity and one round preauricular excrescence could be seen. The CT and MRI results showed maxillary and mandibular bone hypoplasia of the patient, sclerotin absent of the posterior portion of the right mandible ramus and smaller right parotid gland than the contralateral one. The color ultrasound results showed a subcutaneous 1.6 cm×1.1 cm echo on the right cheek containing cystic and solid components in which that cystic component was main. The postoperative pathological diagnosis was dermoid cyst. Conclusion: The first branchial arch syndrome exists unclear swelling; when anti-inflammatory treatment is ineffective, the first branchial arch syndrome complicated with dermoid cyst could be firstly considered. This disease has a familial hereditary tendency and the operation is the primary treatment method.

Key words: first branchial arch syndrome, dermoid cyst, congenital malformation, oral and maxillofacial region