Congenital syngnathia: a case report of osseous fusion between the maxilla and mandible.

Congenital fusion of the maxilla and mandible is an extremely rare craniofacial anomaly that can present at birth with trismus and feeding difficulties. We report a case of a neonate with right-sided osseous fusion between the maxilla and mandibular body, initially unrecognized at multiple centers. The patient developed severe hyperbilirubinemia and dehydration due to impaired feeding. Computed tomography with three-dimensional reconstruction confirmed the diagnosis and revealed no involvement of the temporomandibular joint or tooth buds. Ultrasonic osteotomy was used to resect the fusion, restoring partial mouth opening and enabling enteral feeding. This case emphasizes the importance of early imaging for accurate diagnosis and timely multidisciplinary intervention. Prompt recognition and surgical correction can improve oral function and help prevent potential neurologic complications, highlighting a critical diagnostic and therapeutic pathway for this rare but manageable condition.