Management of Complete Pediatric Extraarticular Ankylosis of the Temporomandibular Joint Progressive Osseous Heteroplasia.

INTRODUCTION: Progressive osseous heteroplasia (POH) is an exceptionally rare genetic disorder characterized by heterotopic bone formation within soft tissues. There are currently no evidence-based guidelines for its management, and involvement of the temporomandibular joint (TMJ) has not previously been reported. We present the first documented case of complete pediatric ankylosis of the TMJ secondary to POH. CASE DESCRIPTION: A 12-year-old girl presented with progressive, painless trismus and facial dermal calcifications, with an interincisal opening of 3 mm. Imaging demonstrated extensive heterotopic ossification involving the mandible, masticatory muscles, and right TMJ. Following failure of conservative management and significant deterioration in quality of life, a multidisciplinary team and ethics committee recommended surgical intervention. The patient underwent right disarticulation hemimandibulectomy with resection of involved masticatory muscles and reconstruction using an anterolateral thigh free flap.Intraoperatively, a mouth opening of 30 mm was achieved. Postoperative recovery was uncomplicated, with temporary facial nerve weakness resolving fully. At 2-year follow-up, the patient maintained a functional mouth opening of 25 mm with no radiologic evidence of recurrent ossification. Histopathology confirmed features consistent with POH. CONCLUSION: This case demonstrates that, despite traditional concerns about surgery in POH, carefully planned surgical resection combined with soft-tissue reconstruction can provide meaningful functional improvement without recurrence. Multidisciplinary decision-making and individualized treatment planning are essential when managing complex craniofacial manifestations of this rare condition.