Medication-related osteonecrosis of the jaw (MRONJ) is a rare yet serious complication of antiresorptive therapy. The aetiology remains unclear. Established risk factors include prolonged exposure to antiresorptive agents, dental procedures like extractions, denture use and concomitant use of corticosteroids or chemotherapy (1). MRONJ is defined as exposed jaw bone that fails to heal within 8 weeks (2).
We present the case of a 78-year-old male with bone mineral density criteria osteoporosis and negative fracture history, managed with six-monthly Denosumab, who developed severe osteonecrosis of the jaw with two fistulae opening at his chin. His medical history includes rheumatoid arthritis treated with Methotrexate, Hydroxychloroquine, and a short course of prednisolone in 2017. He had Zoledronic acid infusions in 2017 and 2018. He transitioned to Denosumab 60mg subcutaneous injection every six months from August 2020 to August 2022. Following complaints of throat pain in 2022, diagnostic imaging revealed osteonecrosis, warranting referral to an Oral Maxillofacial surgeon. Subsequent procedures included debridement and fistulectomy in February 2023, with additional surgery in December 2023 due to ongoing bone necrosis and grade 4/4 ONJ. Notably, serum bone markers remained suppressed six months after his last Denosumab dose, a period when rebound is expected.
This case highlights severe osteonecrosis of the jaw despite short-term Denosumab treatment. It contrasts with literature associating MRONJ with higher antiresorptive agent doses or with the frequency used in cancer treatment rather than osteoporosis management doses (1). The patient's preceding Zoledronic acid doses may have contributed to his risk but were given more than four years prior to the MRONJ diagnosis. Specific risk factors for MRONJ with Denosumab use warrant further investigation. Identifying these factors would aid in identifying patients at heightened risk of MRONJ.