Rare Subtype of Medication-Related Osteonecrosis of the Jaw: Imaging Findings and Treatment Outcomes of Periosteal Reaction Dominant Type

Abstract Purpose In our previous study,we found a rare type of medication-related osteonecrosis of the jaw (MRONJ), which shows periosteal reaction (PR) at a site distant from the osteolytic lesions or extraction site (periosteal reaction dominant type: PRd type), even though the osteolytic lesions in the bone marrow are localized. Given that the causes and treatment of MRONJ remain unclear, this study aimed to describe the imaging and clinical features of the PRd type. Methods Patients with MRONJ who visited Nagasaki University Hospital during 2009-2020 and received conservative therapy as the initial treatment were included in this study. Site of PR, imaging findings, initial symptoms, outcome, and time to progression were examined. Results Of the 59 MRONJ patients treated with conservative therapy, 38 did not show PR (PR- type), 15 showed PR near the osteolytic region (PR+ type), and six had the PRd type. All patients with the PRd type had submental abscesses, and computed tomography (CT) images demonstrated PR on the lingual side of the anterior mandible. Osteolytic lesions progressed in 6/6 PRd type (100%), 5/15 PR+ type (33.3%), and 2/38 PR- type (5.3%) patients. Time to progression for the osteolytic region on CT was short for the PRd type, at 56-148 days (median, 79 days). Conclusion Among the MRONJ types, the PRd type has a poor prognosis. Therefore, it is necessary to accumulate and analyze more PRd cases in the future. This is the first report to report the presence of this specific subtype of MRONJ,