A case of recurrent multiple myeloma showing clinical features similar to medication-related osteonecrosis of the jaw (MRONJ)

We report a case of recurrent multiple myeloma in the mandibular ramus showing clinical features similar to those of medication-related osteonecrosis of the jaw (MRONJ) at the initial visit. A 53-year-old man was referred to our department for suspected MRONJ following repeated intravenous bisphosphonate administration, with the chief complaint of hypaesthesia in the mandible. The patient had been treated with bortezomib and cyclophosphamide plus dexamethasone for multiple myeloma as well as intravenous bisphosphonate (zoledronic acid). Radiographic examination revealed sclerotic bone and resorptive lesions in the mandibular angle and ramus. Given the history of myeloma, biopsy was performed for histopathological diagnosis. Biopsy results indicated a diagnosis of recurrent multiple myeloma and not MRONJ, and the patient was treated with lenalidomide and dexamethasone. Consequently, the hypaesthesia in the mandible improved without further growth of the lesion, and the tumor has remained under control so far during the follow-up of about 1 year.