Denosumab: A potential new treatment option for recurrent Aneurysmal Bone Cyst of the spine.

ABCs are expansile osteolytic lesions typically containing blood-filled spaces separated by fibrous septae. Standard treatment includes surgical resection or curettage and packing; however, for some spinal lesions, the standard approach is not optimal. One therapeutic strategy is to treat spinal ABC with an agent that targets a pathway that is dysregulated in a disease with similar pathophysiology. Denosumab, a human monoclonal antibody to RANKL is effective in the treatment of GCT's. Spinal ABCs are a therapeutic challenge and local recurrence is a concern. We report a case of aggressive recurrent ABC of dorsal spine in a 14-year old female with progressive neurologic deficit who underwent surgical excision and decompression with a recurrence in a short period for which a decompression and fixation was done. She had a recurrence after an asymptomatic period of 6 months and neurologic worsening. Having ruled out use of embolization and radiotherapy, a remission was achieved by treatment with Denosumab using the regimen for GCTs for a duration of 6 months. Follow-up MRI and CT scans at 24 months following inception of Denosumab depicted complete resolution and no recurrence. We conclude that Denosumab can result in symptomatic and radiological improvement in the recurrent locally aggressive ABC and may be useful in selected cases. Long-term results are mandatory to confirm the efficacy of Denosumab and to evaluate local recurrence after stopping Denosumab.