Denosumab-Induced Rebound Hypercalcemia Treated With Bisphosphonates in a Pediatric Patient

Denosumab is a RANK-L inhibitor used off-label as a treatment for a variety of pediatric bone disorders, including aneurysmal bone cysts (ABC). Rebound hypercalcemia is a known side effect after denosumab therapy and is more commonly reported in pediatric patients. Although there are no established treatment guidelines, denosumab-induced rebound hypercalcemia is usually managed with a combination of intravenous fluids, diuretics, corticosteroids, denosumab, and/or bisphosphonates. We present the case of a 10-year-old female patient with history of a right sacral ABC treated with denosumab who presented with recurrent episodes of rebound hypercalcemia beginning 3 months after denosumab cessation. After the third hospitalization for hypercalcemia, which was treated with zoledronic acid, normocalcemia was achieved. This case demonstrates an increasingly recognized side effect of denosumab therapy that occurs mainly in skeletally immature patients and presents a possible approach to initial therapy of rebound hypercalcemia with a long-acting bisphosphonate.