A DRAMATIC RESPONSE TO DENOSUMAB: PROTRACTED HYPOCALCEMIA RELATED TO HTLV-1 ASSOCIATED ADULT T-CELL LEUKEMIA/LYMPHOMA

Introduction: Adult T-cell leukemia/lymphoma (ATL) is known for its aggressive behavior, frequently presenting with hypercalcemia. ATL tumor cells uniquely secrete PTH-rP, viral peptides and inflammatory cytokines, inducing a state of high bone turnover and activation of the receptor activator of nuclear factor kappa-B (RANK) signaling pathway resulting in hypercalcemia. Case Presentation: A 54-year-old woman diagnosed with ATL presented with severe hypercalcemia refractory to bisphosphonate therapy. Treatment with denosumab was followed by protracted hypocalcemia and hypophosphatemia lasting approximately 5 months. Conclusion: Hypercalcemia due to acute ATL was responsive in this case to denosumab therapy. Clinicians should be aware of the possibility of protracted hypocalcemia in patients with ATL exposed to denosumab therapy.