Severe hypocalcemia and prolonged QT interval due to denosumab in an elderly woman with rheumatoid arthritis and chronic kidney disease.

Denosumab has been approved for the prevention of skeletal-related events of bone metastases (120 mg at every 4 weeks) and for the treatment of osteoporosis (60 mg at every 6 months). Post-denosumab hypocalcemia occurred in 5.2% of the cancer patients (1), but such an event was rarely reported in osteoporosis patients (2). Recently, severe hypocalcemia because of a lower dose of denosumab for osteoporosis has been reported in chronic kidney disease (CKD) patients (3, 4). We describe the first case of rheumatoid arthritis (RA) and CKD associated with severe hypocalcemia and prolonged QT interval after the administration of a lower dose of denosumab.