Introduction: Hypocalcemia is a condition characterized by the following signs and symptoms: perioral numbness, paresthesias, muscle cramps, carpopedal spams and/or seizures. Denosumab causes hypocalcemia through the inhibition of the Receptor activator of nuclear factor kappa-Β (RANK) ligand which prevents osteoclast formation and activation. In rare instances, intractable hypocalcemia occurs during treatment. This case report will discuss the clinical presentation and treatment of intractable hypocalcemia induced by Denosumab.
Case Description: Our patient is a 71-year-old, Filipino male diagnosed with prostate cancer, who developed intractable hypocalcemia after being given Denosumab for bone metastasis. Prior to administration of Denosumab, his serum calcium was low at 6.9 mg/dL and had a vitamin D level of 14.13 ng/dL. Patient was asymptomatic and on physical examination, he did not manifest any signs of hypocalcemia such as tetany. Patient tested negative for Chvostek's sign. Patient remained asymptomatic despite having persistently low serum calcium even after multiple intravenous infusions of calcium gluconate. Patient was also maintained on 3 tablets of calcium carbonate four times a day and calcitriol 4 tablets 4 times a day. The patient had weekly monitoring of calcium levels and had normal calcium levels at the 12th week from the start of treatment (with ionized calcium levels approximately 1.0 mmol/L).
Conclusion: Although based on limited data and reports, Denosumab-induced hypocalcemia will most likely resolve in about 3 months with supportive treatment. Baseline calcium and vitamin D levels should be obtained prior to starting and then periodically measured. If found to have hypocalcemia and vitamin D deficiency, these should be repleted prior to initiation of Denosumab.
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