A case of severe, irreversible hypocalcemia after one dose of pamidronate administered for hypercalcemia of malignancy

This is a case report of a patient who developed severe, irreversible hypocalcemia after receiving one dose of pamidronate 90 mg for hypercalcemia of malignancy. Hypocalcemia is a known risk of bisphosphonate treatments, but the incidence of severe hypocalcemia is rare, and the risk factors are well established. However, in the treatment of hypercalcemia of malignancy, the treatment objective is to reduce the elevated serum calcium level, and the bisphosphonate is usually given as one time dose only. The potential for developing severe hypocalcemia may not be considered a significant concern in this setting compared to the setting of the treatment of bone metastasis, where the baseline serum calcium level is not elevated and the bisphosphonate is administered at a regular interval of every three to four weeks. Furthermore, there is unawareness of prevalence of vitamin D deficiency in cancer patients, especially in those with advanced cancer, which may lead to inadvertent, severe hypocalcemia from bisphosphonate treatment. The objective of this case report is to bring awareness to the risk of severe hypocalcemia in patients with hypercalcemia of malignancy and the high prevalence of unrecognized vitamin D deficiency in cancer patients.