Abstract: SA-PO1019

Acute Hypocalcemia in Patients on Denosumab Therapy Following Transfusion

Session Information

Category: Nephrology Education

  • 1302 Fellows and Residents Case Reports

Authors

  • Zaman, Warda, Northwell Health Lenox Hill Hospital, New York, New York, United States
  • Patel, Komal, Northwell Health Lenox Hill Hospital, New York, New York, United States
Background

We present two patients on denosumab therapy with acute hypocalcemia following pRBC transfusion.

Methods

An 84-year old man with CKD III presented with fatigue 12 days after denosumab therapy to treat bone metastases from carcinoid tumor. Initial labs showed Ca 7.9mg/dL, albumin 2.5g/mL, Cr 1.57mg/dL, and eGFR 40mL/min. He received 1 unit pRBC and developed muscle cramps 2 hours post transfusion. Repeat blood work revealed Ca< 5.0mg/dL, ionized Ca 0.77mmol/L, albumin 2.5g/mL, Cr 1.46mg/dL, eGFR 40mL/min, 25-OH Vitamin D 4ng/mL, 1,25-di(OH) Vitamin D 41.6pg/mL and PTH 340pg/mL. He required calcium infusion for 4 days, and maintained his calcium level above 8.0 mg/dL with oral supplementation.

A 77-year old man with CKD IV and metastatic prostate cancer who had received denosumab 4 weeks prior presented with a right pathologic femoral neck fracture. Labs revealed Ca 7.7mg/dL, albumin 2.7g/mL, Cr 2.57mg/dL, and eGFR 23mL/min. On hospital day 9, after a second pRBC transfusion, Ca level was < 5.0mg/dL from 6.1mg/dL, ionized Ca 0.83mmol/L, albumin 2.0g/mL, Cr 2.73mg/dL, eGFR 21mL/min, 25-OH Vitamin D 21.4ng/mL, 1,25-di(OH) Vitamin D 112pg/mL and PTH 1321pg/mL. He reported lethargy with perioral paresthesia without Chvostek sign or carpopedal spasm. He required calcium infusion for 24 hours, along with oral supplementation and subsequently maintained a calcium level of 8.3 mg/dL.

Conclusion

Denosumab, a monoclonal antibody to RANK ligand, inhibits osteoclast formation decreasing bone resorption and increasing bone mineral density. It is not metabolized or excreted renally. Hypocalcemia post-denosumab is reported in 5.5% to 20.8% of patients. It is known to cause a nadir in calcium 10 days after administration, with effects lasting up to twelve months. Renal insufficiency results in activated vitamin D deficiency and secondary hyperparathyroidism increasing risk of hypocalcemia with denosumab. Symptomatic hypocalcemia with citrated blood is rare unless citrate metabolism is impaired in hepatic or renal failure. Our case report demonstrates the need for providers to adhere to guidelines advising against blood transfusion with Hgb >7.0g/dl. Furthermore, providers should maintain a high degree of suspicion for hypocalcemia and closely monitor Vitamin D and calcium levels when using denosumab in CKD patients.