Bisphosphonate therapy for persistent hyperparathyroidism after kidney transplantation-A case report

Post-transplant hyperparathyroidism (PT-HPT) is common in kidney transplant recipients (KTRs) and can cause nephrocalcinosis and graft dysfunction. Cinacalcet is commonly used for treating PT-HPT but may induce calciuria and exacerbate nephrocalcinosis. The concurrent use of bisphosphonates with cinacalcet to prevent this complication has not been reported. We report a case of PT-HPT-associated graft dysfunction. The patient had ESRD due to IgAN. She had been on continuous ambulatory peritoneal dialysis (CAPD) for 7 years before undergoing kidney transplantation (KT). Pre-KT intact parathyroid hormone (iPTH) was 101 pmol/L, alkaline phosphatase (ALP) 205 IU/L, Ca 2.40 mmol/L and PO4 2.2 mmol/L. There was immediate graft function after KT and the existence of persistent hyperparathyroidism (Cr 72 μmol/L, eGFR > 60 mL/min/1.73 m², Ca 2.85 mmol/L, PO4 0.6 mmol/L, ALP 315 IU/L, iPTH 16.4 pmol/L). Progressive renal impairment ensued over the next 10 months (Cr 146 μmol/L, eGFR 34 mL/min/1.73 m², Ca 2.77 mmol/L, PO4 0.9 mmol/L, ALP 142 IU/L, iPTH 24.4 pmol/L). Graft biopsy at 10 months post-KT revealed widespread tubular calcifications and no evidence of rejection. Intravenous pamidronate 60 mg was given quarterly for 3 doses in addition to cinacalcet therapy. ALP decreased from 147 to 81 IU/L despite refractory PT-HPT and renal function improved. Total parathyroidectomy was performed 1 month after the last pamidronate dose. Renal function remained stable for up to 4 years post-KT (Cr 151 μmol/L, eGFR 33 mL/min/1.73 m², Ca 2.19 mmol/L, PO4 1.3 mmol/L, ALP 70 IU/L, iPTH < 0.1 pmol/L). Our case report highlights the therapeutic potential of pamidronate in addition to cinacalcet in the management of PT-HPT-associated nephrocalcinosis.