Abstract: FR-PO1220
Tacrolimus-Associated Severe Hypercalcemia After Living-Related Kidney Transplantation: A Case Report
Session Information
- Transplantation: Clinical - Rejection, Biomarkers, and Pharmacology
October 23, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Transplantation
- 2002 Transplantation: Clinical
Authors
- Elhassan, Afra Ahmed Mohamed, Hamad Medical Corporation, Doha, Qatar
- Fituri, Omar, Hamad Medical Corporation, Doha, Qatar
- Abuhelaiqa, Essa, Hamad Medical Corporation, Doha, Qatar
Introduction
Hypercalcemia after kidney transplantation is commonly attributed to persistent hyperparathyroidism, malignancy, granulomatous disease, or excessive calcium/vitamin D supplementation. Tacrolimus-associated hypercalcemia remains poorly described and is rarely considered in differential diagnosis.
Case Description
A 42-year-old woman underwent living-related kidney transplantation from her sister. Induction immunosuppression consisted of 4 doses of anti-thymocyte globulin, followed by steroid free maintenance therapy with tacrolimus and mycophenolate mofetil. Baseline allograft function was stable with serum creatinine ranging from 90 -100 µmol/L. During the early post-transplant period, serum calcium progressively increased and reached severe hypercalcemia level within the first month of transplantation. Extensive work up demonstrated suppressed parathyroid hormone (PTH), low vitamin D level, negative parathyroid hormone-related peptide, negative serum and urine protein electrophoresis, and no evidence of malignancy or infection on PET scan. She was not receiving calcium or vitamin D supplementation. Despite treatment with two doses of Pamidronate, hypercalcemia persisted and recurred. Concurrently, graft function progressively worsened, with serum creatinine reaching 148 µmol/L six months post-transplant. Kidney biopsy demonstrated mild calcineurin toxicity without evidence of rejection. Tacrolimus was subsequently discontinued and replaced with sirolimus, after which both serum calcium and creatinine improved to base line within one month.
Discussion
This case highlights a rare presentation of severe hypercalcemia temporally associated with tacrolimus exposure despite therapeutic trough levels. The resolution of hypercalcemia and improvement in allograft function after tacrolimus withdrawal strongly support tacrolimus-associated hypercalcemia and calcineurin inhibitor toxicity as the likely etiology after exclusion of more common causes. Clinicians should consider tacrolimus-related metabolic complications in transplant recipients with unexplained hypercalcemia and graft dysfunction.
Laboratory trend
| Time Point | Creatinine (µmol/L) | Calcium (mmol/L) | Phosphorus (mmol/L) | PTH (pg/mL) |
| 1 month post-transplant | 122 | 2.95 | 1.29 | 12.9 |
| 3 months post-transplant | 143 | 2.75 | 0.74 | 24 |
| 6 months post-transplant | 148 | 3.10 | 0.89 | 12 |
| 1 month after tacrolimus withdrawal | 105 | 2.41 | 0.70 | 57 |