Abstract: FR-PO285

Kidney and Parathyroid Transplants for Hereditary Hypoparathyroidism Due to a Calcium Sensing Receptor (CaSR) Mutation Reduced Calciuria but Did Not Normalize Serum Calcium

Session Information

Category: Mineral Disease

  • 1202 Mineral Disease: Vitamin D, PTH, FGF-23

Authors

  • Muczynski, Kimberly A., University of Washington, Seattle, Washington, United States
  • Dorschner, Michael O, University of Washington, Seattle, Washington, United States
  • Leca, Nicolae, University of Washington, Seattle, Washington, United States
  • Bakthavatsalam, Ramasamy, University of Washington, Seattle, Washington, United States
  • Reyes, Jorge D, University of Washington, Seattle, Washington, United States
  • Byrd, David R, University of Washington, Seattle, Washington, United States
Background

Parathyroid transplants have been reported for a couple cases of hereditary hypoparathyroidism using allografts from fetal and living donors. We now communicate success in transplantation of a living related kidney and deceased unrelated donor parathyroids into a patient with hereditary undetectable parathyroid hormone (PTH).

Methods

A father and daughter have had undetectable PTH levels since childhood. Calcium and vitamin D are essential to prevent symptomatic, life-threatening hypocalcemia. The father progressed to ESRD at age 52 due to nephrocalcinosis from his required calcium supplements. He received a kidney transplant pre-dialysis from an unaffected sister. The sister was felt not to be an appropriate parathyroid donor due to prior neck radiation for hyperthyroidism. Hence deceased donor parathyroids were transplanted into the father’s forearm one week later, after institutional review board, hospital administration and organ procurement organization collaboration. Induction immunosuppression with ATG was used for the kidney and maintenance immunosuppression with tacrolimus, mycophenolate and prednisone were continued at the time of parathyroid transplant.

Conclusion

The father’s kidney has functioned well, urine calcium excretion has been reduced by over 50%, and PTH levels are 13-15 pg/ml in the peripheral blood and 122 pg/ml from venous drainage of the parathyroid allograft seven months post-transplant. However, supplemental calcium and vitamin D are still required to prevent hypocalcemia. Perplexed by these findings, exome sequencing of genes that might account for hypoparathyroidism was performed by Precision Diagnostics at the University of Washington. PTH gene was normal but a mutation in the CaSR mapping to other gain of function mutations was identified. Having replaced the CaSR in the kidney and parathyroids with the combined allograft transplants we presume that renal calcium metabolism has been normalized and the new kidney will be protected from recurrent nephrocalcinosis. The need for supplemental calcium to prevent hypocalcemia suggests that CaSR in other organs (such as bone or gut), has a greater contribution in maintaining serum calcium levels than preventing calcium loss through the kidney.

Funding

  • Private Foundation Support