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Kidney Week

Abstract: FR-PO588

Better Oxalate than Never: A Diagnosis of Primary Hyperoxaluria Made After Renal Transplantation

Session Information

Category: Genetic Diseases of the Kidneys

  • 1202 Genetic Diseases of the Kidneys: Non-Cystic

Authors

  • Panthappattu, Justin Joseph, Hackensack Meridian Hackensack University Medical Center, Hackensack, New Jersey, United States
  • Suldan, Zalman L., Hackensack Meridian Hackensack University Medical Center, Hackensack, New Jersey, United States
Introduction

Primary hyperoxaluria (PH), a genetic impairment of glycoxylate metabolism, causes kidney injury and end-stage renal disease (ESRD) when left untreated. We present a case of PH diagnosed following deceased donor renal transplantation (DDRT).

Case Description

A 60 year old woman with ESRD on hemodialysis (HD) thought to be from hypertension with no prior kidney stones underwent DDRT. Post-reperfusion biopsy of the transplant showed mild tubular atrophy and interstitial fibrosis occupying 10-15% of the sampled cortex. Immunosuppression was induced with thymoglobulin and methylprednisolone and has been maintained on prednisone, belatacept and mycophenolic acid. Four years later, kidney stones were identified in the transplant. Cystoscopy and lithotripsy were performed with retrieval of a 100% calcium oxalate stone by analysis, prompting initiation of potassium citrate and pyridoxine. A 24-hour urinary oxalate collection revealed markedly elevated oxalate levels. Genetic testing revealed heterozygosity of the GRHPR alleles. One allele contained a known mutation for PH2. The other allele contained a mutation that likely rendered it nonfunctional. Pyridoxine has since been held and potassium citrate dose increased. The patient was counseled on adequate hydration and low oxalate intake. Nedosiran is being considered for this patient.

Discussion

PH is characterized by deranged metabolism of glycoxylate, causing accumulation of oxalate. Calcium oxalate then precipitates in the urine and deposits in the kidneys, causing inflammation and cortical scarring. While PH1 is more prevalent and classically thought to cause more rapidly-progressive disease, PH2 can also cause significant kidney injury despite its relative indolence. The condition is diagnosed by detection of increased urinary oxalate followed by confirmatory genetic testing. In the post-transplantation phase, kidney dysfunction secondary to hyperoxaluria can be confused for delayed graft function, defined as the use of HD in the seven days post-transplantation. In the absence of a clear etiology for the underlying native renal function, and with genetic testing becoming affordable, it may be worthwhile to consider genetic testing for underlying renal diseases that could affect a transplanted kidney with the intention of increasing the longevity of transplanted kidneys in the post-transplantation phase.