Kidney Transplant Outcomes in Patients with Adenine Phosphoribosyltransferase Deficiency.

BACKGROUND: Adenine phosphoribosyltransferase (APRT) deficiency is a rare, hereditary cause of kidney stones and chronic kidney disease (CKD), characterized by 2,8-dihydroxyadenine (DHA) renal parenchymal crystal deposition. The aim of this study was to examine outcomes of kidney transplantation in APRT deficiency patients.

METHODS: Included were 13 patients in the APRT Deficiency Registry of the Rare Kidney Stone Consortium, 2 from Westmead Hospital in Sydney, Australia, and 2 from Necker Hospital in Paris, France. The CKD-EPI and CKiD equations were used to calculate glomerular filtration rate estimates (eGFR). Allograft survival was analyzed employing the Kaplan-Meier method. The Wilcoxon-Mann-Whitney test was used to compare alllograft outcomes by xanthine oxidoreductase (XOR) inhibitor treatment status at transplantation.

RESULTS: Seventeen patients (9 females) received 22 kidney transplants. Age at first transplantation was 47.2 (14.9-67.0) years. Ten patients received XOR inhhibitor therapy pretransplant (11 allografts), while 8 patients did not receive such treatment prior to transplantation (11 allografts). Two-year allograft survival was 91% and 55% in the 2 groups, respectively (p=0.16). The median (range) eGFR at 2 years posttransplant was 61.3 (24.0-90.0) mL/min/1.73 m when XOR inhibitor therapy was initiated before transplantation and 16.2 (10.0-39.0) mL/min/1.73 m (p=0.009) when such treatment was not administered pretransplant.

CONCLUSIONS: Kidney allograft outcomes are good in APRT deficiency patients beginning XOR inhibitor therapy pretransplant. Delay in such treatment is a major cause of premature graft loss in these patients. Increased awareness among clinicians is imperative, promoting early diagnosis of APRT deficiency and pharmacotherapy initiation before kidney transplantation.