Crystalline Nephropathy Due to 2,8-Dihydroxyadeninuria in a Transplanted Kidney: 2 Case Reports

BACKGROUND The renal condition known as 2,8-dihydroxyadeninuria is an autosomal recessive disorder caused by adenine phosphoribosyl transferase (APRT) deficiency, which most commonly manifests as nephrolithiasis. APRT deficiency has also led to the development of chronic kidney disease and end-stage kidney disease in the absence of nephrolithiasis and has also been shown to recur following kidney transplantation. CASE REPORT This report aims to highlight the diagnostic and therapeutic challenges associated with APRT deficiency by presenting 2 patients with end-stage kidney disease who developed 2,8-dihydroxyadenine (DHA) crystalline nephropathy early in their post-transplant course. Neither patient had been diagnosed with APRT deficiency prior to transplantation, and one lacked a history of nephrolithiasis. Allograft biopsies revealed DHA crystal deposition with acute tubular injury, and genetic analysis confirmed APRT deficiency. Management included xanthine oxidase inhibitors, a low-purine diet, and modification of the immunosuppressive regimen with belatacept to reduce long-term tubulointerstitial injury. Both patients achieved stable long-term allograft function at 2 years, with follow-up biopsies at 1 year, showing a significant decrease in crystal deposition. CONCLUSIONS This case report underscores the importance of early recognition of APRT deficiency through timely biopsy, crystal identification, and genetic testing to guide effective treatment and prevent irreversible damage. It highlights the need for heightened clinical suspicion and tailored post-transplant management strategies in patients with recurrent DHA nephropathy.