Allopurinol Use Leading to Xanthine Nephrolithiasis in Pediatric Tumor Lysis Syndrome: a Case Series.

Tumor lysis syndrome (TLS) is a life-threatening metabolic disorder caused by massive tumor lysis. Allopurinol, a xanthine oxidase inhibitor, is initiated during chemotherapy to prevent hyperuricemia and subsequent acute kidney injury (AKI). We report two cases of xanthine nephrolithiasis during TLS in newly diagnosed hematologic malignancy patients receiving prophylactic allopurinol. Allopurinol use likely promoted xanthine crystallization, stone formation, and AKI.