HPRT1 and acute kidney injury: Children with hyperuricosuria can present with recurrent stone episodes or even acute renal failure from urate crystal nephropathy because of inherited defects of enzymes associated with purine metabolism such as hypoxanthine-guanine phosphoribosyltransferase (HPRT), adenine phosphoribosyltransferase (APRT), xanthine dehydrogenase (XDH), or phosphoribosylpyrophosphate synthetase [100].