Transplantation of a kidney with a heterozygous mutation in the SLC22A12 (URAT1) gene causing renal hypouricemia: a case report

Renal hypouricemia (RHUC) is a genetic disorder caused by mutations in the SLC22A12 gene, which encodes the major uric acid (UA) transporter, URAT1. The clinical course of related, living donor-derived RHUC in patients undergoing kidney transplantation is poorly understood. Here, we report a case of kidney transplantation from a living relative who had an SLC22A12 mutation. After the transplantation, the recipient's fractional excretion of UA (FEUA) decreased, and chimeric tubular epithelium was observed. A 40-year-old man underwent kidney transplantation. His sister was the kidney donor. Three weeks after the transplantation, he had low serum-UA, 148.7 μmol/L, and elevated FEUA, 20.8% (normal: