In 2002, a urate transporter, URAT1, was identified in human kidney. URAT1 is located in the apical tubular membrane, and is encoded by the SLC22A12 gene. Uricosuric drugs, probenecid and benzbromarone act on this transporter. Mutations in SLC22A12 are the cause of hereditary renal hypouricemia (Renal hypouricemia-1, RHUC1). Subsequently, a second gene, SLC2A9, was identified that encodes GLUT9 protein and belonging to a family of proteins facilitating the transport of hexoses (fructose, glucose). There is an isoform, GLUT9L, that is expressed primarily in the basolateral membrane of proximal tubule cells, and another isoform GLUT9S that is expressed exclusively in the apical membrane of these cells. This explain why in patients with the second variant of renal tubular hypouricemia (hypouricemia renal-2, RHUC2) the reduction in the urate reabsorption occurs on both sides of the proximal tubules cells and the urate fractional excretion is greater than 150%. GLUT9 is certainly the main regulator of urate levels in humans. For the genetic study it will be necessary samples of the index case and the parents.