Renal hypouricemia (RHUC) is a rare inherited disorder characterized by impaired urate reabsorption in the proximal tubule resulting in low urate serum levels and increased urate excretion. Some patients may present severe complications such as exercise-induced acute renal failure and nephrolithiasis. RHUC is caused by inactivating mutations in theSLC22A12(RHUC type 1) orSLC2A9(RHUC type 2) genes, which encode urate transporters URAT1 and GLUT9, respectively. In this study, our goal was to identify mutations associated with twenty-one new cases with RHUC through direct sequencing ofSLC22A12andSLC2A9coding exons. Additionally, we carried out an SNPs-haplotype analysis to determine whether the rareSLC2A9variant c.374C>T; p.(T125M), which is recurrent in Spanish families with RHUC type 2, had a common-linked haplotype. Six intragenic informative SNPs were analyzed using PCR amplification from genomic DNA and direct sequencing. Our results showed that ten patients carried theSLC22A12mutation c.1400C>T; p.(T467M), ten presented theSLC2A9mutation c.374C>T, and one carried a newSLC2A9heterozygous mutation, c.593G>A; p.(R198H). Patients carrying theSLC2A9mutation c.374C>T share a common-linked haplotype, confirming that it emerged due to a founder effect.