• Childhood Kidney Diseases
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• v.25 no.1
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• pp.44-48
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• 2021

Idiopathic renal hypouricemia (iRHUC) is a rare hereditary disease caused by a defect in urate handling of renal tubules. Type 1 renal hypouricemia (RHUC1) is diagnosed with confirmation of a mutation in SLC22A12 gene which encodes a renal urate-anion exchanger (URAT1). The majority of iRHUC patients are asymptomatic, especially during childhood, and thus many cases go undiagnosed or they are diagnosed late in older age with complications of hematuria, renal stones, or acute kidney injury (AKI). We report a case of a 7-year-old boy with subtle symptoms such as general weakness and dizziness and revealed hypouricemia and incidental nephrolithiasis. Homozygous mutations were detected in the SLC22A12 (c.774G>A) by molecular analysis. The present case suggests that fractional excretion of uric acid (FEUA) screening could be better followed by the coincidental discovery of hypouricemia, to prevent conflicting complications of iRHUC, even with normal urine uric acid to creatinine ratio (U_UA/U_Cr), and sequential genetic analysis if needed.

• Childhood Kidney Diseases
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• v.10 no.1
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• pp.65-71
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• 2006

Idiopathic renal hypouricemia is a disorder characterized by impaired urate handling in the renal tubules. Most patients with hypouricemia are asymptomatic and are found incidentally, but the condition is known to be at high risk for exercise-induced acute renal failure or urolithiasis. URAT1 protein encoded by SLC22A12 gene has been identified recently as a urate/anion exchanger in the human kidney. Inactivation mutations in SLC22A12 gene have been shown to cause renal idiopathic hypouricemia. We experienced a 3-year-old boy who presented with persistent orange-colored urine since infancy. His urine contained many uric acid crystals, while the serum showed hypouricemia(0.7 mg/dL). The fractional excretion of uric acid was increased to 41.7%. SLC22a12 gene analysis revealed W258X homozygote alleles. Renal hypouricemia must be included in the differential diagnosis of red-urine and SLC22A12 gene analysis is recommended in idiopathic renal hypouricemia.

• Clinical and Experimental Pediatrics
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• v.50 no.5
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• pp.489-492
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• 2007

Idiopathic renal hypouricemia is a disorder characterized by impaired urate handling in the renal tubules. This disease usually produces no symptoms, but hematuria, uric acid nephrolithiasis or acute renal failure may develop. A defect in the SLC22A12 gene, which encodes the human urate transporter, is the known major cause of this disorder. We describe a 10-month-old boy with idiopathic renal hypouricemia. He was diagnosed with transient pseudohypoaldosteronism at admission, but hypouricemia was accidentally found through follow-up study. By gene analysis, his diagnosis was confirmed to idiopathic renal hypouricemia. In addition, we report a mutation in the human urate transporter 1 (hURAT1) gene identified in his family.