A Novel Homozygous SLC2A9 Mutation Associated with Renal-Induced Hypouricemia

Hereditary renal hypouricemia (RHUC) is a genetically heterogenous disorder characterized by defective uric acid (UA) reabsorption resulting in hypouricemia and increased fractional excretion of UA; acute kidney injury (AKI) and nephrolithiasis are recognized complications. Type 1 (RHUC1) is caused by mutations in the SLC22A12 gene, whereas RHUC2 is caused by mutations in the SLC2A9 gene. Patient ethnicity is diverse but only few Caucasian families with an SLC2A9 mutation have been reported.

The current report describes the clinical history, biochemical and molecular genetics findings of a native Austrian family with RHUC2. The propositus presented with 2 episodes of exercise-induced AKI and exhibited profound hypouricemia. Mutational screening of the SLC22A12 and SLC2A9 genes was performed.

The molecular analyses revealed the homozygous c.512G>A transition that leads to the p.Arg171His missense substitution in SLC2A9, confirming the diagnosis of RHUC2. Segregation study of the causal mutation revealed that the mother and elder sister were heterozygous carriers, whereas the younger sister was found to be homozygous.

We report the identification of a novel mutation in SLC2A9 as the cause of RHUC2 in a native Austrian family. We show that glucose transporter 9 mutations cause severe hypouricemia in homozygous individuals and confirm the high risk of AKI in male individuals harbouring these mutations. In our literature review, we provide an overview of the putative underlying pathophysiology, potential renal complications, findings on kidney biopsy as well as potential long-time renal sequelae.