RHUC1

Renal hypouricemia type 1 (RHUC1) is a hereditary kidney disorder characterized by persistently low serum uric acid due to impaired renal reabsorption of uric acid in the proximal tubule. It arises from loss-of-function mutations in SLC22A12, the gene encoding the urate transporter URAT1, and is inherited in an autosomal recessive pattern. RHUC1 is one form of renal hypouricemia; other causes include different genetic defects affecting urate transport.

URAT1 normally reclaims filtered uric acid from the urine back into the blood. When URAT1 function is reduced, more uric acid is lost in urine, leading to low serum urate and a high fractional excretion of uric acid (FEUA).

Most individuals with RHUC1 are asymptomatic. Some may experience exercise-induced acute kidney injury (EIAKI), nephrolithiasis, or hematuria, particularly after dehydration or intense physical activity.

Diagnosis relies on laboratory findings: persistently low serum uric acid, elevated FEUA, and increased urinary uric acid excretion. Genetic testing of SLC22A12 can confirm RHUC1.

Management focuses on prevention of complications rather than correction of urate levels. Patients are advised to avoid dehydration, maintain adequate hydration during exertion, and monitor for kidney-related symptoms. There is no disease-modifying cure; treatment addresses acute kidney injury if it occurs and standard stone prevention measures if nephrolithiasis develops.