2018 年 42 巻 1 号 p. 1-6
The world- first clinical practice guideline (CPG) for renal hypouricemia (RHUC) has developed from Japan along MINDS methodology last year. Its first goal is to clarify the criteria for diagnosing RHUC, and another goal is to work towards a consensus on clinical decision-making.
RHUC is caused by a dysfunction of renal urate reabsorption. It does not include congenital purine metabolism abnormalities or secondary hypouricemia, and is relatively common (0.3%) in Japanese populations. Genetic analyses have demonstrated its causes as dysfunctional variants in urate reabsorption transporter URAT1/SLC22A12 and/or GLUT9/SLC2A9 genes, but there should be unknown causative genes. One of the characteristics of RHUC is a low serum uric acid (SUA) level with increased renal excretion of uric acid. CPG proposed its clinical diagnostic guidance for RHUC along clinical algorithm, which enables easy diagnosis with simple tests. RHUC itself is usually asymptomatic, but exercise-induced acute kidney injury (EIAKI, also known as “ALPE”) and urolithiasis are well-known complications. EIAKI cases generally show transient and recurrent acute kidney injury (AKI), and receive common treatment for AKI. For urinary stones, urinary alkalization and citrate compounds are effective therapies and fluid intake is recommended for prevention.
We strongly recommend that individuals with an SUA of ≤ 2.0 mg/dl (120 µmol/l) be considered for differential diagnosis of hypouricemia. Some studies reports that allopurinol, a xanthine oxidoreductase (XOR) inhibiter, was administered as prevention for EIAKI, but due to low evidence, we cannot definitively state that XOR inhibitors are effective. It should be therefore decided in the light of its potential benefits and harms.
We hope that this CPG helps both healthcare providers and patients make clinical decisions, and will also promote the researches on RHUC.