Gout associated with reduced renal excretion of uric acid. Renal tubular disorder that nephrologists do not treat.

Gout is recurrent inflammatory arthritis caused by the deposition of monosodium urate crystals in the joints. The risk factors that predispose to suffering from gout include non-modifiable factors such as gender, age, ethnicity and genetics, and modifiable factors such as diet and lifestyle. It has been shown that the heritability of uric acid levels in the blood is greater than 30%, which indicates that genetics play a key role in these levels. Hyperuricaemia is often a consequence of reduced renal urate excretion since more than 70% is excreted by the kidneys, mainly through the proximal tubule. The mechanisms that explain that hyperuricaemia associated with reduced renal urate excretion is, to a large extent, a proximal renal tubular disorder, have begun to be understood following the identification of two genes that encode the URAT1 and GLUT9 transporters. When they are carriers of loss-of-function mutations, they explain the two known variants of renal tubular hypouricaemia. Some polymorphisms in these genes may have an opposite gain-of-function effect, with a consequent increase in urate reabsorption. Conversely, loss-of-function polymorphisms in other genes that encode transporters involved in urate excretion (ABCG2, ABCC4) can lead to hyperuricaemia. Genome-wide association study (GWAS) methods have made it possible to locate new gout-related loci associated with reduced renal urate excretion (NIPAL1, FAM35A).