Hereditary renal hypouricaemia type 1 and 2 in three Spanish children. Review of published paediatric cases

Abstract

Hereditary renal hypouricemia is a rare autosomal recessive genetic disorder that involves an isolated defect in uric acid reabsorption at the renal tubules. Patients present with serum uric acid concentrations of less than 2mg/dl (119μmol/L) with increased fractional excretion above 10%. Most of the patients are asymptomatic and are detected incidentally. However, complications such us nephrolithiasis, hematuria, acute renal failure exercise-induced or after dehydration for acute gastroenteritis, or posterior reversible encephalopaty syndrome (PRES) may develop.Hereditary renal hypouricemia is confirmed by molecular genetic analysis of the two genes which codify the uric acid transport in the kidney tubules. The renal hypouricemia type 1 (OMIM 220150) is characterised by loss-of-function mutations in the SLC22A12 gene which encodes URAT 1 transporter, and the hypouricemia type 2 (OMIM 612076) is caused by defects in the SLC2A9 gene. Homozygous mutations of SLC2A9 cause the most severe forms of the disease.Most mutations have been identified in Japanese adults, and only a few in children.We describe three asyntomatic paediatric Spanish patients with renal hypouricemia, with genetic confirmation, and we make a revision of all of the paediatric cases with genetic study published in the literature.