The precipitation and crystallization of UA. The occurrence of UA nephrolithiasis
The precipitation and crystallization of UA. The occurrence of UA nephrolithiasis in patients with renal hypouricemia and the finding of renal tubular obstruction by UA crystals in one patient with EIARF support a pathogenetic role for UA precipitation [18]. In our case this pathogenetic mechanism is supported by the findings of relative hypouricemia, urate crystals and red blood cells in urine and loin pain during the most severe episode of EIARF. The second pathogenetic hypothesis is based on the powerful antioxidant activity of UA [6,7]. However, this hypothesis is in discrepancy with the evidence that ARF does not usually occur in patients with low hypouricemia due to classical xanthinuria, either type I, deficient in xanthine dehydrogenase (XDH) activity (MIM#278300); or type II, deficient in both XDH and aldehyde PNPP solubility oxidase (MIM#603592) [19]. This suggests that hypouricemia alone, probably, could not contribute to ARF in patients with primary renal hypouricemia. One could speculate why our patient had only two episodes of EIARF at the age of 24 and not all the times he had anaerobic physical activity. Possibly not all the exercises cause renal failure; other factors like duration and strength of the exercise, environmental temperature, relative humidity, state of normal or reduced hydration of the subject, changes in urine pH due to different foods and use of some drugs could play a role. Due to the severity of renal hypouricemia, our patient was instructed to restrict strenuous anaerobic exercise and take sufficient water after exercise. To prevent recurrence of EIARF prophylaxis with allopurinol, oral supplementation of antioxidants or scavengers, PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/28607003 such as glutathione, vitamins C and E, and beta-carotene, are also recommended [20]. In conclusion, the clinical and molecular findings on the present patient provide new insights into this disorder, which is understood to a limited degree owing to the small number of patients with SLC2A9 mutations described to date. Further investigations of the functional properties of GLUT9, URAT1 and other urate transporters are required to assess their potential research and clinical implications.ConsentAbbreviations CKD: Chronic kidney disease; EIARF: Exercise-induced acute renal failure; FE-UA: Fractional excretion of uric acid; RHUC: Renal hypouricaemia; UA: Uric acid. Competing interests The authors declared they have no competing of interests. Authors’ contributions GJ, NC, MR, MC and GC designed the study. GJ, MG, PM, FV, SP and GC made the clinical diagnosis of the patient and performed the follow-up. MR, NC and SQ performed the molecular analyses. MR, NC, GJ, MC and GC researched the literature, reviewed and prepared the manuscript. MC and GC edited and coordinated the manuscript. All of the authors discussed, read, and approved the final manuscript. Acknowledgments Work funded by Ministero dell’Istruzione dell’Universit?e della Ricerca, Fondo per gli Investimenti della Ricerca di Base 2011?012. Author details Operative Unit of Nephrology, Department of Medical and Surgical Specialties, Radiological Sciences and Public Health, University Hospital Spedali Civili, Brescia, Italy. 2Division of Biology and Genetics, Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123 Brescia, Italy.Received: 3 September 2013 Accepted: 26 December 2013 Published: 7 January 2014 References 1. Enomoto A, Kimura H, Chairoungdua A, Shigeta Y, Jutabha P, Cha SH, Hosoyamada.