• Hrafnhildur Linnet Runolfsdottir, Runolfur Palsson, Inger M Agustsdottir, Olafur S Indridason, and Vidar O Edvardsson.
• Faculty of Medicine, School of Health Sciences, University of Iceland, Reykjavik, Iceland.
• Am. J. Kidney Dis. 2016 Mar 1; 67 (3): 431-8.

BackgroundAdenine phosphoribosyltransferase (APRT) deficiency is a purine metabolism disorder causing kidney stones and chronic kidney disease (CKD). The course of nephrolithiasis and CKD has not been well characterized. The objective of this study was to examine long-term kidney outcomes in patients with APRT deficiency.Study DesignAn observational cohort study.Setting & ParticipantsAll patients enrolled in the APRT Deficiency Registry of the Rare Kidney Stone Consortium.OutcomesKidney stones, acute kidney injury (AKI), stage of CKD, end-stage renal disease, estimated glomerular filtration rate (eGFR), and changes in eGFR.MeasurementsSerum creatinine and eGFR calculated using creatinine-based equations.ResultsOf 53 patients, 30 (57%) were females and median age at diagnosis was 37.0 (range, 0.6-67.9) years. Median duration of follow-up was 10.3 (range, 0.0-31.5) years. At diagnosis, kidney stones had developed in 29 (55%) patients and 20 (38%) had CKD stages 3 to 5, including 11 (21%) patients with stage 5. At latest follow-up, 33 (62%) patients had experienced kidney stones; 18 (34%), AKI; and 22 (42%), CKD stages 3 to 5. Of 14 (26%) patients with stage 5 CKD, 12 had initiated renal replacement therapy. Kidney stones recurred in 18 of 33 (55%) patients. The median eGFR slope was -0.38 (range, -21.99 to 1.42) mL/min/1.73m(2) per year in patients receiving treatment with an xanthine dehydrogenase inhibitor and -5.74 (range, -75.8 to -0.10) mL/min/1.73m(2) per year in those not treated prior to the development of stage 5 CKD (P=0.001).LimitationsUse of observational registry data.ConclusionsProgressive CKD and AKI episodes are major features of APRT deficiency, whereas nephrolithiasis is the most common presentation. Advanced CKD without a history of kidney stones is more prevalent than previously reported. Our data suggest that timely therapy may retard CKD progression.Copyright © 2016 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

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