Long-term renal outcomes of APRT deficiency presenting in childhood
Adenine phosphoribosyltransferase (APRT) deficiency is a hereditary purine metabolism disorder that causes kidney stones and chronic kidney disease (CKD). The purpose of this study was to examine the course of APRT deficiency in patients who presented in childhood.
The disease course of 21 (35%) patients in the APRT Deficiency Registry of the Rare Kidney Stone Consortium, who presented with manifestations of APRT deficiency and/or were diagnosed with the disorder before the age of 18 years, was studied. The effect of pharmacotherapy on renal manifestations and outcomes was thoroughly assessed.
Fourteen children were placed on allopurinol, 100 (25–200) mg/day, at the age of 2.6 (0.6–16.5) years. Six of these patients had experienced kidney stone events and three had developed acute kidney injury (AKI) prior to allopurinol treatment. During 18.9 (1.7–31.5) years of pharmacotherapy, stones occurred in two patients and AKI in three. Six adult patients started allopurinol treatment, 200 (100–300) mg/day, at age 29.8 (20.5–42.4) years. Five of these patients had experienced 28 stone episodes and AKI had occurred in two. Stone recurrence occurred in four patients and AKI in two during 11.2 (4.2–19.6) years of allopurinol therapy. Lack of adherence and insufficient dosing contributed to stone recurrence and AKI during pharmacotherapy. At latest follow-up, estimated glomerular filtration rate (eGFR) was 114 (70–163) and 62 (10–103) mL/min/1.73 m2 in those who initiated treatment as children and adults, respectively. All three patients with CKD stages 3–5 at the last follow-up were adults when pharmacotherapy was initiated.
Timely diagnosis and treatment of APRT deficiency decreases renal complications and preserves kidney function.
KeywordsKidney stones Nephrolithiasis Chronic kidney disease Kidney failure Crystal nephropathy Kidney transplantation Allopurinol Children
Part of this work was presented in an abstract form at the American Society of Nephrology Kidney Week, November 3–8, 2015, San Diego, CA. The authors want to sincerely thank the following physicians for their invaluable assistance in clinical data and biosample collection: Dawn Milliner (Mayo Clinic, Rochester, MN, USA), John Lieske (Mayo Clinic, Rochester, MN, USA), David Goldfarb (New York University, New York, NY, USA), Philipp Eller (Medical University of Graz, Graz, Austria), Hans-Jacob Bangstad (Oslo University Hospital, Oslo, Norway), Amrik Sahota (Rutgers University, Piscataway, NJ, USA), and Lynette Fairbanks (Guy’s and St. Thomas’ Hospital NHS Foundation Trust, London, UK).
This study was supported by the Rare Kidney Stone Consortium (2U54DK083908), a part of the National Center for Advancing Translational Sciences (NCATS) Rare Diseases Clinical Research Network (RDCRN). RDCRN is an initiative of the Office of Rare Diseases Research (ORDR). The Rare Kidney Stone Consortium is funded through collaboration between NCATS and National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).
Compliance with ethical standards
The study was approved by the National Bioethics Committee of Iceland (NBC 09-072) and the Icelandic Data Protection Authority. All living patients or their legal guardians gave a written informed consent for participation in the study. The work described has been carried out in accordance with The Code of Ethics of the World Medical Association (Declaration of Helsinki).
Conflict of interest
The authors declare that they have no conflict of interest.
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