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      Primary Hyperoxaluria – The German Experience

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          Abstract

          Background: Primary hyperoxaluria (PH) is a heterogeneous disease with variable age of onset and inconsistent progression into renal failure (ESRF). Aims: In 1994 we initiated a survey within our Pediatric Nephrology working group to ascertain epidemiologic data and current practices. Updates were performed in 2000 and 2004. Results: Diagnosis of PH was made in 65 patients (42 with PH type I, 3 with PH type II, 12 unclassified and 8 reported dead), which suggests a minimum prevalence of 0.7 per 1 million of the population. First symptoms were urolithiasis, nephrocalcinosis, urinary tract infection or hematuria. Diagnosis was often delayed and was made only in ESRF in 11% of patients. Measurement of urine metabolites or plasma oxalate in ESRF was performed in 76 and 57%, respectively. Determination of enzyme activity in liver biopsy (55% overall) and mutation analysis have increasingly been performed since 2000 (84.2 and 51%). Treatment included high fluid intake, pyridoxine, citrate and magnesium preparations. Pyridoxine response was reported in 21% of patients. No genotype/phenotype correlation was seen. Most patients (39) do not require renal replacement therapy, 5 patients receive chronic hemodialysis. Preemptive liver (n = 5) and combined liver-kidney transplantation (n = 9) were the preferred transplantation procedures. Conclusion: Despite increasing knowledge and awareness, diagnosis of PH is still too often delayed and diagnosis only made in ESRF. Most German patients, however, do currently not require renal replacement therapy. Genotype/phenotype correlations were not found. Combined liver kidney transplantation is the preferred procedure, but has its specific risks. Additional treatment options are clearly needed.

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          Most cited references 11

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          The gene encoding hydroxypyruvate reductase (GRHPR) is mutated in patients with primary hyperoxaluria type II.

          Primary hyperoxaluria type II (PH2) is a rare monogenic disorder that is characterized by a lack of the enzyme that catalyzes the reduction of hydroxypyruvate to D-glycerate, the reduction of glyoxylate to glycolate and the oxidation of D-glycerate to hydroxypyruvate. The disease is characterized by an elevated urinary excretion of oxalate and L-glycerate. The increased oxalate excretion can cause nephrolithiasis and nephrocalci-nosis and can, in some cases, result in renal failure and systemic oxalate deposition. We identified a glyoxylate reductase/hydroxypyruvate reductase (GRHPR) cDNA clone from a human liver expressed sequence tag (EST) library. Nucleotide sequence analysis identified a 1198 nucleotide clone that encoded a 984 nucleotide open reading frame. The open reading frame encodes a predicted 328 amino acid protein with a mass of 35 563 Da. Transient transfection of the cDNA clone into COS cells verified that it encoded an enzyme with hydroxy-pyruvate reductase, glyoxylate reductase and D-glycerate dehydrogenase enzymatic activities. Database analysis of human ESTs reveals widespread tissue expression, indicating that the enzyme may have a previously unrecognized role in metabolism. The genomic structure of the human GRHPR gene was determined and contains nine exons and eight introns and spans approximately 9 kb pericentromeric on chromosome 9. Four PH2 patients representing two pairs of siblings from two unrelated families were analyzed for mutations in GRHPR by single strand conformation polymorphism analysis. All four patients were homozygous for a single nucleotide deletion at codon 35 in exon 2, resulting in a premature stop codon at codon 45. The cDNA that we have identified represents the first characterization of an animal GRHPR sequence. The data we present will facilitate future genetic testing to confirm the clinical diagnosis of PH2. These data will also facilitate heterozygote testing and prenatal testing in families affected with PH2 to aid in genetic counseling.
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            A United States survey on diagnosis, treatment, and outcome of primary hyperoxaluria.

            Primary hyperoxaluria (PH) is a heterogeneous disease with a variable age of onset and a variable progression into kidney failure. Early diagnosis is mandatory to avoid the damaging effects of systemic calcium oxalate deposition. In 1997, we initiated a nationwide survey of American nephrologists to ascertain epidemiological data and current practices. PH was reported in only 102 patients, with PH I in 79 and PH II in 9; 14 patients were not classified. Most patients were Caucasian (84%). Main symptoms at diagnosis were urolithiasis (54.4%) and nephrocalcinosis (30%). A significant delay of diagnosis was seen in 42% of patients and 30% of patients were diagnosed only at end-stage renal disease (ESRD). Diagnosis was usually based on history and urinary oxalate excretion. Glycolate and l-glyceric acid excretion were rarely determined. To determine the enzyme defect, a liver biopsy was performed in 40%. Even at ESRD, only 56% of patients received an adequate diagnostic work-up. Half of the patients showed 'good' or 'fair' pyridoxine sensitivity. In addition to B(6), most patients received either citrate or orthophosphate. Kidney transplantation (KTx) failed in 19 of 32 transplants ( n=27 patients) and was due to recurrent oxalosis in 8 transplants. Liver Tx was performed after KTx in 5 patients (1 patient died). Combined liver-kidney Tx in 21 patients (in 9 patients after failure of KTx) achieved good organ function in 13 patients; 7 patients, however, died shortly after transplantation. In conclusion, the time between first symptom and diagnosis of PH must be minimized, and the diagnostic procedures have to be improved. The cases of unclassified hyperoxaluria suggest the possibility of additional type(s) of PH. As isolated KTx failed in 59% of patients, combined liver-kidney Tx seems to be the better choice in place of isolated KTx as the primary transplant procedure.
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              Evaluation of mutation screening as a first line test for the diagnosis of the primary hyperoxalurias.

              A definitive diagnosis of primary hyperoxaluria type 1 (PH1) and primary hyperoxaluria type 2 (PH2) requires the measurement of alanine:glyoxylate aminotransferase (AGT) and glyoxylate reductase (GR) activities, respectively, in a liver biopsy. We have evaluated a molecular genetic approach for the diagnosis of these autosomal-recessive diseases. Polymerase chain reaction (PCR) was used to detect three common mutations in the AGXT gene (c.33_34insC, c.508G>A, and c.731T>C) and one, c.103delG, in the GRHPR gene in DNA samples from 365 unrelated individuals referred for diagnosis of PH1 and/or PH2 by liver enzyme analysis. One or more of these mutations was found in 183 (68.8%) biopsy proven cases of PH1 and PH2 with a test negative predictive value of 62% and 2%, respectively. 102 (34.1%) patients were homozygous or compound heterozygous, making a molecular diagnosis possible. Age of onset and presenting features were similar in patients homozygous for any of the four mutations. Of the AGXT homozygotes, only the c.508G>A mutant was associated with significant AGT catalytic activity and in two of these activity was in the low normal range, possibly reflecting variation in mitochondrial content of the biopsy as this particular mutation is associated with mitochondrial mistargeting. Limited mutation analysis can provide a useful first line test for PH1 and PH2 in patients in whom primary hyperoxaluria is suspected and in whom secondary causes have been excluded. Those patients in whom a single mutation, or no mutation, is found can then be selectively targeted for liver biopsy.
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                Author and article information

                Journal
                AJN
                Am J Nephrol
                10.1159/issn.0250-8095
                American Journal of Nephrology
                S. Karger AG
                0250-8095
                1421-9670
                2005
                June 2005
                01 July 2005
                : 25
                : 3
                : 276-281
                Affiliations
                aDivision of Pediatric Nephrology, Children’s Hospital Cologne, University of Cologne, Cologne; bClementine Children’s Hospital Frankfurt, Frankfurt; Division of Pediatric Nephrology, University Children’s Hospitals, cFreiburg and dHamburg, Germany
                Article
                86358 Am J Nephrol 2005;25:276–281
                10.1159/000086358
                15961947
                © 2005 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Figures: 1, Tables: 2, References: 20, Pages: 6
                Product
                Self URI (application/pdf): https://www.karger.com/Article/Pdf/86358
                Categories
                7th International Workshop on Primary Hyperoxaluria. October, 2004, Rochester, Minn. ...

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