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Contains fulltext : 291453.pdf (Publisher’s version ) (Open Access) INTRODUCTION: A 6-month course of cyclophosphamide (CP) and steroids is effective in primary membranous nephropathy (MN), but unappealing because of long-term side effects. We evaluated efficacy of an "antibody-guided" treatment schedule. METHODS: Patients with phospholipase A2 receptor (PLA2R)-related MN and high risk of progression were treated with CP 1.5 mg/kg/d and steroids in cycles of 8 weeks. Anti-PLA2R antibodies were measured by indirect immunofluorescence (IIFT) at 8, 16, and 24 weeks, and a negative test resulted in withdrawal of CP, and rapid tapering of prednisone. In patients with persistent anti-PLA2R antibodies at 24 weeks, CP was switched to mycophenolate mofetil. Treatment was repeated in patients with a relapse. RESULTS: Our analysis included 65 patients (48 males, 17 females), age 61 ± 12 years, estimated glomerular filtration rate (eGFR) 46 ml/min per 1.73 m(2) (35-68), urine protein-to-creatinine ratio 7.7 grams/10 mmol creatinine (5.4-11.1) and serum albumin 20 g/l (16-26). Immunologic remission rate was 71% after 8 weeks, 86% after 16 weeks, 88% after 24 weeks, and 94% after 3 years. Twenty-seven patients (42%) had persistent clinical remission after only 8 weeks of therapy. Sixteen patients needed a second course of therapy because of immunologic or clinical relapse. Follow-up was 37 (26-58) months. Overall partial remission rate was 92%. One patient developed end-stage kidney disease. Antibody-guided therapy (ABG) was as effective as the standard 6-month course, whereas providing a lower cumulative dose of CP (11.1 [8.0-18.5] vs. 18.9 [14.2-23.6] grams). CONCLUSION: ABG is effective, and allows individualized therapy, with many patients responding to 8 weeks of CP-based therapy.

Vogt, Bruno/0000-0002-1548-6387; Dufek, Stephanie/0000-0002-6323-6673; Liu, Lili/0000-0002-2622-9669; Paczek, Leszek/0000-0003-0160-3009; Cui, Zhao/0000-0002-5837-1926; amoroso, antonio/0000-0002-9437-9407; Rosen, Raphael/0000-0003-1025-1965; Loos, Ruth/0000-0002-8532-5087; coenen, marieke/0000-0001-8796-2031; zanoni, francesca/0000-0001-9567-6713; CUCCA, Francesco/0000-0002-7414-1995; Ars, Elisabet/0000-0002-4118-4358; Hamilton, Patrick/0000-0001-6703-3745 WOS:000563559600001 PubMed ID: 32231244 Membranous Nephropathy (MN) is a rare autoimmune cause of kidney failure. Here we report a genome-wide association study (GWAS) for primary MN in 3,782 cases and 9,038 controls of East Asian and European ancestries. We discover two previously unreported loci, NFKB1 (rs230540, OR = 1.25, P = 3.4 x 10(-12)) and IRF4 (rs9405192, OR = 1.29, P = 1.4 x 10(-14)), fine-map the PLA2R1 locus (rs17831251, OR = 2.25, P = 4.7 x 10(-103)) and report ancestry-specific effects of three classical HLA alleles: DRB1*1501 in East Asians (OR = 3.81, P = 2.0 x 10(-49)), DQA1*0501 in Europeans (OR = 2.88, P = 5.7 x 10(-93)), and DRB1*0301 in both ethnicities (OR = 3.50, P = 9.2 x 10(-23) and OR = 3.39, P = 5.2 x 10(-82), respectively). GWAS loci explain 32% of disease risk in East Asians and 25% in Europeans, and correctly re-classify 20-37% of the cases in validation cohorts that are antibody-negative by the serum anti-PLA2R ELISA diagnostic test. Our findings highlight an unusual genetic architecture of MN, with four loci and their interactions accounting for nearly one-third of the disease risk. National Institute for Diabetes and Digestive Kidney Diseases (NIDDK) [RC2-DK116690, R01-DK105124, R01-DK097053, R01-DK108805]; National Institute on Minority Health and Health Disparities (NIMHD)United States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute on Minority Health & Health Disparities (NIMHD) [R01-MD009223]; Charles Woodson Clinical Research Fund; Nephrotic Syndrome Study Network Consortium (NEPTUNE) [U54-DK-083912]; Columbia University, Columbia Glomerular Center; Office of Rare Diseases Research, National Center for Advancing Translational Sciences (NCATS); National Institute of Diabetes, Digestive, and Kidney Diseases (NIDDK)United States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute of Diabetes & Digestive & Kidney Diseases (NIDDK); University of MichiganUniversity of Michigan System; NephCure Kidney International; Halpin Foundation; National Key Research and Development Program of China [2016YFC0904100]; Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [81621092]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [81870460, 81570598]; Science and Technology Innovation Action Plan of Shanghai Science and Technology Committee [17441902200]; Shanghai Municipal Education Commission, Gaofeng, Clinical Medicine Grant [20152207]; Shanghai Jiao Tong University School of Medicine, Multi-Center Clinical Research Project [DLY201510]; International Cooperation and Exchange Projects of Shanghai Science and Technology Committee [14430721000]; Outstanding Young Scholar Award [81622009]; Shanghai Health and Family Planning Committee Hundred Talents Program [2018BR37]; Seoul National University Hospital Human Biobank, a member of the National Biobank of Korea - Ministry of Health and Welfare, Republic of Korea; MRCMedical Research Council UK (MRC) [MR/J010847/1]; Manchester Academic Health Science Centre [MAHSC 186/200]; Greater Manchester Local Clinical Research Network; Kidneys for Life Charity; David and Elaine Potter Charitable Foundation; St Peter's Trust for Kidney, Bladder and Prostate Research; Kids Kidney Research UKKidney Research UK (KRUK); Kidney Research UKKidney Research UK (KRUK); Italian Ministry of Health grantMinistry of Health, Italy [GR-2011-02350438]; Department of Excellence Grant 2018-2022 - Italian Ministry of Education for the Department of Medical Sciences of the University of Turin; Columbia University; Poznan University of Medical Sciences, Poland; German Ministry of Education and Research (BMBF)Federal Ministry of Education & Research (BMBF) [01ER0804]; KfH Foundation for Preventive Medicine; Bayer Pharma AG; German Research FoundationGerman Research Foundation (DFG) [CRC 1140, KO 3598/3-1, CRC 992]; European Research CouncilEuropean Research Council (ERC) [ERC-2012ADG_2012-0314, 322947]; 7th Framework Programme of the European Community contract [2012-305608]; National Research Agency grant MNaims [ANR-17-CE17-0012-01]; Dutch Kidney Foundation [OW08, KJPB11.021]; National Human Genome Research Institute (NHGRI)United States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Human Genome Research Institute (NHGRI); NIMHD We are grateful to all study participants across multiple nephrology centres worldwide for their contributions to this work. This work was supported by the following institutions, grants and funding agencies in the US: Columbia University, Columbia Glomerular Center, National Institute for Diabetes and Digestive Kidney Diseases (NIDDK) grants RC2-DK116690 (K.K., M.K.), R01-DK105124 (K.K.), R01-DK097053 (L.H.B., M.K.), R01-DK108805 (M.G.S.), and National Institute on Minority Health and Health Disparities (NIMHD) grant R01-MD009223 (K.K., A.G.G., A.B.). M.G.S. is additionally supported by the Charles Woodson Clinical Research Fund. The Nephrotic Syndrome Study Network Consortium (NEPTUNE), U54-DK-083912, is a part of the National Institutes of Health (NIH) Rare Disease Clinical Research Network (RDCRN), supported through a collaboration between the Office of Rare Diseases Research, National Center for Advancing Translational Sciences (NCATS) and the National Institute of Diabetes, Digestive, and Kidney Diseases (NIDDK). Additional funding and/or programmatic support for this project has also been provided by the University of Michigan, the NephCure Kidney International and the Halpin Foundation. The recruitment and analysis of the Chinese cohorts were supported by the National Key Research and Development Program of China (2016YFC0904100), Natural Science Foundation of China to the Innovation Research Group (81621092), National Natural Science Foundation of China (No. 81870460, 81570598), Science and Technology Innovation Action Plan of Shanghai Science and Technology Committee (No.17441902200), Shanghai Municipal Education Commission, Gaofeng, Clinical Medicine Grant (No.20152207), Shanghai Jiao Tong University School of Medicine, Multi-Center Clinical Research Project (No.DLY201510), International Cooperation and Exchange Projects of Shanghai Science and Technology Committee (No.14430721000), the Outstanding Young Scholar Award for Zhao Cui (No.81622009), and Shanghai Health and Family Planning Committee Hundred Talents Program for Jingyuan Xie (No.2018BR37). The recruitment of the Korean cohort was supported by the Seoul National University Hospital Human Biobank, a member of the National Biobank of Korea, financed by the Ministry of Health and Welfare, Republic of Korea. P.B. and P.H. acknowledge financial support from MRC project "Autoimmunity in Membranous Nephropathy", grant MR/J010847/1 which funded the sample collection from MN patients across the UK. P.B., P.H. and S.H. acknowledge support from Manchester Academic Health Science Centre (MAHSC 186/200), the Greater Manchester Local Clinical Research Network and Kidneys for Life Charity for supporting research in MN in Manchester. We are grateful to the MENTOR study (clinical trials no. NCT01180036), for contributing blood samples of trial participants. The UK cohort was supported in part by grants from the David and Elaine Potter Charitable Foundation (to S.H.P. and R.K.), St Peter's Trust for Kidney, Bladder and Prostate Research (to D.B., H.C.S., S.H.P. and R.K.), Kids Kidney Research UK and Kidney Research UK (to D.B. and R.K.). The Italian cohorts were supported by the Italian Ministry of Health grant GR-2011-02350438 (G.Z., S.G.) and the Department of Excellence Grant 2018-2022 funded by the Italian Ministry of Education for the Department of Medical Sciences of the University of Turin (A.A.).; The recruitment of Polish cases was sponsored by the Polish Kidney Genetics Network (POLYGENES), a collaborative effort between Columbia University and Poznan University of Medical Sciences, Poland. The full list of POLYGENES collaborators can be found in the Supplementary Materials. The GCKD (German Chronic Kidney Disease) study was funded by grants from the German Ministry of Education and Research (BMBF, No. 01ER0804) and the KfH Foundation for Preventive Medicine, with genotyping supported by Bayer Pharma AG. The list of GCKD investigators can be found in the Supplementary Materials. The work of M.W. and A.K. was funded by the CRC 1140 Initiative and by KO 3598/3-1 and CRC 992 (A.K.) of the German Research Foundation. The work of E.H. and R.A.K.S. was funded by the CRC 1192 from the German Research Foundation (Projects B1 and C1). P.R. is a recipient of European Research Council ERC-2012ADG_2012-0314 grant 322947, 7th Framework Programme of the European Community contract 2012-305608 (European Consortium for High-Throughput Research in Rare Kidney Diseases), and the National Research Agency grant MNaims (ANR-17-CE17-0012-01). The Dutch studies were supported by grants from the Dutch Kidney Foundation to JMH and JFW (Nierstichting Nederland grant OW08 and grant KJPB11.021). We would like to thank the Population Architecture Using Genomics and Epidemiology (PAGE) consortium, funded by the National Human Genome Research Institute (NHGRI) with co-funding from the NIMHD, for providing population controls for this study. For full acknowledgment of the PAGE consortium, please see Supplementary Materials. The funding sources were not involved in the study design, collection, analysis, and interpretation of data, writing of the report, or in the decision to submit the paper for publication.

Immunoglobulin A (IgA) nephropathy (IgAN), the most common glomerulonephritis worldwide, is characterized by IgA depositions in the kidney. Deficiency of CD37, a leukocyte-specific tetraspanin, leads to spontaneous development of renal pathology resembling IgAN. However, the underlying molecular mechanism has not been resolved. Here we found that CD37 expression on B cells of patients with IgAN was significantly decreased compared to B cells of healthy donors. Circulating interleukin (IL)-6 levels, but not tumor necrosis factor-α or IL-10, were elevated in Cd37 –/– mice compared to wild-type mice after lipopolysaccharide treatment. Cd37 –/– mice displayed increased glomerular neutrophil influx, immune complex deposition, and worse renal function. To evaluate the role of IL-6 in the pathogenesis of accelerated renal pathology in Cd37 –/– mice, we generated Cd37xIl6 double-knockout mice. These double-knockout and Il6 –/– mice displayed no glomerular IgA deposition and were protected from exacerbated renal failure following lipopolysaccharide treatment. Moreover, kidneys of Cd37 –/– mice showed more mesangial proliferation, endothelial cell activation, podocyte activation, and segmental podocyte foot process effacement compared to the double-knockout mice, emphasizing that IL-6 mediates renal pathology in Cd37 –/– mice. Thus, our study indicates that CD37 may protect against IgA nephropathy by inhibition of the IL-6 pathway.

Objective— An excessive release and impaired degradation of neutrophil extracellular traps (NETs) leads to the continuous exposure of NETs to the endothelium in a variety of hematologic and autoimmune disorders, including lupus nephritis. This study aims to unravel the mechanisms through which NETs jeopardize vascular integrity. Approach and Results— Microvascular and macrovascular endothelial cells were exposed to NETs, and subsequent effects on endothelial integrity and function were determined in vitro and in vivo. We found that endothelial cells have a limited capacity to internalize NETs via the receptor for advanced glycation endproducts. An overflow of the phagocytic capacity of endothelial cells for NETs resulted in the persistent extracellular presence of NETs, which rapidly altered endothelial cell–cell contacts and induced vascular leakage and transendothelial albumin passage through elastase-mediated proteolysis of the intercellular junction protein VE-cadherin. Furthermore, NET-associated elastase promoted the nuclear translocation of junctional β-catenin and induced endothelial-to-mesenchymal transition in cultured endothelial cells. In vivo, NETs could be identified in kidney samples of diseased MRL/lpr mice and patients with lupus nephritis, in whom the glomerular presence of NETs correlated with the severity of proteinuria and with glomerular endothelial-to-mesenchymal transition. Conclusions— These results indicate that an excess of NETs exceeds the phagocytic capacity of endothelial cells for NETs and promotes vascular leakage and endothelial-to-mesenchymal transition through the degradation of VE-cadherin and the subsequent activation of β-catenin signaling. Our data designate NET-associated elastase as a potential therapeutic target in the prevention of endothelial alterations in diseases characterized by aberrant NET release.

BackgroundUrinary excretion of alpha-1-microglobulin and beta-2-microglobulin reflects tubular damage and predicts outcome in patients with idiopathic membranous nephropathy with reasonable accuracy. Urinary kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin are novel biomarkers of tubular damage. We investigated if these markers could improve prediction of outcome in idiopathic membranous nephropathy.MethodsWe measured kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin in urine samples from patients with idiopathic membranous nephropathy, who had nephrotic proteinuria and normal renal function. Excretion of alpha-1-microglobulin and beta-2-microglobulin had been measured previously. Progression was defined as a serum creatinine rise >30%, a rise in serum creatinine to an absolute value of ≥135 µmol/L, or a clinical decision to start immunosuppressive therapy. Remission was defined as proteinuria 50% reduction from baseline.ResultsSixty-nine patients were included. Median follow-up was 35 months (interquartile range 18–63 months). Progression occurred in 30 patients (44%), and spontaneous remission in 36 (52%). Kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin excretion rates were significantly correlated with each other, and with alpha-1-microglobulin and beta-2-microglobulin. The areas under the receiver operating characteristic curves for progression were 0.75 (0.62–0.87) for kidney injury molecule-1 and 0.74 (0.62–0.87) for neutrophil gelatinase-associated lipocalin. In multivariate analysis with either alpha-1-microglobulin and beta-2-microglobulin, kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin did not independently predict outcome.ConclusionKidney injury molecule-1 and neutrophil gelatinase-associated lipocalin excretion rates correlated with excretion rates of other tubular damage markers and predicted outcome in patients with idiopathic membranous nephropathy. They did not add prognostic value compared to measurement of either alpha-1-microglobulin or beta-2-microglobulin.

Contains fulltext : 118864.pdf (Publisher’s version ) (Closed access) BackgroundFocal segmental glomerulosclerosis (FSGS) is a leading cause of steroid-resistant nephrotic syndrome. Hereditary FSGS is frequently caused by mutations in important structural podocyte proteins, including the slit diaphragm-associated transient receptor potential channel C6 (TRPC6).MethodsIn five patients with biopsy-proven autosomal-dominant FSGS from five different Dutch families, all 13 exons of TRPC6 were sequenced. Upon identification of a novel TRPC6 sequence variant, the resultant amino acid change was introduced in the wild-type TRPC6 protein and functionally tested using patch-clamp analyses and cell-surface biotinylation experiments.ResultsNone of the previously described TRPC6 mutations were found in our cohort. In one family, we identified a novel c.524G>A sequence variant resulting in a p.Arg175Gln (R175Q) substitution in the TRPC6 protein. This sequence variant was absent in 449 control subjects and from public SNP databases. The mutation was located in the third ankyrin repeat domain (ANK3) in the cytoplasmic N-tail of TRPC6, important for protein-protein interaction and regulation of ion channel activity. Patch-clamp analyses of the mutant channel indeed showed an increased TRPC6 channel-mediated current. However, cell-surface expression of the mutant channel was not increased.ConclusionsWe identified a novel TRPC6 p.Arg175Gln gain-of-function mutation that shows increased TRPC6-mediated current, which is not due to altered cell-surface expression. This is the first mutation identified in ANK3 of the TRPC6 N-tail and is most likely responsible for the late-onset autosomal dominant FSGS in this family.

Background Autoantibodies against the M-type phospholipase A2 receptor (PLA 2 R1) are specific markers for primary membranous nephropathy (pMN) and anti-PLA 2 R1 serum levels may be useful to monitor disease activity. So far, a recombinant cell-based indirect immunofluorescence assay (RC-IFA) using recombinant PLA 2 R1 as a substrate has been widely available but lacks a finely graduated assessment of antibody concentrations. Methods In order to setup a standardized ELISA, the extracellular domain of human PLA 2 R1 was expressed in HEK293. The purified protein was used to form the solid-phase in an ELISA which was then employed to analyze sera from 200 patients with primary MN, 27 patients with secondary MN, 230 patients with other glomerular diseases, 316 patients with systemic autoimmune diseases, and from 291 healthy blood donors. Results At a set specificity of 99.9% the sensitivity of the anti-PLA 2 R1 IgG ELISA was found to be 96.5%. A similar sensitivity (98.5%) was obtained when binding of only subclass IgG 4 was analyzed. The calibrated assay showed a good class correlation with the results of the RC-IFA, was robust and could be stored for several months without any loss of quality. Conclusion The results demonstrate that the new test system is qualified for routine use and that it has an almost perfect agreement with both, the clinical characterization of the patients and the results generated with RC-IFA.

International audience; The M-type receptor for phospholipase A2 (PLA2R1) is the major target antigen in idiopathic membranous nephropathy (iMN). Our recent genome-wide association study showed that genetic variants in an HLA-DQA1 and phospholipase A2 receptor (PLA2R1) allele associate most significantly with biopsy-proven iMN, suggesting that rare genetic variants within the coding region of the PLA2R1 gene may contribute to antibody formation. Here, we sequenced PLA2R1 in a cohort of 95 white patients with biopsy-proven iMN and assessed all 30 exons of PLA2R1, including canonical (GT-AG) splice sites, by Sanger sequencing. Sixty patients had anti-PLA2R1 in serum or detectable PLA2R1 antigen in kidney tissue. We identified 18 sequence variants, comprising 2 not previously described, 7 reported as rare variants (

Therapy in patients with primary membranous nephropathy is debated. The discovery of anti-PLA2R antibodies provides opportunities for new treatment strategies. Areas covered: The PubMed database and Cochrane library were searched for full-text articles published in English before March 2016. The search terms included 'Glomerulonephritis, Membranous' [MESH], 'membranous glomerulonephritis' [tiab] and, 'idiopathic membranous nephropathy' [tiab] and 'membranous nephropathy' [tiab], in combination with 'Therapeutics' [MESH], 'therapeutic*'[tiab], 'immunosuppression' [MESH] and 'immunosuppression' [tiab]. All randomized trials were included, cohort trials were included dependent of study design and sufficient number of patients. Expert commentary: With the current available immunosuppressive therapies less than 10% of patients will progress to end stage renal disease. Various treatment options are available and can be used adapted to the clinical characteristics of the patient. Treatment in patients with membranous nephropathy can be individualized using measurement of anti-PLA2R antibodies.

Here we conducted a retrospective study to examine the risk of cardiovascular events (CVEs) relative to that of end-stage renal disease (ESRD) in patients with primary membranous nephropathy, in a discovery cohort of 404 patients. The cumulative incidence of CVEs was estimated in the setting of the competing risk of ESRD with risk factors for CVEs assessed by multivariable survival analysis. The observed cumulative incidences of CVEs were 4.4%, 5.4%, 8.2%, and 8.8% at 1, 2, 3, and 5 years respectively in the primary membranous nephropathy cohort. In the first 2 years after diagnosis, the risk for CVEs was similar to that of ESRD in the entire cohort, but exceeded it among patients with preserved renal function. Accounting for traditional risk factors and renal function, the severity of nephrosis at the time of the event (hazard ratio 2.1, 95% confidence interval 1.1 to 4.3) was a significant independent risk factor of CVEs. The incidence and risk factors of CVEs were affirmed in an external validation cohort of 557 patients with primary membranous nephropathy. Thus early in the course of disease, patients with primary membranous nephropathy have an increased risk of CVEs commensurate to, or exceeding that of ESRD. Hence, reduction of CVEs should be considered as a therapeutic outcome measure and focus of intervention in primary membranous nephropathy.

Summary Background and objectives Circulating autoantibodies against the M-type phospholipase A2 receptor (anti-PLA2R) were recently identified in the majority of patients in the United States with idiopathic membranous nephropathy (iMN). The objectives of this study were to assess the prevalence of anti-PLA2R in a separate, European cohort of iMN patients and to correlate the presence of anti-PLA2R with clinical parameters reflective of disease activity. Design, setting, participants, & measurements Anti-PLA2R levels were blindly assessed by a Western blot immunoassay in 54 serum samples from 18 patients with iMN collected in various stages of clinical disease. Anti-PLA2R levels were correlated with other clinical parameters. Results 77.8% of iMN patients in our cohort had antibodies reactive with human PLA2R. The antibody levels in these patients correlated strongly with both clinical status and proteinuria (r = 0.73, P Conclusions The role of PLA2R as a major antigen in iMN was confirmed in an independent, European patient cohort, and levels of circulating anti-PLA2R revealed a strong correlation with clinical disease activity. We propose that detection and measurement of these autoantibodies may provide a tool for monitoring of disease activity and treatment efficacy.

Contains fulltext : 70536.pdf (Publisher’s version ) (Closed access) BACKGROUND: It is suggested that proteinuria contributes to progressive renal failure by inducing tubular cell injury. The site of injury is unknown. Most studies have used markers of proximal tubular cell damage. Fatty acid-binding proteins (FABPs) are intracellular carrier proteins with different expression in the kidney. Liver-type FABP (L-FABP) is found in the cytoplasm of proximal tubules, whereas heart-type FABP (H-FABP) is localized in the distal tubules. We evaluated the urinary excretion of L-FABP and H-FABP in patients with idiopathic membranous nephropathy (iMN). METHODS: We have studied 40 patients (27 males, 13 females) with iMN. The mean age was 48 +/- 15 years, serum creatinine concentration 89 +/- 17 micromol/l and proteinuria 8.9 +/- 5.0 g/24 h. Urinary L-FABP and H-FABP were measured by ELISA. Renal failure was defined as an increase in serum creatinine >25% from baseline with a serum creatinine >135 micromol/l or an increase >50% from baseline. Urinary L-FABP excretion was detectable in all but one patient. The median (range) level was 3.29 (0.7-165.6) microg/mmol creatinine (normal

Summary In addition to disturbed apoptosis and insufficient clearance of apoptotic cells, there is recent evidence for a role of neutrophils in the aetiopathogenesis of systemic lupus erythematosus (SLE). In response to various stimuli, neutrophils can rapidly release DNA fibres decorated with citrullinated histones and anti-microbial peptides. These structures are referred to as neutrophil extracellular traps (NETs). In addition to apoptotic cell-derived microparticles, these NETs may comprise a further source of autoantigens, able to drive the autoimmune response in SLE. Our group recently identified specific histone modifications occurring during apoptosis that play an important role in the autoimmune response in SLE. In the current study, we evaluated the presence and immunostimulatory potential of these previously identified histone modifications in NETs. Compared to NETs from healthy donors, the histones present in NETs formed by SLE-derived neutrophils contain increased amounts of acetylated and methylated residues, which we previously observed to be associated with apoptosis and SLE. Treatment of neutrophils with histone deacetylase (HDAC) inhibitor Trichostatin A (TSA), prior to induction of NETosis, induced NETs containing hyperacetylated histones, endowed with an increased capacity to activate macrophages. This implies that specific histone modifications, in particular acetylation, might enhance the immunostimulatory potential of NETs in SLE.

To the Editor: Antibodies against phospholipase A2 receptor (aPLA2R) are undetectable in 30% of patients with idiopathic membranous nephropathy (iMN). Yet, in some of these patients iMN is PLA2R related, as suggested by the presence of PLA2R in the immune complexes detected in kidney biopsies.1 This apparent discrepant finding has not been explained.

The optimal timing and duration of immunosuppressive therapy for idiopathic membranous nephropathy (iMN) have been debated. This study aimed to evaluate whether measuring the antibody against the phospholipase A2 receptor (PLA2R-ab) at start and end of therapy predicts long-term outcome and therefore may inform this debate.This observational study included all consecutive high-risk patients with progressive iMN observed from 1997 to 2005 and treated with oral cyclophosphamide (CP) or mycophenolate mofetil (MMF) in combination with corticosteroids for 12 months. Patients were prospectively followed, and outcome was ascertained up to 5 years after completion of immunosuppressive therapy. Serum samples were collected before and after completion of therapy. PLA2R antibodies were determined retrospectively in stored samples using ELISA.In total, 48 patients (37 men) were included. The median age was 55 years (range, 34-75), and the median serum creatinine level was 1.60 mg/dl (range, 0.98-3.37 mg/dl). Twenty-two patients received MMF and 26 received CP. At baseline, PLA2R-abs were present in 34 patients (71%). Baseline characteristics and outcome did not significantly differ between patients negative or positive for PLA2R-ab. In PLA2R-ab-positive patients, treatment resulted in a rapid decrease of antibodies: median anti-PLA2R-ab, 428 U/ml (range, 41-16,260 U/ml) at baseline and 24 U/ml (range, 0-505 U/ml) after 2 months. The PLA2R-ab levels at baseline did not predict initial response, but antibody status at end of therapy predicted long-term outcome: After 5 years, 14 of 24 (58%) antibody-negative patients were in persistent remission compared with 0 of 9 (0%) antibody-positive patients (P=0.003).These data suggest that in PLA2R-ab-positive patients, measuring PLA2R-abs at the end of therapy predicts the subsequent course.

Item does not contain fulltext BACKGROUND AND OBJECTIVES: Cyclophosphamide treatment improves renal survival in patients with idiopathic membranous nephropathy. However, use of cyclophosphamide is associated with cancer. The incidence of malignancies in patients with idiopathic membranous nephropathy was evaluated, and the cancer risk associated with cyclophosphamide use was estimated. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Patients who attended the clinic were included prospectively from 1995 on. A crude incidence ratio for the occurrence of malignancy was calculated. Incidence ratios were subsequently standardized to potential confounders. Latency between cyclophosphamide therapy and the occurrence of cancer was estimated by stratifying for time since the start of treatment. Finally, Poisson regression was used to obtain a multiple adjusted incidence ratio and investigate the dose-response relationship between cyclophosphamide and cancer. RESULTS: Data were available for 272 patients; the mean age was 51 years, and 70% of the patients were men. Median follow-up was 6.0 years (interquartile range=3.6-9.5), and 127 patients were treated with cyclophosphamide. Cancer incidence was 21.2 per 1000 person-years in treated patients compared with 4.6 per 1000 person-years in patients who did not receive cyclophosphamide, resulting in crude and adjusted incidence ratios of 4.6 (95% confidence interval, 1.5 to 18.8) and 3.2 (95% confidence interval, 1.0 to 9.5), respectively. CONCLUSION: Cyclophosphamide therapy in idiopathic membranous nephropathy gives a threefold increase in cancer risk. For the average patient, this finding translates into an increase in annual risk from approximately 0.3% to 1.0%. The increased risk of malignancy must be balanced against the improved renal survival.

The discovery of the M-type phospholipase A2 receptor (PLA2R) as a major antigen in idiopathic membranous nephropathy (iMN) was a breakthrough and established iMN as an autoimmune disease.1 Subsequent studies confirmed that antibodies against PLA2R were present in approximately 70% of incident iMN patients (reviewed by Hofstra and Wetzels2). The potential role of measuring PLA2R antibodies for clinical practice was suggested by studies showing that the presence of PLA2R antibodies supported a diagnosis of iMN,2–4 changes in antibody levels paralleled clinical disease activity,5 disappearance of antibodies preceded and predicted subsequent decrease of proteinuria,6 and high titers of antibodies were associated with a low likelihood of spontaneous remission.7 In this issue of JASN, Hoxha et al. report their findings in a large cohort of 163 patients with MN.8 PLA2R antibodies (both IgG and IgG4) were measured in serum obtained within 6 months from kidney biopsy. The authors used an ELISA assay and immunofluorescence testing (IFT) (both commercially available in Europe).9 PLA2R antibodies were detected in 133 patients (82%). The median follow-up was 12 months, and the majority of patients (101 of 133) started immunosuppressive therapy within 3 months after presentation. Hoxha et al. show that PLA2R antibodies decreased during follow-up. The decrease in PLA2R antibodies preceded the decrease in proteinuria. The authors concluded that “there was a remarkable time lag between the rather rapid fall in antibody levels at 3 months and the protracted reduction in proteinuria.”8 These data confirm earlier findings and indicate that an immunologic remission precedes clinical remission in patients with iMN.6,10 Although no PLA2R antibodies were found in patients with complete remission, PLA2R antibodies were still present in a low titer in 50% of patients with a partial remission. These data indicate that a partial remission may not always reflect the absence of disease activity. The authors next analyzed the association between antibody levels at baseline and remission at 12 months after presentation. PLA2R antibody levels were significantly higher in 28 patients without remission than in 39 patients with remission. The median time to remission was significantly longer in patients with antibody levels above versus below the median (15 versus 9 months). The authors concluded that the PLA2R antibody level was “an independent risk factor for not achieving remission.”8 Such a conclusion, if valid and applicable to untreated patients, could improve individualized patient care. However, the data from the study by Hoxha et al. do not allow to conclude that antibody levels can help to accurately identify patients who will develop a spontaneous remission because most of Hoxha's patients were treated. Moreover, because treated patients nearly all developed a remission, the antibody levels merely predicted the time to remission. Although their patient cohort is large, the study by Hoxha et al. is limited because of the relatively short follow-up period, the use of various immunosuppressive treatment regimens, and the unnecessary early start of immunosuppressive therapy in many patients. The reported findings cannot change current guidelines for diagnosis and treatment of patients with iMN. Evidently, more rigid study protocols are needed to reliably answer the most relevant questions. Certainly, Hoxha et al. could perform additional analyses to answer some of the following unresolved questions.

Item does not contain fulltext BACKGROUND: The optimal timing and duration of immunosuppressive therapy for idiopathic membranous nephropathy (iMN) have been debated. This study aimed to evaluate whether measuring the antibody against the phospholipase A2 receptor (PLA2R-ab) at start and end of therapy predicts long-term outcome and therefore may inform this debate. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This observational study included all consecutive high-risk patients with progressive iMN observed from 1997 to 2005 and treated with oral cyclophosphamide (CP) or mycophenolate mofetil (MMF) in combination with corticosteroids for 12 months. Patients were prospectively followed, and outcome was ascertained up to 5 years after completion of immunosuppressive therapy. Serum samples were collected before and after completion of therapy. PLA2R antibodies were determined retrospectively in stored samples using ELISA. RESULTS: In total, 48 patients (37 men) were included. The median age was 55 years (range, 34-75), and the median serum creatinine level was 1.60 mg/dl (range, 0.98-3.37 mg/dl). Twenty-two patients received MMF and 26 received CP. At baseline, PLA2R-abs were present in 34 patients (71%). Baseline characteristics and outcome did not significantly differ between patients negative or positive for PLA2R-ab. In PLA2R-ab-positive patients, treatment resulted in a rapid decrease of antibodies: median anti-PLA2R-ab, 428 U/ml (range, 41-16,260 U/ml) at baseline and 24 U/ml (range, 0-505 U/ml) after 2 months. The PLA2R-ab levels at baseline did not predict initial response, but antibody status at end of therapy predicted long-term outcome: After 5 years, 14 of 24 (58%) antibody-negative patients were in persistent remission compared with 0 of 9 (0%) antibody-positive patients (P=0.003). CONCLUSIONS: These data suggest that in PLA2R-ab-positive patients, measuring PLA2R-abs at the end of therapy predicts the subsequent course.

Item does not contain fulltext Recently published Kidney Disease Improving Global Outcomes (KDIGO) guidelines recommend limiting the use of immunosuppressive drugs in idiopathic membranous nephropathy to patients at the highest risk of kidney failure. However, recommendations are based on natural history rather than direct assessment of a restrictive treatment strategy. Here, we describe the long-term outcomes of treating a large cohort of patients with idiopathic membranous nephropathy according to a restrictive treatment policy. We analyzed data for 254 patients who visited our outpatient clinic between 1995 and 2009. All patients were treated with angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers. Immunosuppressive therapy was recommended in cases of deteriorating renal function or untreatable nephrotic syndrome. Primary outcomes for the present study were renal replacement therapy and death. Secondary outcomes included adverse events during follow-up and remission of proteinuria. In total, 124 patients (49%) received immunosuppressive therapy, which predominantly consisted of cyclophosphamide combined with steroids. Ten-year cumulative incidence rates were 3% for renal replacement therapy and 10% for death. Partial remission rates were 39%, 70%, and 83% after 1, 3, and 5 years, respectively; complete remission rates were 5%, 24%, and 38% at 1, 3, and 5 years, respectively. A serious adverse event occurred in 23% of all patients. The most notable complications were infections (17%), leukopenia (18%), cardiovascular events (13%), and malignancies (8%). In conclusion, the use of a restrictive treatment strategy in this cohort of patients with idiopathic membranous nephropathy yielded favorable outcomes while limiting the number of patients exposed to toxic drugs. These results support current KDIGO guidelines.

Item does not contain fulltext Membranous nephropathy, focal segmental glomerulosclerosis (FSGS), and minimal change disease (MCD) are the most common causes of idiopathic nephrotic syndrome. For many years prednisone, alkylating agents, and calcineurin inhibitors have been the standard of therapy for these patients. More effective or better tolerated treatment modalities are needed. B cell targeted therapy was recently introduced in clinical practice. In this review, we briefly summarize the current standard therapy and discuss the efficacy of B cell targeted therapy in primary glomerular diseases. Observational, short-term studies suggest that rituximab is effective and comparable to standard therapy in maintaining remissions in patients with frequently relapsing or steroid-dependent MCD or FSGS. In contrast, response is limited in patients with steroid-resistant nephrotic syndrome. Rituximab also induces remissions in patients with membranous nephropathy. Controlled clinical trials on kidney endpoints are urgently needed to position B cell targeted therapy in clinical practice.

Item does not contain fulltext Immunosuppressive treatment of patients with idiopathic membranous nephropathy (iMN) is heavily debated. The controversy is mainly related to the toxicity of the therapy and the variable natural course of the disease-spontaneous remission occurs in 40-50% of patients. The 2012 Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guideline for Glomerulonephritis provides guidance for the treatment of iMN. The guideline suggests that immunosuppressive therapy should be restricted to patients with nephrotic syndrome and persistent proteinuria, deteriorating renal function or severe symptoms. Alkylating agents are the preferred therapy because of their proven efficacy in preventing end-stage renal disease. Calcineurin inhibitors can be used as an alternative although efficacy data on hard renal end points are limited. In this Review, we summarize the KDIGO guideline and address remaining areas of uncertainty. Better risk prediction is needed to identify patients who will benefit from immunosuppressive therapy, and the optimal timing and duration of this therapy is unknown because most of the randomized controlled trials were performed in low-risk or medium-risk patients. Alternative therapies, directed at B cells, are under study. The discovery of anti-M type phospholipase A2 receptor-antibodies is a major breakthrough and we envisage that in the near future, antibody-driven therapy will enable more individualized treatment of patients with iMN.

Item does not contain fulltext BACKGROUND AND OBJECTIVES: Accurate prediction of prognosis may improve management of patients with idiopathic membranous nephropathy. This study compared the Toronto Risk Score and urinary low-molecular weight proteins. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: One hundred four patients with biopsy-proven idiopathic membranous nephropathy who presented between 1995 and 2008 with a well-preserved kidney function and nephrotic range proteinuria were included. Urinary beta2-microglobulin and alpha1-microglobulin measurements were obtained by timed standardized measurements, and the Toronto Risk Score was calculated using data obtained from medical records. The endpoint was progression, which was defined as an increase in serum creatinine>50% or >25% with a concentration>135 mumol/L. RESULTS: Forty-nine patients showed progression. The area under the receiver-operating characteristics curve was 0.78 (95% confidence interval=0.69-0.88) for the risk score versus 0.80 (0.71-0.89) and 0.79 (0.71-0.88) for urinary beta2- and alpha1-microglobulin, respectively. Differences were not significant. Persistent proteinuria did not add accuracy to the Toronto Risk Score. Conversely, its accuracy was not reduced when data from the first 6 months of follow-up were used. Furthermore, a score based on GFR estimated with the six-variable Modification of Diet in Renal Disease equation, calculated in the first 6 months of follow-up, gave an area under the receiver-operating characteristics curve of 0.83 (0.74-0.92), which was not statistically different from other markers. CONCLUSIONS: The prognostic accuracies of the Toronto Risk Score and urinary low-molecular weight proteins were not significantly different. The risk score can be calculated within 6 months of diagnosis, and a simplified risk score using estimated GFR-Modification of Diet in Renal Disease may be sufficient. 01 augustus 2012

Membranous nephropathy (MN) is the most common causeof the nephrotic syndrome in Europe, with an incidence of5–10/million/year in adults [1]. Although MN can occur sec-ondary to infections, systemic diseases, use of drugs or ma-lignancies, in most patients n o underlying cause is identified[idiopathic membranous nephr opathy (iMN)]. Recent studieshave identified antibodies against the M-type PLA2-receptor,an antigen present on podocytes, in 70% of patients withiMN, thus establishing iMN as an autoimmune disease [ 2].These findings were supported by a genome wide associationstudy that found an association between PLA2R and iMN [ 3].In this comment, we describe the management of pa-tients with MN (Figure 1).

Circulating autoantibodies against the M-type phospholipase A(2) receptor (anti-PLA(2)R) were recently identified in the majority of patients in the United States with idiopathic membranous nephropathy (iMN). The objectives of this study were to assess the prevalence of anti-PLA(2)R in a separate, European cohort of iMN patients and to correlate the presence of anti-PLA(2)R with clinical parameters reflective of disease activity.Anti-PLA(2)R levels were blindly assessed by a Western blot immunoassay in 54 serum samples from 18 patients with iMN collected in various stages of clinical disease. Anti-PLA(2)R levels were correlated with other clinical parameters.77.8% of iMN patients in our cohort had antibodies reactive with human PLA(2)R. The antibody levels in these patients correlated strongly with both clinical status and proteinuria (r = 0.73, P0.01).The role of PLA(2)R as a major antigen in iMN was confirmed in an independent, European patient cohort, and levels of circulating anti-PLA(2)R revealed a strong correlation with clinical disease activity. We propose that detection and measurement of these autoantibodies may provide a tool for monitoring of disease activity and treatment efficacy.

Accurate prediction of prognosis in idiopathic membranous nephropathy (iMN) allows restriction of immunosuppressive therapy to patients at high risk for ESRD. Here we re-evaluate urinary low-molecular-weight proteins as prognostic markers and explore causes of misclassification.In a cohort of 129 patients with serum creatinine concentration135 μmol/L and proteinuria ≥3.0 g/10 mmol, urinary α1- (uα1m) and β2-microglobulin (uβ2m) excretion rate was determined. Urinary α1m and uβ2m-creatinine ratio was also obtained. We defined progression as a rise in serum creatinine ≥50% or ≥25% and an absolute level ≥135 μmol/L.Median survival time was 25 months, and 47% of patients showed progression. The area under the receiver operating characteristic curve for uβ2m was 0.81 (95% CI: 0.73 to 0.89). Using a threshold value of 1.0 μg/min, sensitivity and specificity were 73% and 75%, respectively. Similar accuracy was observed for the uβ2m-creatinine ratio with sensitivity and specificity of 75% and 73%, respectively, at a threshold of 1.0 μg/10 mmol creatinine. Similar accuracy was found for uα1m and uα1m-creatinine ratio. Blood Pressure and cholesterol contributed to misclassification. Repeated measurements improved accuracy in patients with persistent proteinuria: the positive predictive value of uβ2m increased from 72% to 89% and the negative predictive value from 76% to 100%.Urinary excretion of uα2m and uβ2m predict prognosis in iMN. A spot urine sample can be used instead of a timed sample. A repeated measurement after 6 to 12 months increases prognostic accuracy.

Contains fulltext : 97321.pdf (Publisher’s version ) (Open Access) BACKGROUND: Idiopathic membranous nephropathy is a major cause of the nephrotic syndrome in adults, but its etiologic basis is not fully understood. We investigated the genetic basis of biopsy-proven cases of idiopathic membranous nephropathy in a white population. METHODS: We performed independent genomewide association studies of single-nucleotide polymorphisms (SNPs) in patients with idiopathic membranous nephropathy from three populations of white ancestry (75 French, 146 Dutch, and 335 British patients). The patients were compared with racially matched control subjects; population stratification and quality controls were carried out according to standard criteria. Associations were calculated by means of a chi-square basic allele test; the threshold for significance was adjusted for multiple comparisons (with the Bonferroni method). RESULTS: In a joint analysis of data from the 556 patients studied (398 men), we identified significant alleles at two genomic loci associated with idiopathic membranous nephropathy. Chromosome 2q24 contains the gene encoding M-type phospholipase A(2) receptor (PLA(2)R1) (SNP rs4664308, P=8.6x10(-29)), previously shown to be the target of an autoimmune response. Chromosome 6p21 contains the gene encoding HLA complex class II HLA-DQ alpha chain 1 (HLA-DQA1) (SNP rs2187668, P=8.0x10(-93)). The association with HLA-DQA1 was significant in all three populations (P=1.8x10(-9), P=5.6x10(-27), and P=5.2x10(-36) in the French, Dutch, and British groups, respectively). The odds ratio for idiopathic membranous nephropathy with homozygosity for both risk alleles was 78.5 (95% confidence interval, 34.6 to 178.2). CONCLUSIONS: An HLA-DQA1 allele on chromosome 6p21 is most closely associated with idiopathic membranous nephropathy in persons of white ancestry. This allele may facilitate an autoimmune response against targets such as variants of PLA2R1. Our findings suggest a basis for understanding this disease and illuminate how adaptive immunity is regulated by HLA.

Item does not contain fulltext BACKGROUND: Immunosuppressive therapy in idiopathic membranous nephropathy (iMN) is debated. Accurate identification of patients at high risk for end-stage renal disease (ESRD) allows early start of therapy in these patients. It is unknown if early start of therapy is more effective and/or less toxic than late start (i.e. when GFR deteriorates). METHODS: We conducted a randomized open-label study in patients with iMN, a normal renal function and a high risk for ESRD (urinary beta2m >0.5 microg/min, UIgG >125 mg/day). Patients started with immunosuppressive therapy (cyclophosphamide for 12 months, and steroids) either immediately after randomization or when renal function deteriorated (DeltasCr > or =+25% and sCr >135 micromol/l or DeltasCr > or =+50%). End points were remission rates, duration of the nephrotic syndrome (NS), renal function and complications. RESULTS: The study included 26 patients (24 M/2 F), age 48 +/- 12 years; sCr 96 micromol/l (range 68-126) and median proteinuria 10.0 g/10 mmol Cr. Early treatment resulted in a more rapid onset of remission (P = 0.003) and a shorter duration of the NS (P = 0.009). However, at the end of the follow-up (72 +/- 22 m), there were no differences in overall remission rate, sCr (93 versus 105 micromol/l), proteinuria, relapse rate and adverse events. CONCLUSIONS: In high-risk patients with iMN, immunosuppressive treatment is effective in inducing a remission. Early treatment shortens the duration of the nephrotic phase, but does not result in better preservation of renal function. Our study indicates that treatment decisions must be based on risk and benefit assessment in the individual patient. 01 januari 2010

Item does not contain fulltext 01 juni 2010

Contains fulltext : 70106.pdf (Publisher’s version ) (Closed access) BACKGROUND: An accurate prediction of prognosis in patients with idiopathic membranous nephropathy (iMN) would allow restriction of immunosuppressive treatment to patients who are at highest risk for end-stage renal disease (ESRD). Several markers of proximal tubular cell injury have been used as predictors of prognosis. In this study we compared the accuracy of urinary beta-2-microglobulin (U beta 2m) and N-acetyl-beta-glucosaminidase (U beta-NAG) in predicting renal insufficiency and remission rates. METHODS: Fifty-seven patients with iMN (38 M, 19 F; age 48 +/- 16 years), a nephrotic syndrome and a serum creatinine level 50%. Remission was defined as a proteinuria

Item does not contain fulltext BACKGROUND: The efficacy of immunosuppressive therapy in preventing ESRD in patients with idiopathic membranous nephropathy (iMN) is debated. From 1991 onwards, we have advocated a restrictive treatment strategy in our university hospital and regional referring hospitals. We advised the use of immunosuppressive therapy, consisting of a combination of steroids and oral cyclophosphamide for 12 months, in patients with iMN at high risk for ESRD. METHODS: Primary renal diagnosis of all patients who start renal replacement therapy in the Netherlands is registered in the RENINE database. We studied the incidence of ESRD due to iMN in the Netherlands in the period 1991-2005. We mailed a questionnaire to all nephrology centres that entered a patient with ESRD and iMN in the RENINE database after 2000. RESULTS: The introduction of the cyclophosphamide-based treatment strategy in the Nijmegen region resulted in a significant 70% reduction in the incidence of ESRD in patients with iMN as compared to an unchanged incidence in other parts of the Netherlands. The response rate to the questionnaire was 65%. There were 45 patients (34 M, 11 F) with a mean age of 49 +/- 17 years at diagnosis and a median serum creatinine of 138 micromol/l (range 60-1798). Overall, only 22 patients (49%) had been treated with immunosuppressive therapy, consisting of prednisone monotherapy in 7. CONCLUSIONS: Our data suggest that the introduction of a cyclophosphamide-based restrictive treatment policy has reduced the risk of ESRD in iMN. The questionnaires reflect the differences in opinion on the optimal treatment of high-risk patients with iMN.

Contains fulltext : 53390.pdf (Publisher’s version ) (Closed access)

Single gene disorders are estimated to account for ~30% of children and ~10% of adult patients attending renal outpatient services. For mutation detection by exome sequencing, deep phenotyping, reverse phenotyping and family history information are important. A multidisciplinary nephrogenetic outpatient clinic for children and adult patients with (genetic) kidney diseases has been established by a team of (pediatric) nephrologists and a clinical geneticist in the Radboudumc. Clinical exome sequencing for a broad spectrum of isolated- and syndromic renal (ciliary) disorders has been developed. The approach consists of a two-tier analysis in which the first step is to screen for pathogenic variants in genes that are known to be mutated in renal diseases (170 genes) or (renal) ciliopathies (125 genes). If causative mutations are not identified in the first step, the complete exome data set can be analysed with informed consent. The first results with the renal disease gene panel in 35 unrelated patients with undiagnosed renal disease led to pathogenic mutations in the CC2D2A, CLCN5, NPHP1 and UMOD gene, detected in four cases and in six other cases likely pathogenic variants needed follow-up studies. Further analysis of the complete exome data set in 13 patients, revealed possible pathogenic mutations in two cases. While variant and copy number variation analysis in the rest of exome is expected to further increase diagnostic yield, we can already conclude that the combination of the multidisciplinary outpatient clinic with diagnostic exome sequencing provides a powerful tool for detecting causative mutations of renal disease.

In this commentary, we discuss a study conducted by Ohisa et al., in which the sensitivity and specificity of different approaches to differentiating glomerular from nonglomerular hematuria were compared. Urine specimens (n = 579) from patients with microscopic hematuria of known origin were evaluated both morphologically (by use of phase-contrast microscopy) and biochemically (by calculation of urinary albumin:total protein, albumin:creatinine, and total protein:creatinine ratios). The study showed that the albumin:total protein ratio had the highest sensitivity and specificity for identifying glomerular hematuria (97.3% and 100%, respectively). We highlight important limitations of the study and question whether the results can be generalized to patients with asymptomatic hematuria.

To the Editor: In their recent article, Stevens et al.1 have reported that factors other than glomerular filtration rate (GFR) affect serum cystatin C (CysC) levels. Specifically, they mentioned the impact of diabetes mellitus, which was associated with 8.5% higher levels of CysC. However, proteinuria was also associated with CysC and, as admitted by the authors, diabetes and proteinuria were strongly associated in their patient cohorts. Thus, their data did not allow for determining the independent effects of diabetes mellitus or proteinuria. We have previously reported GFR data of a cohort of patients with normo-albuminuric diabetes type I and age- and sex-matched controls.2 From this cohort, we have selected 33 patients and 38 controls with matching GFR (inulin clearance) and evaluated the relationship between CysC and GFR.