Immune Complex-mediated Membranoproliferative Glomerulonephritis Research Articles

Clinicopathological characteristics and outcomes of adult patients with idiopathic membranoproliferative glomerulonephritis according toan immunofluorescence-based classification.

The classification of membranoproliferative glomerulonephritis (MPGN) into immune complex-mediated MPGN and complement-mediated MPGN on immunofluorescence has provided insights into two distinct disease processes. There are limited data available on renal outcomes of MPGN from developing countries. A retrospective analysis was conducted on biopsy-proven MPGN cases diagnosed between 1998 and 2018 at the Sindh Institute of Urology and Transplantation (SIUT). Secondary causes were excluded. Patients were reclassified as immune complex-mediated-MPGN and complement-mediated-MPGN based on immunofluorescence results. The clinicopathological findings and outcomes of the two groups were compared. In total, 213 patients with idiopathic MPGN were identified. Among these, 163 (76.5%) were reclassified as immune complex-mediated-MPGN and 50 (23.4%) as complement-mediated-MPGN. No significant differences were found between the two groups regarding age, gender, clinical characteristics, biopsy indications, biopsy findings, and renal function at presentation. Overall, 63 subjects (38.7%) with immune complex-mediated-MPGN and 27 (54%) with complement-mediated-MPGN received immunosuppressive agents (p = 0.08). Complete and partial remission rates were higher in immune complex-mediated-MPGN than in complement-mediated-MPGN (76% vs 58%, p < 0.05). At two years, median estimated glomerualr filtration rate (eGFR) tended to be higher in patients with immune complex-mediated-MPGN 91.2 (45.4-113.7) vs 83.45(34.6-102.50)ml/min/1.73 m2, p = 0.22) with significantly better renal survival (76% vs 58%, p = 0.03). Comparatively, more patients progressed to end-stage kidney disease (ESKD) in the complement-mediated-MPGN group (32% vs 19.6%, p = 0.06), with increased overall mortality (5 (10%) vs 7 (4.3%), p = 0.12). The clinicopathological features at presentation of complement-mediated-MPGN are similar to those of immune complex-mediated-MPGN. However, it is less frequent and overall prognosis is less favorable.

Outcome of Patients Transplanted for C3 Glomerulopathy and Primary Immune Complex-Mediated Membranoproliferative Glomerulonephritis

IntroductionAround 50% of C3 glomerulopathy and primary immune-complex-mediated membranoproliferative glomerulonephritis (C3G, IC-MPGN) patients reach kidney failure at 10 years after diagnosis. Since these patients are generally young, the majority will be listed for kidney transplantation. However, reported outcomes in patients transplanted for C3G and IC-MPGN are heterogeneous and conflicting, as they are mainly based on retrospective monocentric studies. We thus aimed to provide detailed multicenter data on these patients, taking advantage of the ongoing nationwide Swiss Transplant Cohort Study. MethodsWe analyzed patient and graft outcome, including the risk of graft loss in relation to recurrence of glomerulopathy. ResultsForty-one (10 C3G, 31 IC-MPGN) transplanted recipients were included with a mean age at transplantation of 48+16 years. Living donation provided 53% of the organs. During a mean follow-up of 4.7 years, 7 patients (4 C3G, 3 IC-MPGN) presented disease recurrence with a mean time to recurrence of 1.2 years. New-onset or rapidly increasing proteinuria was an early marker of recurrence, preceding significant decline in eGFR. Following recurrence, 28% lost their graft, compared to 11% of patients without recurrence. Disease recurrence was the primary cause of graft loss in all patients. Finally, 14% of patients died during follow-up. ConclusionThis study provides important insights into the epidemiology and outcome of C3G and IC-MPGN patients and their grafts after kidney transplantation. The data also suggest that proteinuria may serve as an early biomarker of disease recurrence and should be considered in patient management as well as an endpoint in current clinical trials using novel complement modulators.

Immune Complex-Mediated Membranoproliferative Glomerulonephritis Secondary to Primary Biliary Cholangitis: A Rare Case Report

Immune Complex-Mediated Membranoproliferative Glomerulonephritis Secondary to Primary Biliary Cholangitis: A Rare Case Report

#2113 Membranoproliferative glomerulonephritis experience over 20 years in a tertiary centre in the United Kingdom

Abstract Background and Aims Membranoproliferative Glomerulonephritis (MPGN) is a histological pattern of injury which typically accounts for light microscopy findings on 1-3% of kidney biopsies. It is classified based on immunofluorescence into complement-mediated, immune complex-mediated (IC) and immunofluorescence negative. The underlying aetiologies such as C3 Glomerulopathy are rare diseases, and thus longitudinal real-world experience in terms of underlying causes, treatment and outcomes is valuable. Method This study presents a retrospective review of biopsy data from January 2000 through to December 2020 in a tertiary renal referral centre in the United Kingdom (UK). This review was conducted using the organisation's biopsy database, with patient demographics and clinical information obtained from the Electronic Patient Record. All patients with an MPGN pattern on biopsy were reviewed. Those with new MPGN post-transplant, with an MPGN pattern on biopsy but subsequently diagnosed as IgA Nephropathy, and with an MPGN pattern but a known lupus diagnosis, were excluded. Results A histological finding of MPGN on kidney biopsy was found in 67 patients. Of these, 41 remained in the study following application of the exclusion criteria, with an additional 3 excluded as there was insufficient information available for classification in their biopsy reports. Of the 38 remaining, 28 had IC MPGN and 10 had C3 Glomerulopathy (C3G) - 8 with C3 Glomerulonephritis (C3GN) and 2 with C3 Dense Deposit Disease (DDD). Median follow up was 72 (range 45-126) months. Median age was 64 years in the IC MPGN and 55 years in the C3G groups (p 0.125). The majority in both groups were female, 60.7% (17) and 60% (6) respectively. There was no significant difference in renal function, blood pressure, or proteinuria at presentation between the groups. MPGN was associated with infections in 8 patients (21.1%), connective tissue disease in 3 patients (7.9%), monoclonal gammopathies or haematological malignancies in 8 patients (21.1%), and 2 had identified complement deficiencies (5.3%). Over the study period 47.4% (18) of patients progressed to end stage kidney disease and 50% (19) died. There was no significant difference in these outcomes between the IC MPGN and the C3G groups. Progression to renal replacement therapy (RRT) was seen in 42.9% (12) of the IC MPGN group, and 60% (6) of the C3G group (p=0.287). This included two patients who received a kidney transplant (both in the C3G group), one of whom developed recurrence during the available follow up. Conclusion This study adds a UK perspective with long term data and outcomes in a rare condition. Almost half of patients progressed to RRT and half of patients died during the follow-up period. These outcomes were seen at similar rates in those with IC MPGN and those with C3G. A variety of associated conditions were observed, and the low number of complement deficiencies identified is likely due to the historical nature of the review with reduced screening for complement abnormalities and genetics in the earlier period. Outcomes on follow-up:

#1640 Alternative complement pathway disorders in the transplant setting—experience from a large volume center

Abstract Background and Aims Complement alternative pathway disorders, atypical hemolytic-uremic syndrome (aHUS) and C3 glomerulopathy (C3G), are rare diseases with a high rate of recurrence after kidney transplantation. Due to limited availability of testing, patients may go undiagnosed, indicating testing during pretransplant evaluation. Posttransplant thrombotic microangiopathy (TMA) is a rare complication of transplantation. A large number of post transplant TMAs is regarded as secondary, either to immunosuppressive drugs or transplant itself. In select cases, complement alternative pathway disorders analysis is warranted. Method We retrospectively reviewed all patients in whom complement system diagnostic work-up was performed in the transplant setting in our center, from 2017 to 2022. Complement system analysis in isolated histological TMA of the allograft, without extrarenal manifestations and with known cause of native kidneys ESRD, was not performed routinely. Patients in whom alternative pathway disorders were confirmed were compared with those with no abnormalities detected by complement system analysis. Results 12 patients were identified, 75% male, median age 39.5 years (IQR 28-60.25). 8 patients were evaluated before transplantation. 4 of the 8 patients were referred for transplantation with diagnosed aHUS. Genetic testing was used for recurrence risk stratification. In living donor transplantations 2 donors were tested as well. One patient was referred from a neighboring resource poor country and was not on eculizumab therapy. He was homozygous for a high risk causative mutation. He was declined for living related donor kidney transplant, due to risk to the donor and unavailability of eculizumab. Compassionate use request was initiated. One patient was referred as possible C3G and repeat complement analysis revealed elevated C3Nef. Out of 3 patients, previously diagnosed as CKD of unknown origin or immune complex-mediated membranoproliferative glomerulonephritis, 2 were diagnosed during pretransplant evaluation: one as C3G and the other as aHUS. 4 patients were evaluated posttransplant. One analysis was performed due to recurrent C3G of the allograft, with confirmed competent dysregulation. 2 analyses were in liver transplant recipients, both with systemic TMA. Severe overactivation with consumption of complement was proven in one and treated with eculizumab. The characteristics of patients with diagnosed disorders of the complement system and those without are shown in Table 1. Conclusion Transplant physicians should keep a high volume of suspicion for complement dysregulation disorders, both during the pretransplant work-up and when evaluating TMA and recurrent GN posttransplant. Special caution should be advised when a patient is referred as chronic GN, MPGN or unknown cause ESKD at a young age.

Diagnostic Challenges and Emerging Pathogeneses of Selected Glomerulopathies.

Recent progress in glomerular immune complex and complement-mediated diseases have refined diagnostic categories and informed mechanistic understanding of disease development in pediatric patients. Herein, we discuss selected advances in 3 categories. First, membranous nephropathy antigens are increasingly utilized to characterize disease in pediatric patients and include phospholipase A2 receptor (PLA2R), Semaphorin 3B (Sema3B), neural epidermal growth factor-like 1 (NELL1), and protocadherin FAT1, as well as the lupus membranous-associated antigens exostosin 1/2 (EXT1/2), neural cell adhesion molecule 1 (NCAM1), and transforming growth factor beta receptor 3 (TGFBR3). Second, we examine advances in techniques for paraffin and light chain immunofluorescence (IF), including the former's function as a salvage technique and their necessity for diagnosis in adolescent cases of membranous-like glomerulopathy with masked IgG kappa deposits (MGMID) and proliferative glomerulonephritis with monotypic Ig deposits (PGNMID), respectively. Finally, progress in understanding the roles of complement in pediatric glomerular disease is reviewed, with specific attention to overlapping clinical, histologic, and genetic or functional alternative complement pathway (AP) abnormalities among C3 glomerulopathy (C3G), infection-related and post-infectious GN, "atypical" post-infectious GN, immune complex mediated membranoproliferative glomerulonephritis (IC-MPGN), and atypical hemolytic uremic syndrome (aHUS).

Membranoproliferative Glomerulonephritis over 20 Years at a Tertiary Referral Center in the UK.

Membranoproliferative glomerulonephritis (MPGN) is a pattern of injury seen on kidney biopsy, with various underlying etiologies. The component types, including complement-mediated MPGN, are relatively rare. This study presents longitudinal real-world data over 20 years in a tertiary renal center in the UK. All patients with an MPGN pattern on kidney biopsy between 2000 and 2020 were identified. After applying exclusion criteria, 38 patients remained. Data including patient demographics, details of the renal histology from the kidney biopsy, baseline laboratory results, treatments received, and clinical outcomes including renal replacement therapy and death were collected from the organization's electronic patient record. Twenty-eight of the cohort had immune complex-mediated MPGN, and 10 had complement-mediated MPGN (8 with C3 glomerulonephritis and 2 with dense deposit disease). Median follow-up was 72 months. Median age was 61 years. Overall, 60.5% were female, and 92.1% white. At presentation, median eGFR was 31.5 mL/min/1.73 m2 and uPCR 394 mg/mmol. Here, 78.9% received renin-angiotensin-aldosterone system inhibitors and 71.1% received any immunosuppression. In total, 47.4% progressed to ESKD and 50% died during follow-up. The study found an older patient population than typically reported. Poor outcomes were observed in the overall cohort with progression to ESKD and mortality both at almost 50%. This may be influenced by the older patient population. Individualized management of patients with an MPGN biopsy finding is paramount, with comprehensive evaluation for triggers and complement abnormalities. Going forward, registry enrolment and collaborative studies may enhance knowledge and outcomes.

Genetic investigation of Nordic patients with complement-mediated kidney diseases.

Complement activation in atypical hemolytic uremic syndrome (aHUS), C3 glomerulonephropathy (C3G) and immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) may be associated with rare genetic variants. Here we describe gene variants in the Swedish and Norwegian populations. Patients with these diagnoses (N=141) were referred for genetic screening. Sanger or next-generation sequencing were performed to identify genetic variants in 16 genes associated with these conditions. Nonsynonymous genetic variants are described when they have a minor allele frequency of <1% or were previously reported as being disease-associated. In patients with aHUS (n=94, one also had IC-MPGN) 68 different genetic variants or deletions were identified in 60 patients, of which 18 were novel. Thirty-two patients had more than one genetic variant. In patients with C3G (n=40) 29 genetic variants, deletions or duplications were identified in 15 patients, of which 9 were novel. Eight patients had more than one variant. In patients with IC-MPGN (n=7) five genetic variants were identified in five patients. Factor H variants were the most frequent in aHUS and C3 variants in C3G. Seventeen variants occurred in more than one condition. Genetic screening of patients with aHUS, C3G and IC-MPGN is of paramount importance for diagnostics and treatment. In this study, we describe genetic assessment of Nordic patients in which 26 novel variants were found.

42 APPARENT: A multicenter, randomized, double-blind, placebo-controlled Phase 3 study to assess the efficacy and safety of iptacopan in idiopathic (primary) immune complex-mediated membranoproliferative glomerulonephritis

42 APPARENT: A multicenter, randomized, double-blind, placebo-controlled Phase 3 study to assess the efficacy and safety of iptacopan in idiopathic (primary) immune complex-mediated membranoproliferative glomerulonephritis

Utility of C4d Immunohistochemistry as an Adjunct Stain in Diagnostic Renal Pathology of Glomerular Diseases.

C4d is a byproduct of the activation of the classic and lectin complement pathways. Being routinely used as a marker for antibody-mediated rejection, the significance of C4d in native kidney disease is currently being widely studied. We evaluated glomerular and extraglomerular C4d staining in 82 biopsies of proliferative and nonproliferative glomerulonephritis diagnosed in our institution. The staining pattern of C4d was tabulated in various glomerular diseases. All biopsies of membranous nephropathy including membranous lupus nephritis (Class V) and immune complex-mediated membranoproliferative glomerulonephritis (MPGN) consistently showed C4d deposits along glomerular basement membrane mirroring the location of immunoglobulin and complement in these conditions. Conversely, other glomerular diseases like IgA nephropathy, postinfectious glomerulonephritis, focal segmental glomerulosclerosis, minimal change disease, and diabetic nephropathy showed variable mesangial and capillary wall C4d deposits. To summarize, the consistent pattern of C4d staining in membranous nephropathy (primary and secondary)and immune complex-mediated MPGN can be used as a valuable adjunct tool in establishing the diagnosis, especially when immunofluorescence findings are limited by inadequate sampling.C4d reactivity in other glomerular diseases are variable and may not aid as a diagnostic tool in renal biopsy evaluation.

Kidney Disease in Ankylosing Spondylitis: a case series and review of the literature.

Kidney disease is a rare manifestation of ankylosing spondylitis (AS) and its pathological alterations remain poorly described. The aim of this study was to investigate the clinical presentation and pathological alterations on kidney biopsy of AS patients and review and discuss the current literature on the issue. We retrospectively studied the clinical presentation and kidney pathological alterations of 15 Caucasian AS patients submitted to kidney biopsy between October 1985 and March 2021. Patients were predominantly male (66.7%) with median age at the time of kideney biopsy of 47 years [IQR 34 - 62]. Median serum creatinine at presentation was 1.3 mg/dL [IQR 0.9 - 3] and most patients also had either proteinuria (85.7%) and/or hematuria (42.8%). The most common indication for kidney biopsy was nephrotic syndrome (33.3%), followed by acute or rapidly progressive kidney injury (20%) and chronic kidney disease of unknown etiology (20%). Chronic interstitial nephritis (CIN) (n=3) and AA amyloidosis (n=3) were the most common diagnosis. Others included IgA nephropathy (IgAN) (n=2), focal segmental glomerulosclerosis (n=2), membranous nephropathy (n=1), and immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN)(n=1). We present one of the largest series of biopsy-proven kidney disease in Caucasian AS patients. We found a lower prevalence of IgAN than previously reported in Asian cohorts. We found a higher prevalence of CIN and a lower prevalence of AA amyloidosis than that described in previous series of Caucasian patients. We also present the first case of AS-associated IC-MPGN.

Clinical Outcomes of Patients with C3G or IC-MPGN Treated with the Factor D Inhibitor Danicopan: Final Results from Two Phase 2 Studies

Introduction: C3 glomerulopathy (C3G) is an ultrarare, chronic and progressive nephropathy mediated by dysregulation of the alternative pathway of complement (AP), with poor prognosis and limited treatment options. Targeted inhibition of proximal AP through factor D (FD) blockade represents a rational treatment approach. We present two phase 2 proof-of-concept clinical studies of the orally active FD inhibitor danicopan in patients with C3G and immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) (NCT03369236 and NCT03459443). Methods: A double-blind, placebo-controlled study in patients with C3G and a single-arm, open-label study in patients with C3G or IC-MPGN treated with danicopan are reported. The studies evaluated pharmacokinetic/pharmacodynamic (PK/PD), efficacy, and safety outcomes. The co-primary endpoints were change from baseline in composite biopsy score and the proportion of patients with a 30% reduction in proteinuria relative to baseline at 6 or 12 months. Results: Optimal systemic concentrations of danicopan were not achieved for complete and sustained inhibition of AP, although there was evidence that blockade of FD reduced AP activity shortly after drug administration. Consequently, limited clinical response was observed in key efficacy endpoints. While stable disease or improvement from baseline was seen in some patients, response was not consistent. The data confirmed the favorable safety profile of danicopan. Conclusion: While demonstrating a favorable safety profile, danicopan resulted in incomplete and inadequately sustained inhibition of AP, probably due to limitations in its PK/PD profile in C3G, leading to lack of efficacy. Complete and sustained AP inhibition is required for a clinical response in patients with C3G.

Recurrence of immune complex and complement-mediated membranoproliferative glomerulonephritis in kidney transplantation.

Membranoproliferative glomerulonephritis (MPGN) represents a histologic pattern of glomerular injury that may be due to several aetiologies. Few studies have comprehensively analysed the recurrence of MPGN according to the current classification system. We collected a multicentre, retrospective cohort of 220 kidney graft recipients with biopsy-proven native kidney disease due to MPGN between 1981 and 2021 in 11 hospitals. Demographic, clinical and histologic parameters of prognostic interest were collected. The main outcomes were time to kidney failure, time to recurrence of MPGN and disease remission after recurrence. The study group included 34 complement-mediated and 186 immune complex-mediated MPGN. A total of 81 patients (37%) reached kidney failure in a median follow-up of 79 months. The main predictors of this event were the development of rejection episodes and disease recurrence. In all, 54 patients (25%) had a disease recurrence in a median of 16 months after kidney transplantation. The incidence of recurrence was higher in patients with dysproteinaemia (67%) and complement-mediated MPGN (62%). In the multivariable model, complement-mediated MPGN emerged as a predictor of recurrence. A total of 33 patients reached kidney failure after recurrence. The main determinants of no remission were early time to recurrence (<15months), estimated glomerular filtration rate <30mL/min/1.73m2 and serum albumin <3.5g/dL at the time of recurrence. One-fourth of the patients with native kidney disease due to MPGN developed clinical recurrence in the allograft, especially in cases with complement-mediated disease or in those associated with dysproteinaemia. The kidney outcomes of disease recurrence with currently available therapies are heterogeneous and thus more effective and individualized therapies are needed.

Characteristics and outcomes of glomerulonephritis with membranoproliferative pattern in children.

BackgroundMembranoproliferative glomerulonephritis (MPGN) is a rare histopathologic pattern of glomerular injury with limited studies in pediatric patients. Characteristics and outcomes of children with MPGN have also remained to be further explored.MethodsWe retrospectively reviewed the clinicopathological features, genetic findings, treatments and outcomes in 17 pediatric patients pathologically diagnosed with MPGN from 2007 to 2020 in the Children’s National Medical Center in China.ResultsMedian age at disease onset was 9.9 years (IQR, 5.6–11.9 years). Most of the patients (12/17) had nephrotic range of proteinuria, and nephritic-nephrotic syndrome was the most common clinical presentation (35.2%). Secondary causes were identified in eight patients including hepatitis B virus (HBV) infection (n=4), methylmalonic acidemia (MMA, n=2), rheumatoid arthritis (RA, n=1) and Aymé-Gripp Syndrome (n=1). The nine patients with primary MPGN were further identified as immune-complex mediated MPGN (n=8), and unclassifiable MPGN (U-MGPN, n=1). Genetic analyses identified pathogenic variants of MMACHC gene in two cases of MMA and established the diagnosis for Aymé-Gripp syndrome in one case with a de novo variant of MAF gene. Comparing study between the complete or partial remission group (n=8) and non-response group (n=9) showed a significant difference in the timing of renal biopsy (P<0.05). Normal renal function was preserved in ten patients at the last follow-up. Two patients developed into end-stage renal disease (ESRD).ConclusionsChildren with MPGN pattern present heterogenous clinical features. Genetic detection helps to explore underlying causes of MPGN. Early identification of the primary or secondary causes of MPGN in children is vital.

FHR-5 Serum Levels and CFHR5 Genetic Variations in Patients With Immune Complex-Mediated Membranoproliferative Glomerulonephritis and C3-Glomerulopathy.

BackgroundFactor H-related protein 5 (FHR-5) is a member of the complement Factor H protein family. Due to the homology to Factor H, the main complement regulator of the alternative pathway, it may also be implicated in the pathomechanism of kidney diseases where Factor H and alternative pathway dysregulation play a role. Here, we report the first observational study on CFHR5 variations along with serum FHR-5 levels in immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) and C3 glomerulopathy (C3G) patients together with the clinical, genetic, complement, and follow-up data.MethodsA total of 120 patients with a histologically proven diagnosis of IC-MPGN/C3G were enrolled in the study. FHR-5 serum levels were measured in ELISA, the CFHR5 gene was analyzed by Sanger sequencing, and selected variants were studied as recombinant proteins in ELISA and surface plasmon resonance (SPR).ResultsEight exonic CFHR5 variations in 14 patients (12.6%) were observed. Serum FHR-5 levels were lower in patients compared to controls. Low serum FHR-5 concentration at presentation associated with better renal survival during the follow-up period; furthermore, it showed clear association with signs of complement overactivation and clinically meaningful clusters.ConclusionsOur observations raise the possibility that the FHR-5 protein plays a fine-tuning role in the pathogenesis of IC-MPGN/C3G.

Different Aspects of Classical Pathway Overactivation in Patients With C3 Glomerulopathy and Immune Complex-Mediated Membranoproliferative Glomerulonephritis.

The rare and heterogeneous kidney disorder C3 glomerulopathy (C3G) is characterized by dysregulation of the alternative pathway (AP) of the complement system. C3G is often associated with autoantibodies stabilizing the AP C3 convertase named C3 nephritic factors (C3NeF). The role of classical pathway (CP) convertase stabilization in C3G and related diseases such as immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) remains largely unknown. Here, we investigated the CP convertase activity in patients with C3G and IC-MPGN. Using a refined two-step hemolytic assay, we measured the stability of CP convertases directly in the serum of 52 patients and 17 healthy controls. In four patients, CP convertase activity was prolonged compared to healthy controls, i.e. the enzymatic complex was stabilized. In three patients (2 C3G, 1 IC-MPGN) the convertase stabilization was caused by immunoglobulins, indicating the presence of autoantibodies named C4 nephritic factors (C4NeFs). Importantly, the assay also enabled detection of non-immunoglobulin-mediated stabilization of the CP convertase in one patient with C3G. Prolonged CP convertase activity coincided with C3NeF activity in all patients and for up to 70 months of observation. Crucially, experiments with C3-depleted serum showed that C4NeFs stabilized the CP C3 convertase (C4bC2a), that does not contain C3NeF epitopes. All patients with prolonged CP convertase activity showed clear signs of complement activation, i.e. lowered C3 and C5 levels and elevated levels of C3d, C3bc, C3bBbP, and C5b-9. In conclusion, this work provides new insights into the diverse aspects and (non-)immunoglobulin nature of factors causing CP convertase overactivity in C3G/IC-MPGN.

CFH and CFHR Copy Number Variations in C3 Glomerulopathy and Immune Complex-Mediated Membranoproliferative Glomerulonephritis.

C3 Glomerulopathy (C3G) and Immune Complex-Mediated Membranoproliferative glomerulonephritis (IC-MPGN) are rare diseases characterized by glomerular deposition of C3 caused by dysregulation of the alternative pathway (AP) of complement. In approximately 20% of affected patients, dysregulation is driven by pathogenic variants in the two components of the AP C3 convertase, complement C3 (C3) and Factor B (CFB), or in complement Factor H (CFH) and Factor I (CFI), two genes that encode complement regulators. Copy number variations (CNVs) involving the CFH-related genes (CFHRs) that give rise to hybrid FHR proteins also have been described in a few C3G patients but not in IC-MPGN patients. In this study, we used multiplex ligation-dependent probe amplification (MLPA) to study the genomic architecture of the CFH-CFHR region and characterize CNVs in a large cohort of patients with C3G (n = 103) and IC-MPGN (n = 96) compared to healthy controls (n = 100). We identified new/rare CNVs resulting in structural variants (SVs) in 5 C3G and 2 IC-MPGN patients. Using long-read single molecule real-time sequencing (SMRT), we detected the breakpoints of three SVs. The identified SVs included: 1) a deletion of the entire CFH in one patient with IC-MPGN; 2) an increased number of CFHR4 copies in one IC-MPGN and three C3G patients; 3) a deletion from CFHR3-intron 3 to CFHR3-3′UTR (CFHR34–6Δ) that results in a FHR3-FHR1 hybrid protein in a C3G patient; and 4) a CFHR31–5-CFHR410 hybrid gene in a C3G patient. This work highlights the contribution of CFH-CFHR CNVs to the pathogenesis of both C3G and IC-MPGN.

A clinicopathological study of membranoproliferative glomerulonephritis in the light of new evolving classification

Background: Membranoproliferative glomerulonephritis (MPGN) is a progressive disease with poor prognosis. An emerging consensus on classification based on immunofluorescence findings separates MPGN into two groups: immune complex-mediated MPGN and complement-mediated MPGN. This study was undertaken to investigate the clinical, biochemical, and histopathological parameters in-between these two groups histologically diagnosed as MPGN previously. Materials and Methods: We conduct a retrospective cross-sectional study carried out at the Department of Pathology, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka during the period from June 2016 to December 2017. A total of 67 histologically diagnosed MPGN cases were enrolled in the study. Immunofluorescence evaluations were performed and correlated with retrospective clinical and biochemical data. Results: Immune complex-mediated MPGN and complement-mediated MPGN cannot be differentiated by histopathology. There were no significant differences between clinical (age, sex, clinical presentation) and biochemical (serum creatinine, C3 level, C4 level) parameters between immune complex-mediated MPGN and complement-mediated MPGN. Conclusion: Clinical and biochemical and histopathological parameters in-between these two groups of MPGN show no significant difference.

C4 nephritic factor in patients with immune-complex-mediated membranoproliferative glomerulonephritis and C3-glomerulopathy

BackgroundAcquired or genetic abnormalities of the complement alternative pathway are the primary cause of C3glomerulopathy(C3G) but may occur in immune-complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) as well. Less is known about the presence and role of C4nephritic factor(C4NeF) which may stabilize the classical pathway C3-convertase. Our aim was to examine the presence of C4NeF and its connection with clinical features and with other pathogenic factors.ResultsOne hunfe IC-MPGN/C3G patients were enrolled in the study. C4NeF activity was determined by hemolytic assay utilizing sensitized sheep erythrocytes. Seventeen patients were positive for C4NeF with lower prevalence of renal impairment and lower C4d level, and higher C3 nephritic factor (C3NeF) prevalence at time of diagnosis compared to C4NeF negative patients. Patients positive for both C3NeF and C4NeF had the lowest C3 levels and highest terminal pathway activation. End-stage renal disease did not develop in any of the C4NeF positive patients during follow-up period. Positivity to other complement autoantibodies (anti-C1q, anti-C3) was also linked to the presence of nephritic factors. Unsupervised, data-driven cluster analysis identified a group of patients with high prevalence of multiple complement autoantibodies, including C4NeF.ConclusionsIn conclusion, C4NeF may be a possible cause of complement dysregulation in approximately 10–15% of IC-MPGN/C3G patients.

SUN-042 C3 GLOMERULOPATHY AND IMMUNE COMPLEX MEDIATED MEMBRANOPROLIFERATIVE GLOMERULONEPHRITIS: COMPARING DIALYSIS AND TRANSPLANT OUTCOMES

Membranoproliferative glomerulonephritis (MPGN) is a rare cause of end stage kidney disease (ESKD) that is comprised of two separate pathogenic entities: C3 glomerulopathy (C3GN) and immune complex mediated MPGN (ICMPGN). Whether these conditions have different clinical outcomes is currently unknown. We used the Australian and New Zealand Dialysis and Transplant (ANZDATA) Registry to compare the characteristics and outcomes of patients with ESKD secondary to C3GN and ICMPGN. All patients with ESKD secondary to MPGN who commenced dialysis or kidney transplantation in Australia and New Zealand between 1996 and 2016 were included. Patients with ESKD secondary to C3GN were compared to those with ESKD secondary to ICMPGN. Dialysis patient survival, transplant patient survival and death-censored graft survival were evaluated by Kaplan-Meier and multivariable Cox proportional hazards model analyses. Competing risks regression was performed as a sensitivity analysis. Competing events were transplantation and renal recovery for dialysis patient survival, allograft failure for transplant patient survival and patient death for death-censored allograft survival. Of the total ESKD population of 53,729 patients, 76 had C3GN (mean age 52 ± 20 years, 36% female) and 380 had ICMPGN (mean age 50 ± 18 years, 39% female). Baseline demographic and clinical characteristics were comparable between the two groups. Patients with C3GN had lower 5-year dialysis survival rates compared to those with ICMPGN (42% vs. 62%, p=0.05; Cox-adjusted hazard ratio [HR] 1.40, 95% CI 0.94-2.08; competing risks HR 1.34, 95% CI 1.01-1.8). Renal recovery following dialysis commencement was significantly less common with C3GN compared to ICMPGN (0% vs. 4%, p<0.01). 37 patients with C3GN and 171 patients with ICMPGN proceeded to kidney transplantation. Death-censored graft survival was similar between C3GN and ICMPGN (5 year survival 68% vs. 74%, p=0.42; Cox-adjusted HR 1.47, 95% CI 0.74-2.89; competing risk HR 1.47, 95% CI 0.84-2.55). Graft loss due to disease relapse was a common cause of graft loss in both groups occurring in 16% of patients with C3GN and 9% of those with ICMPGN (p=0.35). Transplant patient survival was comparable between the two groups (5 year survival 96% vs. 92%, p=0.35; Cox-adjusted HR 0.39, 95% CI 0.05-2.97; competing risk HR 0.35, 95% CI 0.06-1.85). Compared to patients with ESKD due to ICMPGN, those with C3GN had poorer survival on dialysis, lower rates of dialysis-independent renal recovery and comparable kidney transplant outcomes. Both groups had high rates of disease relapse causing graft loss. These findings support the notion that ICMPGN and C3GN are different clinical entities.