Membranoproliferative glomerulonephritis: pathogenetic heterogeneity and proposal for a new classification

Pathogenesis of Focal Segmental Glomerulosclerosis and Minimal Change Disease: Insights from Glomerular Proteomics

Podocyte injury is a hallmark of both focal segmental glomerulosclerosis (FSGS) and minimal change disease (MCD), ultimately reflected in foot process effacement and proteinuria. Triggers and pathogenic pathways leading to podocyte cytoskeleton rearrangements are, however, incompletely explained. Here, we aimed to contribute to the understanding of these pathways using tissue bottom-up proteomic profiling of laser-capture microdissected glomeruli from MCD and FSGS. Forty-six differentially expressed proteins were identified between the two groups (p < 0.05, |FC| ≥ 1.2). Pathway analysis showed that 16 out of 46 proteins were associated with the immune system, with E2 ubiquitin-conjugating enzyme (UBE2K) and complement factor H-related protein-1 (CFHR1) yielding the highest fold change in FSGS compared to MCD. The two target proteins were further validated through immunohistochemistry, confirming the podocyte localization of UBE2K and endothelial staining of CFHR. Additionally, several other differentially expressed proteins were linked to the cytoskeleton structure and its regulation. Our results point to the possibility that complement dysregulation may be the source of cytoskeleton rearrangement in FSGS.

Challenges in the Diagnosis and Management of Immune Complex-Mediated Membranoproliferative Glomerulonephritis and Complement 3 Glomerulopathy

Immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) and complement 3 glomerulopathy (C3G) are rare, complement-mediated kidney diseases, previously classified under the group of kidney disorders termed membranoproliferative glomerulonephritis (MPGN) type 1, type 2, and type 3. Despite new advances in our understanding of IC-MPGN and C3G, several unmet needs persist in the diagnosis and management of patients with these nephropathies, due in part to their rarity and their overlapping clinical presentations, histologic features, and underlying pathophysiologies. This review summarizes our current understanding of the role of complement in IC-MPGN and C3G, and underlines the key histopathologic differences between the diseases. Using seven illustrative patient cases, we discuss consensus guideline treatment recommendations and the uncertainties, challenges, and considerations regarding the diagnosis and management of patients with IC-MPGN and C3G in clinical practice. The presented cases emphasize the need for a multidisciplinary approach encompassing primary care providers (PCPs), nephrologists, nephropathologists, and laboratory scientists. Key knowledge gaps are evaluated, including differential diagnoses, underlying pathologic mechanisms, and the lack of effective treatments targeting drivers of disease. As the therapeutic landscape evolves, an improved understanding of IC-MPGN and C3G is crucial to identifying optimal targeted-treatment strategies and facilitating a personalized approach to the management of these complex glomerular diseases.

Repeated Kidney Biopsy in Membranoproliferative Glomerulonephritis

Introduction

Membranoproliferative glomerulonephritis (MPGN) is a heterogeneous pattern of glomerular injury. Repeated kidney biopsies may elucidate pathogenic mechanisms and guide diagnostic strategies.

Methods

We included 82 patients diagnosed with MPGN by kidney biopsy who underwent at least two biopsies between 1997 and 2023 at Peking University First Hospital. Clinical and pathological data were analyzed retrospectively.

Results

Of 342 MPGN patients, 95 (28%) had repeated biopsies (0.9-4.0 years apart). This incidence was higher than in other glomerulonephropathies under immunosuppression. Among the 82 patients analyzed (excluding kidney transplants and ≤3-month biopsy intervals), 42 were initially diagnosed with non-MPGN pathology. At the second biopsy, proteinuria increased (from 2.9 to 6.3 g/day), eGFR declined (from 76 to 47 mL/min/1.73 m2), and renal C3 deposition was stronger (p = 0.04). Thirty patients (37%) had etiological reclassification, mostly to monoclonal gammopathy of renal significance (MGRS). Compared to idiopathic MPGN, MGRS patients were older (53 vs. 35 years) and had worse renal function (eGFR 57 vs. 81 mL/min/1.73 m2) but slower eGFR decline (-7 vs. -12 mL/min/1.73 m2/year). Most MGRS patients (64%) remained negative for monoclonal protein in serum or urine immunofixation, necessitating repeat biopsy and clone-directed therapy.

Conclusion

In this study, about half and one-third of patients underwent morphological and etiological reclassification, respectively. Stronger complement deposition may drive morphological changes. Repeated kidney biopsies are crucial for diagnosing MGRS, especially in patients with negative immunofixation.

Unsupervised Clustering of Membranoproliferative Glomerulonephritis and C3 Glomerulopathy Patients Discovers Distinct Patient Groups unlike the Current Classification

INTRODUCTION

Membranoproliferative glomerulonephritis is currently divided into immunoglobulin-mediated glomerulonephritis (IC-MPGN) and C3 glomerulopathy (C3G); however, the patients often overlap with histology, complement, clinical and prognostic factors. Our aim was to investigate if an unsupervised clustering method finds different patient groups in 44 IC-MPGN/C3G patients using only histological and clinical data available in everyday clinical work.

METHODS

Primary IC-MPGN/C3G adult patients were included whose diagnostic (baseline) native biopsy was obtained in 2006-2017. The biopsies were reassessed and the clinical data at baseline and during follow-up were obtained from the medical records. There were 39 baseline histological and clinical variables included in the unsupervised clustering. Follow-up information was combined with the clustering results.

RESULTS

The clustering resulted in two clusters (n = 24 and n = 20 patients for clusters 1-2, respectively), where cluster 1 had a significantly higher baseline plasma creatinine (mean 213 vs. 104, respectively, p value <0.001) and a lower baseline eGFR than cluster 2 (mean 37 vs. 70, respectively, p value <0.001). Regarding histology, chronic changes such as lobulated glomeruli, mesangial matrix expansion, and glomeruli double contours were more prevalent in cluster 1 (p value <0.001). Biopsy morphology was more often crescentic and membranoproliferative in cluster 1 (p value <0.001). Although the differences were insignificant, cluster 1 patients were in dialysis in the last follow-up or had a progressive disease more often than cluster 2 patients (21% vs. 5%, 38% vs. 10%).

CONCLUSIONS

Our results indicate that these patients share greater similarity than the current classification IC-MPGN versus C3G indicates.

Infection-Related Glomerulonephritis Due to Subacute Bacterial Endocarditis in the Aortic Valve: A Case Report

Infection-related glomerulonephritis (IRGN) is a rare but severe complication of bacterial infections, including subacute bacterial endocarditis (SBE). We present a case of a 15-year-old male with bilateral lower limb swelling, facial puffiness, frothy urine, and dyspnea. Laboratory investigations revealed abnormal kidney function tests and imaging studies confirmed infective endocarditis. Blood cultures isolated Burkholderia cepacia and methicillin-resistant coagulase-negative Staphylococcus. Kidney biopsy confirmed immune complex-mediated glomerulonephritis. The patient received multidisciplinary care, including respiratory support, hemodialysis, antibiotics, and blood transfusion. This case highlights the importance of recognizing and promptly managing IRGN secondary to SBE to prevent irreversible renal damage and systemic complications.

Recurrent C3 glomerulopathy after kidney transplantation

The complement system is part of innate immunity and is pivotal in protecting the body against pathogens and maintaining host homeostasis. Activation of the complement system is triggered through multiple pathways, including antibody deposition, a mannan-binding lectin, or activated complement deposition. C3 glomerulopathy (C3G) is a rare glomerular disease driven by complement dysregulation with high post-transplantation recurrence rates. Its treatment is mainly based on immunosuppressive therapies, specifically mycophenolate mofetil and glucocorticoids. Recent years have seen significant progress in understanding complement biology and its role in C3G pathophysiology. New complement-tergeting treatments have been developed and initial trials have shown promising results. However, challenges persist in C3G, with recurrent post-transplantation cases leading to suboptimal outcomes. This review discusses the pathophysiology and management of C3G, with a focus on its recurrence after kidney transplantation.

Complement Activation in Nephrotic Glomerular Diseases

The nephrotic syndrome holds significant clinical importance and is characterized by a substantial protein loss in the urine. Damage to the glomerular basement membrane or podocytes frequently underlies renal protein loss. There is an increasing belief in the involvement of the complement system, a part of the innate immune system, in these conditions. Understanding the interactions between the complement system and glomerular structures continually evolves, challenging the traditional view of the blood-urine barrier as a passive filter. Clinical studies suggest that a precise inhibition of the complement system at various points may soon become feasible. However, a thorough understanding of current knowledge is imperative for planning future therapies in nephrotic glomerular diseases such as membranous glomerulopathy, membranoproliferative glomerulonephritis, lupus nephritis, focal segmental glomerulosclerosis, and minimal change disease. This review provides an overview of the complement system, its interactions with glomerular structures, and insights into specific glomerular diseases exhibiting a nephrotic course. Additionally, we explore new diagnostic tools and future therapeutic approaches.

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.

To interpret and analyze the changing patterns of histology and direct immunofluorescence findings in membranoproliferative glomerulonephritis

Background

Membranoproliferative glomerulonephritis has in the recent past been regrouped into immune complex-mediated (ICM MPGN) disease (driven by the classical complement pathway) and complement-mediated (C3GN) disease (driven by the alternative complement pathway) based on pathogenetic role of alternative complement pathway and immunofluorescence deposits. The proposed regrouping lent therapeutic and prognostic support in managing the disease of MPGN.

Aims and Objectives

The present study is undertaken to study the patterns of MPGN based on histopathological and DIF examination and sub-categorize the cases into mainly complement dominant and immune complex-mediated diseases for better prognostic and therapeutic utility.

Materials and Methods

This is a prospective observational study carried out in a tertiary care center over a period of 2 yrs. The clinically suspected cases of MPGN were subjected to histopathologic and direct immunofluorescence examination (DIF), and the findings were interpreted in light of complement-mediated and immune complex-mediated MPGN.

Results

Out of 620 renal biopsies, diagnosis of MPGN was confirmed both on histopathology and DIF in 36 cases accounting for 5.8% of all biopsies. Based on DIF findings, the various groups comprised 20 cases (55.6%) of immune complex deposits, 11 (30.5%) of C3 dominant picture, and 5 (13.9%) of Nil immune deposits. On analysis of the patterns on DIF, 16 cases (80%) of C3 + Ig group and 6 (54.5%) of C3GN group showed predominantly MPGN pattern. Crescentic glomerulonephritis, global glomerulosclerosis, and interstitial fibrosis were markedly observed in C3GN group.

Conclusion

DIF is of immense prognostic and therapeutic value in managing cases of MPGN.

Immunofluorescence Use and Techniques in Glomerular Diseases: A Review

Background

Immunofluorescence (IF) studies play an essential role in the evaluation of medical renal biopsies. Particularly, in the study of renal glomerular diseases, where it provides fundamental data for the diagnosis, classification, and etiology of the glomerular pathologies. Diverse techniques may be used to optimize the utilization of IF studies, from variations on the test methodologies to expertise on the interpretation of the results and knowledge of potential pitfalls.

Summary

This manuscript presents a brief review on the history of IF and its utilization in kidney pathology, followed by a description of the IF methods, including the use of IF on paraffin-embedded tissue (paraffin IF), and other novel techniques. Guidelines on how to best report IF findings are reviewed, along with a description of antibodies commonly used in glomerular diseases, highlighting their distribution within the normal kidney and potential pitfalls in interpretation. Finally, the use and interpretation of IF are discussed in more detail in individual entities on a range of glomerular diseases.

Key Messages

IF is crucial for interpretation of renal biopsies and diagnosis of glomerular diseases. Knowledge of IF techniques, alternative procedures, its use and proper interpretation is essential for optimal utilization of IF in renal pathology, and this review proposes to serve as a simplified and practical guide on this topic.

The Association of Class I and II Human Leukocyte Antigen Serotypes With End-Stage Kidney Disease Due to Membranoproliferative Glomerulonephritis and Dense Deposit Disease

RATIONALE & OBJECTIVE

Membranoproliferative glomerulonephritis (MPGN), encompassing several distinct diseases, is a rare but significant cause of kidney failure in the United States. The potential etiologies of MPGN are unclear, but prior studies have suggested dysregulation of the alternative complement pathway and, recently, autoimmunity as potential mechanisms driving MPGN pathogenesis. In this study, we examined HLA associations with end-stage kidney disease (ESKD) due to MPGN and dense deposit disease (DDD) in a large racially and ethnically diverse US-based cohort.

STUDY DESIGN

Case-control study.

SETTING & PARTICIPANTS

Using US Renal Data System (USRDS) and United Network for Organ Sharing (UNOS) data, we identified 3,424 patients with kidney failure due to MPGN and 263 due to DDD. We matched patients to kidney donor controls on designated race and ethnicity in a 1:15 ratio.

EXPOSURE

58 class I and II HLA serotypes.

OUTCOME

Case-control status.

ANALYTICAL APPROACH

For each disease cohort, univariable and multivariable logistic regression analyses were used to investigate associations between the disease and 58 HLA serotypes. In subgroup analyses, we investigated HLA associations in White and Black patients. We also studied antiglomerular basement membrane (anti-GBM) nephritis as a positive-control outcome. We applied a Bonferroni correction to account for multiple comparisons.

RESULTS

Eighteen serotypes were significantly associated with the odds of having MPGN in univariable analyses, with DR17 having the strongest association (odds ratio [OR], 1.55 [95% CI, 1.44-1.68], P=4.33e-28). No significant associations were found between any HLA serotype and DDD. Designated race-specific analyses showed comparable findings. We recapitulated known HLA associations in anti-GBM nephritis.

LIMITATIONS

Reliance on HLA serotypes (rather than genotype), lack of biopsy-confirmed diagnoses.

CONCLUSIONS

HLA-DR17 is associated with ESKD due to MPGN in a racially and ethnically diverse cohort. The strength of association was similar in White and Black patients, suggesting a role in the pathogenesis of MPGN. No HLA associations were observed in patients with DDD.

PLAIN-LANGUAGE SUMMARY

Prior studies have suggested dysregulation of the alternative complement pathway as a potential etiology of membranoproliferative glomerulonephritis (MPGN), but recent evidence from a British White population has implicated an autoimmune mechanism in MPGN pathogenesis. We investigated HLA associations between MPGN and dense deposit disease (DDD) in a large racially and ethnically diverse cohort of patients. We found that HLA-DR17 is associated with end-stage kidney disease (ESKD) due to MPGN in both White and Black patients. By contrast, no significant HLA associations with ESKD due to DDD were identified. These results suggest a role for autoimmunity in some cases of MPGN and highlight differences in the disease etiology of MPGN compared with DDD.

Iptacopan in Idiopathic Immune Complex-Mediated Membranoproliferative Glomerulonephritis: Protocol of the APPARENT Multicenter, Randomized Phase 3 Study

Introduction

Immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) is an ultra-rare, fast-progressing kidney disease that may be idiopathic (primary) or secondary to chronic infection, autoimmune disorders, or monoclonal gammopathies. Dysregulation of the alternative complement pathway is implicated in the pathophysiology of IC-MPGN; and currently, there are no approved targeted treatments. Iptacopan is an oral, highly potent proximal complement inhibitor that specifically binds to factor B and inhibits the alternative pathway (AP).

Methods

This randomized, double-blind, placebo-controlled phase 3 study (APPARENT; NCT05755386) will evaluate the efficacy and safety of iptacopan in patients with idiopathic (primary) IC-MPGN, enrolling up to 68 patients (minimum of 10 adolescents) aged 12 to 60 years with biopsy-confirmed IC-MPGN, proteinuria ≥1 g/g, and estimated glomerular filtration rate (eGFR) ≥30 ml/min per 1.73 m2. All patients will receive maximally tolerated angiotensin-converting enzyme inhibitor/angiotensin receptor blocker and vaccination against encapsulated bacteria. Patients with any organ transplant, progressive crescentic glomerulonephritis, or kidney biopsy with >50% interstitial fibrosis/tubular atrophy, will be excluded. Patients will be randomized 1:1 to receive either iptacopan 200 mg twice daily (bid) or placebo for 6 months, followed by open-label treatment with iptacopan 200 mg bid for all patients for 6 months. The primary objective of the study is to evaluate the efficacy of iptacopan versus placebo in proteinuria reduction measured as urine protein-to-creatinine ratio (UPCR) (24-h urine) at 6 months. Key secondary end points will assess kidney function measured by eGFR, patients who achieve a proteinuria-eGFR composite end point, and patient-reported fatigue.

Conclusion

This study will provide evidence toward the efficacy and safety of iptacopan in idiopathic (primary) IC-MPGN.

Association of monoclonal gammopathy of undetermined significance and C3 glomerulopathy

Monoclonal gammopathy of undetermined significance (MGUS) is usually an asymptomatic pre-malignant condition caused by the proliferation of clonal plasma cells. Often considered a benign condition, it has the potential to progress to malignant plasma cell or lymphoproliferative disorders. Moreover, MGUS can rarely cause glomerular disease by activating the alternative complement pathway resulting in immunoglobulin-negative C3-positive glomerulonephritis called C3 glomerulopathy. Because of its rarity, the diagnosis might not be considered by the treating physicians, leading to delayed diagnosis or misdiagnosis. Untreated C3 glomerulopathy can lead to irreversible glomerular damage and end-stage renal failure, and a high index of suspicion is essential for timely diagnosis and management. Here, we present the case of a patient with a prior diagnosis of MGUS who presented with proteinuria and microscopic haematuria and was diagnosed with C3 glomerulopathy. The patient had complete resolution of the disease after receiving treatment with a combination of dexamethasone, lenalidomide and bortezomib for the underlying MGUS.

Glomerulonephritis

Glomerulonephritis (GN) encompasses several disorders that cause glomerular inflammation and injury through an interplay of immune-mediated mechanisms, host characteristics, and environmental triggers, such as infections. GN can manifest solely in the kidney or in the setting of a systemic illness, and presentation can range from chronic and relatively asymptomatic hematuria to fulminant renal failure. Classic acute GN is characterized by hematuria, edema, and hypertension, the latter 2 of which are the consequence of sodium and water retention in the setting of renal impairment. Although presenting signs and symptoms and a compatible clinical history can suggest GN, serologic and urinary testing can further refine the differential diagnosis, and renal biopsy can be used for definitive diagnosis. Treatment of GN can include supportive care, renin-angiotensin-aldosterone system blockade, immunomodulatory therapy, and renal transplant. Prognosis is largely dependent on the underlying cause of GN and can vary from a self-limited course to chronic kidney disease. This review focuses on lupus nephritis, IgA nephropathy, IgA vasculitis, and postinfectious GN.

KDOQI US Commentary on the 2021 KDIGO Clinical Practice Guideline for the Management of Glomerular Diseases

The KDIGO 2021 Clinical Practice Guideline for the Management of Glomerular Diseases represents the first update to this set of recommendations since the initial set of KDIGO guideline recommendations was published in 2012. The pace of growth in our molecular understanding of glomerular disease has quickened and a number of newer immunosuppressive and targeted therapies have been introduced since the original set of guideline recommendations, making such an update necessary. Despite these updates, many areas of controversy remain. In addition, further updates since the publication of KDIGO 2021 have occurred which this guideline does not encompass. With this commentary, the KDOQI work group has generated a chapter-by-chapter companion opinion article that provides commentary specific to the implementation of the KDIGO 2021 guideline in the United States.

Nephrotic-range proteinuria and membranoproliferative glomerulonephritis-like pattern caused by interferon-β1b in a patient with multiple sclerosis

Interferon-beta (IFN-β) subtypes are widely used as immunomodulatory agents for relapsing-remitting multiple sclerosis (MS). Although generally well tolerated, a growing number of reports have recently shown association of long-term IFN-β therapy with several types of glomerulonephritis. Here, we present the case of a 42-year-old woman with MS who developed nephrotic-range proteinuria after taking IFN-β1b for nine years. Initially, due to the presence of histological features consistent with immunoglobulin A (IgA) nephropathy (granular IgA deposits in mesangial lesions), a tonsillectomy plus steroid pulse therapy was performed. However, proteinuria did not significantly decrease after these treatments. Therefore, a second renal biopsy was performed after three years, revealing a membranoproliferative glomerulonephritis-like pattern without immune complex. Further immunofluorescence analysis showed attenuated IgA staining. Consequently, IFN-β1b was replaced with dimethyl fumarate, resulting in complete remission, with proteinuria decreasing to the level of 0.2 g/day. Although it is a rare adverse effect, physicians should pay careful attention to the symptoms and findings of nephritis during the follow-up of patients under treatment with this agent.

The Long-Term Survival Outcome in Older Patients with Different Pathological Types of Chronic Kidney Disease

INTRODUCTION

Chronic kidney diseases (CKDs) are prevalent in older people, and renal pathological manifestations are important for diagnosis, treatment, and prognosis. However, the long-term survival outcome and risk factors for older CKD patients with different pathological types are not fully understood and need to be further investigated.

METHODS

Medical data were recorded and all-cause mortality was followed up in patients who underwent renal biopsy diagnosed in Guangdong Provincial People's Hospital from 2005 to 2015. Kaplan-Meier analysis was used to identify the incidence of survival outcomes. Multivariate Cox regression models and nomograms were applied to analyze pathological types and other factors for overall survival outcomes.

RESULTS

368 cases were included and the median follow-up was 85 (46.5, 111) months. Overall mortality was 35.6%. The highest mortality was in the mesangioproliferative glomerulonephritis (MPGN) group (88.9%), followed by amyloidosis (AMY) group (84.6%), and the lowest mortality was in the minimal change disease (MCD) group (21.9%). Moreover, multivariate Cox regression model showed that survival times of MPGN {hazard ratio (HR) = 8.215 (95% confidence interval [CI]: 2.735-24.674), p < 0.001} and AMY (HR = 6.130 [95% CI: 2.219-16.94], p < 0.001) were significantly shorter than MCD. In addition, age, lower baseline estimated glomerular filtration rate (eGFR), history of chronic obstructive pulmonary disease (COPD) and cerebrovascular accidents (CVA)/transient ischemic attack (TIA), MPGN, and AMY were independent risk factors for the mortality of older patients with CKD.

CONCLUSION

The long-term survival outcome of older CKD patients showed differences among different pathological types, and MPGN, AMY, age, baseline eGFR, CVA/TIA, and COPD were independent predictors for mortality.

Diagnostic Problems in C3 Glomerulopathy

Background: C3 glomerulopathies (C3GN) are a group of rare kidney diseases associated with impaired complement regulation. The effects of this disease include the accumulation of complement C3 in the kidneys. Based on the clinical data, as well as light, fluorescence, and electron microscopy results, the diagnoses were verified. The study group consisted of biopsy specimens, which were obtained from 332 patients who were diagnosed with C3 glomerulopathy. In all cases, histopathological examinations were performed; deposits of complement C3 and C1q components, as well as the immunoglobulins IgA, IgG, and IgM, were identified using immunofluorescence. Furthermore, electron microscopy was also performed. Results: The histopathological examination results presented cases of C3GN (n = 111) and dense deposit disease (DDD; n = 17). The non-classified (NC) group was the most numerous (n = 204). The lack of classification was due to the poor severity of the lesions, even on the electron microscopic examination or in the presence of intense sclerotic lesions. Conclusions: In cases of suspected C3 glomerulopathies, we believe an electron microscopy examination is necessary. This examination is beneficial in mild-to-extremely-severe cases of this glomerulopathy, where the lesions are barely discernible when using immunofluorescence microscopy.

Diagnostic and Prognostic Comparison of Immune-Complex-Mediated Membranoproliferative Glomerulonephritis and C3 Glomerulopathy

Membranoproliferative glomerulonephritis (MPGN) is subdivided into immune-complex-mediated glomerulonephritis (IC-MPGN) and C3 glomerulopathy (C3G). Classically, MPGN has a membranoproliferative-type pattern, but other morphologies have also been described depending on the time course and phase of the disease. Our aim was to explore whether the two diseases are truly different, or merely represent the same disease process. All 60 eligible adult MPGN patients diagnosed between 2006 and 2017 in the Helsinki University Hospital district, Finland, were reviewed retrospectively and asked for a follow-up outpatient visit for extensive laboratory analyses. Thirty-seven (62%) had IC-MPGN and 23 (38%) C3G (including one patient with dense deposit disease, DDD). EGFR was below normal (≤60 mL/min/1.73 m²) in 67% of the entire study population, 58% had nephrotic range proteinuria, and a significant proportion had paraproteins in their serum or urine. A classical MPGN-type pattern was seen in only 34% of the whole study population and histological features were similarly distributed. Treatments at baseline or during follow-up did not differ between the groups, nor were there significant differences observed in complement activity or component levels at the follow-up visit. The risk of end-stage kidney disease and survival probability were similar in the groups. IC-MPGN and C3G have surprisingly similar characteristics, kidney and overall survival, which suggests that the current subdivision of MPGN does not add substantial clinical value to the assessment of renal prognosis. The high proportion of paraproteins in patient sera or in urine suggests their involvement in disease development.

Membranoproliferative glomerulonephritis: no longer the same disease and may need very different treatment

Membranoproliferative glomerulonephritis (MPGN) is a pattern of glomerular injury that may be primary or secondary to infections, autoimmune diseases and haematological disorders. Primary C3G and IC-MPGN are rare and the prognosis is unfavourable. Based on immunofluorescence findings, MPGN has been classified into complement-mediated C3 glomerulopathy (C3G) and immune complex-mediated MPGN (IC-MPGN). However, this classification leaves a number of issues unresolved. The finding of genetic and acquired complement abnormalities in both C3G and IC-MPGN indicates that they represent a heterogeneous spectrum rather than distinct diseases. An unsupervised hierarchical clustering in a cohort of patients with primary C3G and IC-MPGN identified four distinct pathogenetic patterns, characterized by specific histologic and clinical features, and genetic and acquired complement abnormalities. These results provide the groundwork for a more accurate diagnosis and the development of targeted therapies. The drugs that are currently used, such as corticosteroids and immunosuppressants, are frequently ineffective in primary C3G and IC-MPGN. Eculizumab, an anti-C5 monoclonal antibody, has been used occasionally in single cases or small series. However, only a few patients have achieved remission. This heterogeneous response could be related to the extent of terminal complement activation, which may vary substantially from patient to patient. Several drugs that target the complement system at different levels are under investigation for C3G and IC-MPGN. However, clinical trials to test new therapeutics will be challenging and heavily influenced by the heterogeneity of these diseases. This creates the need to characterize each patient to match the specific complement abnormality with the type of intervention.

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

INTRODUCTION

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.

METHODS

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.

RESULTS

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 (<15 months), estimated glomerular filtration rate <30 mL/min/1.73 m2 and serum albumin <3.5 g/dL at the time of recurrence.

CONCLUSIONS

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.

Kidney diseases

Dysregulation and accelerated activation of the alternative pathway (AP) of complement is known to cause or accentuate several pathologic conditions in which kidney injury leads to the appearance of hematuria and proteinuria and ultimately to the development of chronic renal failure. Multiple genetic and acquired defects involving plasma- and membrane-associated proteins are probably necessary to impair the protection of host tissues and to confer a significant predisposition to AP-mediated kidney diseases. This review aims to explore how our current understanding will make it possible to identify the mechanisms that underlie AP-mediated kidney diseases and to discuss the available clinical evidence that supports complement-directed therapies. Although the value of limiting uncontrolled complement activation has long been recognized, incorporating complement-targeted treatments into clinical use has proved challenging. Availability of anti-complement therapy has dramatically transformed the outcome of atypical hemolytic uremic syndrome, one of the most severe kidney diseases. Innovative drugs that directly counteract AP dysregulation have also opened new perspectives for the management of other kidney diseases in which complement activation is involved. However, gained experience indicates that the choice of drug should be tailored to each patient's characteristics, including clinical, histologic, genetic, and biochemical parameters. Successfully treating patients requires further research in the field and close collaboration between clinicians and researchers who have special expertise in the complement system.

Association of Histologic Parameters with Outcome in C3 Glomerulopathy and Idiopathic Immunoglobulin-Associated Membranoproliferative Glomerulonephritis

BACKGROUND AND OBJECTIVES

C3 glomerulopathy and idiopathic Ig-associated membranoproliferative GN are kidney diseases characterized by abnormal glomerular complement C3 deposition. These conditions are heterogeneous in outcome, but approximately 50% of patients develop kidney failure within 10 years.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

To improve identification of patients with poor prognosis, we performed a detailed analysis of percutaneous kidney biopsies in a large cohort of patients. Using a validated histologic scoring system, we analyzed 156 native diagnostic kidney biopsies from a retrospective cohort of 123 patients with C3 glomerulopathy and 33 patients with Ig-associated membranoproliferative GN. We used linear regression, survival analysis, and Cox proportional hazards models to assess the relationship between histologic and clinical parameters with outcome.

RESULTS

Frequent biopsy features were mesangial expansion and hypercellularity, glomerular basement membrane double contours, and endocapillary hypercellularity. Multivariable analysis showed negative associations between eGFR and crescents, interstitial inflammation, and interstitial fibrosis/tubular atrophy. Proteinuria positively associated with endocapillary hypercellularity and glomerular basement membrane double contours. Analysis of second native biopsies did not demonstrate associations between immunosuppression treatment and improvement in histology. Using a composite outcome, risk of progression to kidney failure associated with eGFR and proteinuria at the time of biopsy, cellular/fibrocellular crescents, segmental sclerosis, and interstitial fibrosis/tubular atrophy scores.

CONCLUSIONS

Our detailed assessment of kidney biopsy data indicated that cellular/fibrocellular crescents and interstitial fibrosis/tubular atrophy scores were significant determinants of deterioration in kidney function.

[Basic nephropathology for pathologists-part 1 : Kidney biopsy-inflammation and immune complexes]

The assessment of kidney biopsies is mainly confined to specialized centres. However, sometimes a kidney biopsy is submitted to a general pathologist, and in addition peritumorous renal parenchyma in tumour nephrectomies can have concomitant non-neoplastic renal disease. Here we present a survey of inflammatory and immunologic changes in all renal compartments, which may in part indicate the need of prompt therapeutic intervention such as in vasculitis, glomerulonephritis and interstitial nephritis. It is important to take into account that renal involvement of vasculitis is mainly centred in glomeruli and only to a much lesser extent in arteries, and that the frequently observed interstitial inflammation very often is an epiphenomenon of another primary kidney disease and not an independent disease process. Typical renal patterns of injury are emphasised.

Precision medicine for the treatment of glomerulonephritis: A bold goal but not yet a transformative achievement

The revolution in our ability to recognize the alterations in fundamental biology brought about by disease has fostered a renewed interest in precision or personalized medicine (“the right treatment, or diagnostic test, for the right patient at the right time”). This nascent field has been led by oncology, immune-hematology and infectious disease, but nephrology is catching up, and quickly. Specific forms of glomerulonephritis thought to represent specific “diseases” have been “downgraded” to “patterns of injury”. New entities have emerged through application of sophisticated molecular technologies; often embraced by the term “multi-omics”. Kidney biopsies are now interpreted by next generation imaging and machine learning. Many opportunities are manifest that will translate these remarkable developments into novel safe and effective treatment regimens for specific pathogenic pathways evoking glomerulonephritis and its progression to kidney failure. A few successes emboldens a positive look to the future. A sustained and highly collaborative engagement with this new paradigm will be required for this field, full of hope and high expectations, to realize its goal of transforming glomerular therapeutics from “one size fits all (or many)” to a true individualized management principle.

Association between fluoride exposure and kidney function in adults: A cross-sectional study based on endemic fluorosis area in China

BACKGROUND

The kidney toxicity of fluoride exposure has been demonstrated in animal studies, and a few studies have reported kidney function injury in children with fluoride exposure. However, epidemiological information for the effects of long-term fluoride exposure on adult kidney function remains limited.

METHODS

We conducted a cross-sectional investigation in Wenshui County, Shanxi Province to examine the association between fluoride exposure and kidney function in adults, and a total of 1070 adults were included in our study. Urinary fluoride concentrations were measured using the national standardized ion selective electrode method. And markers of kidney function injury (urinary NAG, serum RBP, serum Urea, serum C3, serum UA and serum αl-MG) were measured using automatic biochemical analyzer. Multivariate linear regression analysis and binary logistic regression model were used to assess the relationship between urinary fluoride and markers of kidney function injury.

RESULTS

Urinary fluoride was positively correlated with urinary NAG and serum Urea, negatively correlated with serum C3. In multivariate linear regression models, every 1 mg/L increment of urinary fluoride was associated with 1.583 U/L increase in urinary NAG, 0.199 mmol/L increase in serum Urea, 0.037 g/L decrease in serum C3 after adjusting for potential confounding factors. In the binary logistic regression model, higher levels of urinary fluoride were associated with an increased risk of kidney function injury. Determination of kidney function based on urinary NAG, every 1 mg/L increment in the urinary fluoride concentrations was associated with significant increases of 22.8% in the risk of kidney function injury after adjusting for potential confounding factors. Sensitivity analysis for the association between urinary fluoride concentrations and markers of kidney function (urinary NAG, serum Urea, and serum C3) by adjusting for the covariates, it is consistent with the primary analysis.

CONCLUSIONS

Our study suggests that long-term fluoride exposure is associated with kidney function in adults, and urinary NAG is a sensitive and robust marker of kidney dysfunction caused by fluoride exposure, which could be considered for the identification of early kidney injury in endemic fluorosis areas.

Antibody-Mediated Rejection and Recurrent Primary Disease: Two Main Obstacles in Abdominal Kidney, Liver, and Pancreas Transplants

The advances in acute phase care have firmly established the practice of organ transplantation in the last several decades. Then, the next issues that loom large in the field of transplantation include antibody-mediated rejection (ABMR) and recurrent primary disease. Acute ABMR is a daunting hurdle in the performance of organ transplantation. The recent progress in desensitization and preoperative monitoring of donor-specific antibodies enables us to increase positive outcomes. However, chronic active ABMR is one of the most significant problems we currently face. On the other hand, recurrent primary disease is problematic for many recipients. Notably, some recipients, unfortunately, lost their vital organs due to this recurrence. Although some progress has been achieved in these two areas, many other factors remain largely obscure. In this review, these two topics will be discussed in light of recent discoveries.

Characteristics and outcomes of glomerulonephritis with membranoproliferative pattern in children

BACKGROUND

Membranoproliferative 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.

METHODS

We 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.

RESULTS

Median 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).

CONCLUSIONS

Children 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.

Increased risk for central serous chorioretinopathy in nephrotic syndrome patients: A population-based cohort study

BACKGROUND

Nephrotic syndrome (NS) is characterized by various etiologies that damage the glomerulus. Central serous chorioretinopathy (CSCR) is a retinal disease characterized by neurosensory detachment of the retina. Several case reports have described the relationship between both. Therefore, we try to analyze the epidemiological associations between NS and CSCR using the National Health Insurance Research Database in Taiwan.

METHODS

Data spanning 14 years were extracted from the National Health Insurance Research Database and sub-grouped. The variables were analyzed using Pearson's chi-squared test and Fisher's exact test. The risk factors for disease development with or without comorbidities were examined using an adjusted hazard ratio (aHR). Kaplan-Meier analysis was performed to evaluate the cumulative incidence of CSCR with or without NS.

RESULTS

A total of 14 794 patients with NS and 14 794 matched controls without NS were enrolled in this cohort study. The incidence rate of CSCR was higher in the study cohort than in the control cohort (aHR = 3.349, p < 0.001). The overall incidence of CSCR was 44.51 per 100 000 person-years in the study cohort and 33.39 per 100 000 person-years in the control cohort. In both groups, CSCR occurred more frequently in males than in females. Patients aged 40-49, 50-59, and ≥60 years in the study cohort had a significantly higher risk of developing CSCR than those in the control cohort (aHR = 3.445, 5.421, and 4.957, all p < 0.001). NS patient with a 4-week history of steroid usage has a higher risk of developing CSCR (aHR = 2.010, p < 0.001).

CONCLUSION

Our data showed that patients with NS have an increased risk of developing subsequent CSCR. Physician should routinely refer their NS patients to ophthalmologist for ophthalmic evaluation. This is the first nationwide epidemiological study reporting the association between these two diseases. Further studies are needed to clarify this relationship.

Role of Direct Immunofluorescence Microscopy in Spectrum of Diffuse Proliferative Glomerulonephritis: A Single-Center Study

Introduction

Immunofluorescence (IF) microscopy is an essential tool for the analysis of glomerular diseases. In this study, we studied the significance of the IF technique together with light microscopy (LM) and clinical details in the diagnosis of different types of diffuse proliferative glomerulonephritis (GN). We intended to evaluate the spectrum of Diffuse Proliferative Glomerulonephritis (DPGN) in our institute.

Materials and Methods

We evaluated a total of 95 kidney biopsies received in the past 10 years. All biopsies were scrutinized by LM and IF techniques. Clinical details were documented in a predesigned form.

Results

The predominant clinical presentation in this study was nephrotic syndrome (49.4%) followed by systemic lupus erythromatosus with suspected renal involvement (24.2%). On microscopy, lupus nephritis (LN) was the most common DPGN in the study (35.7%), followed by immunoglobulin (Ig) A nephropathy (25.2%) and postinfectious GN (PIGN) (16.8%). The majority of patients were in the <30 years age group (72.6%), with the average age of patients being 24.4 years. The dominant deposit on IF in LN was C3 and IgG (100%). A high deposit of IgA (100%) in IgA nephropathy and of IgG and C3 (100%) in membranoproliferative GN was seen. PIGN showed dominant positive staining of IgG (92.8%).

Conclusion

The predominant clinical presentation was of nephrotic syndrome and on LM LN was the most commonly diagnosed DPGN in this study. Direct IF is vital for classifying DPGN, followed by electron microscopy, which is an essential tool. This article describes a rational evaluation of kidney biopsies with DPGN pattern on LM in a way that guides toward the logical assessment to reach the diagnosis. Using the IF technique and comparing it with LM and clinical details, we evaluated the spectrum DPGN in our center.

Recurrent glomerulonephritis after kidney transplantation: a practical approach

PURPOSE OF REVIEW

This review will provide a practical approach in the assessment of kidney failure patients with primary glomerulonephritides (GN) being considered for kidney transplantation, focusing on high-risk subtypes of immunoglobulin A nephropathy, focal segmental glomerulosclerosis, idiopathic membranous glomerulonephritis and membranoproliferative glomerulonephritis.

RECENT FINDINGS

Recurrent glomerulonephritis remains one of the most common causes of allograft loss in kidney transplant recipients. Although the epidemiology and clinical outcomes of glomerulonephritis recurrence occurring after kidney transplantation are relatively well-described, the natural course and optimal treatment strategies of recurrent disease in kidney allografts remain poorly defined. With a greater understanding of the pathophysiology and treatment responses of patients with glomerulonephritis affecting the native kidneys, these discoveries have laid the framework for the potential to improve the management of patients with high-risk glomerulonephritis subtypes being considered for kidney transplantation.

SUMMARY

Advances in the understanding of the underlying immunopathogenesis of primary GN has the potential to offer novel therapeutic options for kidney patients who develop recurrent disease after kidney transplantation. To test the efficacy of novel treatment options in adequately powered clinical trials requires a more detailed understanding of the clinical and histological characteristics of kidney transplant recipients with recurrent glomerulonephritis.

Immunotactoid Glomerulopathy with Nontuberculous Mycobacterial Infection: A Novel Association

A 70-year-old woman underwent a renal biopsy due to nephrotic syndrome. She had suffered from nontuberculous mycobacterial infection (NTM) for 14 years. The patient was diagnosed as having membranoproliferative glomerulonephritis (MPGN) type 3 and immunoglobulin (Ig)-associated MPGN based upon LM/erythromycin and IF findings, respectively. In high-magnification imaging, electron-dense deposits showed immunotactoid glomerulopathy (ITG). There was no evidence of hematological cancer, and the patient improved after receiving treatments for NTM. To the best of our knowledge, this patient is the first to show an association between ITG and NTM. Although ITG is generally considered as related to lymphoproliferative disease, it is suggested that ITG is driven by bacterial infection and is a potential outcome of Ig-associated 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 (CFHR3_{4 - 6} Δ) that results in a FHR3-FHR1 hybrid protein in a C3G patient; and 4) a CFHR3_{1 - 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.

Dengue Virus Infection Presenting as Membranoproliferative Glomerulonephritis Type 1

The renal complications of dengue virus infection cover a wide spectrum of manifestations from acute kidney injury to glomerular injury with nephritic/nephrotic syndrome. Majority of cases remain symptom free and show full recovery. We present a 61-year-old previously healthy male who developed a pyrexial illness with haemolytic anaemia that was diagnosed on the basis of a positive serological test as a case of dengue fever. He received supportive treatment and showed general recovery except for his renal dysfunction that showed persistent proteinuria at 14 gm/24 hours. A kidney biopsy revealed membranoproliferative glomerulonephritis type 1 (MPGN-l). Complete remission was achieved by steroids and mycophenolate mofetil therapy. We provide convincing biopsy evidence that dengue virus is yet another viral cause of MPGN-l and also document its successful management with mycophenolate mofetil and steroids therapy.

C4d at Crossroads Between Post-Infectious Glomerulonephritis and C3 Glomerulopathy

Background

Post-infectious glomerulonephritis (PIGN) (immune complex-mediated glomerulonephritis) and C3 glomerulopathy are sub-types of glomerulonephritis (GN) with hypercellularity. Both have overlapping clinical and morphologic features on a kidney biopsy, however, the treatment and prognosis of these diseases are quite different making their distinction of utmost importance. Immune complex-mediated glomerulonephritis arises from glomerular deposition of immune-complexes (Igs) and C3 as a result of activation of classical (CP) and lectin pathways (LP). C4d is produced as a result of activation of the CP/LP. On the other hand, C3 glomerulopathy results from activation of alternative pathway of complement.

Aim

To distinguish between PIGN and C3 glomerulopathy with the help of C4d IHC stain.

Materials and Methods

We studied 28 biopsies reported as GN with hypercellularity from January 2015 to January 2020. Clinical information, histological features and immunofluorescence patterns were analyzed. C4d IHC was performed on all the biopsies. Six known cases of immune complex-mediated GN were selected to act as a positive control for C4d staining.

Results

Amongst 28 cases originally reported as GN with hypercellularity, 18 were labeled as post-infectious GN and 10 as C3 glomerulopathy based on clinical information and serological findings. 13 of 18 (72.2%) cases of PIGN had mild to moderate (1-2+) C4d staining, 2 (11.1%) had strong (3+) staining and 3 (16.7%) cases were negative for C4d staining. In the 10 biopsies of C3 glomerulopathy, mild (1+) C4d staining was noted only in 3 (30%) biopsies. C4d had moderate to strong (2-3+) staining in the control group.

Conclusion

C4d IHC stain can be helpful in distinguishing PIGN from C3 glomerulopathy.

A CHILD WITH DENSE DEPOSIT DISEASE AND DECREASED CLASSIC COMPLEMENT PATHWAY ACTIVITY

We report a rare case of nephritic syndrome underlying dense deposit disease (DDD) with alternative complement pathway dysfunction explained with both C3 nephritic factor (C3NeF) antibodies and DDD associated polymorphism of factor H. An 8-year-old boy presented with macroscopic hematuria, hypertension and periorbital edema followed by persistently low C3 during the 8-week follow-up. Positive C3 staining on immunofluorescence microscopy, supported by dense deposits within the glomerular basement membrane on electron microscopy, confirmed the diagnosis of DDD. Preliminary tests for complement activation showed decreased classic pathway and deficient alternative complement pathway, as well as slightly positive C3NeF, supporting the diagnosis of DDD. Genetic analysis revealed a polymorphism of the complement factor H gene with an increased risk of developing DDD. Supportive therapy led to satisfactory recovery of renal function and normalization of C3. Given the poor prognosis of the disease, proper approach to such specific glomerulopathy is important to avoid or at least slow down progression to end-stage renal disease.

Therapy and outcomes of C3 glomerulopathy and immune-complex membranoproliferative glomerulonephritis

BACKGROUND

Data on therapy and outcome of dense deposit disease (DDD), C3 glomerulonephritis (C3GN), and immune-complex MPGN (IC-MPGN) in children are limited.

METHODS

In this retrospective single-center study from 2007 to 2019, kidney biopsies were reviewed to include patients aged <18-years with C3 glomerulopathy and IC-MPGN. Initial immunosuppression comprised prednisolone, mycophenolate mofetil (n = 51), tacrolimus (n = 11), and/or IV cyclophosphamide (n = 20). Clinicopathological features, response to therapy, and adverse outcome (eGFR_cr < 15 mL/min/1.73 m² or death) were evaluated.

RESULTS

A total of 92 patients were classified as DDD (n = 48, 52.2%), C3GN (n = 26, 28.3%), and IC-MPGN (n = 18, 19.6%) by immunohistochemistry and electron microscopy; 8 patients with DDD were misclassified as IC-MPGN on immunofluorescence. At last follow-up (median 4.3 years), complete or partial remission occurred in 28.5, 36.1, and 16.7% patients with DDD, C3GN, and IC-MPGN, respectively. Serum albumin at onset < 2.5 g/dL (HR = 0.29, P = 0.005) and persistently low serum C3 (HR = 0.34, P = 0.02) were associated with lack of remission. The 5-year kidney survival was 62.6, 85.5, and 88.5% in patients with DDD, C3GN, and IC-MPGN, respectively (log-rank, P = 0.006). Presentation as rapidly progressive GN (HR = 11.2, P < 0.001), age > 10 years at onset (HR = 4.0, P = 0.004), and DDD (HR = 4.2, P = 0.02) were independently associated with adverse outcome; achieving remission was protective (HR = 0.04; P < 0.001).

CONCLUSION

Outcome in patients with C3 glomerulopathy and IC-MPGN was unsatisfactory, and only a small proportion of patients achieved complete or partial remission. Patients with DDD were more likely to present with rapidly progressive GN and were at higher risk of adverse outcomes, including kidney failure.

Primary membranoproliferative glomerulonephritis in Sfax, Tunisia: epidemiologic profile and prognostic factors

Introduction

membranoproliferative glomerulo nephritis (MPGN) is a rare kidney disease with a poor prognosis as 50% of patients attend the end stage renal failure after 10 years of follow up. Several factors have been described associated with poor renal prognosis. The aim of our study is to determine the epidemiologic profile and to identify prognostic factors of MPGN.

Methods

our study is retrospective over a period of 16 years (January 1996 - December 2011) including all cases of primary MPGN aged more than 15 years, collected at the nephrology department of Hedi Chaker University Hospital, Sfax, Tunisia.

Results

we collected 118 cases of primary MPGN, with mean age of 45 (SD 19) years. The incidence of MPGN has decreased from 10 cases/year between 1996 and 1999 to 5 cases/year between 2008 and 2011. Seventy-nine percent of patients (n=93) had renal failure at the moment of diagnosis (e-GFR less than 60 ml/min/1.73m²;). After a mean follow-up of 51.9 (SD 44) months, progression to end stage renal failure was observed in 43.5% of followed cases (n=20). On univariate analysis, factors associated with death or progression to end stage renal failure were initial renal failure and sclerotic glomeruli (respectively p at 0.040 and 0.032). Multivariate analysis indicated that initial renal failure was significantly correlated with death or progression to end stage renal failure (HR: 0.14, 95% CI (0.033-0.593), p=0.008).

Conclusion

there has been a decline in the number of cases of MPGN diagnosed in our hospital. The presence of renal failure at diagnosis was associated with death or progression to end stage renal failure.

Treatment of C3 Glomerulopathy in Adult Kidney Transplant Recipients: A Systematic Review

BACKGROUND

C3 glomerulopathy (C3G), a rare glomerular disease mediated by alternative complement pathway dysregulation, is associated with a high rate of recurrence and graft loss after kidney transplantation (KTx). We aimed to assess the efficacy of different treatments for C3G recurrence after KTx.

METHODS

Databases (MEDLINE, EMBASE, and Cochrane Database) were searched from inception through 3 May, 2019. Studies were included that reported outcomes of adult KTx recipients with C3G. Effect estimates from individual studies were combined using the random-effects, generic inverse variance method of DerSimonian and Laird., The protocol for this meta-analysis is registered with PROSPERO (no. CRD42019125718).

RESULTS

Twelve studies (7 cohort studies and 5 case series) consisting of 122 KTx patients with C3G (73 C3 glomerulonephritis (C3GN) and 49 dense deposit disease (DDD)) were included. The pooled estimated rates of allograft loss among KTx patients with C3G were 33% (95% CI: 12-57%) after eculizumab, 42% (95% CI: 2-89%) after therapeutic plasma exchange (TPE), and 81% (95% CI: 50-100%) after rituximab. Subgroup analysis based on type of C3G was performed. Pooled estimated rates of allograft loss in C3GN KTx patients were 22% (95% CI: 5-46%) after eculizumab, 56% (95% CI: 6-100%) after TPE, and 70% (95% CI: 24-100%) after rituximab. Pooled estimated rates of allograft loss in DDD KTx patients were 53% (95% CI: 0-100%) after eculizumab. Data on allograft loss in DDD after TPE (1 case series, 0/2 (0%) allograft loss at 6 months) and rituximab (1 cohort, 3/3 (100%) allograft loss) were limited. Among 66 patients (38 C3GN, 28 DDD) who received no treatment (due to stable allograft function at presentation and/or clinical judgment of physicians), pooled estimated rates of allograft loss were 32% (95% CI: 7-64%) and 53% (95% CI: 28-77%) for C3GN and DDD, respectively. Among treated C3G patients, data on soluble membrane attack complex of complement (sMAC) were limited to patients treated with eculizumab (N = 7). 80% of patients with elevated sMAC before eculizumab responded to treatment. In addition, all patients who responded to eculizumab had normal sMAC levels after post-eculizumab.

CONCLUSIONS

Our study suggests that the lowest incidence of allograft loss (33%) among KTX patients with C3G are those treated with eculizumab. Among those who received no treatment for C3G due to stable allograft function, there is a high incidence of allograft loss of 32% in C3GN and 53% in DDD. sMAC level may help to select good responders to eculizumab.

Kidney transplantation for primary glomerulonephritis: Recurrence risk and graft outcomes with related versus unrelated donors

Primary glomerulonephritis can recur after kidney transplantation and may jeopardize the survival of the renal allograft. The risks of living-related kidney transplantation remain controversial in this group of patients. Living related transplantation offers potentially better HLA matching, therefore improve the long-term graft survival. However, the concern for increased rates of recurrence of the primary glomerulonephritis in the transplanted kidney from living related donors complicates the selection of donors. With the recent dramatic rise in the use of paired kidney exchange, there is now often the option of having a living related donor donate through a paired exchange. This raises the question of whether patients with primary glomerulonephritis should receive living donor kidneys through paired kidney exchange programs to obtain the benefits of a living donor kidney transplant while also reducing the risk of recurrent glomerulonephritis. Our review of the literature suggests that although the recurrence of primary glomerulonephritis occurs more often when donation occurs from a living related donor as compared to an unrelated donor, the graft survival advantage of living related donation is generally maintained despite the recurrence. We suggest that despite the increased risk of recurrence, living related donation should not be avoided in patients with primary glomerulonephritis as the cause of their end-stage renal disease.

The Spectrum of Monoclonal Immunoglobulin-Associated Diseases

The spectrum of immunoglobulin paraprotein-associated diseases requiring therapy extends beyond multiple myeloma and AL amyloidosis. Awareness of these is essential in ensuring timely accurate diagnosis and appropriate treatment. As most paraprotein-associated diseases are fairly uncommon, therapeutic decisions must often be made in the absence of data from randomized controlled trials. Treatment is generally directed at the underlying clonal cell population. This review focuses on the spectrum of the less common paraprotein-associated disorders. In most instances, the monoclonal immunoglobulin plays a direct role in the pathophysiology of the disease course; in a select few, the paraprotein may be a disease marker.

Recurrent Glomerulonephritis after Renal Transplantation: The Clinical Problem

Glomerulonephritis (GN) continues to be one of the main causes of end-stage kidney disease (ESKD) with an incidence rating from 10.5% to 38.2%. Therefore, recurrent GN, previously considered to be a minor contributor to graft loss, is the third most common cause of graft failure 10 years after renal transplantation. However, the incidence, pathogenesis, and natural course of recurrences are still not completely understood. This review focuses on the most frequent diseases that recur after renal transplantation, analyzing rate of recurrence, epidemiology and risk factors, pathogenesis and bimolecular mechanisms, clinical presentation, diagnosis, and therapy, taking into consideration the limited data available in the literature. First of all, the risk for recurrence depends on the type of glomerulonephritis. For example, recipient patients with anti-glomerular basement membrane (GBM) disease present recurrence rarely, but often exhibit rapid graft loss. On the other hand, recipient patients with C3 glomerulonephritis present recurrence in more than 50% of cases, although the disease is generally slowly progressive. It should not be forgotten that every condition that can lead to chronic graft dysfunction should be considered in the differential diagnosis of recurrence. Therefore, a complete workup of renal biopsy, including light, immunofluorescence and electron microscopy study, is essential to provide the diagnosis, excluding alternative diagnosis that may require different treatment. We will examine in detail the biomolecular mechanisms of both native and transplanted kidney diseases, monitoring the risk of recurrence and optimizing the available treatment options.

Standardized classification and reporting of glomerulonephritis

A kidney biopsy is done to determine the etiology of the glomerulonephritis (GN) and the severity of the lesion, to identify whether other lesions, related to or not related to the GN, are present on the kidney biopsy and finally to ascertain the extent of chronicity of the GN. The etiology of GN is based on the classification of GN into five groups: immune complex-mediated GN, antineutrophil cytoplasmic antibody (ANCA)-associated GN, anti-glomerular basement membrane (GBM) GN, monoclonal immunoglobulin-mediated GN and C3 glomerulopathy. Immune complex GN includes multiple specific diseases such as lupus nephritis, IgA nephropathy, infection-related GN and fibrillary GN. ANCA GN, anti-GBM GN and C3 glomerulopathy are specific diseases in themselves, while monoclonal Ig GN includes proliferative GN with monoclonal Ig deposits and monoclonal Ig deposition disease. Thus identification of the class of GN and within it the specific disease determines the etiology of GN. Ancillary studies may be required to confirm the etiology of GN. The severity of the GN is revealed by the pattern of injury, such as crescentic, necrotizing, diffuse proliferative, exudative, membranoproliferative, mesangial proliferative or a sclerosing GN. Secondary diagnosis either related or unrelated to the GN, such as diabetic glomerulosclerosis, acute tubular necrosis or thrombotic microangiopathy, may also be present. The secondary diagnosis may sometimes be the reason for the kidney biopsy. The chronicity of GN is determined by evaluating the extent of glomerulosclerosis, tubular atrophy and interstitial fibrosis and vascular sclerosis present on the biopsy. This review summarizes the approach to standardizing a kidney biopsy report that includes these components in a logical and sequential manner.

Rituximab use in adult glomerulopathies and its rationale

Glomerulopathies are one of the leading causes of end-stage renal disease. In the last years, clinical research has made significant contributions to the understanding of such conditions. Recently, rituximab (RTX) has appeared as a reasonably safe treatment. The Kidney Disease: Improving Global Outcomes guidelines (KDIGO) recommended RTX only as initial treatment in antineutrophil cytoplasm antibody associated vasculitis (AAV) and in non-responders patients with lupus nephritis (LN), but these guidelines have not been updated since 2012. Nowadays, RTX seems to be at least as effective as other immunosuppressive regimens in idiopathic membranous nephropathy (IMN). In minimal-change disease, (MCD) this drug might allow a long-lasting remission period in steroid-dependent or frequently relapsing patients. Preliminary results support the use of RTX in patients with pure membranous LN and immunoglobulin-mediated membranoproliferative glomerulonephritis (MPGN), but not in patients with class III/IV LN or complement-mediated MPGN. No conclusion can be drawn in idiopathic focal segmental glomerulosclerosis (FSGS) and anti-glomerular basement membrane antibody glomerulonephritis (anti-GBM GN) because studies are small, heterogeneous, and scarce. Lastly, immunosuppression including RTX is not particularly useful in IgA nephropathy. This review presents the general background, outcomes, and safety for RTX treatment in different glomerulopathies. In this regard, we describe randomized controlled trials (RCTs) performed in adults, whenever possible. A literature search was performed using clinicaltrials.gov and PubMed.

Rituximab use in adult glomerulopathies and its rationale

Glomerulopathies are one of the leading causes of end-stage renal disease. In the last years, clinical research has made significant contributions to the understanding of such conditions. Recently, rituximab (RTX) has appeared as a reasonably safe treatment. The Kidney Disease: Improving Global Outcomes guidelines (KDIGO) recommended RTX only as initial treatment in antineutrophil cytoplasm antibody associated vasculitis (AAV) and in non-responders patients with lupus nephritis (LN), but these guidelines have not been updated since 2012. Nowadays, RTX seems to be at least as effective as other immunosuppressive regimens in idiopathic membranous nephropathy (IMN). In minimal-change disease, (MCD) this drug might allow a long-lasting remission period in steroid-dependent or frequently relapsing patients. Preliminary results support the use of RTX in patients with pure membranous LN and immunoglobulin-mediated membranoproliferative glomerulonephritis (MPGN), but not in patients with class III/IV LN or complement-mediated MPGN. No conclusion can be drawn in idiopathic focal segmental glomerulosclerosis (FSGS) and anti-glomerular basement membrane antibody glomerulonephritis (anti-GBM GN) because studies are small, heterogeneous, and scarce. Lastly, immunosuppression including RTX is not particularly useful in IgA nephropathy. This review presents the general background, outcomes, and safety for RTX treatment in different glomerulopathies. In this regard, we describe randomized controlled trials (RCTs) performed in adults, whenever possible. A literature search was performed using clinicaltrials.gov and PubMed.

Outcome of C3 glomerulopathy patients: largest single-centre experience from South Asia

BACKGROUND

C3 glomerulopathy (C3G) is related to dysfunction of alternative complement pathway (ACP) because of its hyperactivation. Triggering factors and genetic profile are likely to be different in developing countries as compared to the Western world. Data regarding C3G from South Asian is scanty.

STUDY DESIGN

In the present study, 115 patients of C3G from 2012 to 2017 were analyzed. Clinical details were reviewed; serological levels of C3, C4, complement factor H or B and autoantibody testing was done by nephelometry/ELISA. Limited genetics workup for CFH and CFHR5 genes was done.

RESULTS

The prevalence of C3G was 1.52%. There was no difference in demographic and histopathologic profiles of C3G patients. Majority of patients had low functional assay and C3 levels. C3 nephritic factor was present in 47.5% of DDD and 38.6% of C3GN. Autoantibodies to CFH were present more often in the patients of C3GN (29.5%) than DDD (12.5%). Autoantibodies to CFB were equally common in both groups. Past history of infections was present in one-third patients and monoclonal paraproteins were present only in two patients. No pathogenic variants were noted in CFH/CFHR5 gene. On follow-up (3.2 + 1.6 years), complete and partial remission was achieved in one-fourth patients and 26% had resistance disease. About 40% progressed to ESRD and 18 underwent renal transplantation of which nine had a post-transplant recurrence.

CONCLUSIONS

Indian cohort had some differences in the immunological and genetic profile when compared to the Western literature; most significant was the absence of monoclonal immunoglobulins as a trigger for C3G.

Recurrent and de novo Glomerulonephritis After Kidney Transplantation

The prevalence, pathogenesis, predictors, and natural course of patients with recurrent glomerulonephritis (GN) occurring after kidney transplantation remains incompletely understood, including whether there are differences in the outcomes and advances in the treatment options of specific GN subtypes, including those with de novo GN. Consequently, the treatment options and approaches to recurrent disease are largely extrapolated from the general population, with responses to these treatments in those with recurrent or de novo GN post-transplantation poorly described. Given a greater understanding of the pathogenesis of GN and the development of novel treatment options, it is conceivable that these advances will result in an improved structure in the future management of patients with recurrent or de novo GN. This review focuses on the incidence, genetics, characteristics, clinical course, and risk of allograft failure of patients with recurrent or de novo GN after kidney transplantation, ascertaining potential disparities between “high risk” disease subtypes of IgA nephropathy, idiopathic membranous glomerulonephritis, focal segmental glomerulosclerosis, and membranoproliferative glomerulonephritis. We will examine in detail the management of patients with high risk GN, including the pre-transplant assessment, post-transplant monitoring, and the available treatment options for disease recurrence. Given the relative paucity of data of patients with recurrent and de novo GN after kidney transplantation, a global effort in collecting comprehensive in-depth data of patients with recurrent and de novo GN as well as novel trial design to test the efficacy of specific treatment strategy in large scale multicenter randomized controlled trials are essential to address the knowledge deficiency in this disease.

Autoimmune abnormalities of the alternative complement pathway in membranoproliferative glomerulonephritis and C3 glomerulopathy

Membranoproliferative glomerulonephritis (MPGN) is a rare chronic kidney disease associated with complement activation. Recent immunofluorescence-based classification distinguishes between immune complex (IC)-mediated MPGN, with glomerular IgG and C3 deposits, and C3 glomerulopathies (C3G), with predominant C3 deposits. Genetic and autoimmune abnormalities causing hyperactivation of the complement alternative pathway have been found as frequently in patients with immune complex-associated MPGN (IC-MPGN) as in those with C3G. In the last decade, there have been great advances in research into the autoimmune causes of IC-MPGN and C3G. The complement-activating autoantibodies called C3-nephritic factors (C3NeFs), which are present in 40-80% of patients, form a heterogeneous group of autoantibodies that stabilise the C3 convertase or the C5 convertase of the alternative pathway or both. A few patients, mainly with IC-MPGN, carry autoantibodies directed against the two components of the alternative pathway C3 convertase, factors B and C3b. Finally, autoantibodies against factor H, the main regulator of the alternative pathway, have been reported in a small proportion of patients with IC-MPGN or C3G. The identification of distinct pathogenetic patterns leading to kidney injury and of targets in the complement cascade may pave the way for tailored therapies for IC-MPGN and C3G, with specific complement inhibitors in the development pipeline.