Pre-transplant phospholipase A2 receptor autoantibody concentration is associated with clinically significant recurrence of membranous nephropathy post-kidney transplantation

Pretransplant Treatment to Avoid Recurrent Membranous Nephropathy in a Kidney Transplant Recipient: A Case Report

Kidney transplant candidates with high anti-M-type phospholipase A2 receptor antibody activity may be at increased risk for early postkidney transplant recurrence and allograft loss. Pretransplant treatment to induce serological remission may be warranted to improve allograft survival. In this case report, a patient seeking their third kidney transplant, who lost 2 prior living donor transplants from early recurrent membranous nephropathy, underwent pretransplant treatment for membranous nephropathy with serological remission and no evidence of recurrent disease.

Recurrence of membranous nephropathy after kidney transplantation: A multicenter retrospective cohort study

Membranous nephropathy (MN) is a leading cause of kidney failure worldwide and frequently recurs after transplant. Available data originated from small retrospective cohort studies or registry analyses; therefore, uncertainties remain on risk factors for MN recurrence and response to therapy. Within the Post-Transplant Glomerular Disease Consortium, we conducted a retrospective multicenter cohort study examining the MN recurrence rate, risk factors, and response to treatment. This study screened 22,921 patients across 3 continents and included 194 patients who underwent a kidney transplant due to biopsy-proven MN. The cumulative incidence of MN recurrence was 31% at 10 years posttransplant. Patients with a faster progression toward end-stage kidney disease were at higher risk of developing recurrent MN (hazard ratio [HR], 0.55 per decade; 95% confidence interval [CI], 0.35-0.88). Moreover, elevated pretransplant levels of anti-phospholipase A2 receptor (PLA2R) antibodies were strongly associated with recurrence (HR, 18.58; 95% CI, 5.37-64.27). Patients receiving rituximab for MN recurrence had a higher likelihood of achieving remission than patients receiving renin-angiotensin-aldosterone system inhibition alone. In sum, MN recurs in one-third of patients posttransplant, and measurement of serum anti-PLA2R antibody levels shortly before transplant could aid in risk-stratifying patients for MN recurrence. Moreover, patients receiving rituximab had a higher rate of treatment response.

Recurrence of Idiopathic Membranous Nephropathy in the Kidney Allograft: A Systematic Review

INTRODUCTION

The recurrence of idiopathic membranous nephropathy (iMN) after kidney transplantation is common, although its exact clinical significance remains unclear. This systematic review aims to elucidate the effects of iMN recurrence on graft survival.

MATERIALS AND METHODS

A literature search was performed by systematically searching Medline, Scopus, Web of Science, and Google Scholar from inception. Cohort studies examining iMN recurrence after kidney transplantation were deemed eligible. Meta-analysis was performed by fitting random-effects models.

RESULTS

Twelve (12) articles published from 1995 to 2016 reporting on 139 transplant patients with recurrent iMN were included. The median time of the diagnosis of recurrent iMN was 18 months during follow-up from 35 to 120 months. Risk factors for iMN recurrence in the renal allograft are a positive serum test for anti-PLA2R antibodies pretransplant, female sex, younger age, high proteinuria pretransplant, the longest interval from initial disease to end-stage chronic kidney disease, and the combination of alleles HLA DQA1 05:01 and HLA DQB1 02:01. In the pretransplant period, 37 (26.61%) patients had a positive serum test and 18 (12.94%) patients had a positive biopsy stain for anti-PLA2R antibodies. The sensitivity of the pretransplant positive serum test for these antibodies ranges from 57% to 85.30% and the specificity is 85.10-100%. A total of 81.80% of patients who received rituximab as treatment for iMN recurrence achieved complete and partial remission, while 18.20% had no response to treatment. iMN recurrence was not associated with significantly different rates of graft loss (odds ratio = 1.03, 95% CI: 0.52-2.04, p = 0.524, I2 = 0.00%). Recurrence of iMN was not associated with increased risk of graft loss independently of whether patients were treated with rituximab (OR: 0.98, 95% CI: 0.39-2.50, I2: 0%) or not (OR: 1.22, 95% CI: 0.58-2.59, I2: 3.8%). Patients with iMN recurrence who achieved remission had significantly reduced risk of graft loss (OR: 0.14, 95% CI: 0.03 to 0.73).

CONCLUSION

The main outcome from this systematic review is that there is no statistically significant difference in graft survival in patients with iMN recurrence compared to those without recurrence in long-term follow-up. The achievement of remission is associated with significantly reduced risk of graft loss.

THSD7A-positive membranous nephropathy after kidney transplantation: A case report

Membranous nephropathy (MN) is a common cause of nephrotic syndrome after kidney transplantation (KT); however, scarce is known regarding post-KT thrombospondin type-1 domain-containing 7A (THSD7A)-positive MN. Herein, we report on a 72-year-old woman with end-stage kidney disease due to chronic interstitial nephritis (1996). In February 2020, she received a second deceased-donor KT, achieving optimal kidney function but presenting early post-KT proteinuria, reaching up to 1800mg/24h six months after transplantation, controlled with renin-angiotensin-aldosterone system (RAAS) blockade. In July 2021, a kidney allograft biopsy revealed features consistent with MN. Immunohistochemical stains showed diffuse and granular THSD7A and C4d deposition in glomerular capillary walls and negative PLA2R and IgG4 staining. No anti-THSD7A antibodies were detected in the serum. The pre-implantation biopsy showed no MN-associated lesions and negative THSD7A staining. Secondary triggers such as malignancy were discarded. The present report illustrates a THSD7A-positive MN in a KT recipient. Despite lacking native kidney biopsy and early presentation, a recurrent MN seemed unprovable due to documented native kidney disease and a long time span between native kidney disease and MN diagnosis. We, therefore, presumed primary de novo disease. Two years after KT, kidney function remains stable, and the patient has reached complete remission of proteinuria.

High exposure to tacrolimus is associated with spontaneous remission of recurrent membranous nephropathy after kidney transplantation

Introduction

We aimed to characterize the incidence and clinical presentation of membranous nephropathy (MN) after kidney transplantation (KT), and to assess allograft outcomes according to proteinuria rates and immunosuppression management.

Methods

Multicenter retrospective cohort study including patients from six Spanish centers who received a KT between 1991-2019. Demographic, clinical, and histological data were collected from recipients with biopsy-proven MN as primary kidney disease (n = 71) or MN diagnosed de novo after KT (n = 4).

Results

Up to 25.4% of patients with biopsy-proven MN as primary kidney disease recurred after a median time of 18.1 months posttransplant, without a clear impact on graft survival. Proteinuria at 3-months post-KT was a predictor for MN recurrence (rMN, HR 4.28; P = 0.008). Patients who lost their grafts had higher proteinuria during follow-up [1.0 (0.5-2.5) vs 0.3 (0.1-0.5) g/24 h], but only eGFR after recurrence treatment predicted poorer graft survival (eGFR < 30 ml/min: RR = 6.8). We did not observe an association between maintenance immunosuppression and recurrence diagnosis. Spontaneous remission after rMN was associated with a higher exposure to tacrolimus before recurrence (trough concentration/dose ratio: 2.86 vs 1.18; P = 0.028). Up to 94.4% of KT recipients received one or several treatments after recurrence onset: 22.2% rituximab, 38.9% increased corticosteroid dose, and 66.7% ACEi/ARBs. Only 21 patients had proper antiPLA2R immunological monitoring.

Conclusions

One-fourth of patients with biopsy-proven MN as primary kidney disease recurred after KT, without a clear impact on graft survival. Spontaneous remission after rMN was associated with a higher exposure to tacrolimus before recurrence.

Membranous nephropathy

Membranous nephropathy is a glomerulopathy, which main affected target is the podocyte, and has consequences on the glomerular basement membrane. It is more common in adults, especially over 50 years of age. The clinical presentation is nephrotic syndrome, but many cases can evolve with asymptomatic non-nephrotic proteinuria. The mechanism consists of the deposition of immune complexes in the subepithelial space of the glomerular capillary loop with subsequent activation of the complement system. Great advances in the identification of potential target antigens have occurred in the last twenty years, and the main one is the protein "M-type phospholipase-A2 receptor" (PLA2R) with the circulating anti-PLA2R antibody, which makes it possible to evaluate the activity and prognosis of this nephropathy. This route of injury corresponds to approximately 70% to 80% of cases of membranous nephropathy characterized as primary. In the last 10 years, several other potential target antigens have been identified. This review proposes to present clinical, etiopathogenic and therapeutic aspects of membranous nephropathy in a didactic manner, including cases that occur during kidney transplantation.

Novel Biomarkers in Membranous Nephropathy

Membranous nephropathy (MN) is the main cause of adult nephrotic syndrome (NS). The pathogenesis of MN is complex and involves subepithelial immune complex deposition. Approximately one-third of patients with MN develop end-stage renal disease (ESRD). Timely diagnosis and reasonable intervention are the keys to improving prognosis. In recent years, with the development of high-throughput technologies, such as mass spectrometry (MS), microarray, and sequencing technologies, the discovery of biomarkers for MN has become an important area of research. In this review, we summarize the significant progress in biomarker identification. For example, a variety of podocyte target antigens and their autoantibodies have been reported. Phospholipase A2 receptor (PLA2R) is the most well-established target antigen in MN. PLA2R and its autoantibodies have clinical significance, with both diagnostic and therapeutic value for MN. In addition, a variety of new biomarkers, including proteins, metabolites, noncoding RNAs (ncRNAs), and immune cells, have recently been found. These MN-related biomarkers have great significance in the diagnosis, progression, prognosis, and treatment response of MN.

The role of PLA2R antibody monitoring: what we know and what we don't know

For a long time, kidney biopsy was the only diagnostic mean for membranous nephropathy (MN), and proteinuria and serum creatinine the only markers of disease activity. The discovery of PLA2R antibody in 2009 has induced a paradigm shift in both the diagnostic and monitoring of patients. Two serological tests are routinely used: the ELISA which is quantitative and the immunofluorescence assay (IFA) which is more sensitive. In centers where the 2 assays are available, the recommendation is to use IFA for screening and diagnostic of immunological remission, and ELISA for monitoring effectiveness of therapy. In patients with positive PLA2R antibody serology, normal kidney function and no evidence for an underlying disease, a kidney biopsy is not mandatory given the almost 100% specificity of the assays. Because MN has different phases, one cannot base a clinical or therapeutic decision on a single measurement of PLA2R antibody at baseline. Risk evaluation of disease progression is a dynamic process that should be performed repeatedly to capture the trajectory of the disease based on both the traditional biomarkers (proteinuria, serum creatinine) and PLA2R antibody levels. Effectiveness of therapy is also evaluated on the PLA2R antibody trajectory, particularly during the first 6 months. Finally, PLA2R antibody monitoring has transformed the management of patients with a kidney allograft. Future studies are needed to develop more subtle immunological tests, including monitoring of antigen-specific memory B cells.

Recurrent Glomerular Disease after Kidney Transplantation: Diagnostic and Management Dilemmas

Recurrent glomerular disease after kidney transplant remains an important cause of allograft failure. Many of the different entities post-transplant still suffer from incomplete knowledge on pathophysiology, and therefore lack targeted and effective therapies. In this review, we focus on specific clinical dilemmas encountered by physicians in managing recurrent glomerular disease by highlighting new insights into the understanding and treatment of post-transplant focal segmental glomerulosclerosis, membranous nephropathy, atypical hemolytic uremic syndrome, C3 glomerulopathy, amyloid light-chain (AL) amyloidosis, and IgA nephropathy.

Membranous nephropathy

Membranous nephropathy (MN) is a glomerular disease that can occur at all ages. In adults, it is the most frequent cause of nephrotic syndrome. In ~80% of patients, there is no underlying cause of MN (primary MN) and the remaining cases are associated with medications or other diseases such as systemic lupus erythematosus, hepatitis virus infection or malignancies. MN is an autoimmune disease characterized by a thickening of the glomerular capillary walls due to immune complex deposition. Identification of the phospholipase A2 receptor (PLA2R) as the major antigen in adults in 2009 induced a paradigm shift in disease diagnosis and monitoring and several other antigens have since been characterized. Disease outcome is difficult to predict and around one-third of patients will undergo spontaneous remission. In those at high risk of progression, immunosuppressive therapy with cyclophosphamide plus corticosteroids has substantially reduced the need for kidney replacement therapy. Owing to carcinogenic risk, other treatments (calcineurin inhibitors and CD20-targeted B cell depletion therapy (rituximab)) have been developed. However, disease relapses are frequent when calcineurin inhibitors are stopped and the remission rate with rituximab is lower than with cyclophosphamide, particularly in patients with high PLA2R antibody titres. Other new drugs are already available and antigen-specific immunotherapies are being developed.

Biomarkers in pediatric glomerulonephritis and nephrotic syndrome

Glomerular diseases are often chronic or recurring and thus associated with a tremendous physical, psychological, and economic burden. Their etiologies are often unknown, and their pathogeneses are frequently poorly understood. The diagnoses and management of these diseases are therefore based on clinical features, traditional laboratory markers, and, often, kidney pathology. However, the clinical presentation can be highly variable, the kidney pathology may not establish a definitive diagnosis, and the therapeutic responses and resulting clinical outcomes are often unpredictable. To try to address these challenges, significant research efforts have been made over the last decade to identify potential biomarkers that can help clinicians optimize the diagnosis and prognosis at clinical presentation, as well as help predict long-term outcomes. Unfortunately, these efforts have to date only identified a single biomarker for glomerular disease that has been fully validated and developed for widespread clinical use (anti-PLA2R antibodies to diagnose membranous nephropathy). In this manuscript, we review the definitions and development of biomarkers, as well as the current knowledge on both historical and novel candidate biomarkers of glomerular disease, with an emphasis on those associated with idiopathic nephrotic syndrome.

Posttransplant nephrotic syndrome resulting from NELL1-positive membranous nephropathy

Membranous nephropathy (MN) constitutes a major cause of nephrotic syndrome (NS) in adults. After kidney transplantation (KTx), both recurrent and de novo MN has been reported. In addition to PLA2R and THSD7A, recent identification of neural EGFL-like-1 protein, NELL1, as a potential disease antigen has enriched our understanding of MN pathogenesis. To date, NELL1-positive MN has only been described in native kidneys, but never been diagnosed in renal allografts. We here report on a 56-year-old male kidney transplant recipient suffering from amyotrophic lateral sclerosis (ALS), who developed NS 25 years after KTx. Allograft biopsy revealed NELL1-positive MN. Using specifically established immunoblotting techniques, we detected new-onset NELL1-IgG1, IgG3, and IgG4 antibodies in the patient´s serum correlating with the course of proteinuria. While primary renal disease was undetermined, MN recurrence seemed unlikely given the long-time span since KTx. By clinical investigation of de novo etiologies, we did not detect an underlying malignancy. However, previous self-medication with dimercaptopropane sulfonate (DMPS) and alpha lipoic acid (ALA) represented a potential trigger and cessation associated with partial remission of proteinuria. This report illustrates the first case of posttransplant NS due to NELL1-positive MN. Monitoring NELL1 antibodies in the serum promise to be a non-invasive diagnostic tool guiding disease management.

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.

A Comprehensive Overview of the Clinical Relevance and Treatment Options for Antibody-mediated Rejection Associated With Non-HLA Antibodies

Although solid organ transplant results have improved significantly in recent decades, a pivotal cause of impaired long-term outcome is the development of antibody-mediated rejection (AMR), a condition characterized by the presence of donor-specific antibodies to HLA or non-HLA antigens. Highly HLA-sensitized recipients are treated with desensitization protocols to rescue the transplantation. These and other therapies are also applied for the treatment of AMR. Therapeutic protocols include removal of antibodies, depletion of plasma and B cells, inhibition of the complement cascade, and suppression of the T-cell-dependent antibody response. As mounting evidence illustrates the importance of non-HLA antibodies in transplant outcome, there is a need to evaluate the efficacy of treatment protocols on non-HLA antibody levels and graft function. Many reviews have been recently published that provide an overview of the literature describing the association of non-HLA antibodies with rejection in transplantation, whereas an overview of the treatment options for non-HLA AMR is still lacking. In this review, we will therefore provide such an overview. Most reports showed positive effects of non-HLA antibody clearance on graft function. However, monitoring non-HLA antibody levels after treatment along with standardization of therapies is needed to optimally treat solid organ transplant recipients.

Mechanisms of Primary Membranous Nephropathy

Membranous nephropathy (MN) is an autoimmune disease of the kidney glomerulus and one of the leading causes of nephrotic syndrome. The disease exhibits heterogenous outcomes with approximately 30% of cases progressing to end-stage renal disease. The clinical management of MN has steadily advanced owing to the identification of autoantibodies to the phospholipase A2 receptor (PLA2R) in 2009 and thrombospondin domain-containing 7A (THSD7A) in 2014 on the podocyte surface. Approximately 50–80% and 3–5% of primary MN (PMN) cases are associated with either anti-PLA2R or anti-THSD7A antibodies, respectively. The presence of these autoantibodies is used for MN diagnosis; antibody levels correlate with disease severity and possess significant biomarker values in monitoring disease progression and treatment response. Importantly, both autoantibodies are causative to MN. Additionally, evidence is emerging that NELL-1 is associated with 5–10% of PMN cases that are PLA2R- and THSD7A-negative, which moves us one step closer to mapping out the full spectrum of PMN antigens. Recent developments suggest exostosin 1 (EXT1), EXT2, NELL-1, and contactin 1 (CNTN1) are associated with MN. Genetic factors and other mechanisms are in place to regulate these factors and may contribute to MN pathogenesis. This review will discuss recent developments over the past 5 years.

Autoantibodies in the Diagnosis, Monitoring, and Treatment of Membranous Nephropathy

The discovery of anti-podocyte antibodies in primary membranous nephropathy (MN) has revolutionized our approach toward the diagnosis and treatment of this disease. Evaluation of serum levels of anti-podocyte antibodies paved the way for non-invasive diagnosis and helped distinguish between primary and secondary MN although the relationship between anti-podocyte antibodies and cancer remains to be elucidated. Serum levels of anti-PLA2R antibodies directed against the major podocyte autoantigen are related to MN activity and the decrease in serum levels of anti-PLA2R antibodies in response to treatment (immunologic remission) also serves as an early indicator of the later putative proteinuric remission, enabling personalization of the treatment. The serum levels of anti-podocyte antibodies also enable the prediction of renal outcomes in terms of both remission and the risk of progression to end-stage renal disease. The positivity of anti-PLA2R antibodies before renal transplantation is associated with the risk of recurrence of MN. It remains to be established if all these relations observed in patients with anti-PLA2R antibodies are also valid for expanding spectrum of antibodies directed against recently discovered minor antigens (e.g., THSD7A, NELL-1, semaphorin 3B).

Is primary membranous nephropathy a complement mediated disease?

Membranous nephropathy (MN) is an immune complex mediated disease. Although limited to the kidney, in up to 20% of patients MN is associated with other autoimmune, infectious or malignant diseases. The initial pathogenetic event in what is still considered "primary" MN is the binding of circulating autoantibodies to proteins (autoantigens) expressed in glomerular podocytes. This antibody binding leads to the formation of immune complexes in the glomerular basement membrane. There is clinical and experimental evidence that these immune deposits lead to the activation of the complement system. Experimental studies in the MN model of Heymann's nephritis show that the terminal membrane attack complex (MAC) of the complement system induces a disturbance of the glomerular filtration barrier and leads to proteinuria, the clinical hallmark of MN. After the discovery of the phospholipase A₂ receptor 1 and thrombospondin type 1 domain containing protein 7A as endogenous antigens, it is assumed that IgG4 antibodies directed against these proteins induce MN in over 85% of patients with primary MN. As a result, the role of complement in the pathogenesis of MN needs to be defined in light of these developments. In this review we describe the current knowledge on the function of the complement system in primary MN and discuss the open questions, which have to be solved for a better understanding of the potential role of complement in the pathophysiology of primary MN.

Phospholipase-A2 receptor antibody, 24 hours proteinuria, and serum albumin as indicators of cyclophosphamide efficacy in idiopathic membranous nephropathy

Background

We aimed to evaluate cyclophosphamide efficacy in the treatment of idiopathic membranous nephropathy (IMN) and explore the efficacy of phospholipase‐A2 receptor antibody (PLA2R‐Ab), 24 hours proteinuria, and serum albumin in predicting 6‐ and 12‐month treatment effects.

Methods

A retrospective analysis was performed on 135 patients with IMN who followed up after treatment. The observation points were before, and after 3, 6, and 12 months of treatment. We collected clinical indicator data at each observation point and measured PLA2R‐Ab levels before and after 3‐month treatment.

Results

The remission rates at 3, 6, and 12 months of cyclophosphamide therapy for patients with IMN were 41.4, 74.8, and 76.1%, respectively. Patients in whom PLA2R‐Ab turned negative within 3 months had high remission rates at 3, 6, and 12 months after treatment (P < .05). PLA2R‐Ab change at 3 months had a strong correlation with 24 hours proteinuria change at 6 months. The change in albumin concentration before and after 3‐month treatment was an independent variable related to remission rate at 6 months, and 24 hours proteinuria change before and after 6‐month treatment was an independent variable related to remission rate at 12 months after treatment.

Conclusion

Cyclophosphamide showed good efficacy at 3, 6, and 12 months for patients with IMN. Serum albumin change and PLA2R‐Ab change at 3 months can be used as indicators to predict remission at 6 months, respectively. Moreover, 24 hours proteinuria change at 6 months can predict remission at 12 months.

Serum Albumin at Partial Remission Predicts Outcomes in Membranous Nephropathy

Background

In primary membranous nephropathy (MN), partial remission (PR) (≥50% reduction of proteinuria to <3.5 g/d) is associated with a greater risk of relapse and end-stage kidney disease (ESKD) compared with complete remission (CR). We aimed to determine factors associated with relapse or renal failure in patients who attain the standard definition of PR.

Methods

We captured PR, CR, relapse, and the composite of doubling of serum creatinine or ESKD in a cohort of 267 patients with MN, nephrotic syndrome, and >12 months of follow-up. Characteristics at the time of PR associated with the composite outcome or relapse were evaluated using a time-to-event analysis.

Results

A total of 192 patients attained PR and 86 attained CR. Serum albumin at PR (hazard ratio [HR]: 1.58 per 0.5 g/dl decrease from 4.0 g/dl; 95% confidence interval [CI]: 1.03-2.43) and duration of nephrotic proteinuria (HR: 1.01 per month increase; 95% CI: 1.00-1.03) were independent risk factors for the composite endpoint. Serum albumin at PR was associated with an increased risk of relapse (HR: 1.58 per 0.5 g/dl decrease below 4.0 g/dl; 95% CI: 1.24-2.01). A cutoff for serum albumin ≤3.5 g/dl at PR performed best in predicting relapse and composite outcome.

Conclusions

Patients with serum albumin >3.5 g/dl at PR have decreased risk of composite outcome or relapse compared with PR with low albumin. A definition of PR that includes normalization of serum albumin may be a more robust surrogate endpoint in MN than the traditional definition of PR.

Association of HLA Typing and Alloimmunity With Posttransplantation Membranous Nephropathy: A Multicenter Case Series

RATIONALE & OBJECTIVES

Posttransplantation membranous nephropathy (MN) represents a rare complication of kidney transplantation that can be classified as recurrent or de novo. The clinical, pathologic, and immunogenetic characteristics of posttransplantation MN and the differences between de novo and recurrent MN are not well understood.

STUDY DESIGN

Multicenter case series.

SETTING & PARTICIPANTS

We included 77 patients from 5 North American and European medical centers with post-kidney transplantation MN (27 de novo and 50 recurrent). Patients with MN in the native kidney who received kidney allografts but did not develop recurrent MN were used as nonrecurrent controls (n = 43). To improve understanding of posttransplantation MN, we compared de novo MN with recurrent MN and then contrasted recurrent MN with nonrecurrent controls.

FINDINGS

Compared with recurrent MN, de novo MN was less likely to be classified as primary MN (OR, 0.04; P < 0.001) and had more concurrent antibody-mediated rejection (OR, 12.0; P < 0.001) and inferior allograft survival (HR for allograft failure, 3.2; P = 0.007). HLA-DQ2 and HLA-DR17 antigens were more common in recipients with recurrent MN compared with those with de novo MN; however, the frequency of these recipient antigens in recurrent MN was similar to that in nonrecurrent MN controls. Among the 93 kidney transplant recipients with native kidney failure attributed to MN, older recipient age (HR per each year older, 1.03; P = 0.02), recipient HLA-A3 antigen (HR, 2.5; P = 0.003), steroid-free immunosuppressive regimens (HR, 2.84; P < 0.001), and living related allograft (HR, 1.94; P = 0.03) were predictors of MN recurrence.

LIMITATIONS

Retrospective case series, limited sample size due to rarity of the disease, nonstandardized nature of data collection and biopsies.

CONCLUSIONS

De novo and recurrent MN likely represent separate diseases. De novo MN is associated with humoral alloimmunity and guarded outcome. Potential predisposing factors for recurrent MN include recipients who are older, recipient HLA-A3 antigen, steroid-free immunosuppressive regimen, and living related donor kidney.

Role of Serum and Urine Biomarkers (PLA2R and THSD7A) in Diagnosis, Monitoring and Prognostication of Primary Membranous Glomerulonephritis

Differentiating primary and secondary membranous glomerulonephritis (MGN) using biomarkers for MGN is essential in patients' diagnosis, treatment and follow-up. Although biopsy has been the primary tool in making the diagnosis, not all patients can withstand it due to its invasive nature, and it cannot be used to monitor treatment. Hence, there is the need for less invasive or even non-invasive biomarkers for effective diagnosis, treatment monitoring and prognostication. This study aimed at providing an alternative way of differentiating primary and secondary MGN using enzyme-linked immunosorbent assay (ELISA) technique for serum and urine biomarkers (M-type phospholipase A2 receptor (PLA2R) and thrombospondin type-1 domain-containing 7A (THSD7A)) for prompt diagnosis, treatment and prognosis. A total of 125 subjects, including 81 primary and 44 secondary MGN subjects, were diagnosed from January 2012 to October 2019 at Hospital Serdang and Hospital Kuala Lumpur from which 69 subjects consisting of 45 primary and 24 secondary MGN subjects participated in the study. Of these, 13 primary MGN subjects were positive for both serum and urine anti-PLA2R antibodies (Ab) whereas only one secondary MGN subject associated with hepatitis B virus was positive for both serum and urine anti-PLA2R Ab. At the same time, anti-THSD7A Ab was found positive in four primary MGN subjects and two secondary MGN subjects with malignancy.

Rituximab in Patients With Phospholipase A2 Receptor-Associated Membranous Nephropathy and Severe CKD

Introduction

Patients with phospholipase A2 receptor (PLA2R)–associated membranous nephropathy and stage 4 or 5 chronic kidney disease are at high risk of end-stage kidney disease. In recent years, rituximab (RTX) emerged as a safe and efficient treatment for patients with PLA2R-associated membranous nephropathy. Whether its use is also appropriate in patients with an estimated glomerular filtration rate <30 ml/min per 1.73 m² has not been investigated.

Methods

We retrospectively reviewed characteristics and outcome of 13 patients with PLA2R-associated membranous nephropathy and stage 4 or 5 chronic kidney disease who received a total of 14 consecutive RTX treatments from January 2012 to March 2018. The treatment regimen consisted of either 2 weekly infusions of 375 mg/m² or 2 RTX infusions of 1 g/d two weeks apart. When needed, the regimen was repeated to achieve immunological remission.

Results

The mean estimated glomerular filtration rate, serum albumin level, and urinary protein level at the first RTX infusion were 18 ± 7 ml/min per 1.73 m², 25.2 ± 5.4 g/l, and 13.2 ± 7.5 g/d, respectively, with all patients being tested positive for serum PLA2R antibodies. Ten treatment courses led to an increase in estimated glomerular filtration rate and remission of nephrotic syndrome after a median follow-up of 40.8 months (interquartile range, 14.8–46.8). Conversely, 4 RTX treatments were unsuccessful, with patients requiring chronic hemodialysis within 1 year. The urinary albumin-to-protein ratio before treatment was predictive of renal response. Immunological remission occurred after 11 treatment courses and was associated with clinical response in 10 of 11 patients. Three patients experienced severe adverse events.

Conclusion

RTX seems effective and reasonably safe in PLA2R-associated membranous nephropathy with stage 4 or 5 chronic kidney disease. Immunological remission is associated with a good clinical outcome.

Antibodies against ARHGDIB are associated with long-term kidney graft loss

The clinical significance of non-HLA antibodies on renal allograft survival is a matter of debate, due to differences in reported results and lack of large-scale studies incorporating analysis of multiple non-HLA antibodies simultaneously. We developed a multiplex non-HLA antibody assay against 14 proteins highly expressed in the kidney. In this study, the presence of pretransplant non-HLA antibodies was correlated to renal allograft survival in a nationwide cohort of 4770 recipients transplanted between 1995 and 2006. Autoantibodies against Rho GDP-dissociation inhibitor 2 (ARHGDIB) were significantly associated with graft loss in recipients transplanted with a deceased-donor kidney (N = 3276) but not in recipients of a living-donor kidney (N = 1496). At 10 years after deceased-donor transplantation, recipients with anti-ARHGDIB antibodies (94/3276 = 2.9%) had a 13% lower death-censored covariate-adjusted graft survival compared to the anti-ARHGDIB-negative (3182/3276 = 97.1%) population (hazard ratio 1.82; 95% confidence interval, 1.32-2.53; P = .0003). These antibodies occur independently from donor-specific anti-HLA antibodies (DSA) or other non-HLA antibodies investigated. No significant relations with graft loss were found for the other 13 non-HLA antibodies. We suggest that pretransplant risk assessment can be improved by measuring anti-ARHGDIB antibodies in all patients awaiting deceased-donor transplantation.

Primary Membranous Glomerulonephritis: The Role of Serum and Urine Biomarkers in Patient Management

The detection of phospholipase A2 receptor (PLA2R) and thrombospondin domain containing 7A THSD7A among primary membranous glomerulonephritis (MGN) patients transformed the diagnosis, treatment monitoring, and prognosis. Anti-PLA2R can be detected in 70-90% of primary MGN patients while anti-THSD7A in 2-3% of anti-PLA2R negative primary MGN patients depending on the technique used. Serum and urine samples are less invasive and non-invasive, respectively, and thus can detect the presence of anti-PLA2R and anti-THSD7A with higher sensitivity and specificity, which is significant in patient monitoring and prognosis. It is better than exposing patients to a frequent biopsy, which is an invasive procedure. Different techniques of detection of PLA2R and THSD7A in patients' urine and sera were reviewed to provide newer and alternative techniques. We proposed the use of biomarkers (PLA2R and THSD7A) in the diagnosis, treatment decision, and follow-up of patients with primary MGN. In addition, other prognostic renal biomarkers like retinol binding protein (RBP) and beta-2 microglobulin were reviewed to detect the progression of renal damage for early intervention.

Membranous Nephropathy Posttransplantation: An Update of the Pathophysiology and Management

Membranous nephropathy (MN) is a common cause of nephrotic syndrome after transplantation and is associated with an increased risk of allograft loss. MN may occur either as a recurrent or as a de novo disease. As in native kidneys, the pathophysiology of the MN recurrence is in most cases associated with antiphospholipid A2 receptor antibodies. However, the posttransplant course has some distinct features when compared with primary MN, including a lower chance of spontaneous remission and a greater requirement for adjuvant immunosuppressive therapy to induce complete remission. Although the efficacy of rituximab in primary MN is now well established, no randomized studies have assessed its effectiveness in MN after transplant, and there are no specific recommendations for the management of these patients. This review aims to synthesize and update the pathophysiology of posttransplant MN, as well as to address unsolved issues specific to transplantation, including the prognostic value of antiphospholipid A2 receptor, the risk of living-related donation, the link between de novo MN and rejection, and different therapeutic strategies so far deployed in posttransplant MN. Lastly, we propose a management algorithm for patients with MN who are planning to receive a kidney transplant, including pretransplant considerations, posttransplant monitoring, and the clinical approach after the diagnosis of recurrence.

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.

Membranous Nephropathy (MN) Recurrence After Renal Transplantation

Primary membranous nephropathy (MN) is a frequent cause of NS in adults. In native kidneys the disease may progress to ESRD in the long term, in some 40–50% of untreated patients. The identification of the pathogenic role of anti-podocyte autoantibodies and the development of new therapeutic options has achieved an amelioration in the prognosis of this disease. MN may also develop in renal allograft as a recurrent or a de novo disease. Since the de novo MN may have some different pathogenetic and morphologic features compared to recurrent MN, in the present paper we will deal only with the recurrent disease. The true incidence of the recurrent form is difficult to assess. This is mainly due to the variable graft biopsy policies in kidney transplantation, among the different transplant centers. Anti-phospholipase A2 receptor (PLA2R) autoantibodies are detected in 70–80% of patients. The knowledge of anti-PLA2R status before transplant is useful in predicting the risk of recurrence. In addition, the serial survey of the anti-PLA2R titers is important to assess the rate of disease progression and the response to treatment. Currently, there are no established guidelines for prevention and treatment of recurrent MN. Symptomatic therapy may help to reduce the signs and symptoms related to the nephrotic syndrome. Anecdotal cases of response to cyclical therapy with steroids and cyclophosphamide have been published. Promising results have been reported with rituximab in both prophylaxis and treatment of recurrence. However, these results are based on observational data, and prospective controlled trials are still missing.

Prognostic value of phospholipase A2 receptor in primary membranous nephropathy: a systematic review and meta-analysis

PURPOSE

We aimed to evaluate the prognostic value of serum anti-PLA2R and glomerular PLA2R deposit (gPLA2R) in predicting remission of proteinuria in Primary Membranous Nephropathy (PMN) patients.

METHODS

PUBMED, EMBASE, WEB OF SCIENCE, COCHRANE LIBRARY and CNKI were searched from 2008 January to December 2018. Heterogeneity was assessed by Cochran Q test and I². Source of heterogeneity was explored by subgroup analysis and sensitivity analysis.

RESULTS

Totally 2345 patients from 29 cohort studies were eligible for inclusion. The results suggested that PMN patients with negative anti-PLA2R at the time of biopsy had a 1.31 times (95% CI 1.12-1.46, p < 0.05) higher possibility in achieving remission than those with positive anti-PLA2R. The clearance of anti-PLA2R at the end of immunosuppressive therapy showed an even greater chance of achieving remission (RR = 2.86, 95% CI 1.75-4.69, p < 0.05). The relative ratios for complete remission and spontaneous remission with negative anti-PLA2R were 1.65 (95% CI 1.46-1.87, p < 0.05) and 1.93, respectively (95% CI 1.53-2.45, p < 0.05), and heterogeneity percentages were I² = 18% and 46%, respectively. The possibility for remission was significantly greater among PMN patients with negative gPLA2R (RR = 1.30, 95% CI 1.13-1.50, p < 0.05). Subgroup analyses revealed that retrospective design of study might be the potential source of heterogeneity.

CONCLUSIONS

Negative anti-PLA2R or gPLA2R might predict higher possibility of remission, and the presence of anti-PLA2R or gPLA2R might serve as a useful biomarker for clinical outcome and predicting response to immunosuppressive therapy in PMN.

Clinical value of a serum anti-PLA2R antibody in the diagnosis and monitoring of primary membranous nephropathy in adults

OBJECTIVE

To compare the positive rate of anti-PLA2R antibodies in patients with primary membranous nephropathy (PMN), secondary membranous nephropathy (SMN), and non-membrane nephropathy (non-MN); evaluate serum anti-PLA2R antibodies in the diagnosis of PMN; quantify the serum anti-PLA2R antibody levels during the treatment of PMN patients; and evaluate the clinical value of monitoring changes in serum anti-PLA2R antibody quantification levels.

METHODS

The kidney tissue was collected by kidney biopsy. The expression of PLA2R in glomeruli was detected by immunofluorescence, and ELISA was used to quantify the serum anti-PLA2R antibody. The positive rate of PLA2R expression in renal tissue and positive rate of the anti-PLA2R antibody in the three groups were compared and calculated using a statistical method. The specificity and coincidence rate of anti-PLA2R used in the differential diagnosis of PMN and SMN were evaluated. The clinical value of monitoring changes in serum anti-PLA2R antibody quantification levels was evaluated.

RESULT

The serum levels of the anti-PLA2R antibody were significantly higher in patients with PMN than in patients with SMN and non-MN group. The difference was statistically significant (P<0.05). The serum anti-PLA2R antibody became negative in the complete remission group. The serum anti-PLA2R antibody levels were significantly lower than before treatment in the partial remission group, and the difference was statistically significant (P<0.05). However, in the non-remission group, the serum anti-PLA2R antibody levels remained high.

CONCLUSION

Detection of the serum anti-PLA2R antibody has a high specificity for diagnosing PMN. The change of the serum anti-PLA2R antibody level is closely related to the status of the PMN: if the anti-PLA2R antibody level has decreased, it indicates that the condition has improved; and if the serum anti-PLA2R antibody continues to show high levels of positive or quantitative increase, the condition is not in remission or has relapsed.

Anti-CD20 Blocker Rituximab in Kidney Transplantation

Rituximab is a chimeric anti-CD20 monoclonal protein used in various clinical scenarios in kidney transplant recipients. However, its evidence-based use there remains limited due to lack of controlled studies, limited sample size, short follow-up and poorly defined endpoints. Rituximab is indicated for CD20+ posttransplant lymphoproliferative disorder. It may be beneficial for treating recurrent membranous nephropathy and recurrent allograft antineutrophilic cytoplasmic antibody vasculitis and possibly for recurrent focal segmental glomerulosclerosis. Rituximab, in combination with IVIg/plasmapheresis, appears to decrease antibody level and increase the odds of transplantation in sensitized recipients. The role of Rituximab in ABOi transplant remains unclear, as similar outcomes are achieved without its use. Rituximab is not efficacious in antibody-mediated rejection/chronic antibody-mediated rejection. Strict randomized control trials are necessary to elucidate its true role in these settings.

[Current insights about recurrence of glomerular diseases after renal transplantation]

Recurrence of glomerular disease after renal transplantation is a frequent cause of graft loss. Incidence, risk factors and outcome of recurrence are widely due to the underlying glomerular disease. Graft biopsy analysis is required to confirm the definitive diagnosis of recurrence and to start an appropriate therapy that, in some cases, remains challenging to prevent graft failure. Increased use of protocol biopsy and recent advances in our understanding of the pathogenesis of some glomerular diseases with the identification of some relevant biomarkers provide a unique opportunity to initiate kidney-protective therapy at early stages of recurrence on the graft. This review summarizes our current knowledge on the management of many recurrent primary and secondary glomerulonephritis after kidney transplantation.

The Most N-Terminal Region of THSD7A Is the Predominant Target for Autoimmunity in THSD7A-Associated Membranous Nephropathy

Background Thrombospondin type 1 domain-containing 7A (THSD7A) has been identified as a pathogenic autoantigen in membranous nephropathy (MN). However, the THSD7A epitopes targeted by patient autoantibodies are unknown.Methods We performed an in silico analysis of the THSD7A multidomain structure, expressed the folded domains in HEK293 cells, and tested for domain reactivity with 31 serum samples from patients with THSD7A-associated MN using Western and native blotting. Immunogenicity of the antigen domains was further investigated by cDNA immunization of rabbits and mice.Results We characterized the extracellular topology of THSD7A as a tandem string of 21 thrombospondin type 1 domains. Overall, 28 serum samples (90%) recognized multiple epitope domains along the molecule. Detailed epitope mapping revealed that the complex consisting of the first and second N-terminal domains (amino acids 48-192) was recognized by 27 of 31 patient serum samples (87%). Serum recognizing one or two epitope domains showed lower anti-THSD7A antibody levels than serum recognizing three or more epitope domains. During follow-up, a loss of epitope recognition was observed in seven of 16 patients, and it was accompanied by decreasing antibody levels and remission of proteinuria. In four of 16 patients, epitope recognition patterns changed during follow-up. Notably, immunization experiments in rabbits and mice revealed that induced antibodies, like patient autoantibodies, preferentially bound to the most N-terminal domains of THSD7A.Conclusions Our data show that the immune response in THSD7A-associated MN is polyreactive and that autoantibodies predominantly target the most N-terminal part of THSD7A.

Membranous Nephropathy and Anti-Podocytes Antibodies: Implications for the Diagnostic Workup and Disease Management

The discovery of circulating antibodies specific for native podocyte antigens has transformed the diagnostic workup and greatly improved management of idiopathic membranous nephropathy (iMN). In addition, their identification has clearly characterized iMN as a largely autoimmune disorder. Anti-PLA2R1 antibodies are detected in approximately 70% to 80% and anti-THSD7A antibodies in only 2% of adult patients with iMN. The presence of anti-THSD7A antibodies is associated with increased risk of malignancy. The assessment of PLA2R1 and THSD7A antigen expression in glomerular immune deposits has a better sensitivity than measurement of the corresponding autoantibodies. Therefore, in the presence of circulating anti-podocytes autoantibodies and/or enhanced expression of PLA2R1 and THSD7A antigens MN should be considered as primary MN (pMN). Anti-PLA2R1 or anti-THSD7A autoantibodies have been proposed as biomarkers of autoimmune disease activity and their blood levels should be regularly monitored in pMN to evaluate disease activity and predict outcomes. We propose a revised clinical workup flow for patients with MN that recommends assessment of kidney biopsy for PLA2R1 and THSD7A antigen expression, screening for circulating anti-podocytes antibodies, and assessment for secondary causes, especially cancer, in patients with THSD7A antibodies. Persistence of anti-podocyte antibodies for 6 months or their increase in association with nephrotic proteinuria should lead to the introduction of immunosuppressive therapies. Recent data have reported the efficacy and safety of new specific therapies targeting B cells (anti-CD20 antibodies, inhibitors of proteasome) in pMN which should lead to an update of currently outdated treatment guidelines.

The utility of phospholipase A2 receptor autoantibody in membranous nephropathy after kidney transplantation

Membranous nephropathy (MN) is estimated to cause end-stage renal disease in ∼ 5% of patients, in whom renal transplantation is the therapy of choice. Among patients receiving a transplant for MN, the disease will recur in the graft in 30–50%; among these, graft loss will occur in 50% within 10 years. Several studies have suggested that phospholipase A2 receptor autoantibody (aPLA2R) levels before transplantation might be useful in predicting recurrence, and their titration after transplantation is clinically relevant to assess the risk of recurrence and progression, to guide treatment indications and to monitor treatment response. In this review we describe the evolving role of aPLA2R as a biomarker in primary MN and its current usefulness in predicting recurrence of this autoimmune podocytopathy after renal transplantation.

Recent Progress in Deciphering the Etiopathogenesis of Primary Membranous Nephropathy

Primary membranous nephropathy (MN) is the leading cause of nephrotic syndrome in adults. Discovery of several antibodies has contributed to an increased understanding of MN. Antibodies against the M-type phospholipase A2 receptor (PLA2R) are present in 50-100% with primary MN and are associated with a lower frequency of spontaneous remission. High levels are linked with a higher probability of treatment resistance, higher proteinuria, and impaired renal function, as well as a more rapid decline of kidney function during follow-up. Immunologic remission precedes reduction of proteinuria by months. Pretransplant evaluation of PLA2R antibodies is warranted to predict recurrence of disease following renal transplantation. Several risk alleles related to the PLA2R1 gene and within the HLA loci have been identified, whereas epitope spreading of PLA2R may predict treatment response. More recently, thrombospondin type 1 domain-containing 7A (THSD7A) antibodies have been discovered in primary MN. Several other rare antigens have been described, including antibodies against neutral endopeptidase as a cause of antenatal MN and circulating cationic bovine serum albumin as an antigen with implications in childhood MN. This review focuses on the progress with a special focus on diagnostic accuracy, predictive value, and treatment implications of the established and proposed antigens.

Primary Membranous Nephropathy

Membranous nephropathy (MN) is a unique glomerular lesion that is the most common cause of idiopathic nephrotic syndrome in nondiabetic white adults. About 80% of cases are renal limited (primary MN, PMN) and 20% are associated with other systemic diseases or exposures (secondary MN). This review focuses only on PMN. Most cases of PMN have circulating IgG4 autoantibody to the podocyte membrane antigen PLA2R (70%), biopsy evidence PLA2R staining indicating recent immunologic disease activity despite negative serum antibody levels (15%), or serum anti-THSD7A (3%-5%). The remaining 10% without demonstrable anti-PLA2R/THSd7A antibody or antigen likely have PMN probably secondary to a different, still unidentified, anti-podocyte antibody. Considerable clinical and experimental data now suggests these antibodies are pathogenic. Clinically, 80% of patients with PMN present with nephrotic syndrome and 20% with non-nephrotic proteinuria. Untreated, about one third undergo spontaneous remission, especially those with absent or low anti-PLA2R levels, one-third progress to ESRD over 10 years, and the remainder develop nonprogressive CKD. Proteinuria can persist for months after circulating anti-PLA2R/THSD7A antibody is no longer detectable (immunologic remission). All patients with PMN should be treated with supportive care from the time of diagnosis to minimize protein excretion. Patients with elevated anti-PLA2R/THSD7A levels and proteinuria >3.5 g/d at diagnosis, and those who fail to reduce proteinuria to <3.5 g after 6 months of supportive care or have complications of nephrotic syndrome, should be considered for immunosuppressive therapy. Accepted regimens include steroids/cyclophosphamide, calcineurin inhibitors, and B cell depletion. With proper management, only 10% or less will develop ESRD over the subsequent 10 years.

A Proposal for a Serology-Based Approach to Membranous Nephropathy

Primary membranous nephropathy (MN) is an autoimmune disease mainly caused by autoantibodies against the recently discovered podocyte antigens: the M-type phospholipase A2 receptor 1 (PLA2R) and thrombospondin type 1 domain-containing 7A (THSD7A). Assays for quantitative assessment of anti-PLA2R antibodies are commercially available, but a semiquantitative test to detect anti-THSD7A antibodies has been only recently developed. The presence or absence of anti-PLA2R and anti-THSD7A antibodies adds important information to clinical and immunopathologic data in discriminating between primary and secondary MN. Levels of anti-PLA2R antibodies and possibly, anti-THSD7A antibodies tightly correlate with disease activity. Low baseline and decreasing anti-PLA2R antibody levels strongly predict spontaneous remission, thus favoring conservative therapy. Conversely, high baseline or increasing anti-PLA2R antibody levels associate with nephrotic syndrome and progressive loss of kidney function, thereby encouraging prompt initiation of immunosuppressive therapy. Serum anti-PLA2R antibody profiles reliably predict response to therapy, and levels at completion of therapy may forecast long-term outcome. Re-emergence of or increase in antibody titers precedes a clinical relapse. Persistence or reappearance of anti-PLA2R antibodies after kidney transplant predicts development of recurrent disease. We propose that an individualized serology-based approach to MN, used to complement and refine the traditional proteinuria-driven approach, will improve the outcome in this disease.