Demographic, clinical characteristics and treatment outcomes of immune-complex membranoproliferative glomerulonephritis and C3 glomerulonephritis in Japan: A retrospective analysis of data from the Japan Renal Biopsy Registry

Expert Discussion on Immune Complex-Mediated Membranoproliferative Glomerulonephritis: Challenges and Considerations

Immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) is a rare pattern of kidney injury and a progressive nephropathy characterized by the glomerular deposition of immune complexes and complement proteins. The IC-MPGN pattern of injury exhibits a membranoproliferative glomerulonephritis appearance by light microscopy and occurs secondary to various conditions or, more rarely, idiopathically, when no underlying etiology can be determined. Kidney biopsy is the only method for identifying IC-MPGN, distinguishing between IC-MPGN and complement 3 glomerulopathy (C3G), and for providing critical pathologic insights that guide further clinical evaluation for underlying etiologies and inform patient management. Given the progressive nature of IC-MPGN, it is crucial to identify patients early and to define the underlying pathophysiology for timely and appropriate treatment. However, several challenges remain in the accurate interpretation of kidney biopsy specimens and the effective treatment of idiopathic disease. In this commentary, two nephrologists and a nephropathologist review best practices in the clinical and histopathologic evaluation of IC-MPGN and discuss the central role of kidney biopsy in the differentiation of IC-MPGN and C3G. The challenges and considerations discussed are explored through an illustrative case of idiopathic disease, drawn from the authors' clinical experiences. Finally, remaining unmet needs are highlighted, and future perspectives on targeted treatments under investigation for patients with idiopathic IC-MPGN are provided.

Clinical characteristics and short term outcomes of childhood immune complex membranoproliferative glomerulonephritis and C3 glomerulopathy: a single centre retrospective study

BACKGROUND

Membranoproliferative glomerulonephritis, with its immune complex variety and C3 glomerulopathy, is a rare glomerular disease in children. The objective of this study was to determine the clinical features and short-term outcomes in children.

METHODS

This retrospective cohort study was conducted at the Department of Pediatric Nephrology, Sindh Institute of Urology and Transplantation, Karachi, from January 2020, to June 2022. All the children with membranoproliferative lesions identified via light microscopy and less than 18 years were included.

RESULTS

A total of 35 children were diagnosed MPGN, 7 (20%) with C3 glomerulopathy and 28 (80%) idiopathic immune complex MPGN. In the IC-MPGN group, 14 patients (50%) had crescentic glomerulonephritis. Induction therapy consisted of cyclophosphamide and methylprednisolone followed by steroids, azathioprine was prescribed for maintenance phase. At the 18-month follow-up, 9 (64%) patients were in complete remission (CR), 3 (21%) were in partial remission (PR), and 2 (15%) progressed to chronic kidney disease. The remaining 14 (50%) had non-crescentic idiopathic IC-MPGN and were prescribed steroids only, cyclophosphamide with steroids and angiotensin converting enzyme inhibitors. The outcomes at 18 months were relatively poorer than those with the crescentic variety. Four (28%) patients achieved CR, 8 (56%) PR, and 2 (14%) did not respond. In the C3 glomerulopathy cohort, 3 (43%) had crescentic glomerulonephritis, one child was in CR, and two were in PR. The non-crescentic C3G were kept on ACEI 3 (43%) and Mycophenolate mofetil 1 (14%). One child treated with ACEIs achieved a PR, two were in CR, and one child treated with MMF did not respond.

CONCLUSIONS

The outcome of MPGN (immune complex and C3G) is quite variable, and aggressive therapy for crescentic glomerulonephritis may show a favourable response. Considering the similar clinical presentations and patient outcomes, C3G and IC-MPGN might represent two facets of the same disease.

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

Introduction

Approximately 50% of patients with C3 glomerulopathy (C3G) and primary immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) reach kidney failure 10 years after diagnosis. Because these patients are generally young, the majority will be listed for kidney transplantation (KTx). However, reported outcomes in patients transplanted for C3G and IC-MPGN are heterogeneous and conflicting, because they are mainly based on retrospective monocentric studies. We thus aimed to provide detailed multicenter data on these patients, taking advantage of the ongoing nationwide Swiss Transplant Cohort Study (STCS).

Methods

We analyzed patient and graft outcomes, including the risk of graft loss in relation to recurrence of glomerulopathy.

Results

Forty-one (10 C3G and 31 IC-MPGN) transplanted recipients were included with a mean age at transplantation of 48 ± 16 years. Living donors provided 53% of the organs. During a mean follow-up of 4.7 years, 7 patients (4 C3G and 3 IC-MPGN) presented disease recurrence with a mean time to recurrence of 1.2 years. New-onset or rapidly increasing proteinuria was an early marker of recurrence, preceding significant decline in estimated glomerular filtration rate (eGFR). Following recurrence, 28% lost their graft, compared to 11% of patients without recurrence. Disease recurrence was the primary cause of graft loss in all patients. Finally, 14% of patients died during follow-up.

Conclusion

This study provides important insights into the epidemiology and outcome of patients with C3G and IC-MPGN and their grafts after KTx. The data also suggest that proteinuria may serve as an early biomarker of disease recurrence and should be considered in patient management as well as an endpoint in current clinical trials using novel complement modulators.

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.

Short-term renal and patient outcomes of primary immunoglobulin-associated mesangiocapillary glomerulonephritis: Insights from a developing country

BACKGROUND

Primary immunoglobulin (Ig)-associated mesangiocapillary glomerulonephritis (Ig-MCGN) is an immune complex glomerulonephritis of unknown etiology. It is a common cause of chronic kidney disease in developing countries. There is limited data available on renal and patient outcomes of this disease from developing countries.

AIM

To determine the short-term renal and patient outcomes of adults with a tissue-confirmed diagnosis of primary Ig-MCGN at a single center in Pakistan.

METHODS

A retrospective cohort study of adult patients was conducted on biopsy-proven Ig-MCGN cases diagnosed between 1998 and 2019 at the Sindh Institute of Urology and Transplantation, Karachi, Pakistan. Secondary causes were excluded. The primary endpoint was renal survival without end-stage kidney disease (ESKD) or mortality. The secondary endpoint was the rate of remission during the 2-year follow-up period. Survival curves were made with the use of Kaplan-Meier estimates.

RESULTS

A total of 163 patients were included in the study and their mean follow-up duration was 29.45 months ± 21.28 months. Among baseline characteristics, young age, lower estimated glomerular filtration rate, requirement of kidney replacement therapy, presence of crescents, and severity of interstitial fibrosis and tubular atrophy were found to have a significant association with renal outcomes. The renal outcomes were negatively correlated with the presence of hypertension, level of complements, and degree of proteinuria. In all, 63 (37.4%) patients were treated with steroids and 21 (13%) received combination therapy (cyclophosphamide with steroids). At 2 years, 124 (76.07%) patients were in complete remission or partial remission [56 (34.3%) and 68 (41.71%), respectively], while 32 (19.63%) patients progressed to ESKD and 7 (4.29%) patients died.

CONCLUSION

The outcomes of primary Ig-MCGN are guarded in Pakistan and require further prospective studies to improve our understanding of this relatively common disease so that more personalized treatment approaches can be developed.

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

BACKGROUND

The classification of membranoproliferative glomerulonephritis (MPGN) into immune complex-mediated MPGN and complement-mediated MPGN on immunofluorescence has provided insights into two distinct disease processes. There are limited data available on renal outcomes of MPGN from developing countries.

METHODS

A retrospective analysis was conducted on biopsy-proven MPGN cases diagnosed between 1998 and 2018 at the Sindh Institute of Urology and Transplantation (SIUT). Secondary causes were excluded. Patients were reclassified as immune complex-mediated-MPGN and complement-mediated-MPGN based on immunofluorescence results. The clinicopathological findings and outcomes of the two groups were compared.

RESULTS

In total, 213 patients with idiopathic MPGN were identified. Among these, 163 (76.5%) were reclassified as immune complex-mediated-MPGN and 50 (23.4%) as complement-mediated-MPGN. No significant differences were found between the two groups regarding age, gender, clinical characteristics, biopsy indications, biopsy findings, and renal function at presentation. Overall, 63 subjects (38.7%) with immune complex-mediated-MPGN and 27 (54%) with complement-mediated-MPGN received immunosuppressive agents (p = 0.08). Complete and partial remission rates were higher in immune complex-mediated-MPGN than in complement-mediated-MPGN (76% vs 58%, p < 0.05). At two years, median estimated glomerualr filtration rate (eGFR) tended to be higher in patients with immune complex-mediated-MPGN 91.2 (45.4-113.7) vs 83.45(34.6-102.50) ml/min/1.73 m2, p = 0.22) with significantly better renal survival (76% vs 58%, p = 0.03). Comparatively, more patients progressed to end-stage kidney disease (ESKD) in the complement-mediated-MPGN group (32% vs 19.6%, p = 0.06), with increased overall mortality (5 (10%) vs 7 (4.3%), p = 0.12).

CONCLUSION

The clinicopathological features at presentation of complement-mediated-MPGN are similar to those of immune complex-mediated-MPGN. However, it is less frequent and overall prognosis is less favorable.

Demographics and treatment of patients with primary membranoproliferative glomerulonephritis in Japan using a national registry of clinical personal records

BACKGROUND

Membranoproliferative glomerulonephritis (MPGN) is a rare glomerular injury that causes nephrotic syndrome and end-stage kidney disease. The nationwide demographics and treatment of Japanese patients with primary MPGN have not yet been reported.

METHODS

We collected clinical personal records of patients with primary MPGN between 2015 and 2018 from the national registry organized by the Japanese Ministry of Health, Labour, and Welfare and investigated the characteristics of primary MPGN throughout Japan.

RESULTS

Of 258 patients with primary MPGN, 199 and 59 showed nephrotic and non-nephrotic syndrome, respectively. The median age at onset was higher in patients with nephrotic syndrome than in those with non-nephrotic syndrome (45 [24-63] vs. 35 [14-53] years, respectively; P = 0.010). The use of oral prednisolone was significantly higher in patients with nephrotic syndrome than in those with non-nephrotic syndrome (73.9% vs. 59.3%, respectively; P = 0.032). When patients were divided into three age groups: adolescent and young adult group (≤ 39 years; n = 80), middle adult group (40-64 years; n = 111), and older adult group (≥ 65 years; n = 67), the use of oral prednisolone, cyclosporine, and mizoribine was significantly higher in the adolescent and young adult group than in the middle adult group. The mean dosage of oral prednisolone and mizoribine showed no differences among the three age groups.

CONCLUSION

The national registry of clinical personal records of primary MPGN could provide an informative insight into the characteristics, clinical features, and treatment approaches for patients with primary MPGN in Japan.

Demographics and treatment of patients with primary nephrotic syndrome in Japan using a national registry of clinical personal records

The nationwide clinical features of Japanese patients with primary nephrotic syndrome (NS), including minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), or membranous nephropathy (MN), have not yet been reported. We collected the clinical personal records of patients with primary NS between 2015 and 2018 from the national registry organized by the Japanese Ministry of Health, Labour, and Welfare. Overall, the demographics, chronic kidney disease classification based on glomerular filtration rate and albuminuria, and treatment of 6036 patients were collected: 3394 (56.2%) with MCD, 677 (11.2%) with FSGS, 1455 (24.1%) with MN, and 510 (8.5%) with others. MN patients were older than MCD and FSGS patients (67 vs. 42 and 47 years, respectively). Steroid-dependent NS or frequently relapsing NS was found in 70.2%, 40.5%, and 24.6%, whereas steroid-resistant NS was found in 6.4%, 36.0%, and 37.9% of patients in the MCD, FSGS, and MN, respectively. The present oral prednisolone use (mean dose, mg/day) was 87.2% (21.2), 80.9% (20.0), and 77.5% (18.8) of patients in the MCD, FSGS, and MN, respectively. The national registry of clinical personal records of primary NS could provide an informative insight into the characteristics, clinical features, and treatment approaches for patients with primary NS in Japan.

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.

C3 glomerulopathy: Understanding an ultra-rare complement-mediated renal disease

C3 glomerulopathy (C3G) describes a pathologic pattern of injury diagnosed by renal biopsy. It is characterized by the dominant deposition of the third component of complement (C3) in the renal glomerulus as resolved by immunofluorescence microscopy. The underlying pathophysiology is driven by dysregulation of the alternative pathway of complement in the fluid-phase and in the glomerular microenvironment. Characterization of clinical features and a targeted evaluation for indices and drivers of complement dysregulation are necessary for optimal patient care. Autoantibodies to the C3 and C5 convertases of complement are the most commonly detected drivers of complement dysregulation, although genetic mutations in complement genes can also be found. Approximately half of patients progress to end-stage renal disease within 10 years of diagnosis, and, while transplantation is a viable option, there is high risk for disease recurrence and allograft failure. This poor outcome reflects the lack of disease-specific therapy for C3G, relegating patients to symptomatic treatment to minimize proteinuria and suppress renal inflammation. Fortunately, the future is bright as several anti-complement drugs are currently in clinical trials.

Remissions and progression of C3 glomerulopathy

Aim. To analyze the outcomes of C3-glomerulopathy (C3-GP) and determine the associated factors. Materials and methods. A retrospective single-center study included 60 patients with newly diagnosed C3-GP (with primary C3-GP pC3-GP 82%). Of these, 48 (80%) patients had clinical data to assess the following disease outcomes: development of remission and disease progression (by a composite endpoint that included initiation of chronic dialysis or a decrease in estimated glomerular filtration rate eGFR 15 mL/min/1.73 m2 or a decrease in eGFR30% of baseline at the time of renal biopsy). The median follow-up period was 25 (7; 52) months. Results. At early follow-up (median 4 [3; 9] months) remission was registered in 35% of patients; at the end of follow-up, in 48% (for pC3-GP, 32 and 41%). Disease progression occurred in 17 patients. In the overall group the likelihood of achieving early remission was higher with treatment (Exp=6.4, 95% confidence interval CI 1.429.3; p=0.017). Early remission was associated with the presence of remission at the end of follow-up (Exp=6.3, 95% CI 2.218.4; p=0.001). Specific treatment (Exp=0.308, 95% CI 0.1080.881; p=0.028) and late remission (Exp=0.079, 95% CI 0.0170.368; p=0.001) were associated with reduced risk of disease progression in multivariable models (adjusted for eGFR, mean blood pressure). The same results were obtained for the group of patients with pC3-GP. Conclusion. C3-GP is a variant of severe complement-mediated glomerular damage with unfavorable renal prognosis, which requires timely personalized expert-level diagnostics with clarification of etiopathogenesis of the disease followed by therapy aimed at achieving remission to improve outcomes.

New-onset and relapse of nephrotic syndrome following COVID-19 vaccination: a questionnaire survey in Japan

Background

Recent clinical reports indicate a correlation between new-onset and relapse of nephrotic syndrome (NS) following coronavirus 2019 (COVID-19) vaccination in patients with glomerular diseases. However, there are no reports of a nationwide survey on NS following COVID-19 vaccination in Japan.

Methods

We conducted a web-based survey of council members of the Japanese Society of Nephrology (581 members, 382 facilities) to elucidate the relationship between COVID-19 vaccination and new-onset and relapse of NS.

Results

Following COVID-19 vaccination, 27 patients (male: 15, 55.6%) with new-onset (n = 6) and relapse (n = 21) of NS were reported. Of them, 12 (44.4%) patients were diagnosed with minimal change disease at the occurrence of NS. Five patients developed a slight increase in serum creatinine levels; however, none progressed to severe renal dysfunction.

Conclusion

Our findings clarify the clinical features of new-onset and relapse of NS following COVID-19 vaccination. Although there was no obvious progression to severe renal dysfunction, clinicians and pathologists should be aware that NS is a potential adverse effect of the vaccines.