Clinico-pathologic spectrum of C3 glomerulopathy-an Indian experience

C3 glomerulopathy in children: experience at a resource-limited center

BACKGROUND

In children, C3 glomerulopathy (C3G) is a heterogeneous disease characterized by diverse clinicopathological profiles and kidney outcomes. However, diagnostic work-up in resource-limited settings is challenging because of the unavailability of complement assays and limited access to electron microscopy or genetic testing.

PURPOSE

This study aimed to describe the clinicopathological features and response to immunosuppression and evaluate renal outcomes among children with C3G in a resource-limited setting.

METHODS

This retrospective cohort study involved a review of the hospital records of 46 children (2013-2021) diagnosed with C3G on kidney biopsy. Their clinical, laboratory, treatment, and outcome details at onset and follow-up were noted.

RESULTS

The mean (standard deviation) age was 9 (4) years. The common presentation was acute nephritis (27 [58.6%]), while 1 in 5 (19.5%) presented with rapidly progressive glomerulonephritis. Focal crescentic glomerulonephritis (14 [30.4%]) was the common histological pattern. Electron microscopy was performed in 22 (47.8%), of which 17 were C3 glomerulonephritis and 4 were dense deposit disease (DDD). None of the patients underwent complement assay or genetic testing. Almost two-thirds (63%) received empirical immunosuppressive therapy, most commonly steroids. Of the 31/46 who completed follow-up (median [interquartile range] duration, 11.5 [6-24] months), 6 (19.4%) demonstrated complete kidney recovery, while the other 25 (80.7%) had kidney sequelae; of them, 5 (16.1%) progressed to end-stage kidney disease and 2 (4.3%) died by the last follow-up.

CONCLUSION

Pediatric C3G has a variable clinicopathological spectrum, while DDD is less common. Most patients present with glomerulonephritis and significant morbidities. The lack of genetic and C3Nephritic factor testing is a barrier to the comprehensive phenotyping and management of C3G in resource-limited settings.

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.

Long-term follow-up including extensive complement analysis of a pediatric C3 glomerulopathy cohort

BACKGROUND

C3 glomerulopathy (C3G) is a rare kidney disorder characterized by predominant glomerular depositions of complement C3. C3G can be subdivided into dense deposit disease (DDD) and C3 glomerulonephritis (C3GN). This study describes the long-term follow-up with extensive complement analysis of 29 Dutch children with C3G.

METHODS

Twenty-nine C3G patients (19 DDD, 10 C3GN) diagnosed between 1992 and 2014 were included. Clinical and laboratory findings were collected at presentation and during follow-up. Specialized assays were used to detect rare variants in complement genes and measure complement-directed autoantibodies and biomarkers in blood.

RESULTS

DDD patients presented with lower estimated glomerular filtration rate (eGFR). C3 nephritic factors (C3NeFs) were detected in 20 patients and remained detectable over time despite immunosuppressive treatment. At presentation, low serum C3 levels were detected in 84% of all patients. During follow-up, in about 50% of patients, all of them C3NeF-positive, C3 levels remained low. Linear mixed model analysis showed that C3GN patients had higher soluble C5b-9 (sC5b-9) and lower properdin levels compared to DDD patients. With a median follow-up of 52 months, an overall benign outcome was observed with only six patients with eGFR below 90 ml/min/1.73 m² at last follow-up.

CONCLUSIONS

We extensively described clinical and laboratory findings including complement features of an exclusively pediatric C3G cohort. Outcome was relatively benign, persistent low C3 correlated with C3NeF presence, and C3GN was associated with higher sC5b-9 and lower properdin levels. Prospective studies are needed to further elucidate the pathogenic mechanisms underlying C3G and guide personalized medicine with complement therapeutics.

C3 glomerulopathy: experience of a pediatric nephrology center

Background: C3 glomerulopathy (C3G) is an uncommon disease characterized by the deposition of complement factors in the glomeruli due to overactivation and dysregulation of the alternative pathway of complement.Objectives: This study aimed to describe the clinicopathological features, laboratory testing, clinical course, treatment, and outcomes of pediatric patients with C3G.Patients and Methods: We reviewed retrospectively the laboratory testing, kidney biopsy reports, and clinical features of 18 patients at our hospital from 2007 to 2019.Results: There were 18 cases, and the majority of the patients were girls (61.1%). The mean age at diagnosis was 11.3 ± 3.7 (5-17) years, and nephritic-nephrotic syndrome presentation in patients was more common (11 cases, 61.1%). Hematuria was found in 66.7% of the patients, of which the majority had microscopic hematuria (58.3%). Hypertension was observed in 10 (55.6%) patients. The mean glomerular filtration rate (eGFR) was 95.7 ± 47.3 mL/min/1.73 m², and 24-h urinary protein excretion was 76.2 ± 48.6 mg/m²/h. Sixteen patients (88.9%) received renin-angiotensin-aldosterone system blockers (RASB), and two of them were taking RASB only. The majority of patients (83.3%) were treated with immunosuppressive therapy. Eculizumab was also given to one of them. At the last follow-up, two patients had levels of less than 60 mL/min/1.73 m² for eGFR. Seven patients with immunosuppressive treatment achieved complete remission.Conclusion: C3G shows a variable clinical presentation and response to immunosuppressive therapy. In the present study, we observed that the most common presentation was nephritic and/or nephrotic syndrome and partially responded to treatment to RASB and immunosuppressants.

Pediatric C3 glomerulopathy: a 12-year single-center experience

BACKGROUND

Complement component 3 glomerulopathy (C3G) is a disease with limited data in children. We aimed to compare childhood C3G cases with adults. We also studied subgroups of pediatric C3G and predictors of poor outcome.

METHODS

This is a 12-year retrospective, single-center cohort, observational study. All cases of C3G were defined based on the 2013 consensus guidelines.

RESULTS

C3G was diagnosed in 162 patients (119 adults, 43 pediatric) predominantly affecting males. With varied light microscopic patterns, pediatric C3G cases were categorized as follows: 23 C3 glomerulonephritis (C3GN) and 11 dense deposit disease (DDD) on electron microscopy. The pediatric DDD patients were relatively younger with more severe disease at presentation (more crescents in biopsy) but with lesser chronicity in biopsy compared with pediatric C3GN patients; however, both had a similar outcome. On comparing pediatric and adult C3G cases, adults had lower median eGFR and a higher degree of chronicity in the biopsy. The prognosis of C3G was better in pediatric patients. Predictors of kidney failure in pediatric C3G were low eGFR (HR = 0.82, p = 0.05) and severe interstitial fibrosis/tubular atrophy (HR = 1.05, p = 0.02).

CONCLUSIONS

Electron microscopy-based subgroups of pediatric C3G differ in clinical presentation and course of the disease but have similar prognosis and long-term outcomes. Pediatric C3G differs from adult C3G with respect to presentation, laboratory results, biopsy features, treatment, and outcome, and as such, it should be considered as a separate entity rather than a smaller version of adult C3G.

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.

Clinicopathological Significance and Renal Outcomes of Light Microscopic Patterns in Complement Component 3 Glomerulopathy

BACKGROUND

Complement component 3 glomerulopathy (C3G) is a disease diagnosed based on the predominance of C3 immunostaining in glomeruli. The popular electron microscopic subtyping of C3G into dense deposit disease and C3 glomerulonephritis (GN) is not without limitations. We aimed to study the light microscopic (LM) patterns of C3G along with their clinicopathological correlation and treatment outcome.

METHODS

C3G biopsies were classified into 4 LM patterns (membranoproliferative GN [MPGN], mesangial proliferative GN [MesPGN], diffuse proliferative GN [DPGN], and crescentic GN [CrGN]). These patterns were compared for clinicopathological profile, treatment outcome, and renal survival. Further, predictors of end-stage renal disease (ESRD) were determined using the Cox proportional hazards model.

RESULTS

Of 162 biopsies, there were 83 MPGN, 36 DPGN, 22 MesPGN, and 21 CrGN. Majority of the patients were young, with males being more than females. About half (48%) of the patients received immunosuppression, steroids alone (29%) or steroids with other immunosuppressants (19%). The overall remission rate was 32.7% (median follow-up = 14 months). CKD developed in 46 patients and 31 patients progressed to ESRD. Predictors of progression to ESRD were older age (hazard ratio [HR] = 1.04, p < 0.01), advanced renal failure at presentation (HR = 3.73, p < 0.01), glomerulosclerosis (HR = 5.07, p < 0.01), and severity of interstitial fibrosis and tubular atrophy (HR = 8.25, p = 0.01).

CONCLUSIONS

The LM patterns differed in their clinicopathological profiles, without any significant difference in their renal outcomes. Glomerulosclerosis and interstitial fibrosis portend a poor prognosis. Besides CrGN, MesPGN pattern of C3G presented as a severe form of disease.

Clinico-pathological Profile and Outcome of C-3 Glomerulopathy in Indian Children

Introduction:

There is paucity of data of C3 glomerulopathy in Indian children.

Methods:

First Indian pediatric case series where consecutive renal biopsies done over a period of ten years were reviewed to identify those patients who had isolated or predominant C3 deposits on immunofluorescent microscopy, fulfilling the criteria for C-3 glomerulopathy. The clinical, biochemical, serological, histopathological profile, eGFR and the need for renal replacement therapy was analyzed.

Results:

Eighteen patients, comprising 5.3% (18/298) of all renal biopsies, had C3 glomerulopathy, four with Dense Deposit Disease (DDD) and fourteen with C3 Glomerulonephritis (C3GN) with a median follow-up of 38.2 months. Median age of presentation was 7.45±3.03 years (2.5yrs- 13.5yrs) with nine boys and nine girls. Presentation was nephrotic syndrome in seven (39%), acute nephritic syndrome in three (16.7%), hematuria in five (27.7%) and acute kidney injury in three (16.7%). Median eGFR was 69 ml/min/1.73m² (8.2-107 ml/min/1.73m²). Hematuria was seen in 16 (88%), proteinuria in 18 (100%) and low C3 in 16 (88%) at the time of presentation. Mesangioproliferative glomerulonephritis was the predominant pattern in DDD while C3GN showed a mix of mesangioproliferative, membranoproliferative, endocapillary and crescentic GN (p = 0.43).Complete or partial remission was seen in seven patients who received long term alternate day steroids alone or with added mycophenolate mofetil. The cumulative patient survival was 70.8%. Kaplan Meir analyses for renal survival without progression to ESRD was 60.2% at one year and 48.1% at five and ten years.

Conclusion:

Interstitial fibrosis and tubular atrophy on renal biopsy was an independent predictor of adverse renal outcome in the cohort (p = 0.013, HR8.1;95% CI -1.6-42).

Poor allograft outcome in Indian patients with post-transplant C3 glomerulopathy

Background

Complement 3 glomerulopathy (C3G) results from dysfunction of the alternative complement pathway (ACP). No data are available on post-transplant C3G in South Asia.

Methods

In this study, renal allograft biopsies of C3G patients performed from 2012 to 2017 were analysed for ACP functional assay (APFA), serum complement levels, complement factor H (CFH), complement factor B (CFB) and autoantibodies to CFH and CFB. Limited genetic screening for CFH/CFHR5 genes was carried out. All study patients were also followed up.

Results

A total of 21 cases of C3G were included, of which 11 had native C3G disease (that is, recurrent C3G). Of these 11 recurrent cases, 7 presented with allograft dysfunction and 4 with proteinuria and renal dysfunction. Early post-transplant recurrence (<1 month) was noted in six patients, whereas recurrence in five patients occurred within 8–17 months of transplant. Biopsies showed mild focal mesangial expansion with or without endocapillary proliferation and thrombotic microangiopathy. Rejection was also noted in six patients. APFA/C3 levels were low in all cases. Serum CFH levels were low [dense deposit disease (DDD), 44%; C3 glomerulonephritis (C3GN), 25%], whereas CFB levels were normal. Autoantibodies to CFH, CFB and C3 nephritic factor were present in 11, 0 and 44% of DDD cases, respectively, and in 17, 17 and 33% of C3GN cases, respectively. Genetic analysis revealed only non-pathogenic CFH gene variants (93%). No novel mutation was found. At follow-up (140 months), stable graft was noted in 28% of cases, progressive renal failure in 19%, graft loss in 34%, and 19% of patients died.

Conclusion

Post-transplant C3G can present with graft dysfunction and/or proteinuria. Subtle histological findings demand careful interpretation of immunofluorescence results. Autoantibodies to complement pathway regulatory proteins are common, and no novel mutation has been found from limited genetic workup. Clinical outcome is poor.

Dense deposit disease: a greatly increased biopsy incidence in India versus the USA

Background

We present the largest clinicopathologic case series to date of dense deposit disease (DDD) in an Indian population and compare the renal biopsy incidence rate to that seen in a large renal laboratory in USA.

Methods

Cases of DDD were identified and evaluated from native kidney biopsies reported at Renopath, India and at Arkana Laboratories, in the USA. Renopath receives biopsies from four states, located in the South and Eastern part of India. Arkana Laboratories’ biopsies came from 37 states across the USA.

Results

During the study period, there were a total of 25 patients diagnosed with DDD among the 7335 native kidney biopsies at Renopath. Thus, the biopsy incidence rate (cases of DDD/total renal biopsies/year) is 0.0034. By comparison, there were 10 cases of DDD diagnosed among 26 319 native kidney biopsies at Arkana Laboratories during the same time period, with a renal biopsy incidence rate of 0.00038.

Conclusions

DDD in this Indian subpopulation has similar clinical and pathologic characteristics when compared to previously reported studies. However, the biopsy incidence rate is about 890% or 8.9 times more common in this subset of the Indian population when compared with a broad cross-section of the US population. In addition to potential genetic factors, environmental conditions and chronic infections likely contribute to the markedly higher biopsy incidence rate. Given the much greater number of patients with DDD in this population, further retrospective and prospective studies would allow more rapid progress in understanding the pathogenesis of DDD and thus potential treatment of patients with DDD.

Usefulness of mycophenolate mofetil in Indian patients with C3 glomerulopathy

Background

C3 glomerulopathy (C3G) is a heterogeneous disease caused by alternative complement pathway abnormalities without any standardized treatment. An immunosuppressive agent, mycophenolate mofetil (MMF), has been recently shown to be useful in treating C3G, mainly in studies from the west. We report the clinical outcome of 17 Indian C3G patients treated with MMF with or without steroids.

Methods

The clinical and histology details of the C3G patients treated with MMF for at least 6 months with a follow-up of at least 12 months were retrieved from the medical records of our center.

Results

The median serum creatinine and proteinuria at presentation were 0.8 mg/dL and 3.7 g/day, respectively, with the majority (88.2%) presenting as nephrotic syndrome. The mean dose of MMF was 1.65 (±0.56) g/day, and the median duration of MMF therapy was 18 months. Two-thirds (64%) of the patients responded to the treatment, with complete remission in 4 (23%) and partial remission in 7 (41%) (median time: 9 months). Three patients progressed to end-stage renal disease (ESRD) on follow-up. Of the three patients, one (33%) had an initial response in proteinuria to MMF but did not respond after a relapse and subsequently progressed to ESRD and two (67%) other patients were nonresponsive to MMF from the start of the therapy.

Conclusion

Despite a small sample size and lack of a control arm, this study describes the effectiveness of MMF in treating C3G patients from Asia and forms a basis for future randomized trials.

Renal Tubular Complement 3 Deposition in Children with Primary Nephrotic Syndrome

Background

This study aimed to investigate the clinical significance of complement 3 (C3) deposition in renal tubules of children with primary nephrotic syndrome (PNS).

Methods

The clinical and pathological characteristics of PNS were retrospectively reviewed in 99 PNS pediatric patients, who were divided into the C3 deposition and the non-C3 deposition groups.

Results

A total of 39 patients (39.39%) had renal tubule C3 deposition. In the C3 deposition group, the ratios of urine N-acetylglucosaminidase/creatinine (UNAG/Cr), urine β2 microglobulin/creatinine (Uβ2MG/Cr), and urine transferrin/creatinine (UTRF/Cr) were significantly higher than those of the non-C3 deposition group. The patients of the C3 deposition group had lower serum total protein and albumin, higher cholesterol and D-dimer (DD), lower proportion of CD3+CD8+ cells, and higher proportion of CD19+CD23+ cells. The number of the patients with interstitial fibrosis, renal cell vacuolar degeneration, renal tubular immunoglobulin deposition, and severe tubulointerstitial injury in the C3 deposition group was higher than that of the non-C3 deposition group. The C3 deposition intensity was positively correlated with the number of recurrences.

Conclusion

PNS pediatric patients with C3 deposition in renal tubules have more severe disease condition, tubulointerstitial injury, and recurrence suggesting a worse long-term prognosis.

Evaluation of cases of membranoproliferative glomerulonephritis according to newer classification: A retrospective record-based study

Background

Membranoproliferative glomerulonephritis (MPGN) has traditionally been classified on electron microscopy (EM) into different types based on the location of the immune complexes. Sethi et al. subsequently suggested a more relevant etiology-based and clinically useful classification based on immunofluorescence.

Methods

In this retrospective study, 18 diagnosed cases of MPGN over a one-year period for which direct immunofluorescence (DIF) study results were available, were selected. Cases without archived records of immunofluorescence photographs/reports were excluded. Histological diagnosis of MPGN was confirmed and DIF results were analyzed with reference to antibodies to IgG, IgA, IgM, C3, C1q, kappa, and lambda light chains.

Results

Evaluation of cases revealed 8 males and 10 females with age range from 11 to 66 years. Fifteen cases presented with nephrotic syndrome. On evaluation, 88.89% cases (16/18) were immune complex mediated while two (11.11%) were of complement mediated type of MPGN. Among immune complex-mediated cases, a single case of monoclonal gammopathy associated or light chain mediated MPGN was present.

Conclusion

The classification described by Sethi et al. is easy to use since it relies on DIF instead of EM which is not readily available. Most of the cases were immune complex mediated whereas incidence of complement mediated MPGN, that is, C3 glomerulopathy was low (11.11%). Application of the new classification allows more relevant categorization of cases based on etiology and without the requirement of EM.