C3 Glomerulopathy Research Articles

An update to the pathogenesis for monoclonal gammopathy of renal significance.

Monoclonal gammopathy of renal significance (MGRS) is characterized by the nephrotoxic monoclonal immunoglobulin secreted by an otherwise asymptomatic or indolent B cell or plasma cell clone, without hematologic criteria for treatment. These MGRS-associated diseases can involve one or more renal compartments, including glomeruli, tubules, and vessels. Hydrophobic residue replacement, N-glycosylated, increase in isoelectric point in monoclonal immunoglobulin (MIg) causes it to transform from soluble form to tissue deposition, and consequently resulting in glomerular damage. In addition to MIg deposition, complement deposition is also found in C3 glomerulopathy with monoclonal glomerulopathy, which is caused by an abnormality of the alternative pathway and may involve multiple factors including complement component 3 nephritic factor, anti-complement factor auto-antibodies, or MIg which directly cleaves C3. Furthermore, inflammatory factors, growth factors, and virus infection may also participate in the development of the diseases. In this review, for the first time, we discussed current highlights in the mechanism of MGRS-related lesions.

Anti-Factor B Antibodies and Acute Postinfectious GN in Children.

The pathophysiology of the leading cause of pediatric acute nephritis, acute postinfectious GN, including mechanisms of the pathognomonic transient complement activation, remains uncertain. It shares clinicopathologic features with C3 glomerulopathy, a complement-mediated glomerulopathy that, unlike acute postinfectious GN, has a poor prognosis. This retrospective study investigated mechanisms of complement activation in 34 children with acute postinfectious GN and low C3 level at onset. We screened a panel of anticomplement protein autoantibodies, carried out related functional characterization, and compared results with those of 60 children from the National French Registry who had C3 glomerulopathy and persistent hypocomplementemia. All children with acute postinfectious GN had activation of the alternative pathway of the complement system. At onset, autoantibodies targeting factor B (a component of the alternative pathway C3 convertase) were found in a significantly higher proportion of children with the disorder versus children with hypocomplementemic C3 glomerulopathy (31 of 34 [91%] versus 4 of 28 [14%], respectively). In acute postinfectious GN, anti-factor B autoantibodies were transient and correlated with plasma C3 and soluble C5b-9 levels. We demonstrated that anti-factor B antibodies enhance alternative pathway convertase activity in vitro, confirming their pathogenic effect. We also identified crucial antibody binding sites on factor B, including one correlated to disease severity. These findings elucidate the pathophysiologic mechanisms underlying acute postinfectious GN by identifying anti-factor B autoantibodies as contributing factors in alternative complement pathway activation. At onset of a nephritic syndrome with low C3 level, screening for anti-factor B antibodies might help guide indications for kidney biopsy to avoid misdiagnosed chronic glomerulopathy, such as C3 glomerulopathy, and to help determine therapy.

C3 glomerulopathy and MPGN - current classification

Membranoproliferative glomerulonephritis (MPGN) and glomerulopathy with dominant C3 deposits are very rare autoimmune disorders of the kidney that had been classified in its current form in 2010 due to a better understanding of the underlying pathophysiology.Today, the immune complex-associated membranoproliferative glomerulonephritis (IC-MPGN) and C3 glomerulopathy (C3G) represent a disease spectrum which is heterogeneous in terms of pathophysiology and the clinical time course. Interestingly, recent research demonstrated more common pathophysiological aspects with respect to secondary causes, autoantibodies, and genetics of IC-MPGN and C3G than it had been suggested with the creation of the 2010 classification.This knowledge of the underlying pathophysiology is of specific importance for the identification of potential secondary causes. Therefore, following histologic diagnosis a comprehensive complement analysis, accompanied by antibody screening and human genetics should be carried out consistently. The published evidence provides a robust basis for the use of available therapeutic approaches for these often rapidly progressive and relapsing diseases.

Monoclonal gammopathy of renal significance: A novel combination of C3 glomerulopathy and light-chain proximal tubulopathy

Introduction: According to the recent International Kidney and Monoclonal Gammopathy Research Group Consensus report, the spectrum of monoclonal gammopathies of renal significance merges more than 12 conditions; and combinations of various patterns of monoclonal gammopathies of renal significance–associated kidney damage have already been described. We present a case of a previously unreported combination of C3 glomerulopathy and light-chain proximal tubulopathy. Case description: A 53-year-old Caucasian man presented with general weakness. Three years prior, a check-up revealed proteinuria and microhematuria, later accompanied by arterial hypertension, elevated serum creatinine, and a low serum C3 levels. On admission, his creatinine was 1.5 mg/dL; his protein excretion was 1900 mg/24 h with microhematuria at 150 hpf. His serum C3 was 79 mg/dL with a normal C4 level. Serum protein electrophoresis revealed an M-spike, immunochemistry confirmed monoclonal immunoglobulin G kappa secretion of 920 mg/dL, and traces of Bence–Jones protein kappa in his urine. A kidney biopsy showed mesangial hypercellularity with diffuse fine granular C3 mesangial expression and tubular atrophy with diffuse coarse granular kappa light-chain tubular epithelial cytoplasmic expression. Computed tomography did not reveal any destructive lesions. A bone marrow smear showed 5% plasma cells, and bone marrow cell flow cytometry demonstrated 87.4% of plasma cells with an aberrant phenotype. The patient was diagnosed with an monoclonal gammopathy of renal significance and administered bortezomib–cyclophosphamide–dexamethasone. After four courses, his monoclonal immunoglobulin G kappa secretion halved, but his serum creatinine and proteinuria remained almost unchanged. Chemotherapy was switched to lenalidomide–dexamethasone, and after five courses his immunoglobulin G kappa secretion decreased to traces, Bence–Jones protein was not observed and his urinalysis, serum creatinine, and C3 levels were detected as normal. Conclusion: The combination of kidney damage patterns, one of which was directly and the other indirectly associated with monoclonal gammopathy, complements the monoclonal gammopathies of renal significance spectrum. Chemotherapy led to a very good partial response and kidney function recovery.

CFHR Gene Variations Provide Insights in the Pathogenesis of the Kidney Diseases Atypical Hemolytic Uremic Syndrome and C3 Glomerulopathy.

Sequence and copy number variations in the human CFHR-Factor H gene cluster comprising the complement genes CFHR1, CFHR2, CFHR3, CFHR4, CFHR5, and Factor H are linked to the human kidney diseases atypical hemolytic uremic syndrome (aHUS) and C3 glomerulopathy. Distinct genetic and chromosomal alterations, deletions, or duplications generate hybrid or mutant CFHR genes, as well as hybrid CFHR-Factor H genes, and alter the FHR and Factor H plasma repertoire. A clear association between the genetic modifications and the pathologic outcome is emerging: CFHR1, CFHR3, and Factor H gene alterations combined with intact CFHR2, CFHR4, and CFHR5 genes are reported in atypical hemolytic uremic syndrome. But alterations in each of the five CFHR genes in the context of an intact Factor H gene are described in C3 glomerulopathy. These genetic modifications influence complement function and the interplay of the five FHR proteins with each other and with Factor H. Understanding how mutant or hybrid FHR proteins, Factor H::FHR hybrid proteins, and altered Factor H, FHR plasma profiles cause pathology is of high interest for diagnosis and therapy.

Spectrum of renal biopsies; a three-year data from a tertiary care centre of eastern India

Introduction: Biopsy registries are important in studying the frequency of kidney diseases, their trends over time and allow comparison of data from different geographical regions. Objectives: We report the spectrum of biopsy-proven glomerular and tubular diseases in a single centre in Eastern India. Patients and Methods: Medical records of 1293 patients with biopsy-proven glomerular diseases (GDs) and tubular diseases over a period of three years (March 2013 to March 2016) were retrospectively analysed. All biopsy specimens were examined by the same pathologist with light and immunofluorescence microscopy. Electron microscopic (EM) analysis was performed only in selected cases. Histologic spectrum of various GDs was studied along with its correlation with the clinical and laboratory parameters. Results: The clinical diagnosis was nephrotic syndrome (NS) in 820 (63.41%), rapidly progressive glomerulonephritis in 194 (15.2%), asymptomatic urinary abnormalities (AUA) in 108 (8%), acute kidney injury (AKI)/acute nephritic syndrome in 118 (9.3%), and macroscopic hematuria (MH) in 3 (0.43%) patients. Male: Female ratio was 0.95. Around 22.42% were < 18 years, 72.2% were between 18to 59 years, and 5.3% were ≥ 60 years of age. The most common GD overall as well as primary glomerular disease (PGD) was minimal change disease (MCD) (21.6 and 83.44%). Secondary GD was present in 20.87%; most common being lupus nephritis (84.58%). Among the NS, the most common GD was MCD (33.17%), followed by FSGS (17.56%), membranous nephropathy (MN) (13.90%), lupus nephritis (LN) (9.39%), IgA-nephropathy (0.49%), and MPGN (7.32%). Thrombotic microangiopathy (TMA) constituted 24.6% of AKI presentation particularly common in pregnancy. Diffuse proliferative glomerulonephritis (DPGN) with severe renal dysfunction was present in 14% of elderly patients. Conclusion: The spectrum of GD varies according to the area of study and changes over time. Some entities which have not been reported earlier from this region that are uncommon but are significant were pregnancy associated TMA, C3 glomerulopathy (C3G) and DPGN in adults.

Orphan designation: Poly(oxy-1,2-ethanediyl), alpha-hydro-omega-hydroxy-,15,15'-diester with N-acetyl-L-isoleucyl-L-cysteinyl-L-valyl-1-methyl-L-tryptophyl-L-glutaminyl-L-alpha-aspartyl-L-tryptophylglycyl-L-alanyl-L-histidyl-L-arginyl-L-cysteinyl-L-threonyl-2-[2-(2-aminoethoxy)ethoxy]acetyl-N6-carboxy-L-lysinamide cyclic (2.fwdarw.12)-(disulfide); where two identical synthetic peptide domains are covalently linked at the ends of the polyethylene glycol chain, Treatment of C3 glomerulopathy

Orphan designation: Poly(oxy-1,2-ethanediyl), alpha-hydro-omega-hydroxy-,15,15'-diester with N-acetyl-L-isoleucyl-L-cysteinyl-L-valyl-1-methyl-L-tryptophyl-L-glutaminyl-L-alpha-aspartyl-L-tryptophylglycyl-L-alanyl-L-histidyl-L-arginyl-L-cysteinyl-L-threonyl-2-[2-(2-aminoethoxy)ethoxy]acetyl-N6-carboxy-L-lysinamide cyclic (2.fwdarw.12)-(disulfide); where two identical synthetic peptide domains are covalently linked at the ends of the polyethylene glycol chain, Treatment of C3 glomerulopathy

A Narrative Review on C3 Glomerulopathy: A Rare Renal Disease.

In April 2012, a group of nephrologists organized a consensus conference in Cambridge (UK) on type II membranoproliferative glomerulonephritis and decided to use a new terminology, “C3 glomerulopathy” (C3 GP). Further knowledge on the complement system and on kidney biopsy contributed toward distinguishing this disease into three subgroups: dense deposit disease (DDD), C3 glomerulonephritis (C3 GN), and the CFHR5 nephropathy. The persistent presence of microhematuria with or without light or heavy proteinuria after an infection episode suggests the potential onset of C3 GP. These nephritides are characterized by abnormal activation of the complement alternative pathway, abnormal deposition of C3 in the glomeruli, and progression of renal damage to end-stage kidney disease. The diagnosis is based on studying the complement system, relative genetics, and kidney biopsies. The treatment gap derives from the absence of a robust understanding of their natural outcome. Therefore, a specific treatment for the different types of C3 GP has not been established. Recommendations have been obtained from case series and observational studies because no randomized clinical trials have been conducted. Current treatment is based on corticosteroids and antiproliferative drugs (cyclophosphamide, mycophenolate mofetil), monoclonal antibodies (rituximab) or complement inhibitors (eculizumab). In some cases, it is suggested to include sessions of plasma exchange.

C3 glomerulopathy: experience of a pediatric nephrology center

ABSTRACT 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.

Evaluation of the children with C3 glomerulopathy.

C3 glomerulopathy (C3G) is a clinical spectrum that presents with a variety of symptoms, ranging from a mild disease with asymptomatic microhematuria and/or proteinuria to severe disease with nephritic or nephrotic syndrome and renal impairment. Herein, we aim to document the clinical and laboratory findings, response to immunosuppressive and supportive treatment and prognosis of the children with C3G. We retrospectively reviewed the medical records of patients diagnosed with membranoproliferative glomerulonephritis (MPGN). Kidney biopsy materials were reexamined for the diagnosis of C3G. The inclusion criteria for C3G are the dominant C3 staining with or without scanty immunoglobulins (Ig) deposition on immuno- fluorescence (IF) and MPGN patterns on light microscope. Twelve of 69 patients with MPGN were included in the study based on the definition criteria of C3G. Ten of them had only C3 staining and the rest of the patients had both C3 staining and a small amount of IgG/M staining on IF microscopy. One patient was on remission with only ACEI. The rest of the patients used immunosuppressive treatment and two of them needed eculizumab therapy. One of them did not respond to the treatment of eculizumab and progressed to end-stage renal failure. C3G is a disease characterized by a heterogeneous clinical presentation and outcome. Because of this broad spectrum of disease, treatment may vary widely. We think that complement-targeting therapy with eculizumab should be an alternative option for refractory cases, especially in the early stage of disease, if they did not respond to immunosuppressive treatment.

Recurrence and Outcomes of Complement-Related Renal Disease After Pediatric Renal Transplantation

Complement dysregulation is related to different glomerular pathologies. Patients with complement dysregulation have high recurrence risk after transplant; however, with trough-effective therapeutics, renal transplant can be an option for these patients. Here, we present 2 boys with renal disease related to complement dysregulation and their outcomes after renal transplant. Patient 1 had atypical hemolytic uremic syndrome, which was treated with eculizumab before renal transplant; eculizumab therapy was also continued after transplant as preventive therapy. Eculizumab therapy was stopped at year 2 post-transplant. At year 4 post-transplant, his serum creatinine level was 0.87 mg/dL. Patient 2, who had chronic renal disease related to C3 glomerulopathy, was not responsive to eculizumab before renal transplant. At month 4 posttransplant, C3 glomerulopathy recurrence was demonstrated with biopsy, and serum creatinine level was 1.96 mg/dL at this time. Eculizumab was started as a rescue therapy. At year 4 posttransplant, his serum creatinine level was 2.07 mg/dL. In our 2 patients with complement dysregulation, eculizumab was an effective and preventive therapy after renal transplant. However, more studies are needed to understand the long-term efficacy and safety of eculizumab after renal transplant.

Early recurrence of C3 glomerulopathy postrenal transplant manifesting as rapid progressive glomerulonephritis

Renal transplant is the definitive treatment of choice for patients with end-stage renal failure and owing to the cost and problems involved with the surgery, long-term survival of the graft is a very important aspect of care. Primary glomerular disease recurrence is a dreaded complication of any kidney graft since it is impossible to prevent it with no guidelines or recommendations. C3 glomerulopathy is a condition which has very high recurrence rate after renal transplant, but rapid recurrence in a case who had a benign course of illness pretransplant is unique to this patient and needs to be discussed.

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).

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

C3 glomerulopathy (C3G) is related to dysfunction of alternative complement pathway (ACP) because of its hyperactivation. Triggering factors and genetic profile are likely to be different in developing countries as compared to the Western world. Data regarding C3G from South Asian is scanty. In the present study, 115 patients of C3G from 2012 to 2017 were analyzed. Clinical details were reviewed; serological levels of C3, C4, complement factor H or B and autoantibody testing was done by nephelometry/ELISA. Limited genetics workup for CFH and CFHR5 genes was done. The prevalence of C3G was 1.52%. There was no difference in demographic and histopathologic profiles of C3G patients. Majority of patients had low functional assay and C3 levels. C3 nephritic factor was present in 47.5% of DDD and 38.6% of C3GN. Autoantibodies to CFH were present more often in the patients of C3GN (29.5%) than DDD (12.5%). Autoantibodies to CFB were equally common in both groups. Past history of infections was present in one-third patients and monoclonal paraproteins were present only in two patients. No pathogenic variants were noted in CFH/CFHR5 gene. On follow-up (3.2 + 1.6years), complete and partial remission was achieved in one-fourth patients and 26% had resistance disease. About 40% progressed to ESRD and 18 underwent renal transplantation of which nine had a post-transplant recurrence. Indian cohort had some differences in the immunological and genetic profile when compared to the Western literature; most significant was the absence of monoclonal immunoglobulins as a trigger for C3G.

Evaluation of a Renin Inhibitor, Aliskiren, Compared to Enalapril, in C3 Glomerulopathy

Evaluation of a Renin Inhibitor, Aliskiren, Compared to Enalapril, in C3 Glomerulopathy

Атипичный гемолитико-уремический синдром: современные представления о патогенезе, клинике, подходах к диагностике и лечению

Атипичный гемолитикоуремический синдром (аГУС) ультраредкое (орфанное) заболевание прогрессирующего течения, представляющее собой системную тромботическую микроангиопатию (ТМА) вследствие хронической неконтролируемой активации альтернативного пути комплемента. В настоящее время установлено, что генетические аномалии комплемента, которые раньше рассматривали как основную причину заболевания, являются лишь фактором, предрасполагающим к возникновению ТМА. Классическую триаду клинических проявлений аГУС составляют тромбоцитопения, микроангиопатическая гемолитическая анемия и острое повреждение почек. У большинства пациентов независимо от возраста отмечается артериальная гипертензия, основными причинами которой являются гиперренинемия вследствие ишемии ткани почек, обусловленной ТМА, и перегрузка объемом при наличии олиго/анурии. Атипичный ГУС представляет собой системную ТМА, при которой могут поражаться не только почки, но и другие жизненно важные органы головной мозг, сердце, легкие, пищеварительный тракт, глаза и др. Диагноз аГУС это диагноз исключения. Он устанавливается на основании характерной клинической картины после исключения других форм ТМА, как первичных, так и вторичных. Для исключения тромботической тромбоцитопенической пурпуры (ТТП) всем больным с ТМА необходимо определение активности ADAMTS13: снижение ее до 10 и менее является диагностическим маркером ТТП. У пациентов с аГУС и другими ТМА активность ADAMTS13 может быть снижена, однако всегда превышает 10. Инновационным подходом к лечению аГУС, используемым в клинической практике в течение последнего десятилетия, стало применение экулизумаба препарата группы комплеменингибирующих антител, который является препаратом патогенетической терапии аГУС. Экулизумаб является средством первой линии для лечения детей с установленным диагнозом аГУС, при семейном характере заболевания, наличии экстраренальных проявлений. Совершенствование методов диагностики и внедрение новых подходов к лечению позволяет быстрее заподозрить и купировать проявления аГУС, добиться стойкой ремиссии и улучшить прогноз. Atypical hemolytic uremic syndrome (aHUS) is an ultra rare (orphan) progressive disease that is a systemic thrombotic microangiopathy (TMA) due to chronic uncontrolled activation of the alternative complement pathway. It is currently established that complement genetic abnormalities that were previously considered the main cause of the disease, are only a factor predisposing to TMA occurrence. The classic triad of aHUS clinical manifestations is thrombocytopenia, microangiopathic hemolytic anemia andacute kidney damage. Most patients, regardless of age, have arterial hypertension the main reasons of hypertension are hyperreninemia (due to kidney tissue ischemia because of TMA) and volume overload in the presence of oligo/anuria. Atypical HUS is a systemic TMA that affected not only the kidneys, but also other vital organs brain, heart, lungs, digestive tract, eyes, etc. The diagnosis of aHUS is a diagnosis of exclusion that is established on the basis of specifi c clinical picture after exclusion of other forms of TMA, both primary and secondary. To exclude thrombotic thrombocytopenic purpura (TTP), all patients with TMA need to determine ADAMTS13 activity: its reducing to 10 or less is a diagnostic marker of TTP. In patients with aHUS and other TMA, ADAMTS13 activity may be reduced, but always exceeds 10. The innovative pathogenetic approach to aHUS treatment over the last decade became the application of eculizumab that is a drug from complementinhibitory antibodies group. Eculizumab is a fi rstline treatment for children with proven aHUS diagnosis, with familial disease, with extrarenal manifestations. Progress in diagnostic methods and new treatment approaches allows us to quickly suspect and stop the manifestations of aHUS, achieve stable remission and improve the prognosis.

Treatment of Non-Amyloid Monoclonal Gammopathies of Renal Significance (MGRS) with Clone Directed Therapies-Single Center Experience

Background: MGRS is a group of heterogeneous disorders characterized by renal dysfunction related to monoclonal immunoglobulin deposition where the underlying plasma cell or B cell clone does not cause tumor complications or meets current hematological criteria for specific therapy (1). The diagnosis of these disorders is established by renal biopsy demonstrating glomerular or tubulointerstitial monoclonal protein deposition. The glomerular disorders include proliferative glomerulonephritis with monoclonal Ig deposition (PGNMID), paraprotein associated C3 glomerulopathy, immunotactoid glomerulopathy, and paraprotein associated fibrillary glomerulonephritis and Type 1 cryoglobulinemic glomerulonephritis. The tubulointerstitial disorders include fanconi syndrome and proximal light chain tubulopathy (2). Given the pathogenesis of the disorders, therapies targeting the underlying plasma cell and/or B cell clone have been used in the past but standard therapy has not been established. Given the rarity of MGRS as defined above, we report our single center experience for therapy of such disorders. Methods: We retrospectively reviewed the charts of patients treated for MGRS at Columbia University Medical Center and collected information on the renal pathologic diagnosis, presence or absence of monoclonal gammopathy and therapy and response. The diagnosis of MGUS and MGRS was based on standard criteria (3). For the assessment of renal response, we used criteria for renal organ response for AL amyloidosis (4). Results: A total of 8 patients were treated at our center for MGRS between 3/2015 and 1/2019. The type of MGRS diagnosis was PGNMID in 5 patients, C3 glomerulopathy in 1 patient, immunotactoid GN in 1 patient and MGUS associated dense deposit disease (DDD) in 1 patient. Monoclonal Ig deposit was IgG kappa type in 3, IgG Lambda in 2, IgM lambda in 1 patient and only Complement deposits C3 glomerulopathy and DDD. All pts had proteinuria at diagnosis with median proteinuria 4g/24hr (range 2.8-11.7g/24hr). Impaired renal function was present 5/8 pts with median serum creatinine 1.4mg/dl (range 1-4.6). None of the patients with PGNMID (N=5) had a concurrent monoclonal gammopathy by standard testing but the rest 3 patients had MGUS with positive SPEP and bone marrow involvement by a clonal plasma cells. First line treatment regimens included use of Bortezomib based regimen (Bortezomib, cyclophosphamide, dexamethasone) in 3 patients, Rituximab based regimens (Rituximab, Prednisone and Rituximab, cyclophosphamide, prednisone) in 4 patients and Daratumumab in one patient. Second line Daratumumab based therapy was used in 2 patients who did not respond to the first line therapy and lead to response in one patient. Improvement in proteinuria was seen in 6/8 patients with >30% decrease in proteinuria (range 50-90% reduction). The median time to response was 2 months (range 1-4 months). Improvement in eGFR was seen in 1/8 patients but majority of patients continuing to have stable eGFR and 1/8 patient progressed to ESRD. The responses were durable and after a median follow-up of 11.8 months only one patient had recurrent disease. Conclusion: Currently there is no standard of care therapy for treatment of patients diagnosed with MGRS disorders. Clone directed therapies including Bortezomib, Daratumumab and Rituximab based regimens aimed at suppressing the production of the involved immunoglobulin are effective for treatment of these disorders both in the presence and absence of a concurrent MGUS. These therapies should be explored further in a larger prospective multi-center trial for MGRS disorders.

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

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

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

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

Clinicopathological features of C3 glomerulopathy in children: a single-center experience.

C3 glomerulopathy (C3G) is defined by dominant glomerular deposition of C3 and minimal or no immunoglobulin, with two subtypes-dense deposit disease (DDD) and C3 glomerulonephritis (C3GN)-distinguished by features on electron microscopy (EM). Given that this rare disease has generally unfavorable yet highly variable outcomes, we sought out to review the histopathology, complement/genetic studies, and renal outcomes of pediatric patients with C3G at our institution. All native kidney biopsies performed in a single pediatric hospital over a 10-year period were reviewed for features of C3G. Of 589 biopsy reports, we identified 9 patients fulfilling the diagnostic criteria for C3G and retrospectively reviewed their clinical chart and renal biopsy findings. We identified 4 patients with DDD, 4 with C3GN, and 1 indeterminate case, with features of both C3GN and DDD. Five patients were positive for one or more nephritic factors (C3NeF, C4NeF, C5NeF) with 1 patient additionally positive for complement factor H (CFH) autoantibody. Genetic testing done in 5 of the 9 patients failed to identify any causative mutations. Three patients showed progressive renal dysfunction over a mean follow-up period of 33 months. Complement and genetic studies are now routinely recommended for patients with a histopathological diagnosis of C3G. Careful interpretation of these studies and their prognostic and therapeutic implications in conjunction with biopsy findings is needed to further understand the pathophysiology of this rare disease in children.