C3 glomerulopathy: a new classification

Recurrent atypical haemolytic uraemic syndrome post kidney transplant due to a CD46 mutation in the setting of SMARCAL1-mediated inherited kidney disease

Disorders in the regulation of the alternate complement pathway often result in complement-mediated damage to the microvascular endothelium and can be associated with both glomerulonephritis and atypical haemolytic uraemic syndrome. Inherited defects in complement regulatory genes or autoantibodies against complement regulatory proteins are predictive of the severity of the disease and the risk of recurrence post kidney transplantation. Heterozygous mutations in CD46, which codes for a transmembrane cofactor glycoprotein membrane cofactor protein, usually have a lower incidence of end-stage kidney disease and decreased risk of recurrent disease post transplant, as wild-type membrane cofactor protein is present in the transplanted kidney. However, some patients with CD46 mutations have a second variant in other complement regulatory genes increasing the severity of disease. The following case report illustrates the course of a young adult patient with end-stage kidney disease initially ascribed to seronegative systemic lupus erythematosus, who presented with biopsy-proven thrombotic microangiopathy following kidney transplantation. It highlights the complexity associated with disorders of complement regulation and the need for a high index of suspicion and genetic testing in patients who present with thrombotic microangiopathy post-transplant.

Atypical Plasmacytic Proliferation in a Case of C3 Glomerulopathy: Pathophysiology Demystified

An 11-year-old Hispanic female underwent evaluation of asymptomatic proteinuria and hematuria. The patient denied fever, edema, and gross hematuria. Urinalysis showed mild proteinuria, and a urine microscopic examination revealed red blood cells. Screening tests for glomerulonephritis revealed a low C3 and negative ANA, ASO, DNAse-B, and ANCA. Histological examination of a renal biopsy specimen showed glomeruli with endocapillary proliferation, a predominant C3 deposition in the capillary loops by immunofluorescence, and electron dense deposits in the mesangium, paramesangium, and capillary walls by electron microscopy consistent with a diagnosis of C3 glomerulopathy. An interstitial plasmacytosis was also present with focal clustering of plasma cells, which were found to be kappa light chain restricted by in situ hybridization suggestive of a clonal proliferation. One can speculate that these plasma cells may be directly responsible for the renal pathology that was seen.

C5 inhibition prevents renal failure in a mouse model of lethal C3 glomerulopathy

C3 glomerulopathy is a potentially life-threatening disease of the kidney caused by dysregulated alternative pathway complement activation. The specific complement mediator(s) responsible for kidney injury in C3 glomerulopathy are yet to be defined and no specific therapy is currently available. We previously developed a mouse model of lethal C3 glomerulopathy with factor H and properdin gene double mutations. Therefore, we used this model to examine the role of C5 and C5a receptor (C5aR) in the pathogenesis of the disease. Disease severity in these factor H/properdin double-mutant mice was found to be correlated with plasma C5 levels, and prophylactic anti-C5 mAb therapy was effective in preventing lethal C3 glomerulopathy. When given to these double-mutant mice that had already developed active disease with severe proteinuria, anti-C5 mAb treatment also prevented death in half of the mice. Deficiency of C5aR significantly reduced disease severity, suggesting that C5aR-mediated inflammation contributed to C3 glomerulopathy. Thus, C5 and C5aR have a critical role in C3 glomerulopathy. Hence, early intervention targeting these pathways may be an effective therapeutic strategy for patients with C3 glomerulopathy.

Treatment of B-cell disorder improves renal outcome of patients with monoclonal gammopathy-associated C3 glomerulopathy

The high frequency of monoclonal gammopathy in adult patients with C3 glomerulopathy (C3G) emphasizes the role of monoclonal immunoglobulin (MIg) in the occurrence of renal disease and raises the issue of the therapeutic management. The aim of the study was to evaluate the effect of chemotherapy in a large cohort of patients with MIg-associated C3G. Fifty adult patients with MIg and biopsy-proven C3G were extracted from the French national database of C3G. We retrospectively compared renal outcomes in patients who either received or did not receive chemotherapy targeting the underlying B-cell clone. At diagnosis, renal disease was severe, with nephrotic-range proteinuria in 20/46 (43%) patients and chronic kidney disease stage 3 or above in 42/49 (86%) patients. Monoclonal gammopathy was of IgG type in 47 (94%) patients. Hematological diagnosis was monoclonal gammopathy of renal significance in 30 (60%), multiple myeloma in 17 (34%), and chronic lymphocytic leukemia in 3 (6%) patients. Complement studies showed low C3 level in 22/50 (43%) and elevated soluble C5b-9 level in 27/34 (79%) patients. Twenty-nine patients received chemotherapy (including bortezomib in 22), whereas 8 and 13 patients received various immunosuppressive drugs or symptomatic measures alone, respectively. Patients who achieved hematological response after chemotherapy had higher renal response rates (P = .0001) and median renal survival (hazard ratio, 0.22; 95% confidence interval, 0.05-0.92; P = .009) than those receiving conservative/immunosuppressive therapy. In conclusion, our results suggest that chemotherapy adapted to the B-cell clone may constitute an efficient strategy for C3G in the setting of MIg, as rapid achievement of hematological response appears to result in improved renal survival.

C3 glomerulopathy and current dilemmas

C3 glomerulopathy (C3G) is a recently identified disease entity caused by dysregulation of the alternative complement pathway, and dense deposit disease (DDD) and C3 glomerulonephritis (C3GN) are its components. Because laboratory detection of complement dysregulation is still uncommon in practice, "dominant C3 deposition by two orders greater than that of immunoglobulins in the glomeruli by immunofluorescence", as stated in the consensus report, defines C3G. However, this morphological definition possibly includes the cases with glomerular diseases of different mechanisms such as post-infectious glomerulonephritis. In addition, the differential diagnosis between DDD and C3GN is often difficult because the distinction between these two diseases is based solely on electron microscopic features. Recent molecular and genetic advances provide information to characterize C3G. Some C3G cases are found with genetic abnormalities in complement regulatory factors, but majority of cases seem to be associated with acquired factors that dysregulate the alternative complement pathway. Because clinical courses and prognoses among glomerular diseases with dominant C3 deposition differ, further understanding the background mechanism, particularly complement dysregulation in C3G, is needed. This may resolve current dilemmas in practice and shed light on novel targeted therapies to remedy the dysregulated alternative complement pathway in C3G.

Recent advances in our understanding of recurrent primary glomerulonephritis after kidney transplantation

Recurrent glomerulonephritis (GN) is an important cause of kidney allograft failure, particularly in younger recipients. Approximately 15% of death-censored graft failures are due to recurrent GN, but this incidence is likely an underestimation of the magnitude of the problem. Overall, 18% to 22% of kidney allografts are lost due to GN, either recurrent or presumed de novo. The impact of recurrent GN on allograft survival was recognized from the earliest times in kidney transplantation. However, progress in this area has been slow, and our understanding of GN recurrence remains limited, in large part due to incomplete understanding of the pathogenesis of these diseases. This review focuses on recent advances in our general understanding of the pathophysiology of primary GN, the risk of recurrence in the allograft, and the consequences for kidney graft survival. We focus specifically on the most common forms of primary GN, including focal segmental glomerulosclerosis, membranous nephropathy, membranoproliferative glomerulonephritis, and IgA nephropathy. New understanding of the pathogenesis of these diseases has had direct clinical implications for transplantation, allowing better identification of candidates at high risk of recurrence and earlier diagnoses, and it is expected to lead to significance improvements in the therapy and perhaps even prevention of GN recurrence. More than ever, it is essential to fully characterize GN before transplantation as this information will direct our management posttransplantation. Further, the relative rarity of recurrent GN dictates the need for multicenter studies in order to evaluate, test, and validate recent advances and therapies.

C3 Glomerulopathy and post-infectious glomerulonephritis define a disease spectrum

BACKGROUND

Post-infectious glomerulonephritis (PIGN) usually follows a benign course, but few children have an atypical, severe presentation, and these exceptional cases have been linked to the dysregulation of the complement alternative pathway (CAP). There is a considerable overlap in the histopathological features of PIGN and C3 glomerulopathy (C3G), which is also associated with CAP dysregulation but has a poorer outcome. We hypothesized that PIGN and C3G define a disease spectrum, and that in the past there may be some children with C3G who were misclassified with PIGN before C3G was described as a separate disease entity.

METHODS

Children with PIGN (n = 33) diagnosed between 1985 and 2010 who underwent a renal biopsy due to their unusual course were reviewed and of them, 8 were reclassified into C3G based on the current classification criteria. Outcome was based on the degree of proteinuria, C3 level, and renal function at follow-up.

RESULTS

Sixteen (72.7%) children with typical PIGN recovered completely as compared to only 2 (25%) with C3G. Of note, children with "typical" PIGN had a more severe disease course at onset; however, the outcome at last follow up was favorable.

CONCLUSIONS

Our results support the hypothesis that PIGN and C3G form a disease spectrum and have different long-term clinical implications and management strategies.

C3 glomerulonephritis in multiple myeloma: A case report and literature review

BACKGROUND

C3 glomerulonephritis (C3 GN) is a recently defined entity characterized by predominant C3 deposition in glomeruli due to abnormal activation of the alternative pathway of complement system. C3 GN has been reported to be associated with several systemic diseases. However, the association between C3 GN and multiple myeloma (MM) has not been well established.

METHODS

We herein describe a case presenting with C3 GN on top of MM.

RESULTS

A 64-year-old Chinese female presented with gross hematuria, renal dysfunction, anemia, and weight loss. Results of serum immunofixation assay and bone marrow biopsy confirmed the diagnosis of IgG-λ-type MM. In addition, renal biopsy demonstrated histological findings characteristic of C3 GN, including mesangial and endocapillary proliferation under light microscope, electron-dense deposits under electron microscope, and diffuse granular deposition of C3 with no immunoglobulin under immunofluorescence microscope. These histological findings, combined with low serum C3 level, suggested the occurrence of C3 GN in the context of MM.

CONCLUSION

This case study provides additional evidence to the literature in terms of the association between C3 GN and MM. We hypothesize that C3 GN may present as a new variant of nephropathy in MM and the mechanism behind this association merits further study.

Use of C4d as a diagnostic tool to classify membranoproliferative glomerulonephritis

BACKGROUND

Membranoproliferative glomerulonephritis (MPGN type I, II and III) was reclassified in 2013 as MPGN and C3 glomerulopathy (C3G) based on the complement system activation mechanism.

OBJECTIVES

To evaluate whether C4d, a component of the classical pathway, could be a diagnostic tool in differentiating between MPGN and C3G.

METHODS

We conducted a retrospective study of 15 MPGN type I, II and III and 13 minimal change disease (MCD) patients diagnosed between 2000 and 2012. C4d staining using the peroxidase method was employed.

RESULTS

Using the 2013 C3G consensus classification, the 15 MPGN types I, II and III biopsies were re-classified as MPGN (8) and C3G (7). Following C4d staining, of the 8 biopsies diagnosed as MPGN, 4 had classical pathway involvement [C1q (+), C3 (+), C4d (+)]; two had lectin pathway involvement [C1q (-), C3 (+), C4d (+)]; and, two were reclassified as C3G because the absence of C4d and C1q suggested the presence of the alternative pathway [C1q (-), C3 (+), C4d (-)]. Three of the seven C3G biopsies presented classical pathway involvement and were reclassified as MPGN. The alternative pathway was present in one of the other 4 biopsies considered to be C3G. Two C3G biopsies involved the lectin pathway and the one case of dense deposit disease had lectin pathway involvement.

CONCLUSIONS

C4d staining may help to differentiate between MPGN and C3G. In addition, the lectin pathway could play a role in the pathogenesis of these glomerulopathies.

C3 mesangial proliferative glomerulonephritis initially presenting with atypical hemolytic uremic syndrome: a case report

BACKGROUND

Hemolytic uremic syndrome is characterized by acute renal failure, thrombocytopenia, and Coombs-negative hemolytic anemia. In C3 mesangial proliferative glomerulonephritis, an increase in mesangial cell proliferation without thickening in the glomerular capillary wall can be seen under light microscopy, but the definitive diagnosis is made with the immunohistologic demonstration of isolated C3 deposits in the mesangium. C3 glomerulonephritis may be detected in childhood; however, in this case report we describe the first case of isolated C3 glomerulonephritis together with atypical hemolytic uremic syndrome in an adult patient.

CASE PRESENTATION

Here we present a case of a 27-year-old white man with anuria who was hospitalized after being diagnosed as having hemolytic uremic syndrome accompanied by acute renal failure. Renal biopsy results revealed C3 glomerulonephritis. There was a complete recovery of renal function after hemodialysis, and prednisolone and plasma exchange treatment.

CONCLUSIONS

C3 glomerulopathy is distinct from atypical hemolytic uremic syndrome although both diseases are due to abnormal control of the alternative complement pathway. In atypical hemolytic uremic syndrome activation of complement occurs on glomerular or microvascular endothelium causing a thrombotic microangiopathy; in most cases, no electron-dense deposits are seen on electron microscopy and glomerular C3 is not detected on immunofluorescence.

Likely Recurrence of C3 Glomerulonephritis in Kidney Transplantation: An Entity to Bear in Mind: Case Report

BACKGROUND

C3 glomerulonephritis (C3GN) is an unusual entity that is caused by dysregulation and hyperactivity of the alternative complement pathway. Renal biopsy immunofluorescence study shows C3 deposits with absence of immunoglobulins and markers of the classical complement pathway. More than 50% of cases develop end-stage renal disease. Less well-known is the course of C3GN after kidney transplantation.

CASE REPORT

We present the case of a 60-year-old woman with chronic kidney disease secondary to chronic glomerulonephritis of unknown origin who received a kidney transplant. Two years later, she presented worsening renal function with non-nephrotic proteinuria and microhematuria. Complement testing revealed low serum levels of C3. Kidney biopsy showed alterations compatible with C3GN that we interpreted as a relapse of the underlying disease.

Reclassification of membranoproliferative glomerulonephritis: Identification of a new GN: C3GN

This review revises the reclassification of the membranoproliferative glomerulonephritis (MPGN) after the consensus conference that by 2015 reclassified all the glomerulonephritis basing on etiology and pathogenesis, instead of the histomorphological aspects. After reclassification, two types of MPGN are to date recognized: The immunocomplexes mediated MPGN and the complement mediated MPGN. The latter type is more extensively described in the review either because several of these entities are completely new or because the improved knowledge of the complement cascade allowed for new diagnostic and therapeutic approaches. Overall the complement mediated MPGN are related to acquired or genetic cause. The presence of circulating auto antibodies is the principal acquired cause. Genetic wide association studies and family studies allowed to recognize genetic mutations of different types as causes of the complement dysregulation. The complement cascade is a complex phenomenon and activating factors and regulating factors should be distinguished. Genetic mutations causing abnormalities either in activating or in regulating factors have been described. The diagnosis of the complement mediated MPGN requires a complete study of all these different complement factors. As a consequence, new therapeutic approaches are becoming available. Indeed, in addition to a nonspecific treatment and to the immunosuppression that has the aim to block the auto antibodies production, the specific inhibition of complement activation is relatively new and may act either blocking the C5 convertase or the C3 convertase. The drugs acting on C3 convertase are still in different phases of clinical development and might represent drugs for the future. Overall the authors consider that one of the principal problems in finding new types of drugs are both the rarity of the disease and the consequent poor interest in the marketing and the lack of large international cooperative studies.

Complement-Mediated Glomerular Diseases: A Tale of 3 Pathways

A renewed interest in the role of complement in the pathogenesis of glomerular diseases has improved our understanding of their basic, underlying physiology. All 3 complement pathways—classical, lectin, and alternative—have been implicated in glomerular lesions both rare (e.g., dense deposit disease) and common (e.g., IgA nephropathy). Here we review the basic function of these pathways and highlight, with a disease-specific focus, how activation can lead to glomerular injury. We end by exploring the promise of complement-targeted therapies as disease-specific interventions for glomerular diseases.

Differences in clinical findings, pathology, and outcomes between C3 glomerulonephritis and membranoproliferative glomerulonephritis

BACKGROUND

To clarify the clinical manifestations of pediatric complement component C3 glomerulonephritis (C3GN), we retrospectively evaluated differences in the clinicopathological findings and prognosis between C3GN and immune-complex-mediated membranoproliferative glomerulonephritis (IC-MPGN).

METHODS

Thirty-seven patients diagnosed with "idiopathic MPGN" were enrolled in this retrospective study. The patients were divided into two groups, with Group 1 consisting of 19 patients diagnosed with IC-MPGN and Group 2 consisting of 18 patients diagnosed with C3GN. The clinical findings and the prognosis were investigated for both groups.

RESULTS

Thirteen patients in Group 2 were identified by mandatory annual school screening for urinary abnormalities. The incidence of macro-hematuria and the frequency of low serum C4 values were lower in Group 2 patients than in Group 1 patients. At the time of the second renal biopsy, urinary protein excretion, incidence of hematuria, frequency of low serum C3 values, and scores for mesangial proliferation, glomerular sclerosis, and interstitial fibrosis were higher in Group 2 patients than in Group 1 patients. At the most recent follow-up examination, the number of patients categorized as non-responding or with end-stage renal disease was higher in Group 2 patients than in Group 1 patients.

CONCLUSIONS

Our results suggest that the treatment response and prognosis of patients with C3GN are worse than those of patients with IC-mediated MPGN. Therefore, in the clinical context regarding treatment options and prognosis, it may be useful to classify idiopathic MPGN as C3GN or IC-MPGN. In addition, long-term follow-up of C3GN is necessary.

Understanding the complement-mediated glomerular diseases: focus on membranoproliferative glomerulonephritis and C3 glomerulopathies

An enhanced understanding of the role of complement in the pathogenesis of membranoproliferative glomerulonephritis has led to reclassification of the latter into immunoglobulin-mediated and non-immunoglobulin-mediated disease. The new classification schema resulted in improved diagnostic clinical algorithms, while it brought into light again the diseases, which are characterized by the presence of glomerular deposits, composed predominantly by C3, in the absence of significant amounts of immunoglobulins in renal biopsy, namely, C3 glomerulopathies (dense deposit disease and C3 glomerulonephritis). Despite the lack of randomized controlled trials following the advances in the understanding of the pathogenetic pathways involved in membranoproliferative glomerulonephritis, it is important that the new mechanistic approach has opened new roads for the exploration and discovery of targeted therapies.

Modeling complement-driven diseases in transgenic mice: Values and limitations

Remarkable advances have been made over past decades in understanding the pathogenesis of complement-mediated diseases. This has led to development of new therapies for, and in some cases re-classification of, complement-driven diseases. This success is due to not only insight from human patients but also studies using transgenic animal models. Animal models that mimic human diseases are useful tools to understand the mechanism of disease and develop new therapies but there are also limitations due to species differences in their complement systems. This review provides a summary of transgenic animal models for three human diseases that are at the forefront of anti-complement therapy, paroxysmal nocturnal hemoglobinuria (PNH), atypical hemolytic uremic syndrome (aHUS) and C3 glomerulopathy (C3G). They are discussed here as examples to highlight the values and limitations of animal modeling in complement-driven diseases.

Protracted Clinical Course of Postinfectious Glomerulonephritis in a Previously Healthy Child

Acute postinfectious glomerulonephritis (PIGN) affects children typically after upper respiratory tract or skin infections with streptococci but can complicate the course of other infections. In children, it is generally a self-limiting disease with excellent prognosis. This paper reports a previously healthy 4-year-old boy who experienced a protracted course of PIGN with persisting episodes of gross haematuria, proteinuria, decreased complement C3c levels but normal P-creatinine levels. Due to the protracted course and the nephrotic-range proteinuria, a renal biopsy was performed 6 months after the initial presentation and the overall pathology was consistent with acute endocapillary glomerulonephritis.

Kidney transplant outcomes in familial C3 glomerulopathy

C3 glomerulopathy, a newly designated entity, is characterized by glomerular disease associated with dysregulation of the alternative complement pathway and is a rare cause of end-stage kidney disease. Overall disease characteristics that include clinical presentation, laboratory assessment, histopathology and genetic background have only been unravelled in recent years and have led to the development of anti-complement therapies targeting different levels of the alternative pathway. We describe the long-term outcomes following kidney transplantation in an Irish family with familial C3 glomerulopathy due to a hybrid CFHR3-1 gene.

Post-infectious glomerulonephritis with crescents in adults: a retrospective study

Background

Crescent formation generally reflects severe glomerular injury. There is sparse literature on post-infectious glomerulonephritis (PIGN) with crescents in adults. This retrospective study looked at nine such cases to see if there is a correlation between the severity of presentation, steroid treatment, histological severity and outcome.

Methods

Biopsy reports of all the adults who underwent kidney biopsy from February 2010 to June 2014 in a tertiary care hospital were screened and all the cases with the diagnosis of PIGN with crescents were selected. Clinical presentation, laboratory data, histology, treatment and outcome were analysed.

Results

Six patients had evidence of recent/current infection, but all except two were non-streptococcal. The mean creatinine was 360.67 μmol/L (range 70.72–770.85) and the mean estimated glomerular filtration rate (MDRD eGFR) was 30.28 mL/min/1.73 m² (range 6.4–111.1) on presentation. All five patients who were treated with steroids had an excellent response. Among the four patients who did not receive steroids, two were left with significant renal impairment (mean MDRD eGFR 23.5 mL/min/1.73 m²) at a mean follow-up of 15.5 months (range 10–21). The mean percentage of glomeruli with crescents was 36.13% (range 11.76–100) and except in one, there was no tubular atrophy or interstitial fibrosis and none had glomerulosclerosis. None of the patients progressed to end-stage renal disease.

Conclusion

Non-streptococcal infections are more common precipitants. There was no correlation between histological and clinical severity. Patients treated with steroids had better renal outcomes.

[Clinical approach to primary membranoproliferative glomerulonephritis]

Membranoproliferative glomerulonephritis represent a heterogeneous group of nephropathies. During the last five years, our understanding of membranoproliferative glomerulonephritis has greatly improved. Animal models and the study of complement genetics led to the dissection of the physiopathology of membranoproliferative glomerulonephritis, to the individualization of a new entity, C3 glomerulopathy, and to a new classification of these nephropathies. The study of large cohorts has also changed the clinical picture of membranoproliferative glomerulonephritis that has been long dominated by the severity of a single type of dense deposits disease. Finally, the rediscovery of complement through the study of the atypical haemolytic uremic syndrome and the availability in clinical practice of complement inhibitors have paved the way for new therapeutic approaches of membranoproliferative glomerulonephritis.

Eculizumab use in kidney transplantation

PURPOSE OF REVIEW

Eculizumab suppresses the effector functions of the complement system and represents a therapeutic breakthrough for patients with paroxysmal nocturnal hemoglobinuria or atypical hemolytic uremic syndrome (aHUS). Safety monitoring is ongoing; so far, most notable is the expected increase in infection risk with encapsulated organisms. Despite potential applicability in multiple complement-mediated disorders, the off-label use of eculizumab has been limited, mainly by its prohibitive cost. The purpose of this review is to summarize the current data relevant to the use of eculizumab in kidney transplantation.

RECENT FINDINGS

In aHUS, prone to high rates of recurrence and allograft loss, eculizumab has made the most notable therapeutic impact. Further clarification of complement defects may help predict therapeutic responses and hopefully guide treatment duration. In C3 glomerulopathies, the clinical response to eculizumab appears more heterogeneous and less effective in processes mediated by upstream to C5 complement deregulation. A large clinical trial of eculizumab for prevention of delayed graft function is ongoing. In antibody-mediated rejection, the role of eculizumab is unclear as its use has been limited to very complex, mostly presensitized, patients in mixed combinations of therapeutic modalities.

SUMMARY

Overall, eculizumab has raised awareness of complement-mediated disorders as an exciting, new therapeutic option with multiple potential applications in kidney transplantation. Further research is needed to develop a better understanding of eculizumab applicability, efficacy, and treatment monitoring and beyond, to future therapeutic tools targeting the complement.

Biologics for the treatment of autoimmune renal diseases

Biological therapeutics (biologics) that target autoimmune responses and inflammatory injury pathways have a marked beneficial impact on the management of many chronic diseases, including rheumatoid arthritis, psoriasis, inflammatory bowel disease, and ankylosing spondylitis. Accumulating data suggest that a growing number of renal diseases result from autoimmune injury - including lupus nephritis, IgA nephropathy, anti-neutrophil cytoplasmic antibody-associated glomerulonephritis, autoimmune (formerly idiopathic) membranous nephropathy, anti-glomerular basement membrane glomerulonephritis, and C3 nephropathy - and one can speculate that biologics might also be applicable to these diseases. As many autoimmune renal diseases are relatively uncommon, with long natural histories and diverse outcomes, clinical trials that aim to validate potentially useful biologics are difficult to design and/or perform. Some excellent consortia are undertaking cohort studies and clinical trials, but more multicentre international collaborations are needed to advance the introduction of new biologics to patients with autoimmune renal disorders. This Review discusses the key molecules that direct injurious inflammation and the biologics that are available to modulate them. The opportunities and challenges for the introduction of relevant biologics into treatment protocols for autoimmune renal diseases are also discussed.

Retinal disease in the C3 glomerulopathies and the risk of impaired vision

BACKGROUND

Dense deposit disease and atypical hemolytic uremic syndrome are often caused by Complement Factor H (CFH) mutations. This study describes the retinal abnormalities in dense deposit disease and, for the first time, atypical haemolytic uremic syndrome. It also reviews our understanding of drusen pathogenesis and their relevance for glomerular disease.

METHODS

Six individuals with dense deposit disease and one with atypical haemolytic uremic syndrome were studied from 2 to 40 years after presentation. Five had renal transplants. All four who had genetic testing had CFH mutations. Individuals underwent ophthalmological review and retinal photography, and in some cases, optical coherence tomography, and further tests of retinal function.

RESULTS

All subjects with dense deposit disease had impaired night vision and retinal drusen or whitish-yellow deposits. Retinal atrophy, pigmentation, and hemorrhage were common. In late disease, peripheral vision was restricted, central vision was distorted, and there were scotoma from sub-retinal choroidal neovascular membranes and atypical serous retinopathy. Drusen were present but less prominent in the young person with atypical uremic syndrome due to a heterozygous CFH mutation.

CONCLUSIONS

Drusen are common in forms of C3 glomerulopathy caused by compound heterozygous or heterozygous CFH mutations. They are useful diagnostically but also impair vision. Drusen have an identical composition to glomerular deposits. They are also identical to the drusen of age-related macular degeneration, and may respond to the same treatments. Individuals with a C3 glomerulopathy should be assessed ophthalmologically at diagnosis, and monitored regularly for vision-threatening complications.

Complement Pathway Associated Glomerulopathies

The complement system causes kidney injury in a variety of different diseases, and clinical evaluation of the complement system is an important part of the diagnostic workup of patients with glomerulonephritis. In cases of ongoing, uncontrolled complement activation, the kidney is susceptible to complement hyperactivation, and thrombotic microangiopathy associated kidney injury can occur. Two principle modes of complement-mediated kidney injury have been proposed: classical pathway mediated injury in immune complex diseases and/or alternative pathway mediated renal injury causing atypical haemolytic uraemic syndrome (aHUS) and C3 glomerulopathy in patients with abnormalities in alternative pathway regulation. Recent advances have also provided new insights into the pathogenesis of glomerular and tubulointerstitial injury associated with aberrant complement activation. Complement inhibition is effective for treatment of aHUS, and there is growing evidence of the favourable effect of the anti-C5 monoclonal antibody eculizumab. Measurement of ex vivo serum-induced endothelial C5b-9 deposits is supposed to be a sensitive tool to monitor complement activation and eculizumab effectiveness. Although understanding the role of the complement system in the pathogenesis of many kidney diseases is improved, there is not a simple algorithm for identifying which patients should be treated with complement inhibitors or for how long complement inhibition should be continued.

A Familial C3GN Secondary to Defective C3 Regulation by Complement Receptor 1 and Complement Factor H

C3 glomerulopathy is a recently described form of CKD. C3GN is a subtype of C3 glomerulopathy characterized by predominant C3 deposits in the glomeruli and is commonly the result of acquired or genetic abnormalities in the alternative pathway (AP) of the complement system. We identified and characterized the first mutation of the C3 gene (p. I734T) in two related individuals diagnosed with C3GN. Immunofluorescence and electron microscopy studies showed C3 deposits in the subendothelial space, associated with unusual deposits located near the complement receptor 1 (CR1)-expressing podocytes. In vitro, this C3 mutation exhibited decreased binding to CR1, resulting in less CR1-dependent cleavage of C3b by factor 1. Both patients had normal plasma C3 levels, and the mutant C3 interacted with factor B comparably to wild-type (WT) C3 to form a C3 convertase. Binding of mutant C3 to factor H was normal, but mutant C3 was less efficiently cleaved by factor I in the presence of factor H, leading to enhanced C3 fragment deposition on glomerular cells. In conclusion, our results reveal that a CR1 functional deficiency is a mechanism of intraglomerular AP dysregulation and could influence the localization of the glomerular C3 deposits.

Eculizumab in Pediatric Dense Deposit Disease

BACKGROUND AND OBJECTIVES

Dense deposit disease (DDD), a subtype of C3 glomerulopathy, is a rare disease affecting mostly children. Treatment options are limited. Debate exists whether eculizumab, a monoclonal antibody against complement factor C5, is effective in DDD. Reported data are scarce, especially in children.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The authors analyzed clinical and histologic data of five pediatric patients with a native kidney biopsy diagnosis of DDD. Patients received eculizumab as therapy of last resort for severe nephritic or nephrotic syndrome with alternative pathway complement activation; this therapy was given only when the patients had not or only marginally responded to immunosuppressive therapy. Outcome measures were kidney function, proteinuria, and urine analysis.

RESULTS

In all, seven disease episodes were treated with eculizumab (six episodes of severe nephritic syndrome [two of which required dialysis] and one nephrotic syndrome episode). Median age at treatment start was 8.4 (range, 5.9-13) years. For three treatment episodes, eculizumab was the sole immunosuppressive treatment. In all patients, both proteinuria and renal function improved significantly within 12 weeks of treatment (median urinary protein-to-creatinine ratio of 8.5 [range, 2.2-17] versus 1.1 [range, 0.2-2.0] g/g, P<0.005, and eGFR of 58 [range, 17-114] versus 77 [range, 50-129] ml/min per 1.73 m(2), P<0.01). A striking finding was the disappearance of leukocyturia within 1 week after the first eculizumab dose in all five episodes with leukocyturia at treatment initiation.

CONCLUSIONS

In this case series of pediatric patients with DDD, eculizumab treatment was associated with reduction in proteinuria and increase in eGFR. Leukocyturia resolved within 1 week of initiation of eculizumab treatment. These results underscore the need for a randomized trial of eculizumab in DDD.

Effectiveness of mycophenolate mofetil in C3 glomerulonephritis

C3 glomerulonephritis is a clinicopathologic entity defined by the presence of isolated or dominant deposits of C3 on immunofluorescence. To explore the effect of immunosuppression on C3 glomerulonephritis, we studied a series of 60 patients in whom a complete registry of treatments was available over a median follow-up of 47 months. Twenty patients had not received immunosuppressive treatments. In the remaining 40 patients, 22 had been treated with corticosteroids plus mycophenolate mofetil while 18 were treated with other immunosuppressive regimens (corticosteroids alone or corticosteroids plus cyclophosphamide). The number of patients developing end-stage renal disease was significantly lower among treated compared with untreated patients (3 vs. 7 patients, respectively). No patient in the corticosteroids plus mycophenolate mofetil group doubled serum creatinine nor developed end-stage renal disease, as compared with 7 (significant) and 3 (not significant), respectively, in patients treated with other immunosuppressive regimens. Renal survival (100, 80, and 72% at 5 years) and the number of patients achieving clinical remission (86, 50, and 25%) were significantly higher in patients treated with corticosteroids plus mycophenolate mofetil as compared with patients treated with other immunosuppressive regimens and untreated patients, respectively. Thus, immunosuppressive treatments, particularly corticosteroids plus mycophenolate mofetil, can be beneficial in C3 glomerulonephritis.

Eculizumab-induced reversal of dialysis-dependent kidney failure from C3 glomerulonephritis

C3 glomerulopathy (C3G) is characterized by C3 deposits with minimal immunoglobulin deposition caused by alternative complement pathway dysregulation. Unfortunately, no therapeutic intervention has consistently improved outcomes for patients with C3G. Eculizumab, a monoclonal antibody to C5, is currently the only approved complement-specific agent with some efficacy in the treatment of C3 glomerulonephritis (C3GN). Here, we describe a patient with acute crescentic C3GN with no identified complement mutation or family history of renal disease who required dialysis for 6 months. Five months after initiation of eculizumab, she became dialysis independent, showing improvement is possible after adequate time on eculizumab.

Complement System Part II: Role in Immunity

The complement system has been considered for a long time as a simple lytic cascade, aimed to kill bacteria infecting the host organism. Nowadays, this vision has changed and it is well accepted that complement is a complex innate immune surveillance system, playing a key role in host homeostasis, inflammation, and in the defense against pathogens. This review discusses recent advances in the understanding of the role of complement in physiology and pathology. It starts with a description of complement contribution to the normal physiology (homeostasis) of a healthy organism, including the silent clearance of apoptotic cells and maintenance of cell survival. In pathology, complement can be a friend or a foe. It acts as a friend in the defense against pathogens, by inducing opsonization and a direct killing by C5b–9 membrane attack complex and by triggering inflammatory responses with the anaphylatoxins C3a and C5a. Opsonization plays also a major role in the mounting of an adaptive immune response, involving antigen presenting cells, T-, and B-lymphocytes. Nevertheless, it can be also an enemy, when pathogens hijack complement regulators to protect themselves from the immune system. Inadequate complement activation becomes a disease cause, as in atypical hemolytic uremic syndrome, C3 glomerulopathies, and systemic lupus erythematosus. Age-related macular degeneration and cancer will be described as examples showing that complement contributes to a large variety of conditions, far exceeding the classical examples of diseases associated with complement deficiencies. Finally, we discuss complement as a therapeutic target.

Pathogenesis of glomerular haematuria

Haematuria was known as a benign hallmark of some glomerular diseases, but over the last decade, new evidences pointed its negative implications on kidney disease progression. Cytotoxic effects of oxidative stress induced by hemoglobin, heme, or iron released from red blood cells may account for the tubular injury observed in human biopsy specimens. However, the precise mechanisms responsible for haematuria remain unclear. The presence of red blood cells (RBCs) with irregular contours and shape in the urine indicates RBCs egression from the glomerular capillary into the urinary space. Therefore glomerular haematuria may be a marker of glomerular filtration barrier dysfunction or damage. In this review we describe some key issues regarding epidemiology and pathogenesis of haematuric diseases as well as their renal morphological findings.

The role of complement in C3 glomerulopathy

C3 glomerulopathy describes a spectrum of disorders with glomerular pathology associated with C3 cleavage product deposition and with defective complement action and regulation (Fakhouri et al., 2010; Sethi et al., 2012b). Kidney biopsies from these patients show glomerular accumulation or deposition of C3 cleavage fragments, but no or minor deposition of immunoglobulins (Appel et al., 2005; D'Agati and Bomback, 2012; Servais et al., 2007; Sethi and Fervenza, 2011). At present the current situation asks for a better definition of the underlining disease mechanisms, for precise biomarkers, and for a treatment for this disease. The complement system is a self activating and propelling enzymatic cascade type system in which inactive, soluble plasma components are activated spontaneously and lead into an amplification loop (Zipfel and Skerka, 2009). Activation of the alternative pathway is spontaneous, occurs by default, and cascade progression leads to amplification by complement activators. The system however is self-controlled by multiple regulators and inhibitors, like Factor H that control cascade progression in fluid phase and on surfaces. The activated complement system generates a series of potent effector components and activation products, which damage foreign-, as well as modified self cells, recruit innate immune cells to the site of action, coordinate inflammation and the response of the adaptive immune system in form of B cells and T lymphocytes (Kohl, 2006; Medzhitov and Janeway, 2002; Ogden and Elkon, 2006; Carroll, 2004; Kemper and Atkinson, 2007; Morgan, 1999; Muller-Eberhard, 1986; Ricklin et al., 2010). Complement controls homeostasis and multiple reactions in the vertebrate organism including defense against microbial infections (Diaz-Guillen et al., 1999; Mastellos and Lambris, 2002; Nordahl et al., 2004; Ricklin et al., 2010). In consequence defective control of the spontaneous self amplifying cascade or regulation is associated with numerous human disorders (Ricklin and Lambris, 2007; Skerka and Zipfel, 2008; Zipfel et al., 2006). Understanding the exact action and regulation of this sophisticated homeotic cascade system is relevant to understand disease pathology of various complement associated human disorders. Furthermore this knowledge is relevant for a better diagnosis and appropriate therapy. At present diagnosis of C3 glomerulopathy is primarily based on the kidney biopsy, and histological, immmunohistological and electron microscopical evaluation (D'Agati and Bomback, 2012; Fakhouri et al., 2010; Medjeral-Thomas et al., 2014a,b; Sethi et al., 2012b). The challenge is to define the actual cause of the diverse glomerular changes or damages, to define how C3 deposition results in the reported glomerular changes, the location of the cell damage and the formation of deposits.

Anti-factor H autoantibodies in C3 glomerulopathies and in atypical hemolytic uremic syndrome: one target, two diseases

Autoantibodies targeting factor H (FH), which is a main alternative complement pathway regulatory protein, have been well characterized in atypical hemolytic uremic syndrome (aHUS) but have been less well described in association with alternative pathway-mediated glomerulopathies (GP). In this study, we studied 17 patients presenting with GP who were positive for anti-FH IgG. Clinical data were collected and biological characteristics were compared with those of patients presenting with anti-FH Ab-associated aHUS. In contrast to the aHUS patients, the GP patients had no circulating FH-containing immune complexes, and their anti-FH IgG had a weaker affinity for FH. Functional studies demonstrated that these Abs induced no perturbations in FH cell surface protection or the binding of FH to its ligand. However, anti-FH IgG samples isolated from three patients were able to affect the factor I cofactor activity of FH. Epitope mapping identified the N-terminal domain of FH as the major binding site for GP patient IgG. No homozygous deletions of the CFHR1 and CFHR3 genes, which are frequently associated with the anti-FH Ab in aHUS patients, were found in the GP patients. Finally, anti-FH Abs were frequently associated with the presence of C3 nephritic factor in child GP patients and with monoclonal gammopathy in adult GP patients, who frequently showed Ig Lchain restriction during reactivity against factor H. These data provide deeper insights into the pathophysiological differences between aHUS and GP, demonstrating heterogeneity of anti-FH IgG.

Clinico-pathologic spectrum of C3 glomerulopathy-an Indian experience

Background

C3 glomerulopathy (C3GP) is characterized by deposition of complement C3 with absence/traces of immunoglobulins in the glomeruli and categorized into dense deposit disease (DDD), C3 glomerulonephritis (C3GN), complement factor H related protein 5(CFHR5) nephropathy etc. Collaborative efforts of pathologists, complement biologists and nephrologists worldwide are expanding the histomorphological pattern and laboratory findings related to C3GP. Hence, we studied point prevalence and morphological spectrum of C3GP in Indian patients to correlate morphological patterns with standard therapies and outcome of the patients.

Methods

Retrospective analysis of renal biopsies (2007-2012,n-4565), which on immunofluorescence (IF) had C3 dominant deposits with absence or trace amount of immunoglobulin was carried out. Histopathology and electronmicroscopy (EM) were reviewed; cases were re-classified as DDD and C3GN. Histomorphological patterns of both groups were compared and correlated with treatment. Clinical details and follow up of patients were retrieved from the department of nephrology.

Results

There were 31 cases (0.7%) of C3GP sub-classified as DDD (n-13) and C3GN (n-14). It was difficult to sub-classify 4 cases since EM showed overlapping features. C3GN and DDD had distinct clinical characteristics and disease outcome, though pathological features were overlapping. Majority of C3GP patients were males and were in 2^nd to 4^th decade of life. Nephrotic syndrome in DDD and nephritic-nephrotic presentation in C3GN patients was more common.

Hypertension and oliguria were more often observed in C3GN than DDD. Membranoproliferative pattern (MPGN) was commonest pattern in DDD; other patterns seen were mesangial proliferative, mesangial expansive/nodular, exudative and crescentic. C3GN also had all the above patterns, the predominant ones being MPGN and mesangial proliferative. Limited follow-up revealed response to therapy only in C3GN (33%). Progression to ESRD was 33% in DDD and 10% cases in C3GN.

Conclusion

C3GP comprise 0.7% of all renal biopsies. MPGN pattern was the commonest morphological pattern in DDD whereas MPGN and mesangial proliferative pattern were equally dominant patterns in C3GN. EM of 4 cases (13%) showed intermediate features. Evaluation of alternate complement pathway must be done in all cases to identify the point of dysregulated alternate complement pathway and to confirm the diagnosis in ambiguous cases.

Virtual slides

The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1730070964135632

An athletic adolescent girl with proteinuria and hypertension

An 18-year-old athletic adolescent presents with hypertension found during a routine screening. Her prior history includes familial hyperlipidemia. Hypertension in the adolescent is classified based on percentiles for age, sex, and height. The most common secondary cause of hypertension in the pediatric and adolescent patient is renal disease. This patient was found to have nephrotic syndrome and because of her age, a renal biopsy was required to make the diagnosis and to direct subsequent treatment plans. She was diagnosed with C3 glomerulopathy, which is the result of dysregulation and uncontrolled activation of the alternative complement pathway; new therapies are emerging for this disease. In this case, we review the diagnosis and initial assessment of hypertension in the pediatric patient, and the causes of nephrotic syndrome with a focus on C3 glomerulopathy.

Incidence and profile of C3 Glomerulopathy: A single center study

C3 glomerulopathy has recently been described as a distinct entity. The underlying mechanism is unregulated activation of the alternate pathway of the complement system. The most common presentation is with an acute nephritic syndrome. The diagnosis is made on immunofluoroscence by the presence of isolated or dominant C3 staining. In this retrospective study, renal biopsy data were collected from 2010 to 2013 patients with C3 glomerulopathy identified and their clinical and biochemical parameters analyzed. Out of 514 biopsies available for analysis, the incidence of C3 glomerulopathy was 1.16% (n = 6). The mean age of the presentation was 26 years and the average estimated glomerular filtration rate was 30.65 ml/min/1.73 m(2). The most common histopathological pattern was membranoproliferative glomerulonephritis (n = 4).

CD11b is protective in complement-mediated immune complex glomerulonephritis

In chronic serum sickness, glomerular immune complexes form, yet C57BL/6 mice do not develop glomerulonephritis unless complement factor H (CfH) is absent, indicating the relevance of complement regulation. Complement receptor 3 (CD11b) and Fcγ receptors on leukocytes, and CfH on platelets, can bind immune complexes. Here we induced immune complex–mediated glomerulonephritis in CfH^−/− mice chimeric for wild-type, CfH^−/−, CD11b^−/−, or FcRγ^−/− bone marrow stem cells. Glomerulonephritis was worse in CD11b^−/− chimeras compared with all others, whereas disease in FcRγ^−/− and wild-type chimeras was comparable. Disease tracked strongly with humoral immune responses, but not glomerular immune complex deposits. Interstitial inflammation with M1 macrophages strongly correlated with glomerulonephritis scores. CD11b^−/− chimeras had significantly more M1 macrophages and CD4⁺ T cells. The renal dendritic cell populations originating from bone marrow–derived CD11c⁺ cells were similar in all experimental groups. CD11b⁺ cells bearing colony-stimulating factor 1 receptor were present in kidneys, including CD11b^−/− chimeras; these cells correlated negatively with glomerulonephritis scores. Thus, experimental immune complex–mediated glomerulonephritis is associated with accumulation of M1 macrophages and CD4⁺ T cells in kidneys and functional renal insufficiency. Hence, CD11b on mononuclear cells is instrumental in generating an anti-inflammatory response in the inflamed kidney.

Histopathology of MPGN and C3 glomerulopathies

'Membranoproliferative' describes glomerular injury characterized by capillary wall thickening and mesangial expansion owing to increased matrix deposition and hypercellularity. The presence of immune deposits is indicative of membranoproliferative glomerulonephritis (MPGN). Historically, MPGN was further classified into three types according to the appearance and site of the electron-dense deposits seen by electron microscopy, but it is now recognized that many cases show only deposition of the complement component C3, owing to abnormal control of the alternative pathway of complement activation-these cases are now classified as C3 glomerulopathies. Not all cases of C3 glomerulopathy, however, show an MPGN pattern. C3 glomerulopathies include dense deposit disease, which shows dense osmiophilic deposits, and C3 glomerulonephritis, which shows isolated deposits. In many cases, the genetic mutations or autoantibodies responsible for C3 deposition have been identified. Some patients in whom complement control is abnormal will accumulate small amounts of immunoglobulin in their glomeruli and so, in everyday practice, the morphological diagnosis of 'glomerulonephritis with dominant C3' is useful for identifying patients who require investigation of the complement pathway. The recognition that many cases of MPGN are C3 glomerulopathies and that the underlying cause can often be identified in immunoglobulin-associated cases means that the diagnosis of idiopathic MPGN is now very uncommon.

Glomerulonefritis C3: una nueva categoría de glomerulonefritis con implicaciones etiopatogénicas

Introducción: las glomerulonefritis con depósitos exclusivos de la fracción C3 del complemento (GN-C3) pueden implicar alteración en la vía alterna de este. Objetivos: describir retrospectivamente una serie de casos de GN-C3 y determinar la frecuencia con que los pacientes continúan con alteraciones renales y/o hipocomplementemia. Métodos: se evaluaron las características histológicas y clínicas y la evolución de los 22 casos de GN-C3 diagnosticados entre 2004 y 2012 en el Departamento de Patología (Facultad de Medicina, Universidad de Antioquia). Resultados: 14 de los pacientes fueron niños y 12 fueron hombres; la mediana de edad fue de 13 años (rango: 3-65). Diez se presentaron como síndrome nefrítico, siete como GN rápidamente progresiva, tres como insuficiencia renal aguda, uno como insuficiencia renal crónica y uno como síndrome nefrótico-nefrítico; 21 tenían hipocomplementemia C3. Todas las biopsias mostraron GN proliferativa. Ocho pacientes tuvieron remisión completa; cuatro, alteraciones persistentes del uroanálisis; seis desarrollaron enfermedad renal crónica, en cinco de ellos terminal; en cuatro no hubo seguimiento. En nueve pacientes hubo seguimiento de los niveles séricos de C3 y en todos ellos se normalizaron entre 1 y 3 meses después de la biopsia. Conclusiones: las GN-C3 pueden producir alteraciones renales persistentes o recurrentes y evolucionar a la insuficiencia renal terminal. Es recomendable el seguimiento clínico a largo plazo, con mediciones repetidas de los niveles de C3.

Eculizumab for treatment of rapidly progressive C3 glomerulopathy

C3 glomerulopathy (C3G) is a prototypic complement-mediated kidney disease. Rapidly progressive forms of C3G usually respond poorly to conventional treatments. We report on the efficacy of the terminal complement inhibitor eculizumab in 3 adult patients with rapidly progressive C3G. In all 3 patients, serum creatinine levels had increased by >50% in the 2 months preceding initiation of eculizumab treatment despite the use of conventional immunosuppressive drugs and/or plasma exchanges in 2 of these individuals. Of note, 2 patients had long-standing nephrotic syndrome. Kidney biopsy performed prior to eculizumab treatment disclosed marked glomerular inflammatory changes and increased C5b-9 deposition in all patients. Eculizumab use was associated with significant improvement in kidney function, with estimated glomerular filtration rates of patients increasing 22 to 38 mL/min/1.73 m(2). Eculizumab use also was associated with remission of nephrotic syndrome in the 2 affected patients, an effect observed as early as one week after treatment initiation. Repeat kidney biopsy disclosed regression of glomerular inflammatory changes and decreases in glomerular staining for C5b-9 in all patients. These results warrant further assessment of eculizumab for treatment of rapidly progressive forms of C3G with markedly increased glomerular C5b-9 deposits.

Reanalysis of membranoproliferative glomerulonephritis patients according to the new classification: a multicenter study

BACKGROUND

All types of membranoproliferative glomerulonephritis (MPGN) are progressive diseases with poor prognoses. Recently, a newly proposed classification of these diseases separated them into immune complex- and complement-mediated diseases. We investigated the frequency of C3 glomerulonephritis among previously diagnosed MPGN patients.

METHODS

We conducted a retrospective study of patients diagnosed with MPGN at three tertiary care institutions between 2001 and 2010. We investigated the incidence of complement-mediated disease among patients diagnosed with MPGN. Progressive renal dysfunction was defined as a 50% reduction in the glomerular filtration rate or the need for renal replacement therapy.

RESULTS

Among the 3,294 renal biopsy patients, 77 (2.3%) were diagnosed with MPGN; 31 cases were excluded, of which seven were diagnosed with systemic lupus nephritis, and the others were not followed for a minimum of 12 months after biopsy. Based on the new classification, complement-mediated MPGN was diagnosed in two patients (4.3%); only one patient developed progressive renal dysfunction. Among the immune complex-mediated MPGN patients, 17 patients developed progressive renal dysfunction. Serum albumin and creatinine levels at the time of MPGN diagnosis were risk factors of renal deterioration, after adjusting for low C3 levels and nephrotic syndrome.

CONCLUSION

Complement-mediated glomerulonephritis was present in 4.3% of patients previously diagnosed with MPGN.

Successful treatment of infectious endocarditis associated glomerulonephritis mimicking c3 glomerulonephritis in a case with no previous cardiac disease

We report a 42-year-old man with subacute infectious endocarditis (IE) with septic pulmonary embolism, presenting rapidly progressive glomerulonephritis and positive proteinase 3-anti-neutrophil cytoplasmic antibody (PR3-ANCA). He had no previous history of heart disease. Renal histology revealed diffuse endocapillary proliferative glomerulonephritis with complement 3- (C3-) dominant staining and subendothelial electron dense deposit, mimicking C3 glomerulonephritis. Successful treatment of IE with valve plastic surgery gradually ameliorated hypocomplementemia and renal failure; thus C3 glomerulonephritis-like lesion in this case was classified as postinfectious glomerulonephritis. IE associated glomerulonephritis is relatively rare, especially in cases with no previous history of valvular disease of the heart like our case. This case also reemphasizes the broad differential diagnosis of renal involvement in IE.

Eculizumab in the treatment of membranoproliferative glomerulonephritis

A major shift in our understanding of the membranoproliferative glomerulonephritis (MPGN) lesion is the focus on which components of the complement pathway are involved in mediating renal injury. Hence, MPGN is no longer classified solely by ultrastructural findings on biopsy but instead divided into immune complex-mediated lesions versus complement-mediated lesions. This emphasis on complement, in turn, leads to interest in therapies that target complement as potential disease-modifying agents. Eculizumab, the first available anticomplement therapy, blocks at the level of C5 and has revolutionized the treatment of complement-mediated diseases such as paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome. Whether this agent will work equally well for the far more heterogeneous complement-mediated MPGN lesions, also known as C3 glomerulopathy, remains unclear. To date, the experience and published data on using eculizumab in MPGN suggests this agent will work for some, but not all, patients with this pathologic lesion.

Successful management of a patient with a C3 Glomerulonephritis and crescentic pattern: a case report

BACKGROUND

Crescentic glomerulonephritis is a rare condition in children and is typically associated with renal insufficiency. Dysfunction of the alternative complement pathway is an unusual aetiology with an unknown mechanism.

CASE PRESENTATION

We report a case of a previously healthy 12-year-old Caucasian girl who was examined on emergency owing to an asymptomatic gross haematuria. An active urinary sediment and nephrotic-range proteinuria were identified, and serologic examination showed a decreased serum C3 concentration not associated with any immunologic or infectious cause. Oedema, hypertension, and renal insufficiency were not observed. A renal biopsy was performed, and crescentic glomerulonephritis associated with C3 glomerulonephritis was diagnosed. Prompt treatment with intravenous steroids resulted in complete resolution of the gross haematuria. Further examination did not detect any underlying acquired cause. A combination of oral steroids and cyclophosphamide, followed by mycophenolate mofetil, was maintained and resulted in clinical remission during an 8-month follow-up.

CONCLUSION

The presence of severe injury such as crescentic glomerulonephritis secondary to C3 glomerulonephritis is extremely unusual in children. This is the first known case of paediatric crescentic glomerulonephritis secondary to C3 glomerulonephritis that presented with gross haematuria and was treated early and effectively with immunosuppressive therapy based on its severe histologic features.