Pathogenic mechanisms in membranoproliferative glomerulonephritis

Glomerulonephritis during Mycobacterium tuberculosis infection: scoping review

INTRODUCTION

People with Tuberculosis (TB) infection may present with glomerulonephritis (GN). The range of presentations, renal pathologies, and clinical outcomes are uncertain. Whether clinical features that establish if GN etiology is medication or TB related, and possible benefits of immunosuppression remain uncertain.

METHODS

A scoping review was completed, searching MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Web of Science and Conference Abstracts from Inception to December, 2023. The study population included patients with TB infection who developed GN and underwent renal biopsy. All data regarding presentation, patient characteristics, renal pathology, management of TB and GN, and outcomes were summarized.

RESULTS

There were 62 studies identified, with 130 patients. These cases included a spectrum of presentations including acute kidney injury, nephrotic syndrome and hypertension, and a range of 10 different renal pathology diagnoses. Cases that included immunosuppression and outcomes ranged from complete remission to long-term dialysis dependence. The presence of granulomas (4/4, 100%), anti-glomerular basement membrane disease (3/3, 100%), amyloidosis (75/76, 98.7%), and focal segmental glomerulosclerosis (2/2, 100%) were specific for GN being TB-infection related. On the other hand, minimal change disease was specific for anti-TB therapy related (7/7, 100%). While patients with more aggressive forms of GN commonly were prescribed immunosuppression, this study was unable to confirm efficacy. Only rifampin or isoniazid were implicated in drug-associated GN.

DISCUSSION

This study provides a clear rationale for renal biopsy in patients with TB and GN, and outlines predictors for the GN etiology. Thus, this study establishes key criteria to optimize diagnosis and management of patients with TB and GN.

Mesangiocapillary glomerulonephritis complicating pulmonary tuberculosis

Glomerulonephritis in tuberculosis may be a direct manifestation of renal infection or a result of immune-complex deposition complicating extra-renal infection, such as in pulmonary tuberculosis. A 17-year-old adolescent boy from Somalia was found to have pulmonary tuberculosis during routine health screening performed on entering Malta, with computed tomography of the chest showing scarring and calcification of the left upper lobe, left lower lobe consolidation, and a small left-sided pleural effusion. Five days after starting anti-tuberculous therapy, he developed lower limb and sacral oedema: urinary albumin: creatinine ratio was > 400 µg albumin/mg creatinine, and 24-h urinary protein showed nephrotic-range proteinuria of 4.963 g/day. In view of worsening lower limb, sacral and periorbital oedema and ascites, he was started on oral prednisolone, omeprazole and penicillin V prophylaxis. As heavy proteinuria persisted, a renal biopsy was performed after 8 days of prednisolone treatment, which confirmed the presence of mesangiocapillary glomerulonephritis (MCGN), with electron microscopy showing effacement of the podocytes, with hypercellularity and subendothelial immune deposits, confirming an immune-mediated pathophysiology. Ziehl-Neelsen staining did not reveal acid-fast organisms. The patient received a total of 3 weeks of oral prednisolone with subsequent tailing doses, 2 months of pyrazinamide and ethambutol and 6 months of rifampicin and isoniazid with complete resolution of his clinical and radiological signs, though heavy proteinuria persisted, so he was commenced on oral enalapril. This case highlights the potential association of MCGN with tuberculosis in adolescence. Timely recognition and treatment can prevent progression to chronic kidney disease.

Immunotactoid Glomerulopathy with Nontuberculous Mycobacterial Infection: A Novel Association

A 70-year-old woman underwent a renal biopsy due to nephrotic syndrome. She had suffered from nontuberculous mycobacterial infection (NTM) for 14 years. The patient was diagnosed as having membranoproliferative glomerulonephritis (MPGN) type 3 and immunoglobulin (Ig)-associated MPGN based upon LM/erythromycin and IF findings, respectively. In high-magnification imaging, electron-dense deposits showed immunotactoid glomerulopathy (ITG). There was no evidence of hematological cancer, and the patient improved after receiving treatments for NTM. To the best of our knowledge, this patient is the first to show an association between ITG and NTM. Although ITG is generally considered as related to lymphoproliferative disease, it is suggested that ITG is driven by bacterial infection and is a potential outcome of Ig-associated MPGN.

Case Report: Membranoproliferative Glomerulonephritis, a Rare Clinical Manifestation of Abernethy Malformation Type II

This report describes an 8-year-old male who presented with clinical manifestations including systemic edema, heavy proteinuria, hypoproteinemia, and persistent hypocomplementemia. Arachnoid cysts and focal nodular hyperplasia were also detected. Imaging examination and renal biopsy were performed, and Abernethy malformation type II with immune complex-mediated membranoproliferative glomerulonephritis was considered the diagnosis. Due to the persistence of embryonic vessels, Abernethy malformation is a rare congenital vascular malformation of the splanchnic venous system, which can be classified as type I (end-to-side shunt) and type II (side-to-side shunt). Abernethy malformation with glomerulonephritis remains extremely rare. In the patient described, glomerulonephritis mediated by immune complex with "full-house" positive immunohistochemistry was confirmed on renal biopsy. In addition, he was treated with glucocorticoids and tacrolimus. Whether surgical treatment is necessary should be determined according to the state of the disease in the later stages. The present case reflects the association between the congenital portosystemic shunt and the renal region and, to the authors' knowledge, may be the first report to describe arachnoid cysts as a symptom of Abernethy malformation.

Clinical and Pathophysiological Insights Into Immunological Mediated Glomerular Diseases in Childhood

The kidney is often the target of immune system dysregulation in the context of primary or systemic disease. In particular, the glomerulus represents the anatomical entity most frequently involved, generally as the expression of inflammatory cell invasion or circulant or in situ immune-complex deposition. Glomerulonephritis is the most common clinical and pathological manifestation of this involvement. There are no universally accepted classifications for glomerulonephritis. However, recent advances in our understanding of the pathophysiological mechanisms suggest the assessment of immunological features, biomarkers, and genetic analysis. At the same time, more accurate and targeted therapies have been developed. Data on pediatric glomerulonephritis are scarce and often derived from adult studies. In this review, we update the current understanding of the etiologic events and genetic factors involved in the pathogenesis of pediatric immunologically mediated primitive forms of glomerulonephritis, together with the clinical spectrum and prognosis. Possible new therapeutic targets are also briefly discussed.

Mixed cryoglobulinemic membranoproliferative glomerulonephritis due to monoclonal gammopathy of undetermined significance: A case report

RATIONALE

Membranoproliferative glomerulonephritis (MPGN) can be induced by autoimmune diseases, chronic infection, chronic hepatitis, and paraproteins (including cryoglobulinemia). In addition, the mixed cryoglobulinemic MPGN is reported to be highly correlated with hepatitis C virus (HCV) infection.

PATIENT CONCERNS

We reported a rare case of a 61-year-old woman without a history of viral hepatitis infection; she presented with bilateral leg edema and proteinuria. Renal pathology revealed MPGN with multiple positive immunofluorescent staining. The consequent serum survey revealed positive cryoglobulin and monoclonal gammopathy of kappa type of immunoglobulin M. However, bone marrow study showed no obvious plasma cell proliferation, indicating that multiple myeloma was less likely.

DIAGNOSES

This patient's cryoglobulinemic MPGN could be related to monoclonal gammopathy of undetermined significance.

INTERVENTIONS

Oral immunosuppressant.

OUTCOMES

After steroid treatment, her renal function normalized and proteinuria kept in low level.

LESSONS

We demonstrated a rare cause of cryoglobulinemic MPGN without HCV infection, which led to a favorable prognosis after receiving steroid therapy. Moreover, the diagnosis of monoclonal gammopathy should be considered when facing such case and aggressive steroid therapy might be beneficial.

Respuesta a la farmacoterapia en pacientes con glomerulonefritis membranoproliferativa en una clínica de Barranquilla, Colombia. 2007-2014

Introducción. La glomerulonefritis membranoproliferativa (GnMP) es un patrón de lesión glomerular hipercelular mesangial con adelgazamiento de la membrana basal glomerular y proliferación endocapilar que está mediado por las inmunoglobulinas o el sistema del complemento en el mesangio y endotelio capilar.Objetivo. Evaluar la respuesta a la farmacoterapia en pacientes diagnosticados con GnMP en una clínica de Barranquilla entre los años 2007 y 2014.Materiales y métodos. Estudio de cohorte retrospectivo en el que se evaluaron 58 pacientes con diagnóstico de GnMP por biopsia renal, quienes se clasificaron como respondedores y no respondedores. Se realizó una evaluación de tratamiento estándar según tipo de GnMP: mediado por complemento y mediado por inmunocomplejos e inmunofluorescencia negativa a los 6 y 12 meses de tratamiento.Resultados. La edad promedio de los participantes fue de 35±13 años. De 58 pacientes, 52% eran mujeres, 63% desarrolló enfermedad renal crónica (ERC) al año de evaluación, 25.8% logró remisión (22.4% completa y 3.4% parcial) y 74.2% no logró entrar en remisión.Conclusión. La GnMP es una causa importante de ERC entre la población estudiada. La respuesta al tratamiento inmunosupresor no demostró beneficios estadísticamente significativos, independiente del tipo de GnMP.

Extrahepatic manifestations of HCV: the role of direct acting antivirals

INTRODUCTION

Hepatitis C virus (HCV) represents a major health concern, as nearly 3 million people become newly infected by this pathogen annually. The majority of infected individuals fail to clear the virus, and chronicity is established. Chronic HCV patients are at high risk for liver disease, ranging from mild fibrosis to cirrhosis and severe hepatocellular carcinoma. Over the last few years, the development of multiple direct acting antivirals (DAA) have revolutionized the HCV infection treatment, demonstrating cure rates higher than 90%, and showing less side effects than previous interferon-based regimens. Areas covered: Besides liver, HCV infection affects a variety of organs, therefore inducing diverse extrahepatic manifestations. This review covers clinical, experimental, and epidemiological publications regarding systemic manifestations of HCV, as well as recent studies focused on the effect of DAA in such conditions. Expert commentary: Though further research is needed; available data suggest that HCV eradication is often associated with the improvement of extrahepatic symptoms. Therefore, the emergence of DAA would offer the opportunity to treat both HCV infection and its systemic manifestations, requiring shorter treatment duration and driving minor adverse effects.

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.

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.

[Minimal-change glomerulonephritis in chronic lymphocytic leukemia: A clinical case]

Chronic lymphocytic leukemia (CLL) in association with glomerulonephritis (GN) and renal failure is a serious problem in terms of therapy. The paper reports a clinical case of a 64-year-old female patient with Binet stage C CLL accompanied by minimal-change GN complicated by nephrotic syndrome and the development of acute renal failure. GN was diagnosed on the basis of electron microscopic studies of renal biopsy specimens. It was treated with rituximab in combination with bendamustine. The former was intravenously injected in a dose of 375 mg/m2 on day 0 of the cycle; the latter was given in a dose of 70 mg/m2 within the first 2 days; the cycle was repeated 28 days after initiation of the previous cycle. Five cycles could result in complete CLL remission (the follow-up duration was 20 months); nephrotic syndrome was completely abolished and kidney function recovered.

Expression of macrophage markers in cryoglobulinemic glomerulonephritis - a possible role of CXCL9

PURPOSE

Cryoglobulinemic glomerulonephritis (CGGN) is a type of membranoproliferative glomerulonephritis (MPGN) that develops in patients with systemic cryoglobulinemia. To date the exact pathogenesis of CGGN remains unclear. It has been suggested that macrophages may be significant contributors to the glomerular injury in this disease. In our study we attempt to characterize the macrophages in human CGGN using classical activation and regulatory macrophage markers.

MATERIAL AND METHOD

We searched our database for renal biopsy cases of CGGN. Macrophages were detected using a monoclonal anti-CD68 antibody. Two groups of macrophage markers were used: classical activation markers, including iNOS, CXCL9 and CCL20, and regulatory markers: SPHK1 and LIGHT. The stains were performed using immunohistochemical method.

RESULTS

Five patients with CGGN were identified. Four patients had systemic cryoglobulinemia and two had a serological evidence of hepatitis C virus infection. In all cases the glomeruli contained numerous macrophages. Staining for activatory macrophage markers revealed a strong nuclear staining for CXCL9 in numerous cells, including those corresponding to the macrophage location. Staining for the other activatory markers, as well as staining for regulatory markers, was not significant.

CONCLUSION

In this study of human CGGN we showed a striking expression of cytokine CXCL9, a classical macrophage activation marker, by the macrophages and possibly other cell types within the glomeruli. This observation points to the possible role of classically activated macrophages in the pathogenesis of MPGN. If this observation is confirmed on a larger group of patients, the cytokine CXCL9 could become a potential therapeutic target for human CGGN.

The complement cascade and renal disease

Serum complement cascade, a part of innate immunity required for host protection against invading pathogens, is also a mediator of various forms of disease and injury. It is activated by classical, lectin, and alternative pathways that lead to activation of C3 component by C3 convertases, release of C3b opsonin, C5 conversion and eventually membrane attack complex formation. The tightly regulated activation process yields also C3a and C5a anaphylatoxins, which target a broad spectrum of immune and non-immune cells. The review discusses the involvement of the complement cascade in kidney disease pathogenesis and injury. The role of the complement pathways in autoantibody-mediated forms of glomerulonephritis (lupus nephritis, anti-glomerular basement membrane disease, anti-neutrophil cytoplasmic autoantibody-induced or membranoproliferative glomerulonephritis, membranous nephropathy), C3 glomerulopathy, atypical forms of hemolytic uremic syndrome, ischemic-reperfusion injury of transplanted kidney, and antibody-mediated renal allograft rejection are discussed. The disturbances in complement activation and regulation with underlying genetics are presented and related to observed pathology. Also promising strategies targeting the complement system in complement-related disorders are mentioned.

Positive C1q staining associated with poor renal outcome in membranoproliferative glomerulonephritis

BACKGROUND

Pathogenesis and clinical prognosis of membranoproliferative glomerulonephritis (MPGN) has not yet been established.

METHODS

We conducted a retrospective study of 41 patients with MPGN (type I and III) and examined the renal survival. In addition, factors contributing to survival time were analyzed.

RESULTS

Fourteen patients (34 %) were classified into the renal death group. Patients with nephrotic syndrome and positive C1q staining of glomerular deposits showed a particularly poor prognosis. Significantly higher frequency of nephrotic syndrome and higher urinary protein excretion were observed in the renal death group (p = 0.0002, p = 0.0002) than in the renal survival group. The intensity of C1q staining was positively correlated with the severity of the proteinuria (p = 0.004). Factors that influenced the survival time were positive C1q staining of glomerular deposits (p = 0.003), presence of nephrotic syndrome (p = 0.004), serum albumin (p = 0.02), and proteinuria (p = 0.04).

CONCLUSIONS

C1q staining in glomerular deposits and nephrotic syndrome were important factors influencing the prognosis and outcome in MPGN patients. C1q deposition may play a key role in the pathogenesis of MPGN, as evidenced by numerous observations, such as induction of proteinuria.

Idiopathic membranoproliferative glomerulonephritis: does it exist?

When membranoproliferative glomerulonephritis (MPGN) was first delineated as a discrete clinico-pathological entity more than a half-century ago, most cases were regarded as idiopathic (or primary) in nature. Advances in analysis of pathogenetic mechanisms and etiologies underlying the lesion of MPGN have radically altered the prevalence of the truly idiopathic form of MPGN. In addition, MPGN as a category among renal biopsies showing glomerulonephritis has diminished over time. In the modern era, MPGN is mainly classified morphologically on the basis of immunoglobulin (Ig; monoclonal or polyclonal) and complement (C3 only or combined with Ig) deposition and secondarily on the basis of its appearance on ultra-structural examination. Idiopathic MPGN is a diagnosis of exclusion, at least in many adults and a portion of children, and a systematic approach to evaluation will often uncover a secondary cause, such as an infection, autoimmune disease, monoclonal gammopathy, neoplasia, complement dysregulation or a chronic thrombotic microangiopathy. Idiopathic MPGN remains an 'endangered species' after its separation from these known causes.

Basic and translational concepts of immune-mediated glomerular diseases

Genetically modified immune responses to infections and self-antigens initiate most forms of GN by generating pathogen- and danger-associated molecular patterns that stimulate Toll-like receptors and complement. These innate immune responses activate circulating monocytes and resident glomerular cells to release inflammatory mediators and initiate adaptive, antigen-specific immune responses that collectively damage glomerular structures. CD4 T cells are needed for B cell-driven antibody production that leads to immune complex formation in glomeruli, complement activation, and injury induced by both circulating inflammatory and resident glomerular effector cells. Th17 cells can also induce glomerular injury directly. In this review, information derived from studies in vitro, well characterized experimental models, and humans summarize and update likely pathogenic mechanisms involved in human diseases presenting as nephritis (postinfectious GN, IgA nephropathy, antiglomerular basement membrane and antineutrophil cytoplasmic antibody-mediated crescentic GN, lupus nephritis, type I membranoproliferative GN), and nephrotic syndrome (minimal change/FSGS, membranous nephropathy, and C3 glomerulopathies). Advances in understanding the immunopathogenesis of each of these entities offer many opportunities for future therapeutic interventions.

Membranoproliferative glomerulonephritis: pathogenetic heterogeneity and proposal for a new classification

Membranoproliferative glomerulonephritis (MPGN) is a pattern of injury that results from subendothelial and mesangial deposition of Igs caused by persistent antigenemia and/or circulating immune complexes. The common causes of Ig-mediated MPGN include chronic infections, autoimmune diseases, and monoclonal gammopathy/dysproteinemias. On the other hand, MPGN also can result from subendothelial and mesangial deposition of complement owing to dysregulation of the alternative pathway (AP) of complement. Complement-mediated MPGN includes dense deposit disease and proliferative glomerulonephritis with C3 deposits. Dysregulation of the AP of complement can result from genetic mutations or development of autoantibodies to complement regulating proteins with ensuing dense deposit disease or glomerulonephritis with C3 deposits. We propose a new histologic classification of MPGN and classify MPGN into 2 major groups: Ig-mediated and complement-mediated. MPGN that is Ig-mediated should lead to work-up for infections, autoimmune diseases, and monoclonal gammopathy. On the other hand, complement-mediated MPGN should lead to work-up of the AP of complement. Initial AP screening tests should include serum membrane attack complex levels, an AP functional assay, and a hemolytic assay, followed by tests for mutations and autoantibodies to complement-regulating proteins.

The 2010 nephrology quiz and questionnaire: part 2

Presentation of the Nephrology Quiz and Questionnaire (NQQ) has become an annual "tradition" at the meetings of the American Society of Nephrology. It is a very popular session judged by consistently large attendance. Members of the audience test their knowledge and judgment on a series of case-oriented questions prepared and discussed by experts. They can also compare their answers in real time, using audience response devices, to those of program directors of nephrology training programs in the United States, acquired through an Internet-based questionnaire. As in the past, the topics covered were transplantation, fluid and electrolyte disorders, end-stage renal disease and dialysis, and glomerular disorders. Two challenging cases representing each of these categories along with single best answer questions were prepared by a panel of experts (Drs. Hricik, Palmer, Bargman, and Fervenza, respectively). The "correct" and "incorrect" answers then were briefly discussed, after the audience responses and the results of the questionnaire were displayed. The 2010 version of the NQQ was exceptionally challenging, and the audience, for the first time, gained a better overall correct answer score than the program directors, but the margin was small. Last month we presented the transplantation and fluid and the electrolyte cases; in this issue we present the remaining end-stage renal disease and dialysis and the glomerular disorder cases. These articles try to recapitulate the session and reproduce its educational value for a larger audience--that of the readers of the Clinical Journal of the American Society of Nephrology. Have fun.

Membranoproliferative glomerulonephritis with isolated C3 deposits: case report and literature review

Membranoproliferative glomerulonephritis with isolated C3 deposits (MPGNC3) is an uncommon condition characterized by overt glomerular C3 deposits in the absence of immunoglobulins and intramembranous dense deposits. Here the authors describe the clinical and morphological features of primary MPGNC3 in a 13-year-old boy and critically review the previously published cases. The patient presented with nephrotic syndrome and microscopic hematuria. Blood tests revealed very low circulating C3 levels. The renal biopsy exhibited subendothelial, subepithelial, and mesangial deposits, with C3 but not immunoglobulins seen on immunofluorescence. This case and the review of the literature indicate that the serum complement profile with decreased levels of C3 and normal levels of classical pathway components together with glomerular deposits containing exclusively complement C3 is highly suggestive of alternative pathway activation. The diagnosis of acquired and/or genetic complement abnormalities in some cases supports that complement dysregulation is implicated in the pathogenesis of MPGNC3. Such data show great promise to provide new therapy strategies based on modulation of the complement system activity.

Membranoproliferative glomerulonephritis

Membranoproliferative glomerulonephritis is an uncommon kidney disorder characterized by mesangial cell proliferation and structural changes in glomerular capillary walls. It can be subdivided into idiopathic and secondary forms, which are differentially diagnosed by a review of clinical features, laboratory data, and renal histopathology. Three types-I, II, and III-have been defined by pathologic features. All three types are associated with hypocomplementemia, but they manifest somewhat different mechanisms of complement activation. Type II, also known as "dense deposit disease", is associated with the presence of C3-nephritic factor. Membranoproliferative glomerulonephritis primarily affects children and young adults, with patients presenting with nephrotic or nephritic syndrome or with asymptomatic renal disease. This type of glomerulonephritis often progresses slowly to end-stage renal disease, and it tends to recur after renal transplantation, especially type II. The efficacy of various forms of treatment remains controversial; however, long-term steroid treatment seems to be effective in children with nephrotic-range proteinuria. Improvement in renal outcomes largely relies on the evaluation of more selective agents in carefully controlled studies.

Neutrophils: game changers in glomerulonephritis?

Glomerulonephritides represent a diverse array of diseases that have in common immune cell-mediated effector mechanisms that cause organ damage. The contribution of neutrophils to the pathogenesis of proliferative glomerulonephritis (GN) is not well recognized. Most equate neutrophils with killing pathogens and causing collateral tissue damage during acute inflammation. However, these phagocytes are endowed with additional characteristics that have been traditionally reserved for cells of the adaptive immune system. They communicate with other cells, exhibit plasticity in their responses and have the potential to coordinate and inform the subsequent immune response, thus countering the notion that they arrive, destroy and then disappear. Therefore, neutrophils, which are the first to arrive at a site of inflammation, are potential game changers in GN.

Management of hepatitis C virus-related mixed cryoglobulinemia

Mixed cryoglobulinemia is a chronic immune complex-mediated disease strongly associated with hepatitis C virus (HCV) infection. Mixed cryoglobulinemia is a vasculitis of small and medium-sized arteries and veins, due to the deposition of complexes of antigen, cryoglobulin and complement in the vessel walls. The main clinical features of mixed cryoglobulinemia vasculitis include the triad of palpable purpura, arthralgias, and weakness, and other pathological conditions such as glomerulonephritis, peripheral neuropathy, skin ulcers, and widespread vasculitis. The treatment of HCV-related mixed cryoglobulinemia is difficult due to the multifactorial origin and clinical polymorphism of the syndrome. It can be directed to eradicate the HCV infection, suppress the B-cell clonal expansion and cryoglobulin production, or ameliorate symptoms. The choice of the most appropriate treatment is strictly related to the assessment of disease activity, and to the extent and severity of organ involvement.

Membranoproliferative glomerulonephritis secondary to monoclonal gammopathy

BACKGROUND AND OBJECTIVES

Membranoproliferative glomerulonephritis (MPGN) is an immune complex-mediated glomerulonephritis characterized by subendothelial and mesangial deposition of immune complexes. Autoimmune diseases and chronic infections, such as hepatitis C, are commonly recognized causes of MPGN; however, monoclonal gammopathy is a less widely recognized cause of MPGN.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We reviewed all renal biopsies of MPGN in Mayo Clinic patients during a 6-year period to determine the association of monoclonal gammopathy with MPGN. Results were correlated with electrophoresis studies and bone marrow biopsies to clarify the relationship between MPGN and gammopathies.

RESULTS

Of 126 patients with MPGN, 20 did not have workup for hepatitis B or C. Of the remaining 106 patients, 25 (23.5%) were positive for hepatitis B or C. Of the 81 hepatitis-negative patients, 13 were not evaluated for gammopathies. Of the remaining 68 patients, 28 (41.1%) had serum and/or urine electrophoresis studies positive for monoclonal gammopathy. Serum immunofixation electrophoresis was the most sensitive method for diagnosing monoclonal gammopathy. Renal biopsy showed a membranoproliferative pattern of injury; immunofluorescence microscopy was often instrumental in diagnosing the underlying gammopathy. On the basis of the bone marrow biopsy, monoclonal gammopathy of undetermined significance was the most common entity associated with MPGN. Other, less common causes included multiple myeloma, low-grade B cell lymphoma, and chronic lymphocytic leukemia.

CONCLUSIONS

Monoclonal gammopathy is an important and common cause of MPGN; therefore, all patients with a diagnosis of MPGN should be evaluated for an underlying monoclonal gammopathy.

Non-Hodgkin's lymphoma associated membranoproliferative glomerulonephritis: rare case of long term remission with chemotherapy: a case report

Introduction

Although membranoproliferative glomerulonephritis has been reported to occur in association with non-Hodgkin's lymphoma, information concerning the long term effects of treatment of non-Hodgkin's lymphoma on the associated membranoproliferative glomerulonephritis is limited.

Case presentation

The current report describes a patient who presented with the abrupt onset of hypertension, mixed nephritic/nephrotic syndrome and acute renal failure. Kidney biopsy was consistent with membranoproliferative glomerulonephritis, type 1. Bone marrow biopsy performed in the evaluation of periaortic lymphadenopathy, hepatosplenomegaly, and thrombocytopenia confirmed the diagnosis of low grade B-cell non-Hodgkin's lymphoma. The patient's renal function improved and proteinuria resolved after initial treatment of non-Hodgkin's lymphoma with chemotherapy. During eleven years of follow up, membranoproliferative glomerulonephritis has remained in remission, as confirmed by repeatedly negative urinalyses, normal blood pressure and absence of clinical signs and symptoms suggestive of nephritic/nephrotic syndrome.

Conclusion

Membranoproliferative glomerulonephritis has been known to be associated with both chronic lymphocytic leukemia and non-Hodgkin's lymphoma, particularly with B cell lymphocytic type non-Hodgkin's lymphoma. There is limited information available concerning the effects of treatment of non-Hodgkin's lymphoma on the progression of non-Hodgkin's lymphoma associated membranoproliferative glomerulonephritis. In the few reported cases we found, long term follow up after initial resolution of the membranoproliferative glomerulonephritis was lacking. This report presented a rare case of non-Hodgkin's lymphoma associated membranoproliferative glomerulonephritis, that continued to be in remission during eleven years of follow up after initial chemotherapy treatment of lymphoma.

Non-Hodgkin's lymphoma associated membranoproliferative glomerulonephritis: rare case of long term remission with chemotherapy: a case report

INTRODUCTION

Although membranoproliferative glomerulonephritis has been reported to occur in association with non-Hodgkin's lymphoma, information concerning the long term effects of treatment of non-Hodgkin's lymphoma on the associated membranoproliferative glomerulonephritis is limited.

CASE PRESENTATION

The current report describes a patient who presented with the abrupt onset of hypertension, mixed nephritic/nephrotic syndrome and acute renal failure. Kidney biopsy was consistent with membranoproliferative glomerulonephritis, type 1. Bone marrow biopsy performed in the evaluation of periaortic lymphadenopathy, hepatosplenomegaly, and thrombocytopenia confirmed the diagnosis of low grade B-cell non-Hodgkin's lymphoma. The patient's renal function improved and proteinuria resolved after initial treatment of non-Hodgkin's lymphoma with chemotherapy. During eleven years of follow up, membranoproliferative glomerulonephritis has remained in remission, as confirmed by repeatedly negative urinalyses, normal blood pressure and absence of clinical signs and symptoms suggestive of nephritic/nephrotic syndrome.

CONCLUSION

Membranoproliferative glomerulonephritis has been known to be associated with both chronic lymphocytic leukemia and non-Hodgkin's lymphoma, particularly with B cell lymphocytic type non-Hodgkin's lymphoma. There is limited information available concerning the effects of treatment of non-Hodgkin's lymphoma on the progression of non-Hodgkin's lymphoma associated membranoproliferative glomerulonephritis. In the few reported cases we found, long term follow up after initial resolution of the membranoproliferative glomerulonephritis was lacking. This report presented a rare case of non-Hodgkin's lymphoma associated membranoproliferative glomerulonephritis, that continued to be in remission during eleven years of follow up after initial chemotherapy treatment of lymphoma.

Cryoglobulinemia and renal disease

PURPOSE OF REVIEW

Cryoglobulinemia occurs in a variety of clinical settings including lymphoproliferative disorders, infection and autoimmune disease. The worldwide pandemic of hepatitis C virus infection has resulted in a significant increase in its extrahepatic complications including cryoglobulinemia and renal disease. Here we review the types of cryoglobulins, mechanisms of cryoglobulin formation, links between hepatitis C virus and renal disease, and current approaches to therapy.

RECENT FINDINGS

The prevalence of cryoglobulinemia in hepatitis C virus-infected individuals is surprisingly large and may be found in more than 50% of some infected subpopulations. Most of these patients will not have overt renal disease, but there is a population of unknown size of patients with subclinical glomerular disease that has the potential to become clinically significant. In cases of hepatitis C virus-associated cryoglobulinemia, treatment remains focused on eradication of viremia, but interventions directed at B lymphocytes are increasingly utilized. The mechanisms of cryoglobulin formation and renal injury remain largely obscure, but recent evidence implicates the innate immune system in the initiation of disease.

SUMMARY

The most common renal injury associated with hepatitis C virus infection, in patients both with and without evidence of cryoglobulinemia, is membranoproliferative glomerulonephritis. There has been increasing focus on defining the mechanisms that link these processes and the evolution of renal injury in all clinical settings of cryoglobulinemia.

TLR4 links podocytes with the innate immune system to mediate glomerular injury

Toll-like receptors (TLR) classically recognize pathogen-associated danger signals but are also activated via endogenous ligands. For evaluation of their role in inflammatory kidney disease, the function of TLR was analyzed in two mouse models of cryoglobulinemic membranoproliferative glomerulonephritis (MPGN; mice transgenic for thymic stromal lymphopoietin [TSLP], with or without deletion of the Fcgamma receptor IIb). Expression of TLR1 through 9 and TLR11 mRNA was detectable in whole kidneys and in isolated glomeruli of wild-type mice, with TLR3 and TLR4 having the highest absolute levels of expression. TLR1, 2, and 4 were increased in TSLP transgenic mice and even higher in TSLP transgenic FcgammaRIIb-deficient mice. TLR5 through 9 and 11 were upregulated to similar degrees in TSLP transgenic and TSLP transgenic FcgammaRIIb-deficient mice. Immunohistochemical studies of nephritic glomeruli localized TLR4 protein to podocytes. Cultured podocytes also expressed TLR4, and stimulation with TLR4-specific ligands resulted in a marked induction of chemokines; this was reduced by specific knockdown of TLR4 with siRNA. Fibrinogen, a potential endogenous TLR4 ligand, was shown to induce a similar profile of chemokines. In conclusion, it was demonstrated that TLR4 is constitutively expressed by podocytes and is upregulated in MPGN, where it may mediate glomerular injury by modulating expression of chemokines; therefore, TLR4 may link podocytes with the innate immune system to mediate MPGN triggered by the deposition of immune complexes.

Emerging Paradigms in the Renal Pathology of Viral Diseases

This review considers recent information that illuminates pathogenetic mechanisms that involve three of the major viral infections that cause renal injury in the form of HIV-associated nephropathy, polyoma virus nephropathy, and hepatitis C virus-associated glomerulonephritis.

Dense deposit disease: new insights

PURPOSE OF REVIEW

Dense deposit disease is a rare but devastating disease primarily affecting children. This review focuses on new information regarding the pathophysiology of dense deposit disease, its appearance histopathologically, its relationship to other diseases including macular degeneration and acquired partial lipodystrophy and potential new therapies.

RECENT FINDINGS

The microscopic features of dense deposit disease have been separated into five patterns with only about 25% of patients showing membranoproliferative features. The subtle interplay between genetic changes in complement regulatory proteins and dysregulation of the alternative pathway of complement is now more evident. Haplotype mapping has shown at-risk phenotypes of complement factor H associated with the development of dense deposit disease. Treatment protocols are empiric and not very effective. New information on complement inhibitors and plasma exchange, however, has brought hope for new therapies in the near future.

SUMMARY

Understanding of the pathology and the pathophysiology of dense deposit disease has advanced rapidly in the last decade. New efforts in genetic mapping along with the development of novel inhibitors of the complement system will lead to improved care for patients afflicted with this uncommon condition.

Cryoglobulinaemic vasculitis: classification and clinical and therapeutic aspects

Cryoglobulinaemia may cause cutaneous vasculitis and glomerulonephritis, potentially leading to end stage renal failure. An important proportion of cryoglobulinaemias are secondary to hepatitis C virus infection. Emerging antiviral treatment options offer a chance for causal therapy of these cases of cryoglobulinaemia. This review summarises the classification and clinical and therapeutic aspects of cryoglobulinaemic vasculitis and glomerulonephritis.