Gammapatías monoclonales de significado renal

C3G and Ig-MPGN-treatment standard

Among the broad spectrum of membranoproliferative glomerulonephritis (MPGN), immunofluorescence distinguishes C3 glomerulopathy (C3G), with predominant C3 deposits, and immunoglobulin-associated MPGN (Ig-MPGN), with combined C3 and Ig. However, there are several intersections between C3G and Ig-MPGN. Primary C3G and Ig-MPGN share the same prevalence of low serum C3 levels and of abnormalities of the alternative pathway of complement, and patients who present a bioptic pattern of Ig-MPGN at onset may show a C3G pattern in a subsequent biopsy. There is no specific therapy for primary C3G and Ig-MPGN and prognosis is unfavourable. The only recommended indications are inhibitors of the renin-angiotensin system, lipid-lowering agents and other renoprotective agents. The other drugs used currently, such as corticosteroids and mycophenolate mofetil, are often ineffective. The anti-C5 monoclonal antibody eculizumab has been tested in several patients, with mixed results. One reason for the uncertainty is the extremely variable clinical course, most likely reflecting a heterogeneous pathogenesis. An unsupervised clustering analysis that included histologic, biochemical, genetic and clinical data available at onset in patients with primary C3G and Ig-MPGN identified four clusters characterized by specific pathogenic mechanisms. This approach may facilitate accurate diagnosis and development of targeted therapies. Several trials are ongoing with drugs targeting different molecules of the complement cascade, however it is important to consider which component of the cascade may be the most appropriate for each patient. We review the current standards of treatment and discuss novel developments in the pathophysiology, diagnosis, outcome prediction and management of C3G and Ig-MPGN.

[Renal involvement in monoclonal gammopathies]

INTRODUCTION

The kidney is one of the organs most frequently affected by disease processes which produce monoclonal immunoglobins, therefore renal morphological and immunopathological alterations should be clearly recognized.

OBJECTIVE

To describe the pathological features of renal involvement in monoclonal gammopathies.

MATERIAL AND METHODS

A descriptive, retrospective and cross-sectional study of renal biopsies studied in a single center during a period of 14 years was carried out.

RESULTS

102 cases were included, of which 53% were male patients and the median age was 62.5 years (range 34 - 79). 97% of the biopsies were from native kidneys. The most frequent histopathological diagnosis (31.4%) was myeloma kidney, with kappa being the light chain most frequently deposited (65.6% of cases). AL amyloidosis was the second most common (29.4%) where the lambda chain predominated in 86.6%, followed by light chain deposition disease (20.6%) with the predominance of the kappa chain in 66.6%.

CONCLUSIONS

The most frequent renal involvement due to monoclonal gammopathies was myeloma kidney with deposition of kappa light chains, followed by AL lambda amyloidosis; these diseases were found more frequently in patients over 50 years of age.

C3 glomerulopathy associated with monoclonal gammopathy: impact of chronic histologic lesions and beneficial effects of clone-targeted therapies

INTRODUCTION

C3 glomerulopathy associated with monoclonal gammopathy (C3G-MIg) is a rare entity. Herein, we analyzed the clinical and histologic features of a cohort of C3G-MIg patients.

METHODS

Retrospective, multicenter, observational study. Patients diagnosed with C3G-MIg between 1995-2021 were enrolled. All had genetic studies of the alternative complement pathway. The degree of disease activity and chronicity was analyzed using the C3G histologic index. Descriptive statistics and propensity-score matching (PSM) analysis were used to evaluate the main outcome of the study (kidney failure [KF]).

RESULTS

The study group included 23 patients: median age 63 years (IQR 48-70), 57% males. IgG kappa was the most frequent MIg (65%). The diagnosis of C3G-MIg was made in transplanted kidneys in 7 patients (30%). Five (22%) had C3 nephritic factor and 5 (22%) anti-factor H antibodies. One patient carried a pathogenic variant in CFH gene.During a follow-up of 40 months (IQR 14-69), 9 patients (39%) reached KF, and these patients had a significant higher total chronicity score in kidney biopsy. Patients who received clone-targeted therapy had a significant higher survival compared to other management. Those who achieved hematological response had a significant higher kidney survival. Outcome was remarkably poor in kidney transplant recipients, 5 of them (71%) reaching KF.By PSM (adjusting for age, kidney function, proteinuria and chronicity score), no significant differences were observed in kidney survival between C3G patients with/without MIg.

CONCLUSIONS

The C3G histologic index can be used in patients with C3G-MIg to predict kidney prognosis, with higher chronicity scores being associated with worse outcomes. Clone-targeted therapies and the development of hematological response, are associated with better kidney prognosis.

Monoclonal gammopathy of renal significance: Early diagnosis is key

Monoclonal gammopathy of renal significance is a clinical-pathological entity grouping renal disorders secondary to the secretion of a monoclonal immunoglobulin synthesized by a B-cell-derived clone and/or plasma cells in a patient with no diagnostic criteria for multiple myeloma. This term applies to a concept recently introduced owing to the need to differentiate this entity from monoclonal gammopathy of undetermined significance, given the negative prognostic impact of its high morbidity and mortality resulting from both renal and systemic involvement, occasionally even progressing to advanced chronic kidney disease. The renal damage occurs via both direct pathogenic mechanisms, with the deposition of the monoclonal protein in different renal structures, as well as indirect mechanisms, acting as an autoantibody provoking dysregulation of the alternative complement pathway. The detection of this monoclonal protein and an early hematologic study are essential, as is the need for a kidney biopsy to establish the associated nephropathological diagnosis. Consequently, this then leads to the start of specific hematologic treatment to detain the production of the monoclonal protein and minimize renal and systemic injury.

Monoclonal gammopathy of renal significance: Early diagnosis is key

Monoclonal gammopathy of renal significance is a clinical-pathological entity grouping renal disorders secondary to the secretion of a monoclonal immunoglobulin synthesized by a B-cell-derived clone and/or plasma cells in a patient with no diagnostic criteria for multiple myeloma. This term applies to a concept recently introduced owing to the need to differentiate this entity from monoclonal gammopathy of undetermined significance, given the negative prognostic impact of its high morbidity and mortality resulting from both renal and systemic involvement, occasionally even progressing to advanced chronic kidney disease. The renal damage occurs via both direct pathogenic mechanisms, with the deposition of the monoclonal protein in different renal structures, as well as indirect mechanisms, acting as an autoantibody provoking dysregulation of the alternative complement pathway. The detection of this monoclonal protein and an early hematologic study are essential, as is the need for a kidney biopsy to establish the associated nephropathological diagnosis. Consequently, this then leads to the start of specific hematologic treatment to detain the production of the monoclonal protein and minimize renal and systemic injury.

Proliferative glomerulonephritis with monoclonal immunoglobulin deposits: Successful treatment for new and rare entity

Proliferative glomerulonephritis with monoclonal immunoglobulin deposits is a new disorder with undefined treatment modalities. We propose cyclophosphamide-bortezomib-dexamethasone and autologous stem cell transplantation as a therapeutic protocol.

Monoclonal Gammopathy of Renal Significance with Deposits of Peculiar Morphology and Injuries of Secondary Thrombotic Microangiopathy: A Case Report and Review of the Literature

We present the case of an 82-year-old woman diagnosed with monoclonal gammopathy of renal significance (MGRS) with the presence of different and peculiar kidney lesions, who began treatment with bortezomib and dexamethasone, presenting during her evolution a relapse. Although the bone marrow biopsy in this case showed plasma cells as pathologic clone and there was also a reduction after chemotherapeutic treatment, rituximab was proposed as a second line. We suspected that the relapse was possibly due to another precursor as B-cell or lymphoplasmacytic cell clone. We review the literature and suggest that the treatment for MGRS should be patient-tailored, preferably by consulting a multidisciplinary team. Future research is needed to better understand the disease course and establish the efficacy and safety of the therapeutic approach for the relapse of MGRS.

[Monoclonal gammopathy of renal significance: consensus of hematologists and nephrologists of Russia on the establishment of nosology, diagnostic approach and rationale for clone specific treatment]

Monoclonal gammopathy of renal significance (MGRS) is a new nosology in modern nephrology and oncohematology. MGRS is defined as kidney injury due to nephrotoxic monoclonal immunoglobulin produced by the B-cell line clone which does not reach the hematological criteria for specific treatment initiation. Monoclonal proteins pathological effects on kidney parenchyma result in irreversible decline of kidney function till the end stage renal disease that in line with the position of International Consensus of hematologists and nephrologists determinates critical necessity for clone specific treatment in patients with MGRS despite the absence of hematological indications for treatment initiation. Main challenge of MGRS in Russian Federation is an inaccessibility of an in-time diagnostic and appropriate treatment for the great majority of patients due to the following reasons: 1) limited knowledge about the MGRS among hematologists and nephrologists; 2) lack of necessary diagnostic resources in most health-care facilities; 3) lack of approved clinical recommendations and medical economic standards for treatment of this pathological entity. Consensus document comprises the opinion of experts leading nephrologists and hematologists of Russian Federation on the problem of MGRS including the incoherence in nosology classification, diagnostics approach and rationale for clone specific treatment. Consensus document is based on conclusions and agreements reached during the conference of leading nephrologists and hematologists of Russia which was held in the framework of symposia Plasma cell dyscrasias and lymphoproliferative diseases: modern approaches to therapy, 1516 of March 2019, Pavlov First Saint Petersburg State Medical University. The present Consensus is intended to define the principal practical steps to resolve the problem of MGRS in Russian Federation that are summarized as final clauses.

Chronological change of renal pathological findings in the proliferative glomerulonephritis with monoclonal IgG deposits considered to have recurred early after kidney transplantation

Proliferative glomerulonephritis with monoclonal immunoglobulin G (IgG) deposits (PGNMID) is a rare disease that recently became recognized. Its pathological findings are characterized by the deposition of a single heavy chain subclass and a single light chain isotype. PGNMID has been proven to recur in renal allografts. Herein, the authors describe the case of a 46-year-old man who presented with nephrotic syndrome and progressive kidney injury following kidney transplantation. One month after transplantation, his clinical condition stabilized; however, the protocol biopsy showed depositions of IgG and complement on the glomeruli by immunofluorescence staining. Electron microscopy (EM) revealed granular electron-dense deposits (EDD) in the mesangium. Thereafter, renal biopsy was repeated because his proteinuria level increased. Proliferative glomerulonephritis, mainly in the mesangium, with IgG and complement deposits and mesangial and subendothelial EDD were observed; however, the pathological diagnosis was difficult. Renal dysfunction then became apparent, and renal biopsy was performed again 4 years and 10 months after kidney transplantation. Glomerular deposits on a single IgG subclass and a single light chain isotype (IgG3 kappa) with membranoproliferative features were observed. Abundant subendothelial EDD were detected on EM. Finally, the patient was diagnosed with PGNMID. Since it seemed that PGNMID had already developed at 1 month after transplantation, we considered recurrent PGNMID case in the allograft. The treatment for PGNMID has not been established yet, and even in this case, the graft function was eventually lost. For improving renal prognosis, early diagnosis and further investigation on the treatment are necessary.

Three cases of monoclonal gammopathy of renal significance after kidney transplantation. De novo C3 glomerulopathy

Monoclonal gammopathy of renal significance includes all renal disorders caused by a monoclonal immunoglobulin secreted by a non-malignant B-cell clone. Patients with MGRS do not, by definition, meet criteria for multiple myeloma, with haematological disorders generally considered to be monoclonal gammopathy of undetermined significance. Nevertheless, the renal involvement can be serious and require specific treatment. Monoclonal gammopathy of renal significance is associated with a wide spectrum of disorders, including the recently discovered C3 glomerulopathy. Development of C3 glomerulopathy in the context of monoclonal gammopathy of renal significance after kidney transplantation is uncommon and very few cases have been published to date. We report on three cases of C3 glomerulopathy in the context of de novo monoclonal gammopathy after kidney transplantation.