Pathophysiology and management of monoclonal gammopathy of renal significance

Monoclonal Gammopathy of Undetermined Cardiovascular Significance; Current Evidence and Novel Insights

Monoclonal gammopathy of undetermined significance (MGUS) is a premalignant condition characterized by the presence of low levels of a monoclonal protein in the serum and a low percentage of clonal plasma cells in the bone marrow. MGUS may progress to multiple myeloma or other plasma cell disorders at a rate of 1% annually. However, MGUS may also have adverse effects on the cardiovascular system independent of its malignant potential. Emerging data have shown that MGUS is associated with cardiovascular disease. The mechanisms underlying this association are not fully understood but may involve genetic abnormalities, vascular calcification, cryoglobulinemia, cold agglutinin disease, autoantibodies and the direct or indirect effects of the monoclonal protein on the vascular endothelium. Herein, we review current evidence in this field and we suggest that patients with MGUS may benefit from regular cardiovascular risk assessment to prevent severe cardiovascular complications, in parallel with close hematological follow-up to monitor potential disease progression.

Combined crystal-storing histiocytosis, light chain proximal tubulopathy, and light chain crystalline podocytopathy in a patient with multiple myeloma: a case report and literature review

BACKGROUND

Crystal-storing histiocytosis (CSH), light chain proximal tubulopathy (LCPT), and light chain crystalline podocytopathy (LCCP) are rare complications of multiple myeloma (MM) or monoclonal gammopathy of renal significance, and their diagnoses are challenging.

CASE PRESENTATION

In this case, a 69-year-old Chinese woman presented with suspicious Fanconi syndrome with renal insufficiency. Immunofixation electrophoresis of both serum and urine revealed elevated immunoglobulin G kappa (IgGkappa) and kappa light chain. Bone marrow aspirate revealed 15% plasma cells with considerable cytoplasmic granular inclusions and needle-shaped crystals. Renal biopsy confirmed the final pathologic diagnosis of kappa-restricted CSH, combined LCPT and LCCP by immunoelectron microscopy. A number of special casts were present which could easily be misdiagnosed as light chain cast nephropathy. Immunofluorescence on frozen tissue presented false negative for kappa light chain, as ultimately proven by paraffin-embedded tissue after pronase digestion. MM and CSH were diagnosed, and two cycles of chemotherapy were given. The patient subsequently refused further chemotherapy, and her renal function remained relatively stable during a 2.5-year follow-up period.

CONCLUSIONS

In conclusion, we report a rare case of generalized kappa-restricted CSH involving bone marrow and kidney, combined with LCPT and LCCP, provide a comprehensive summary of renal CSH, and propose a new nomenclature of monoclonal immunoglobulin-induced crystalline nephrology. The presentation of monoclonal immunoglobulin and Fanconi syndrome should suggest the presence of monoclonal immunoglobulin-induced crystalline nephrology. Use of paraffin-embedded tissue after pronase digestion and immunoelectron microscopy is beneficial to improve the sensitivity of diagnosis.

Monoclonal Gammopathy of Renal Significance with Deposits of Infrequent Morphology: Two Case Reports of Light and Heavy Chain Deposition Disease with Atypical Presentation and Literature Review

BACKGROUND

Monoclonal immunoglobulin deposition disease (MIDD) includes three entities: light chain deposition disease (LCDD), heavy chain deposition disease (HCDD) and light and heavy chain deposition disease (LHCDD). The renal presentation can manifest with varying degrees of proteinuria and/or nephrotic syndrome, microhematuria, and often leads to end-stage renal disease. Given the rarity of LHCDD, therapeutic approaches for this condition remain inconclusive, as clinical trials are limited.

CASE PRESENTATION

We report two male patients with underlying monoclonal gammopathy of renal significance (MGRS) associated with LHCDD lesions. Both cases had non-nephrotic proteinuria, moderately impaired renal function, and normal levels of C3 and C4. Light microscopy of the renal biopsies in both patients did not show lesions of nodular glomerulosclerosis. Immunofluorescence showed a staining pattern with interrupted linear IgA-κ in patient #1 and IgA-λ in patient #2 only along the glomerular basement membrane (GBM). Electron microscopy of patient #1 revealed electrodense deposits in the subendothelial and mesangial areas only along the GBM.

DISCUSSION

In this case series, we discuss the clinical, analytical, and histopathological findings of two rare cases of LHCDD. Both patients exhibited IgA monoclonality and were diagnosed with monoclonal gammopathy of undetermined significance (MGUS) by the hematology department at the time of renal biopsy. Treatment with steroids and cytotoxic agents targeting the clone cells responsible for the deposition disease resulted in a favorable renal and hematologic response.

Contemporary Monoclonal Antibody Utilization in Glomerular Diseases

Therapeutic monoclonal antibodies (MAbs) have been one of the fastest growing drug classes in the past 2 decades and are indicated in the treatment of cancer, autoimmune disorders, solid organ transplantation, and glomerular diseases. The Food and Drug Administration has approved 100 MAbs between 1986 and 2021, and MAbs account for 20% of Food and Drug Administration's new drug approval every year. MAbs are preferred over traditional immunosuppressive agents because of their high specificity, reduced number of drug-drug interactions, and low toxicity, which make them a prime example of personalized medicine. In this review article, we provide an overview of the taxonomy, pharmacology, and therapeutic applications of MAbs in glomerular diseases. We searched the literature through PubMed using the following search terms: monoclonal antibodies, glomerular diseases, pharmacokinetics, pharmacodynamics, immunoglobulin, murine, chimeric,humanized, and fully human, and limited our search to years 2018-2023. We selected peer-reviewed journal articles with an evidence-based approach, prioritizing randomized control trials in specific glomerular diseases, if available. Advances in the MAb field have resulted in a significant paradigm shift in targeted treatment of immune-mediated glomerular diseases, and multiple randomized control trials are currently being conducted. Increased recognition is critical to expand their use in experimental research and personalized medicine.

Monoclonal gammopathy of increasing significance: time to screen?

Monoclonal gammopathy (MG) is a frequently detected clonal B-cell or plasma-cell disorder. Importantly, every multiple myeloma (MM) case is preceded by MG. Although clinical algorithms now allow earlier treatment of patients with biomarkers of malignancy before MM-induced tissue damage (CRAB) occurs, most patients are still diagnosed late. It is important to revisit how MG should be managed in clinical practice and whether screening is required. As the prevalence of MG and other medical co-morbidities both rise with increasing age, the degree of contribution of MG to disease states other than malignant progression is often unclear. This can lead to monitoring lapses and under recognition of the organ dysfunction that can occur with monoclonal gammopathy of clinical significance (MGCS). Therefore, models of progression to MM and/or MGCS require further refinement. While MG is currently detected incidentally, a case for screening has been made with ongoing studies in this area. Screening has the potential benefit of earlier detection and prevention of both MGCS and delayed MM presentations, but important drawbacks include the psychosocial impact on individuals and resource burden on healthcare services. MG terminology should transition alongside our increasing understanding of the condition and genomic characterization that have already begun to revise the MG nomenclature. The biology of MG has been poorly understood and is often inferred from the biology of MM, which is unhelpful. We review the literature and case for MG screening in this paper. In particular, we highlight areas that require focus to establish screening for MG.

Updates in Plasma Cell Dyscrasias and Related Monoclonal Immunoglobulin-Mediated Renal Disease

Pathogenic roles of monoclonal immunoglobulins in kidney disease have been attributed previously to malignant plasma cell and lymphoproliferative disorders such as multiple myeloma, lymphoplasmacytic lymphoma, chronic lymphocytic leukemia, or amyloid light chain amyloidosis. Improved technology, advancements in molecular diagnostics, and highly sensitive imaging techniques have established the need to redefine monoclonal gammopathies and the kidney disorders that are associated with monoclonal immunoglobulins regardless of tumor burden. This has led to the establishment of monoclonal gammopathy with renal significance (MGRS). MGRS was defined by the International Kidney and Monoclonal Gammopathy Research Group in 2012 as a clonal proliferative disorder that produces a nephrotoxic monoclonal immunoglobulin and does not meet previously defined hematological criteria for treatment of a specific malignancy. MGRS encompasses a wide array of pathologies with knowledge surrounding its incidence, prognosis, and management continuously increasing. This review examines the current evidence on the diagnosis, prognosis, pathogenesis, and therapy of plasma cell dyscrasias and related MGRS.

Assessment of current clinical practice throughout the UK for the diagnosis and management of monoclonal gammopathy of renal significance

Since the inception of the term monoclonal gammopathy of renal significance (MGRS) in 2012 by the International Kidney and Monoclonal Gammopathy Research Group, there have been no consensus guidelines specifically pertaining to the UK regarding to patient management. We aimed to identify both regional and cross-discipline variation in current clinical practice, to provide insight and rationale for a potential standardised pathway in the future. A national survey of 88 consultants from the disciplines of haematology and nephrology was conducted between June 2020 and July 2021. Agreement was evident for aspects of the diagnostic pathway, including presenting features likely to raise suspicion of MGRS and the most pertinent confounding factors to consider before renal biopsy. However, significant variability was identified in both the cohort of diagnostic tests used, as well as urinary work-up for patients with suspected MGRS. Treatment and monitoring frequency was also an aspect of management identified as variable. Despite differences in clinical practice across the UK, MGRS diagnosis was widely regarded to be the joint responsibility of both disciplines. The results provide an indication of inter-regional and interdisciplinary differences in practice, highlighting the need for improved awareness and standardised protocol for management of MGRS that applies to the UK population.

Laboratory and Clinical Settings of Heavy/Light Chain (HLC) Assays in the Management of Monoclonal Gammopathies and Multiple Myeloma

The antibody-related immune response is mediated by immunoglobulins (Igs), soluble circulating glycoproteins produced by activated B cells that, upon the recognition of specific epitopes on pathogen surfaces, activate, proliferate, and differentiate into antibody-secreting plasma cells. Although the antibodies are effectors of the humoral immune adaptive response, their overproduction in response to a dysregulated proliferation of clonal plasma cell production in tumoral conditions (i.e., multiple myeloma), enriches the serum and urinary matrices, assuming the crucial role of biomarkers. Multiple myeloma (MM) is a plasma cell dyscrasia characterized by the expansion and accumulation of clonally activated plasma cells in bone marrow, determining the release of high amounts of monoclonal component (MC) that can be detected as intact immunoglobulin (Ig), immunoglobulin fragments, or free light chains (FLCs). The importance of detecting biomarkers for the diagnosis, monitoring, and prognosis of diseases is highlighted by the international guidelines that recommend specific assays for the analysis of intact Igs and FLC. Moreover, a developed assay called Hevylite^® allows for the quantification of immunoglobulins that are both involved (iHLC) and not involved (uHLC) in the tumor process; this is a fundamental aspect of following up the patient's workup and evaluating the progression of disease, together with the treatments response. We here summarize the major points of the complex scenario involving monoclonal gammopathies and MM clinical management in view of advantages derived for the use of Hevylite^®.

Monoclonal gammopathy of renal significance: Multidisciplinary approach to diagnosis and treatment

Monoclonal gammopathy of renal significance (MGRS) is a hemato-nephrological term referring to a heterogeneous group of kidney disorders characterized by direct or indirect kidney injury caused by a monoclonal immunoglobulin (MIg) produced by a B cell or plasma cell clone that does not meet current hematologic criteria for therapy. MGRS-associated kidney diseases are diverse and can result in the development of end stage kidney disease (ESKD). The diagnosis is typically made by nephrologists through a kidney biopsy. Many distinct pathologies have been identified and they are classified based on the site or composition of the deposited Mig, or according to histological and ultrastructural findings. Therapy is directed towards the identified underlying clonal population and treatment decisions should be coordinated between hematologists and nephrologists in a multidisciplinary fashion, depend on the type of MGRS, the degree of kidney function impairment and the risk of progression to ESKD.

Monoclonal Gammopathy of Undetermined Significance: A Comprehensive Review

Monoclonal Gammopathy of Undetermined Significance (MGUS) is an asymptomatic premalignant plasma cell dyscrasia with a predominate rise of the IgG immunoglobulin fraction without end-organ damage, often diagnosed incidentally. Despite its progression into various subsequent forms of hematological malignancies, MGUS remains underdiagnosed. A literature search was conducted using the Medline, Cochrane, Embase, and Google Scholar databases, including articles published until December 2022. Keywords used encompassed "Monoclonal Gammopathy of Undetermined Significance," "Plasma Cell dyscrasia," "Monoclonal gammopathy of renal significance," and "IgM Monoclonal gammopathy of Undetermined Significance," This study aimed to conduct a critical review to update knowledge regarding the pathophysiology, risk factors, clinical features, diagnostic protocols, complications, and current and novel treatments for MGUS. We recommend a multidisciplinary approach to manage MGUS due to the complexity of the illness's etiology, diagnosis, and therapy. This comprehensive review also highlights future prospects, such as developing screening protocols for at-risk populations, prevention of disease progression by early diagnosis through genome-wide association studies, and management using Daratumumab and NSAIDs.

Rhabdomyolysis and Acute Renal Dysfunction as Initial Manifestations of Monoclonal Gammopathy of Renal Significance

Monoclonal gammopathy of renal significance (MGRS) is a rare heterogeneous group of kidney disorders that encompasses all disorders caused by deposition of monoclonal protein (M-protein) and its light or heavy chain fragments secreted by pre-malignant or non-malignant B-cell clones in patients who do not meet the diagnostic criteria for multiple myeloma (MM) or other B-cell malignancies. MGRS can manifest as glomerular diseases, tubulopathies, or vascular involvement with varying clinical presentations, making the diagnosis of MGRS challenging. In patients with high clinical suspicion based on preliminary blood and urine studies, the evaluation of MGRS begins with a renal biopsy followed by monoclonal studies and cytogenetic analysis. There is no standard treatment protocol for MGRS, and the current consensus suggests a clone-directed approach. If not identified and treated early, MGRS often results in poor outcomes and can lead to extrarenal manifestations, such as cardiogenic shock. Herein, we present a case involving a 43-year-old male with a rare presentation of rhabdomyolysis, rapidly progressing renal dysfunction, and cardiac dysfunction. A bone marrow biopsy did not meet the diagnostic criteria for MM or other B-cell malignancies, while a renal biopsy revealed Kappa light chain cast nephropathy, which led to the final diagnosis of MGRS.

Monoclonal Gammopathies of Clinical Significance: A Critical Appraisal

Simple Summary

Monoclonal gammopathy of clinical significance (MGCS) refers to a recently coined term describing a complex and heterogeneous group of nonmalignant monoclonal gammopathies. These patients are characterized by the presence of a commonly small clone and the occurrence of symptoms that may be associated with the clone or with the monoclonal protein through diverse mechanisms. This is an evolving, challenging, and rapidly changing field. Patients are classified according to the key organ or system involved, with kidneys, skin, nerves, and eyes being the most frequently affected. However, multiorgan involvement may be the most relevant clinical feature at the presentation or during the course. This review delves into the definition, history, differential diagnosis, classification, prognosis, and treatment of this group of entities by analyzing the evidence accumulated to date from a critical perspective.

Abstract

Monoclonal gammopathies of clinical significance (MGCSs) represent a group of diseases featuring the association of a nonmalignant B cells or plasma cells clone, the production of an M-protein, and singularly, the existence of organ damage. They present a current framework that is difficult to approach from a practical clinical perspective. Several points should be addressed in order to move further toward a better understanding. Overall, these entities are only partially included in the international classifications of diseases. Its definition and classification remain ambiguous. Remarkably, its real incidence is unknown, provided that a diagnostic biopsy is mandatory in most cases. In fact, amyloidosis AL is the final diagnosis in a large percentage of patients with renal significance. On the other hand, many of these young entities are syndromes that are based on a dynamic set of diagnostic criteria, challenging a timely diagnosis. Moreover, a specific risk score for progression is lacking. Despite the key role of the clinical laboratory in the diagnosis and prognosis of these patients, information about laboratory biomarkers is limited. Besides, the evidence accumulated for many of these entities is scarce. Hence, national and international registries are stimulated. In particular, IgM MGCS deserves special attention. Until now, therapy is far from being standardized, and it should be planned on a risk and patient-adapted basis. Finally, a comprehensive and coordinated multidisciplinary approach is needed, and specific clinical trials are encouraged.

Clinicopathological manifestations of coexistent monoclonal immunoglobulin deposition disease and immunotactoid glomerulopathy

Combination of monoclonal immunoglobulin deposition disease (MIDD) and immunotactoid glomerulopathy (ITG) is a rare form of monoclonal immunoglobulin (MIg)-associated renal disease. We retrospectively reviewed the native kidney biopsy specimens at Peking University People’s Hospital from 2011 to 2020. Five patients were diagnosed as MIDD + ITG. Their clinical and pathological characteristics were studied. The typical clinical features were nephritic syndrome and renal dysfunction with prominent anemia, but hematuria was mild. Unlike single MIDD and single ITG, on light microscopy, segmentally distributed mesangial nodular sclerosis on the basis of mesangial matrix hyperplasia was the major lesion. Others including membranoproliferative glomerulonephritis (MPGN)-like lesion, glomerular basement membrane thickness, and mild to moderate mesangial and endothelial proliferations might presented at the same time and in the same glomeruli. On immunofluorescence, MIg, usually monoclonal light chains, deposited along glomerular basement membranes and tubular basement membranes, while the intact MIg or monoclonal heavy chain deposited in the mesangial regions. Corresponding to the depositions on immunofluorescence, punctate “powdery” deposits along glomerular basement membranes and tubular basement membranes under electronic microscopy indicated the presence of MIDD. Microtubular substructures (diameters of 20–50 nm) exhibiting hollow cores arranged in parallel arrays in mesangial regions indicated the presence of ITG. Patients treated with bortezomib-based regimen seemed to have better outcomes. In conclusion, MIDD + ITG is a rare combination form of MIg-associated renal disease. Accurate diagnosis requires the comprehensive pathological investigations.

Lambda light chain-induced monoclonal gammopathy of renal significance, manifesting with Fanconi Syndrome and osteomalacia

BACKGROUND

Monoclonal gammopathy of renal significance (MGRS) encompasses a heterogeneous group of kidney diseases in which a monoclonal immunoglobulin secreted by a clone of B cells or plasma cells causes kidney damage without meeting the hematological criteria for malignancy. Among the various forms of involvement, MGRS can manifest as a proximal tubule disorder, such as Fanconi syndrome (FS), characterized by urinary loss of phosphate, glucose, amino acids, uric acid and bicarbonate. Few cases of MGRS have been described in the literature, manifesting as FS and monoclonal production of lambda light chains, almost all of which are secondary to the production of kappa light chains.

CASE PRESENTATION

Here we report a clinical case of a 45-year-old Brazilian male, African descent, with proximal weakness of the lower limbs, whose initial assessment showed a urine summary with the presence of proteinuria and glycosuria without hyperglycemia, associated with mild worsening of renal function, hypouricemia, hypocalcemia and phosphaturia. Evolution was characterized by a MGRS manifesting as FS and osteomalacia.

CONCLUSION

The diagnosis of MGRS is not always easy, it requires knowledge of the clinical characteristics, diagnostic criteria and prognosis of each case. Therefore, all possible efforts should be made for multidisciplinary diagnosis.

Immunoglobulin M Monoclonal Gammopathies of Clinical Significance

Immunoglobulin M monoclonal gammopathy of undetermined significance (MGUS) comprises 15-20% of all cases of MGUS. IgM MGUS is distinct from other forms of MGUS in that the typical primary progression events include Waldenstrom macroglobulinaemia and light chain amyloidosis. Owing to its large pentameric structure, IgM molecules have high intrinsic viscosity and precipitate more readily than other immunoglobulin subtypes. They are also more commonly associated with autoimmune phenomena, resulting in unique clinical manifestations. Organ damage attributable to the paraprotein, not fulfilling criteria for a lymphoid or plasma cell malignancy has recently been termed monoclonal gammopathy of clinical significance (MGCS) and encompasses an important family of disorders for which diagnostic and treatment algorithms are evolving. IgM related MGCS include unique entities such as cold haemagglutinin disease, IgM related neuropathies, renal manifestations and Schnitzler's syndrome. The diagnostic approach to, and management of these disorders differs significantly from other categories of MGCS. We describe a practical approach to the evaluation of these patients and our approach to their treatment. We will also elaborate on the key unmet needs in IgM MGCS and highlight potential areas for future research.

Mono/polyclonal free light chains as challenging biomarkers for immunological abnormalities

Free light chain (FLC) kappa (k) and lambda (λ) consist of low molecular weight proteins produced in excess during immunoglobulin synthesis and secreted into the circulation. In patients with normal renal function, over 99% of FLCs are filtered and reabsorbed. Thus, the presence of FLCs in the serum is directly related to plasma cell activity and the balance between production and renal clearance. FLCs are bioactive molecules that may exist as monoclonal (m) and polyclonal (p) FLCs. These have been detected in several body fluids and may be key indicators of ongoing damage and/or illness. International guidelines now recommend mFLC for screening, diagnosis and monitoring multiple myeloma and other plasma cell dyscrasias. In current clinical practice, FLCs in urine indicate cast nephropathy and other renal injury, whereas their presence in cerebrospinal fluid is important for identifying central nervous system inflammatory diseases such as multiple sclerosis. Increased pFLCs have also been detected in various conditions characterized by B cell activation, i.e., chronic inflammation, autoimmune disease and HCV infection. Monitoring the coronavirus (COVID-19) pandemic by analysis of salivary FLCs presents a significant opportunity in clinical immunology worthy of scientific pursuit.

Monoclonal Gammopathy of Renal Significance with Progression to Multiple Myeloma in a Patient with ASIA-MO Syndrome

Background

Autoimmune/inflammatory syndrome induced by adjuvants is a disease associated with an unregulated hyperactivity of the immune system and may also be associated with a high frequency of hematologic malignancies. Report. This is a case of a female with ASIA-MO syndrome secondary to infiltration of mineral oil for aesthetic purposes and presented with multiple episodes of urolithiasis resulting in renal impairment of her left kidney confirmed by scintigraphy and ending in unilateral nephrectomy. Retrospective renal piece analysis confirmed tubulointerstitial infiltration with light chains and plasma cells. Paraffin fixation prevented subsequent immunofluorescence analysis for better follow-up of the patient.

Conclusion

The presence of positive immunofixation kappa chains explained the sudden deterioration of renal function with monoclonal gammopathy of renal significance which concluded in an association between diseases, such as multiple light chain myeloma, as a final diagnosis.

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.

Recurrent glomerulonephritis after kidney transplantation: a practical approach

PURPOSE OF REVIEW

This review will provide a practical approach in the assessment of kidney failure patients with primary glomerulonephritides (GN) being considered for kidney transplantation, focusing on high-risk subtypes of immunoglobulin A nephropathy, focal segmental glomerulosclerosis, idiopathic membranous glomerulonephritis and membranoproliferative glomerulonephritis.

RECENT FINDINGS

Recurrent glomerulonephritis remains one of the most common causes of allograft loss in kidney transplant recipients. Although the epidemiology and clinical outcomes of glomerulonephritis recurrence occurring after kidney transplantation are relatively well-described, the natural course and optimal treatment strategies of recurrent disease in kidney allografts remain poorly defined. With a greater understanding of the pathophysiology and treatment responses of patients with glomerulonephritis affecting the native kidneys, these discoveries have laid the framework for the potential to improve the management of patients with high-risk glomerulonephritis subtypes being considered for kidney transplantation.

SUMMARY

Advances in the understanding of the underlying immunopathogenesis of primary GN has the potential to offer novel therapeutic options for kidney patients who develop recurrent disease after kidney transplantation. To test the efficacy of novel treatment options in adequately powered clinical trials requires a more detailed understanding of the clinical and histological characteristics of kidney transplant recipients with recurrent glomerulonephritis.

Monoclonal Gammopathy of Renal Significance (MGRS): Prospects for Treatment in Integrated Chinese and Western Medicine

Monoclonal gammopathy of renal significance (MGRS) is a pathological state which presents with a spectrum of renal lesions. MGRS is characterized by pathogenic monoclonal immunoglobulins or light chains produced by a premalignant plasma cell or B cell clone. In view of inadequate understanding in the past, the low detection rate of MGRS often results in poor outcomes and reduces quality of life of patients. Thus, MGRS stands for a group of clinical refractory renal diseases. To date, no standard treatment strategy for MGRS is available. Current consensus suggests a clone-directed approach that aims to eradicate the offending clone, but its long-term prognosis is not clear. In this article, we discuss the diagnostic methods, highlight treatment advances, and introduce integrated Chinese and Western medicine in the management of MGRS.

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.

A case of immunotactoid glomerulopathy in a patient with monoclonal gammopathy of renal significance

Monoclonal gammopathy of renal significance is a relatively new diagnosis that attributes kidney disease to damage caused by a monoclonal protein. There is growing recognition of this disease in patients previously diagnosed with monoclonal gammopathy of undetermined significance, as they increasingly develop clinically significant renal impairment requiring treatment. We outline a case of a patient presenting with worsening renal function, found to have a circulating monoclonal protein and ultimately diagnosed with a subtype of monoclonal gammopathy of renal significance referred to as immunotactoid glomerulopathy.

Abbreviations: MGUS: Monoclonal gammopathy of undetermined significance; M-protein: Monoclonal protein; MM: Multiple myeloma; MGRS: Monoclonal gammopathy of renal significance; MGCS: Monoclonal gammopathy of clinical significance; CKD: Chronic kidney disease; C3 and C4: Complement 3 and complement 4, respectively; EF: Ejection fraction; CT: Computed tomography; IgG: Immunoglobulin G; GFR: Glomerular filtration rate; PET: Positron emission tomography; MRI: Magnetic Resonance Imaging.

Onconephrology: The intersections between the kidney and cancer

Onconephrology is a new subspecialty of nephrology that recognizes the important intersections of kidney disease with cancer. This intersection takes many forms and includes drug-induced nephrotoxicity, electrolyte disorders, paraneoplastic glomerulonephritis, and the interactions of chronic kidney disease with cancer. Data clearly demonstrate that, when patients with cancer develop acute or chronic kidney disease, outcomes are inferior, and the promise of curative therapeutic regimens is lessened. This highlights the imperative for collaborative care between oncologists and nephrologists in recognizing and treating kidney disease in patients with cancer. In response to this need, specific training programs in onconephrology as well as dedicated onconephrology clinics have appeared. This comprehensive review covers many of the critical topics in onconephrology, with a focus on acute kidney injury, chronic kidney disease, drug-induced nephrotoxicity, kidney disease in stem cell transplantation, and electrolyte disorders in patients with cancer.

Monoclonal Gammopathy of Renal Significance: Clinical and Histological Efficacy of a Bortezomib-Based Regimen

Monoclonal Gammopathy of Renal Significance (MGRS) is a group of heterogeneous disorders characterized by renal dysfunction secondary to the production of a monoclonal immunoglobulin by a nonmalignant B cell or plasma cell clone. We report the clinical and histological outcomes of two patients with biopsy-proven MGRS: one patient showed membranoproliferative glomerulonephritis with monoclonal k-light chain and C3 deposits, the second patient showed immunotactoid glomerulopathy. Both patients were treated with a 9-month chemotherapy protocol including bortezomib, cyclophosphamide, and dexamethasone. Renal biospy was repeated after 1 year. The estimated glomerular filtration rate (eGFR) increased from 22.5 (baseline) to 40 ml/min per 1.73 m2 after 12 months, then to 51.5 ml/min per 1.73 m2 after 24 months; proteinuria decreased from 4.85 (baseline) to 0.17 g/day after 12 months, then to 0.14 g/day after 24 months. Repeat renal biopsies showed a dramatic improvement of the glomerular proliferative lesions and near complete disappearance of the immune deposits. A bortezomib-based treatment proved very effective and was well-tolerated in the two patients presenting with clinically and histologically aggressive MGRS.

KDIGO Controversies Conference on onco-nephrology: kidney disease in hematological malignancies and the burden of cancer after kidney transplantation

The bidirectional relationship between cancer and chronic kidney disease (CKD) is complex. Patients with cancer, particularly those with hematological malignancies such as multiple myeloma and lymphoma, are at increased risk of developing acute kidney injury and CKD. On the other hand, emerging evidence from large observational registry analyses have consistently shown that cancer risk is increased by at least 2- to 3-fold in kidney transplant recipients, and the observed increased risk occurs not only in those who have received kidney transplants but also in those on dialysis and with mild- to moderate-stage CKD. The interactions between cancer and CKD have raised major therapeutic and clinical challenges in the management of these patients. Given the magnitude of the problem and uncertainties, and current controversies within the existing evidence, Kidney Disease: Improving Global Outcomes (KDIGO) assembled a global panel of multidisciplinary clinical and scientific expertise for a controversies conference on onco-nephrology to identify key management issues in nephrology relevant to patients with malignancy. This report covers the discussed controversies in kidney disease in hematological malignancies, as well as cancer after kidney transplantation. An overview of future research priorities is also discussed.

Time to Redefine Risk-Stratification and Response Criteria in Immunoglobulin Light Chain Amyloidosis?

Immunoglobulin light chain (AL) amyloidosis results from clonal plasma cell (PC)-derived immunoglobulin light chain-mediated end-organ dysfunction, the extent and severity of which predicts survival. Anti-PC therapies reduce clonal light chain burden, which usually results in improvement of organ function, and consequently overall survival. Response assessment is critical to gauge therapeutic efficacy, to report clinical trial outcomes, and to switch therapy in those without response. Response in AL amyloidosis is 2-fold: hematologic response and organ response (OR). Depth of hematologic response is graded on the basis of serum free light chain (sFLC) parameters, but assessment of OR is binary. The role of normal sFLC ratio or complete remission as a treatment end point has been challenged, thus highlighting the need to quantify involved FLC and residual PC beyond the normal sFLC ratio to possibly account for the ongoing organ damage seen in some patients with complete remission. Mass spectrometry and urinary exosome represent ultrasensitive strategies to estimate involved FLC below the detection threshold of current sFLC assays. The role of new sFLC parameters and minimal residual disease as potential prognostic parameters has been recognized. Brain natriuretic peptide (BNP) and 24-hour proteinuria:estimated glomerular filtration rate ratio were identified to overcome certain limitations of N-terminal-Pro-BNP, 24-hour proteinuria, and estimated glomerular filtration rate for cardiac and renal response assessment, respectively. Use of monoclonal antibodies targeting PC and amyloid deposits has expanded the therapeutic armamentarium of AL amyloidosis, and given their excellent efficacy, early ORs are reported. This review provides insights into recent advances in the risk-stratification and response assessment of patients with AL amyloidosis in light of the changing therapeutic paradigms. Incorporation of these advancements into formal consensus guidelines would require further validation.

[Monoclonal gammapathy of renal significance (MGRS) at the current state: terminology, diagnosis and treatment]

In this article we discussed the current state of monoclonal gammapathy of renal significance (Monoclonal Gammopathy of Renal Significance MGRS) and revealed problems of B-cell clone secreting nephrotoxic monoclonal immunoglobulin identification. We followed 276 patients with monoclonal gammapathy including patients with non-amyloid nephropathy. The majority of patients had systemic AL-amyloidosis. We established better survival of the treated patients with systemic AL-amyloidosis in comparison with retrospective untreated cohort. We considered current treatment of patients with non-amyloid nephropathy and focused on the crucial role of multidisciplinary approach in management of these patients.

Immunoglobulin M Paraproteinaemias

Monoclonal paraproteinaemia is an increasingly common reason for referral to haematology services. Paraproteinaemias may be associated with life-threatening haematologic malignancies but can also be an incidental finding requiring only observation. Immunoglobulin M (IgM) paraproteinaemias comprise 15–20% of monoclonal proteins but pose unique clinical challenges. IgM paraproteins are more commonly associated with lymphoplasmacytic lymphoma than multiple myeloma and can occur in a variety of other mature B-cell neoplasms. The large molecular weight of the IgM multimer leads to a spectrum of clinical manifestations more commonly seen with IgM paraproteins than others. The differential diagnosis of B-cell and plasma cell dyscrasias associated with IgM gammopathies can be challenging. Although the discovery of MYD88 L265P and other mutations has shed light on the molecular biology of IgM paraproteinaemias, clinical and histopathologic findings still play a vital role in the diagnostic process. IgM secreting clones are also associated with a number of “monoclonal gammopathy of clinical significance” entities. These disorders pose a novel challenge from both a diagnostic and therapeutic perspective. In this review we provide a clinical overview of IgM paraproteinaemias while discussing the key advances which may affect how we manage these patients in the future.