Dysproteinemias and Glomerular Disease

Unusual Cases of Monoclonal Gammopathy of Renal Significance

Introduction

Monoclonal gammopathy of renal significance (MGRS) is a rare entity describing patients with renal impairment related to the secretion of immunoglobulins without hematological criteria for treatment of a specific disease. We present 3 cases of MGRS identified at our center that were either rare or difficult to diagnose. Case Presentations. The first patient presented with monoclonal membranoproliferative glomerulonephritis in the context of known chronic lymphocytic leukemia (CLL), diagnosed about 10 years prior. She presented with nephritic syndrome with serum protein electrophoresis revealing an IgG/lambda peak of less than 1 g/L, stable from the last few years. A renal biopsy confirmed a diagnosis of monoclonal membranoproliferative glomerulonephritis with granular IgG and C3 deposits of various sizes. The second patient presented with renal TMA in the context of IgM MGUS. The patient was admitted for acute nephritic syndrome and thrombotic microangiopathy. Serum protein electrophoresis demonstrated IgM/kappa paraprotein at 1.8 g/L, with a kappa/lambda ratio of 5.48. Renal biopsy demonstrated endocapillary proliferative glomerulonephritis associated with the presence of numerous monotypic IgM/kappa intracapillary pseudothrombi. Characteristic changes of thrombotic microangiopathy were also described. The third patient presented with immunotactoid glomerulonephritis likely from small B-cell lymphoma that later transformed to DLBCL. The patient presented with acute renal failure with IgM/kappa paraprotein of less than 1 g/L on electrophoresis and with a kappa/lambda ratio of 7.09. A diagnosis of immunotactoid glomerulonephritis was made on renal biopsy. Bone marrow with limited specimen revealed a B-cell infiltrate. Biopsy of a breast lesion was compatible with diffuse large B-cell lymphoma (DLBCL). Lymphomatous cells expressed IgM/kappa, thus confirming paraprotein-associated renal lesion.

Conclusion

We described 3 different cases of MGRS, highlighting the diversity of renal pathohistological presentations and different associated lymphoproliferative disorders. Biopsy should rapidly be considered, as early diagnosis of MGRS is essential to initiate clone-directed therapy promptly to prevent progression to ESRD or hematologic progression to malignancy.

Paraprotein-Mediated Glomerular Diseases

Paraproteinemias are a group of complex diseases associated with an overproduction of a monoclonal immunoglobulin that can cause a diversity of kidney disorders and end-organ damage. In this review, we focus on paraprotein-mediated glomerular diseases. Kidney biopsy plays a crucial role in diagnosing these disorders, enabling the identification of specific histological patterns. These lesions are categorized into organized (such as amyloidosis, immunotactoid glomerulopathy, fibrillary glomerulonephritis, cryoglobulinemic glomerulonephritis, and monoclonal crystalline glomerulopathies) and nonorganized deposits (such as monoclonal Ig deposition disease and proliferative glomerulonephritis with monoclonal Ig deposits) based on the characteristics of immunofluorescence findings and the ultrastructural appearance of deposits on electron microscopy. This review aims to provide an update, highlight, and discuss clinicopathological aspects such as definition, epidemiology, clinical manifestations, mechanisms of kidney injury, histological features, and diagnostic procedures.

IgM kappa proliferative glomerulonephritis with monoclonal immunoglobulin deposition complicated with nocardiosis dermatitis: a case report and review of literature

Rationale

Monoclonal gammopathy of renal significance (MGRS) represents a group of disorders caused by monoclonal immunoglobulin (M protein) secreted by B cells or plasma cells. Proliferative glomerulonephritis with monoclonal immunoglobulin deposition (PGNMID) is a glomerular disease and a form of MGRS. Here, we presented a rare case of a patient with IgM kappa PGNMID complicated with nocardiosis dermatitis.

Patient concerns and diagnoses

A 56-year-old man was admitted to the hospital because of cutaneous purpura and proteinuria. His initial pathological diagnosis indicated membranous proliferative glomerulonephritis, IgM(++), and subacute interstitial nephritis. Based on further examination, he was finally diagnosed to have IgM kappa PGNMID and subacute interstitial nephritis. After the initial diagnosis, the patient received hormonal therapy. During the treatment, nocardiosis dermatitis emerged as a complication, and the hormonal therapy was gradually reduced. The patient refused further treatment with rituximab, and his health is currently stable.

Outcomes

IgM kappa PGNMID complicated with nocardiosis dermatitis is an extremely rare occurrence. Laboratory examination and pathological analysis are required to confirm the diagnosis of this disorder. Timely and accurate diagnosis is essential for the appropriate treatment of PGNMID.

Clinicopathological characteristics and prognosis in patients with monoclonal gammopathy and renal damage in central China: a multicenter retrospective cohort study

Renal involvement is common in monoclonal gammopathy (MG); however, the same patient may have both MG and non-paraprotein-associated renal damage. Accordingly, distinguishing the cause of renal damage is necessary because of the different clinical characteristics and associated treatments. In this multicenter retrospective cohort study, we described the clinicopathological characteristics and prognosis of 703 patients with MG and renal damage in central China. Patients were classified as having MG of renal significance (MGRS), MG of undetermined significance (MGUS), or hematological malignancy. 260 (36.98%), 259 (36.84%), and 184 (26.17%) had MGRS, MGUS, and hematological malignancies, respectively. Amyloidosis was the leading pattern of MGRS (74.23%), followed by thrombotic microangiopathy (8.85%) and monoclonal immunoglobulin deposition disease (8.46%). Membranous nephropathy was the leading diagnosis of MGUS (39.38%). Renal pathological findings of patients with hematological malignancies included paraprotein-associated lesions (84.78%) and non-paraprotein-associated lesions (15.22%). The presence of nephrotic syndrome and an abnormal free light chain (FLC) ratio were independently associated with MGRS. The overall survival was better in patients with MGUS than in those with MGRS or hematological malignancies.

Characteristics of Complement Protein Deposition in Proliferative Glomerulonephritis with Monoclonal Immunoglobulin Deposition

BACKGROUND

Hypocomplementemia and complement co-deposition with monoclonal immunoglobulins in glomeruli are not rare in proliferative glomerulonephritis with monoclonal immunoglobulin deposits (PGNMID). Deposition of monoclonal immunoglobulins in glomeruli has been suggested to activate complement and cause kidney injury. However, the profiles of complement activation in PGNMID and their clinical and pathologic significance need to be clarified.

METHODS

Forty-six patients with PGNMID were enrolled. Proteomic analysis of glomeruli using laser microdissection and mass spectrometry was performed for ten patients with PGNMID to determine the composition of glomerular deposits. Kidney deposition of complement components was detected by immunohistochemistry and immunofluorescence. Urinary and plasma levels of complement components were measured by an enzyme-linked immunosorbent assay. Group differences were assessed using t tests or Mann-Whitney U tests depending on the distribution. Correlation analysis was performed using Spearman rank correlation or Pearson correlation.

RESULTS

Laser microdissection and mass spectrometry-based proteomic analysis showed that complement components were the most enriched proteins deposited in the glomeruli of patients with PGNMID. Glomerular deposition of C3c, C4d, and C5b-9 was detected in most patients. Levels of urinary and plasma C3a, C5a, soluble C5b-9, C4d, Bb, and C1q as well as urinary mannose-binding lectin were significantly higher in patients with PGNMID compared with healthy controls. The intensity of C3c and C4d deposition in glomeruli correlated with serum creatinine and the percentage of crescents, respectively. Furthermore, levels of urinary complement components correlated positively with serum creatinine, urinary protein excretion, percentage of crescents, and global glomerulosclerosis in kidney biopsies, whereas plasma levels of most complement components did not show a significant correlation with clinicopathologic parameters. In multivariable analysis, a higher level of urinary C4d was identified as an independent risk factor of kidney failure.

CONCLUSIONS

The complement system was found to be overactivated in PGNMID, and levels of urinary complements correlated with disease severity. A higher level of urinary C4d was identified as an independent risk factor of kidney failure.

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 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.

Podocytopathy in patients with monoclonal gammopathy: three patients and literature review

BACKGROUND

Renal manifestations of monoclonal gammopathies are of increasing interest among nephrologists. Typical manifestations include light chain cast nephropathy, amyloidosis or renal damage mediated by monoclonal immunoglobulin deposition. Podocytopathies in the setting of an underlying monoclonal gammopathy constitute a rare manifestation of these diseases and, although being described in the literature, remain a challenge since most data derive from case reports.

METHODS

A retrospective review of the clinical data of Hospital del Mar and Hospital Vall d'Hebron was performed to identify patients with minimal change disease (MCD) or focal and segmental glomerulosclerosis (FSGS) in the setting of neoplasms that produce monoclonal (M) protein. Additionally, a literature review on this topic was performed. This study aims to describe the clinical characteristics and outcomes of these patients.

RESULTS

Three patients were identified to have podocytopathy and monoclonal gammopathy between the years 2013 and 2020. All three were males and  >65 years of age. Two patients were diagnosed with MCD and one patient was diagnosed with FSGS. All patients underwent a kidney biopsy and light and electron microscopic studies were performed. The underlying causes of monoclonal gammopathy were multiple myeloma in two cases and Waldeström macroglobulinemia in one case. Two patients developed nephrotic syndrome during the follow-up. All patients were under active hematological treatment. One patient presented a complete remission of proteinuria whereas the other two presented a partial remission.

CONCLUSIONS

Podocytopathies may infrequently be found in patients with monoclonal gammopathies. Patients with overt glomerular proteinuria and hematological disorders with M protein should undergo a kidney biopsy for prompt diagnosis and to specify a prognosis. In addition, further study on this matter must be done to understand the pathophysiology and treat these patients appropriately.

Monoclonal Gammopathy-Related Kidney Diseases

Monoclonal gammopathies occur secondary to a broad range of clonal B lymphocyte or plasma cell disorders, producing either whole or truncated monoclonal immunoglobulins. The kidneys are often affected by these monoclonal proteins, and, although not mutually exclusive, can involve the glomeruli, tubules, interstitium, and vasculature. The nephrotoxic potential of these monoclonal proteins is dependent on a variety of physicochemical characteristics that are responsible for the diverse clinicopathologic manifestations, including glomerular diseases with organized deposits, glomerular diseases with granular deposits, and other lesions, such as C3 glomerulopathy and thrombotic microangiopathy with unique pathophysiologic features. The diseases that involve primarily the tubulointerstitial and vascular compartments are light chain cast nephropathy, light chain proximal tubulopathy, crystal-storing histiocytosis, and crystalglobulin-induced nephropathy with distinct acute and chronic clinicopathologic features. The diagnosis of a monoclonal gammopathy-related kidney disease is established by identification of an underlying active or more commonly, low-grade hematologic malignancy, serologic evidence of a monoclonal gammopathy when detectable, and most importantly, monoclonal protein-induced pathologic lesions seen in a kidney biopsy, confirming the association with the monoclonal protein. Establishing a diagnosis may be challenging at times, particularly in the absence of an overt hematologic malignancy, with or without monoclonal gammopathy, such as proliferative glomerulonephritis with monoclonal immunoglobulin deposits. Overall, the treatment is directed against the underlying hematologic disorder and the potential source of the monoclonal protein.

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.

Acute Kidney Injury in Monoclonal Gammopathies

Monoclonal gammopathies (MG) encompass a variety of disorders related to clonal expansion and/or malignant transformation of B lymphocytes. Deposition of free immunoglobulin (Ig) components (light or heavy chains, LC/HC) within the kidney during MG may result over time in multiple types and degrees of injury, including acute kidney injury (AKI). AKI is generally a consequence of tubular obstruction by luminal aggregates of LC, a pattern known as “cast nephropathy”. Monoclonal Ig LC can also be found as intracellular crystals in glomerular podocytes or proximal tubular cells. Proliferative glomerulonephritis with monoclonal Ig deposits is another, less frequent form of kidney injury with a sizable impact on renal function. Hypercalcemia (in turn related to bone reabsorption triggered by proliferating plasmacytoid B cells) may lead to AKI via functional mechanisms. Pharmacologic treatment of MG may also result in additional renal injury due to local toxicity or the tumor lysis syndrome. The present review focuses on AKI complicating MG, evaluating predictors, risk factors, mechanisms of damage, prognosis, and options for treatment.

Mesenchymal Stromal Cell-Derived Extracellular Vesicles Pass through the Filtration Barrier and Protect Podocytes in a 3D Glomerular Model under Continuous Perfusion

BACKGROUND

Dynamic cultures, characterized by continuous fluid reperfusion, elicit physiological responses from cultured cells. Mesenchymal stem cell-derived EVs (MSC-EVs) has been proposed as a novel approach in treating several renal diseases, including acute glomerular damage, by using traditional two-dimensional cell cultures and in vivo models. We here aimed to use a fluidic three-dimensional (3D) glomerular model to study the EV dynamics within the glomerular structure under perfusion.

METHODS

To this end, we set up a 3D glomerular model culturing human glomerular endothelial cells and podocytes inside a bioreactor on the opposite sides of a porous membrane coated with type IV collagen. The bioreactor was connected to a circuit that allowed fluid passage at the rate of 80 µl/min. To mimic glomerular damage, the system was subjected to doxorubicin administration in the presence of therapeutic MSC-EVs.

RESULTS

The integrity of the glomerular basal membrane in the 3D glomerulus was assessed by a permeability assay, demonstrating that the co-culture could limit the passage of albumin through the filtration barrier. In dynamic conditions, serum EVs engineered with cel-miR-39 passed through the glomerular barrier and transferred the exogenous microRNA to podocyte cell lines. Doxorubicin treatment increased podocyte apoptosis, whereas MSC-EV within the endothelial circuit protected podocytes from damage, decreasing cell death and albumin permeability.

CONCLUSION

Using an innovative millifluidic model, able to mimic the human glomerular barrier, we were able to trace the EV passage and therapeutic effect in dynamic conditions.

Images of the month: Crystalglobulin-induced nephropathy

We report a patient with chronic diabetes and was referred for recent onset proteinuria. Light microscopy of the renal biopsy specimen showed mildly expanded mesangium with mesangial hypercellularity and segmental sclerosis, features compatible with diabetic glomerulosclerosis. However, crystalglobulin-induced nephropathy with crystal deposit was identified on electron microscopy. Renal biopsy is often performed for diabetic patients who present with proteinuria and light microscopy often shows features of diabetic glomerulosclerosis. Additional information may occasionally be revealed on electron microscopy, altering the subsequent plan of management.

Clinical Presentation, Renal Histopathological Findings, and Outcome in Patients with Monoclonal Gammopathy and Kidney Disease

Monoclonal gammopathies are associated with acute and chronic kidney injury. Nephrotoxicity of the secreted monoclonal (M)-protein is related to its biological properties and blood concentration. Little is known about epidemiology, clinical manifestations, and outcome of monoclonal gammopathies in patients with kidney disease. We retrospectively collected data about demographics, clinical manifestations, and renal histological lesions of all patients (n = 1334) who underwent kidney biopsy between January 2000 and March 2017. Monoclonal gammopathy was detected in 174 (13%) patients with a mean age of 66.4 ± 13.1 years. The spectrum of monoclonal gammopathies comprised monoclonal gammopathy of undetermined significate (MGUS) (52.8%), multiple myeloma (MM) (25.2%), primary amyloidosis (AL) (9.1%), smoldering MM (SMM) (4%), non-Hodgkin lymphoma (NHL) (6.8%), and Hodgkin lymphoma (HL) (1.7%). Monoclonal gammopathy of renal significance (MGRS) accounted for 6.5% in patients with MGUS and 14.2% in patients with SMM. Evaluation of kidney biopsy revealed that M-protein was directly involved in causing kidney injury in MM (93.1%). MM was the only gammopathy significantly associated with an increased risk of kidney injury (odds ratio [OR] = 47.5, CI 95%, 13.7–164.9; P ≤ 0.001). While there were no significant differences in the progression toward end-stage renal disease or dialysis (P = 0.776), monoclonal gammopathies were associated with a different risk of death (P = 0.047) at the end of the follow-up. In conclusion, monoclonal gammopathy was a frequent finding (13%) in patients who underwent kidney biopsy. M-protein was secreted by both premalignant (56.8%) and malignant (43.2%) lymphoproliferative clones. Kidney biopsy had a key role in identifying MGRS in patients with MGUS (6.5%) and SMM (14.2%). Among monoclonal gammopathies, only MM was significantly associated with biopsy-proven kidney injury. The rate of end-stage renal disease or dialysis was similar among monoclonal gammopathies, whereas NHL, MM, and SMM showed a higher rate of deaths.

Complement testing in the clinical laboratory

The complement system is the human's first line of defense against microbial pathogens because of its important housekeeping and infection/inflammation roles. It is composed of a series of soluble and cell-bound proteins that are activated in a cascade effect, similar to the coagulation pathways. There are different pattern recognizing molecules that activate the complement system in response to stimuli or threats, acting through three initiation pathways: classical, lectin, and alternative. All three activation pathways converge at the C3 component and share the terminal pathway. The main outputs of the complement system action are lytic killing of microbes, the release of pro-inflammatory anaphylatoxins, and opsonization of targets. Laboratory testing is relevant in the setting of suspected complement deficiencies, as well as in the emerging number of diseases related to dysregulation (over-activation) of complement. Most common assays measure complement lytic activity and the different complement component concentrations. Specialized testing includes the evaluation of autoantibodies against complement components, activation fragments, and genetic studies. In this review, we cover laboratory testing for complement and the conditions with complement involvement, as well as current challenges in the field.

Proliferative glomerulonephritis with monoclonal immunoglobulin G deposits in a young woman: A case report

BACKGROUND

Proliferative glomerulonephritis with monoclonal immunoglobulin G (IgG) deposits (PGNMID) is a newly recognized rare disease. The renal pathology is characterized by prominent manifestations of membranous hyperplasia, which are easy to misdiagnose. The clinical symptoms are severe. Massive proteinuria and hypoproteinemia are conspicuous, and most patients are accompanied by renal insufficiency and microscopic hematuria.

CASE SUMMARY

A 27-year-old woman was admitted to a hospital for macroscopic hematuria and proteinuria 4 years prior, and renal biopsy in the hospital suggested moderate-to-severe mesangial proliferating glomerulonephritis (MsPGN). She had taken a glucocorticoid, cyclophosphamide, mycophenolate mofetil, and other treatments and achieved brief partial remission. Recently, the patient visited our hospital due to massive proteinuria. Repeated renal biopsy and re-evaluation of the first biopsy obtained 4 years previously revealed monoclonal immunoglobulin deposition in the glomeruli. A bone marrow examination was performed to exclude hematologic malignancy, and a diagnosis of PGNMID was established. The patient showed remission after four cycles of a bortezomib + cyclophosphamide + dexamethasone scheme.

CONCLUSION

PGNMID is usually misdiagnosed as MsPGN or membranoproliferative glomerulonephritis. Although it often occurs in middle-aged and elderly individuals, it cannot be readily excluded in young people, even when serum immunofixation electrophoresis is negative. IgG subtype and light chain staining are necessary when this disease is highly suspected. An accurate diagnosis at the earliest stage may avoid the overuse of glucocorticoids and immunosuppressants.

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.

Renal Expression of Light Chain Binding Proteins

Overproduction of human light chains (LCs) and immunoglobulins can result in various forms of renal disease such as cast nephropathy, monoclonal immunoglobulin deposition disease, LC proximal tubulopathy, AL amyloidosis, and crystal storing histiocytosis. This is caused by cellular uptake of LCs and overwhelmed intracellular transport and degradation in patients with high urine LC concentrations. LC kappa and lambda purification was evaluated by sodium dodecyl sulfate gel electrophoresis. LC and myeloma protein binding to immobilized renal proteins was measured by enzyme-linked immunosorbent assay (ELISA). The human protein microarray (HuProt™) was screened with purified kappa and lambda LC. Identified LC partners were subsequently analyzed in silico for renal expression sites using protein databases, Human Protein Atlas, UniProt, and Bgee. Binding of urinary LCs and immunoglobulins to immobilized whole renal proteins from 22 patients with myeloma or plasma cell dyscrasia was shown by ELISA. Forty lambda and 23 kappa interaction partners were identified from HuProt™ array screens, of which 21 were shared interactors. Among the total of 42 interactors, 12 represented cell surface proteins. Lambda binding signals were approximately 40% higher than kappa signals. LC interaction with renal cells and disease-causing pathologies are more complex than previously thought. It involves an extended spectrum of proteins expressed throughout the nephron, and their identification has been enabled by recently developed methods of protein analysis such as protein microarray screening. Further biochemical studies on interacting proteins are warranted to elucidate their clinical relevance.

Continuous function of 80 primary renal allografts for 30-47 years with maintenance prednisone and azathioprine/mycophenolate mofetil therapy: A clinical mosaic of long-term successes

Eighty primary renal allograft recipients, 61 living-related and 19 deceased donor, transplanted from 1963 through 1984 had continuous graft function for 30-47 years. They were treated with three different early immunosuppression programs (1963-1970: thymectomy, splenectomy, high oral prednisone; 1971-1979: divided-dose intravenous methylprednisolone; and 1980-1984: antilymphocyte globulin) each with maintenance prednisone and azathioprine, and no calcineurin inhibitor. Long-term treatment often included the anti-platelet medication, dipyridamole. Although both recipient and donor ages were young (27.2 ± 9.5 and 33.1 ± 12.0 years, respectively), six recipients with a parent donor had >40-year success. At 35 years, death-censored graft survival was 85.3% and death with a functioning graft 84.2%; overall graft survival was 69.5% (Kaplan-Meier estimate). Biopsy-documented early acute cellular and highly probable antibody-mediated rejections were reversed with divided-dose intravenous methylprednisolone. Complications are detailed in an integrated timeline. Hypogammaglobulinemia identified after 20 years doubled the infection rate. An association between a monoclonal gammopathy of undetermined significance and non-plasma-cell malignancies was identified. Twenty-seven azathioprine-treated patients tested after 37 years had extremely low levels of T1/T2 B lymphocytes representing a "low immunosuppression state of allograft acceptance (LISAA)". The lifetime achievements of these patients following a single renal allograft and low-dose maintenance immunosuppression are remarkable. Their success evolved as a clinical mosaic.

A case of monoclonal gammopathy of renal significance presenting as atypical amyloidosis with IgA lambda paraproteinemia

Monoclonal gammopathy of renal significance is defined as any B cell or plasma cell clonal lymphoproliferation which neither causes tumor complications nor meets any current hematological criteria for specific therapy, with one or more kidney lesions related to the produced monoclonal immunoglobulin, such as amyloidosis. A 50-year-old male presented with heavy proteinuria and blood tests showing IgA and Lambda paraproteinemia. Light microscopy showed mesangial eosinophilic ground substance extending into the capillary loops, and positive staining within the glomeruli and vessel walls for amyloid P immunohistochemistry was also noted. Immunofluorescence showed positive staining for IgA and Lambda in the mesangia and capillary loops. Electron microscopy exhibited organized fibrils measuring 4–5 nm in diameter in the mesangia, glomerular basement membranes and vessel walls. We interpreted the overall findings as atypical renal amyloidosis with IgA and Lambda deposition on immunofluorescence. Further amyloid typing using laser microdissection-liquid chromatography and mass spectrometry will be useful.

First case report of monoclonal IgG3-heavy-chain glomerulonephritis with microtubular structures

Our patient was a 69-year-old woman admitted to our hospital for heavy proteinuria and hematuria. A renal biopsy showed findings similar to those of membranoproliferative glomerulonephritis associated with nodular lesions, and immunofluorescence showed marked deposits of IgG, C1q, and C3 on the peripheral capillary walls. IgG3 alone was observed on IgG subclass staining with no κ or λ light chains, and Congo red staining was negative. These findings suggested IgG3-heavy-chain deposition disease (HCDD). However, we did not find a deletion of the first heavy-chain constant domain, which is commonly observed in HCDD. Electron microscopy showed randomly arranged subendothelial microtubular structures with diameters of 70-90 nm. Altogether, the diagnosis of HCDD could not be made, although monoclonal IgG3 deposits in glomeruli were observed. This is the first case report of monoclonal IgG3-heavy-chain glomerulonephritis with subendothelial-based, randomly arranged microtubular structures with diameters of 70-90 nm.

Pathophysiology and management of monoclonal gammopathy of renal significance

Recent years have witnessed a rapid growth in our understanding of the pathogenic property of monoclonal proteins. It is evident that some of these small monoclonal proteins are capable of inducing end-organ damage as a result of their intrinsic physicochemical properties. Hence, an umbrella term, monoclonal gammopathy of clinical significance (MGCS), has been coined to include myriad conditions attributed to these pathogenic proteins. Because kidneys are the most commonly affected organ (but skin, peripheral nerves, and heart can also be involved), we discuss MGRS exclusively in this review. Mechanisms of renal damage may involve direct or indirect effects. Renal biopsy is mandatory and demonstration of monoclonal immunoglobulin in kidney, along with the corresponding immunoglobulin in serum or urine, is key to establish the diagnosis. Pitfalls exist at each diagnostic step, and a high degree of clinical suspicion is required to diagnose MGRS. Recognition of MGRS by hematologists and nephrologists is important, because timely clone-directed therapy improves renal outcomes. Autologous stem cell transplant may benefit selected patients.

Monoclonal Gammopathies of Renal Significance: Renal Biopsy and Beyond

Monoclonal Gammopathies of Renal Significance (MGRS) are a rather heterogeneous group of renal disorders caused by a circulating monoclonal (MC) immunoglobulin (Ig) component, often in the absence of multiple myeloma (MM) or another clinically relevant lymphoproliferative disorder. Nevertheless, substantial kidney damage could occur, despite the "benign" features of the bone-marrow biopsy. One example is renal amyloidosis, often linked to a small clone of plasma cells, without the invasive features of MM. However, patients with amyloidosis may present with a nephrotic syndrome and renal failure, eventually leading to end-stage kidney disease. At the same time, other organs, such as the heart and the liver, may be severely damaged by Ig light chains or amyloid deposits, occasionally resulting in fatal arrhythmias and/or organ failure. Acute kidney injury (AKI) may as well result from massive excretion of MC proteins, with deposition disease in glomeruli or renal tubules, not rarely obstructed by luminal aggregates, or "casts". Proliferative glomerulonephritis with monoclonal Ig deposits is another, less frequent clinical presentation of an MGRS. The present review deals with the implications of MGRS for renal function and prognosis, and the potential of tools, such as the renal biopsy, for assessing clinical risk and guiding therapy of the underlying condition.

Monoclonal Gammopathies After Renal Transplantation: A Single-center Study

INTRODUCTION

Plasma cell disorders (PCDs) are clonal plasma cell disorders that include conditions such as monoclonal gammopathy of undetermined significance (MGUS), monoclonal gammopathy of renal significance (MGRS), multiple myeloma (MM), smoldering MM (SMM), solitary plasmacytoma, and light-chain (AL) amyloidosis. The risk factors associated with and the clinical course of PCDs after renal transplantation is not well established although immunosuppressive protocols may impact the incidence and natural history of PCDs posttransplant.

PATIENTS AND METHODS

This single-center retrospective study evaluated patients with a history of renal transplant who developed a PCD between January 1, 2014-December 31, 2018.

RESULT

A total of 41 patients met the inclusion criteria including 29 with MGUS and 12 with symptomatic PCD (4 with MM, 2 with SMM, 4 with MGRS, 1 with AL amyloidosis, and 1 with solitary plasmacytoma). The median follow-up of survivors was 41.6 months. Three patients (1 with MGUS and 2 with MGRS) progressed to MM during the follow-up period. There was a male preponderance in both groups. There was no correlation between the donor and immunosuppressive regimen and the development of a PCD. Patients with symptomatic PCD had higher serum creatinine and M-protein levels at diagnosis and higher free light chain ratio and plasma cell burden. There was also a higher percentage of allograft failure noted in the symptomatic PCD subset 50% (n = 6), whereas only 23% (n = 7) of patients had allograft failure in the MGUS group.

CONCLUSION

This study shows the importance of considering monoclonal gammopathy in the differential of renal dysfunction after kidney transplant and the need to follow these patients closely to monitor for progression to symptomatic PCD.

Fibrillary Glomerulopathy with a High Level of Myeloperoxidase-ANCA: A Case Report

An elderly woman was admitted with the chief complaint of gross hematuria. Laboratory values indicated a high myeloperoxidase-ANCA level. In renal histological examination, 40% of the glomeruli showed crescent formation, but immunofluorescence staining showed positivity for IgG, C3, and C1q. Furthermore, the deposition of fibrils in the glomerulus was noted on electron microscopy, and immunohistochemical staining showed strong positivity for DNA-J heat shock protein family member B9 (DNAJB9). Crescent formation is a common feature of fibrillary glomerulonephritis (FGN). Thus, in ANCA-positive crescentic glomerulonephritis, immunohistochemical assessments for immunoglobulins and DNAJB9, as well as electron microscopy, are important to correctly diagnose FGN.

Educational Case: Dysproteinemic Nephropathies: Renal Amyloidosis as an Example

The following fictional case is intended as a learning tool within the Pathology Competencies for Medical Education (PCME), a set of national standards for teaching pathology. These are divided into three basic competencies: Disease Mechanisms and Processes, Organ System Pathology, and Diagnostic Medicine and Therapeutic Pathology. For additional information, and a full list of learning objectives for all three competencies, see http://journals.sagepub.com/doi/10.1177/2374289517715040.¹

Light chain only variant of proliferative glomerulonephritis with monoclonal immunoglobulin deposits is associated with a high detection rate of the pathogenic plasma cell clone

IgG (mainly IgG3) is the most commonly involved isotype in proliferative glomerulonephritis with monoclonal immunoglobulin deposits (PGNMID). Here we describe the first series of PGNMID with deposition of monoclonal immunoglobulin light chain only (PGNMID-light chain). This multicenter cohort of 17 patients presented with nephritic or nephrotic syndrome with underlying hematologic conditions of monoclonal gammopathy of renal significance (71%) or multiple myeloma (29%). Monoclonal immunoglobulin was identified by serum and urine immunofixation in 65% and 73%, respectively, with abnormal serum free light chain in 83%, and a detectable bone marrow plasma cell clone in 88% of patients. Renal biopsy showed a membranoproliferative pattern in most patients. By immunofluorescence, deposits were restricted to glomeruli and composed of restricted light chain (kappa in 71%) and C3, with granular appearance and subendothelial, mesangial and subepithelial distribution by electron microscopy. Proteomic analysis in four cases of kappa PGNMID-light chain revealed spectra for kappa constant and variable domains, without evidence of Ig heavy chains; spectra for proteins of the alternative pathway of complement and terminal complex were detected in three. The classical pathway was not detected in three cases. After median follow up of 70 months, the renal response was dependent on a hematologic response and occurred in six of ten patients treated with plasma cell-directed chemotherapy but none of five patients receiving other therapies. Thus, PGNMID-light chain differs from PGNMID-IgG by higher frequency of a detectable pathogenic plasma cell clone. Hence, proper recognition is crucial as anti-myeloma agents may improve renal prognosis. Activation of an alternative pathway of complement by monoclonal immunoglobulin light chain likely plays a role in its pathogenesis.

Emerging role of clinical mass spectrometry in pathology

Mass spectrometry-based assays have been increasingly implemented in various disciplines in clinical diagnostic laboratories for their combined advantages in multiplexing capacity and high analytical specificity and sensitivity. It is now routinely used in areas including reference methods development, therapeutic drug monitoring, toxicology, endocrinology, paediatrics, immunology and microbiology to identify and quantify biomolecules in a variety of biological specimens. As new ionisation methods, instrumentation and techniques are continuously being improved and developed, novel mass spectrometry-based clinical applications will emerge for areas such as proteomics, metabolomics, haematology and anatomical pathology. This review will summarise the general principles of mass spectrometry and specifically highlight current and future clinical applications in anatomical pathology.

Bortezomib-Based Chemotherapy with Autologous Stem Cell Transplantation for Monoclonal Gammopathy of Renal Significance: A Case Report and Literature Review

BACKGROUND/AIMS

The term monoclonal gammopathy of renal significance (MGRS) was introduced in 2012 to emphasize kidney lesions in monoclonal gammopathy patients. Bortezomib-based chemotherapy has become the first-line treatment for MGRS.

OBJECTIVES

The objective of this study was to investigate whether the strategy of combining chemotherapy with autologous stem cell transplantation (ASCT) could improve prognosis and decrease functional kidney impairment in patients with MGRS.

METHODS

We reported the case of a 44-year-old Asian patient who was diagnosed with MGRS and received 5 cycles of Velcade® (a trade name for bortezomib), thalidomide, and dexamethasone therapy (VTD therapy), and subsequently underwent ASCT. In addition, we performed a literature review and summarized the latest advances in the characterization, treatment, and prognosis of MGRS.

RESULTS

The patient was diagnosed with light chain deposition disease by renal biopsy. After 5 cycles of VTD therapy, the patient had a very good partial response characterized by the resolution of M-protein (20.2% before treatment vs. 2.5% after treatment), remission of the level of serum free lambda (FLAM; over 80% decline), and normalization of the serum free light chain (sFLC) ratio (κ to λ). He also had a renal response characterized by a decreased serum creatinine level (1.61 vs.1.34 mg/dL) and less severe proteinuria (6.77 g/24 h vs.1.264 g/24 h) after chemotherapy. Importantly, after ASCT, the patient achieved a complete response (CR) characterized by a negative serum immunofixation electrophoresis (IFE) result and a dramatic decrement in FLAM (over 90%). Furthermore, 6 months after ASCT, the patient still remained in stable condition with a negative IFE result, normal sFLC ratio, and low level of serum creatinine (1.31 mg/dL) and proteinuria (0.339 g/24 h). In our retrospective literature analysis, we found that MGRS patient survival time and renal outcome had been markedly improved by current therapies due to the popularization of bortezomib-based chemotherapy and ASCT.

CONCLUSIONS

The patient successfully achieved CR after VTD therapy followed by ASCT. However, this treatment is controversial, and a standard therapy recommendation for MGRS has not been established. Bortezomib-based chemotherapy combined with ASCT may have prospects for the treatment of MGRS, but the exact effects of ASCT remain unclear and should be thoroughly investigated.

Complete biopsy-proven resolution of deposits in recurrent proliferative glomerulonephritis with monoclonal IgG deposits (PGNMIGD) following rituximab treatment in renal allograft

Background

Proliferative glomerulonephritis with monoclonal IgG deposits (PGNMIGD) is a disease entity classified under the group of “Monoclonal gammopathy-related kidney diseases”, and can recur after transplant. Clinical remission of proteinuria in patients with PGNMIGD has been previously shown following anti-B cell and/or anti-plasma cell therapies. Our case is the first to show complete histologic resolution of the glomerular monoclonal IgG kappa deposits in a case of recurrent PGNMIGD in renal allograft after rituximab and steroid treatment. This is a novel finding and it shows that the deposits are amenable to therapy. This case also highlights the importance of IgG subclass staining in the recognition of the monoclonal nature of the deposits. It is particularly important in PGNMIGD because only 20 to 30% of patients with this disease are reported to have detectable monoclonal gammopathy, and the deposits do not have any organized substructure on electron microscopic examination. Morphologically, they resemble polyclonal immune-type deposits seen in other immune complex glomerulonephritides such as lupus nephritis, infection-associated glomerulonephritis, and membranoproliferative glomerulonephritis (MPGN type I).

Case presentation

The patient is a 44 year old Caucasian male who received a living unrelated donor kidney transplant for end-stage renal disease diagnosed 7 years before transplant. The reported native kidney biopsy diagnosis was membranoproliferative glomerulonephritis (MPGN) with IgG, C3 and kappa restricted deposits. Fourteen months post-transplant, he presented with abrupt worsening of graft function, proteinuria and serum IgG kappa monoclonal spike. Allograft biopsy was consistent with recurrent PGNMIGD, considering the native kidney diagnosis and interval post-transplant. He underwent plasmapheresis, IV pooled immune globulin, steroid pulse and taper, and anti-CD-20 Rituximab therapy. Patient had gradual decline in proteinuria and complete resolution of the immune deposits on repeat biopsy 3 months later. Unfortunately he subsequently developed chronic antibody-mediated rejection and transplant glomerulopathy and graft failure 34 months post-transplant.

Conclusions

In a transplant setting, repeat allograft biopsies are frequently performed for graft dysfunction. This provides a good opportunity to study the evolution of the immune deposits following treatment. Our case shows complete histologic resolution of the deposits in allograft PGNMIGD.

Bortezomib Maintenance for the Treatment of Monoclonal Gammopathy of Renal Significance

Monoclonal gammopathy of renal significance (MGRS) defines renal diseases resulting from the nephrotoxic effects of monoclonal proteins secreted from non-malignant clonal B cells or plasma cells, that do not meet criteria for multiple myeloma, Waldenstrom’s macroglobulinemia, chronic lymphocytic leukemia, or lymphomas. Renal disease in MGRS can result from monoclonal immunoglobulin deposition to different parts of the kidney and includes a wide spectrum of glomerular, tubulointerstitial and vascular renal diseases. Recognizing MGRS is important because renal outcomes are poor and treatments targeting the underlying clonal disease have been associated with improved renal survival. In this case report, we present a case of a patient with proliferative glomerulonephritis with monoclonal immunoglobulin deposits (PGNMID) subtype of MGRS who underwent a phased clone directed treatment of induction and extended maintenance therapy to achieve renal response.

[Diagnosis and treatment of kidney involvement in plasma cell diseases : Renal involvement in multiple myeloma and monoclonal gammopathies]

BACKGROUND

Kidney involvement is a common complication in patients with plasma cell diseases.

OBJECTIVE

This article outlines the spectrum of renal involvement in plasma cell dyscrasia and describes diagnostic and therapeutic measures to guide clinical management.

MATERIAL AND METHODS

Evaluation and discussion of the current literature as well as existing guidelines and recommendations of professional societies.

RESULTS

The clinical manifestations of renal involvement in plasma cell disorders are heterogeneous and range from acute cast nephropathy in multiple myeloma to rare forms of glomerulonephritis. The term monoclonal gammopathy of renal significance (MGRS) was introduced to describe kidney involvement caused by monoclonal gammopathy but without evidence for underlying malignancy. Light chain cast nephropathy is the most common renal manifestation in multiple myeloma, whereas monoclonal immunoglobulin deposition disease (MIDD) and renal light chain (AL) amyloidosis can be found in multiple myeloma and MGRS. Decisive is the extended hematological diagnostics in order to exclude the presence of a hematological neoplasm. The treatment of renal involvement in monoclonal gammopathies involves the reduction of the plasma cell clone with cytoreductive treatment. The reduction of the monoclonal protein in serum is prognostically relevant for the renal response to treatment. In the case of histological evidence of a light chain cast nephropathy, high cut-off dialysis is recommended to reduce the free light chains in serum.

CONCLUSION

The spectrum of renal manifestations in plasma cell dyscrasia has been expanded, particularly since the introduction of the term MGRS. Diagnostic and therapeutic management remain an interdisciplinary challenge.