Thrombotic microangiopathy associated with monoclonal gammopathy

Monoclonal gammopathy is present in one fourth of patients undergoing renal biopsy but is pathogenic only in half of them

BACKGROUND

About 4-7% of renal biopsies show a monoclonal gammopathy-related nephropathy, such as AL amyloidosis, cast nephropathy, or light chain deposition disease. Both a high prevalence and a causal role of monoclonal gammopathy have been observed in patients with C3 glomerulopathy or thrombotic microangiopathy, although a definitive causative role cannot be established in most cases (potentially monoclonal gammopathy-related nephropathies). A coexisting monoclonal gammopathy has been identified in many cases of nephropathy without a defined causative role (monoclonal gammopathy-unrelated nephropathies). The aim of this study was to investigate the prevalence and distribution of monoclonal gammopathy in patients who underwent a renal biopsy and assess its possible causal role in nephropathies not ordinarily related to monoclonal gammopathy.

METHODS

In our single-center retrospective observational study, we considered patients who underwent native kidney biopsy from 2009 to 2023 at the Nephrology Unit, Careggi University Hospital, Florence (Italy) and for whom a complete monoclonal gammopathy workup (serum electrophoresis, serum and urinary immunofixation, serum free light chains) was available.

RESULTS

Overall, 827 patients were included: 208 (25%) had a monoclonal gammopathy: in 104 cases the monoclonal gammopathy was unrelated to the kidney disease; 87 subjects showed renal pathology related to monoclonal gammopathy (monoclonal gammopathy-related nephropathies). Patients with thrombotic microangiopathy and C3 glomerulopathy (potentially monoclonal gammopathy-related nephropathies) exhibited a prevalence of monoclonal gammopathy > 30%. In a subgroup of diagnoses (e.g. tubulointerstitial nephritis, membranoproliferative glomerulonephritis) a possible causal and/or prognostic role of a concomitant monoclonal gammopathy may be hypothesized.

CONCLUSIONS

In our cohort, one fourth of patients undergoing a renal biopsy had a monoclonal gammopathy, although in half of them the monoclonal gammopathy did not have a causative role in the kidney disease. Hence, it is impossible to conclude that a monoclonal gammopathy in the context of renal disease equates to a causal association without performing a renal biopsy because of the high frequency of monoclonal gammopathy in patients undergoing a kidney biopsy.

Outcomes in patients with thrombotic microangiopathy associated with a trigger following plasma exchange: A systematic literature review

Plasma exchange (PE) outcomes in patients with trigger-associated thrombotic microangiopathy (TMA) have not been comprehensively reviewed. Embase and MEDLINE® were searched on 03/14/2022 for English language articles published after 2007, alongside a congress materials search (2019-2022; PROSPERO: CRD42022325170). Studies with patients with trigger-associated TMA (excluding thrombotic thrombocytopenic purpura, 'typical' hemolytic uremic syndrome caused by Shiga toxin-producing Escherichia coli, post-partum TMA, and TMAs with known genetic cause) who received PE or plasma infusion (PI) and reported treatment response (including measures), safety, patient-/caregiver-reported outcomes, or economic burden data were examined. The NICE quality appraisal checklist assessed bias risk. After screening 695 articles, 49 PE or PI studies were identified, of which 42 reported PE exclusively; most were retrospective observational studies (n = 37). The most common TMA trigger was transplantation (n = 12). The median number of PE sessions was 3.5-25.0. Outcomes following PE varied by trigger type. Treatment response rates and definitions varied (0-100 %; 24 studies); in studies of > 25 patients, response rates were 5-63 %. TMA relapse rates were 0-67 % (7 studies). Mortality was 10-91 % (23 studies). Progression to chronic kidney disease (CKD; 5 studies) and end-stage renal disease (ESRD; 6 studies) occurred in 0-93 % and 17-100 % of patients, respectively. Two serious adverse events were identified (transfusion-related injury, acute lung injury; 10 studies; 231 patients). Patients with trigger-associated TMA may experience a substantial burden in terms of mortality, relapse, and progression to CKD and ESRD following PE, leading to increased healthcare resource utilization. Additional interventions may be required.

Kidney disease in multiple myeloma

Renal disease is a frequent complication of symptomatic multiple myeloma, that increases morbidity and reduces quality of life and overall survival. It may result from various lesions, the most frequent being light chain cast nephropathy (LCCN), related to precipitation of monoclonal free light chains (FLC) with uromodulin in distal tubules. Rapid identification of the type of kidney disease with appropriate management is key. LCCN typically reveals the underlying myeloma and manifests with severe acute kidney injury, high serum FLC level (>500 mg/l) and predominant light chain proteinuria (urine albumin/creatinine ratio <10 %). Urgent therapy is required, based on vigorous fluid expansion, correction of precipitating factors and introduction of efficient anti-myeloma therapy which choice should consider renal elimination of each agent and patient frailty. Early and deep reduction in serum FLC level conditions renal recovery, warranting assessment of efficacy by serial serum FLC level monitoring. In newly diagnosed patients, the combination of bortezomib, high-dose dexamethasone and an anti-CD38 monoclonal antibody is commonly used. The benefit to risk balance of quadruplets incorporating cyclophosphamide or an immunodulatory agent requires to be evaluated in prospective studies. In patients with severe acute kidney injury, reinforcing chemotherapy with FLC removal through plasma exchange or high-cutoff hemodialysis may increase the probability of renal response, despite controversial data from randomized trials. Histological assessment of the extent of cast formation and interstitial fibrosis/tubular atrophy may help evaluating renal prognosis and refining therapy. Thanks to improved overall survival, renal transplantation may be considered in selected candidates with end-stage kidney disease.

Clinicopathologic Characteristics of Crystalglobulin-Induced Nephropathy: A Case Series

RATIONALE & OBJECTIVE

Crystalglobulinemia is a rare syndrome characterized by intravascular crystallization of monoclonal immunoglobulins (MIg). Data on kidney involvement are limited to case reports. This series characterizes the clinicopathologic spectrum of crystalglobulin-induced nephropathy (CIN).

STUDY DESIGN

Case series.

SETTING & PARTICIPANTS

Nineteen CIN cases identified from the nephropathology archives of Mayo Clinic and Columbia University. CIN was defined by intravascular (extracellular) MIg crystals visible by light microscopy (LM) and electron microscopy (EM).

RESULTS

Among the cases, 68% were male, and 65% were Caucasian (median age, 56 years). Most patients presented with severe acute kidney injury (AKI) (median creatinine, 3.5mg/dL), hematuria, and mild proteinuria (median, 1.1g/day). Common extrarenal manifestations were constitutional (67%), cutaneous (56%), and rheumatologic (50%). Fifty percent of cases had hypocomplementemia. The hematologic disorders were monoclonal gammopathy of renal significance (MGRS) (72%), lymphoma (17%), or myeloma (11%), with 65% of these disorders discovered concomitantly with CIN. All patients had MIg identified on serum protein electrophoresis/immunofixation (IgGκ in 65%). The serum free light chain ratio was outside the renal range in 40%, and bone marrow biopsy detected the responsible clone in 67%. On LM, crystals involved glomeruli (100%) and vessels (47%), often with an inflammatory reaction (89%) and fibrin (58%). All cases exhibited crystal substructures (mostly paracrystalline) by EM. Immunofluorescence on paraffin-embedded tissue was more sensitive than frozen tissue (92% vs 47%) for demonstrating the crystal composition (IgGκ in 63%). Follow-up observation (median, 20 months) was available in 16 patients. Eighty-one percent received steroids, 44% plasmapheresis, 38% hemodialysis, and 69% chemotherapy. Ninety-percent of patients who received clone-directed therapy achieved kidney recovery versus 20% of those who did not (P=0.02).

LIMITATIONS

Retrospective design, small sample size.

CONCLUSIONS

CIN is a rare cause of nephropathy associated with lymphoplasmacytic disorders (mostly MGRS) and typically presents with severe AKI and extrarenal manifestations. Diagnosis often requires immunofluorescence performed on paraffin-embedded kidney tissue. Prompt initiation of clone-directed therapy, coupled with corticosteroids and plasmapheresis, may lead to recovery of kidney function.

Triple monoclonal protein-related kidney lesions in a patient with plasma cell dyscrasia: a case report

A toxic monoclonal protein typically results in a single kidney pathology due to the specific biophysical characteristics of monoclonal proteins. Multiple monoclonal protein lesions are rarely reported and often portend a poor prognosis. We present a 57-year-old male who developed rapidly progressive glomerulonephritis after concealed ruptured diverticulitis. A kidney biopsy showed light chain cast nephropathy, light chain proximal tubulopathy, and thrombotic microangiopathy. Laboratories showed IgG kappa with an M-spike of 0.2 g/dl and a kappa light chain of 16 mg/dl. A bone marrow biopsy showed 3% kappa-restricted plasma cells. The dramatic renal presentation despite the minimal hematological burden is suggestive of a highly toxic light chain, which is consistent with monoclonal gammopathy of renal significance (MGRS). Clone-directed therapy and a complement blockade were initiated. The patient remained dialysis-dependent despite a hematological response. This case highlights the importance of considering the toxic properties of monoclonal proteins in causing kidney diseases. Our case is the first report of an MGRS patient with three distinct kidney lesions. Triple monoclonal protein-related kidney lesions are very rare and are usually associated with multiple myeloma. Light chain cast nephropathy (LCCN) is a myeloma-defining event but his light chain (LC) (<50 mg/dl) and plasma cell (<10%) burdens were low which makes this case very unusual. Sepsis-induced low-flow stage and the toxic properties of LC may induce LCCN in this patient. Aggressive therapy is likely needed to eradicate the clone in order to achieve an organ response.

Intracapillary monoclonal IgM deposits disease with massive pseudothrombi: A clinicopathologic study of 4 cases and literature review

OBJECTIVES

Intracapillary monoclonal IgM deposits disease (ICMDD) has long been considered a hallmark of Waldenström macroglobulinemia (WM) nephropathy. Intracapillary immunoglobulin thrombi are the characteristic features of cryoglobulinemic glomerulonephritis. Here, we reported 4 cases of ICMDD with massive pseudothrombi but without WM or cryoglobulinemia.

METHODS

We retrospectively analyzed the clinical and pathologic features of patients diagnosed with ICMDD with massive pseudothrombi.

RESULTS

A total of 4 patients (2 men and 2 women) aged 62 to 73 years were enrolled in this study. Microscopic hematuria, edema, and renal insufficiency were present in all patients, along with low serum C3 and C4 in 2 patients. Hematologic examination showed abnormal serum free light chain ratios in all patients and high levels of serum IgM in 3 patients. IgM-κ monoclonal band was identified by serum immunofixation electrophoresis in 3 patients. One patient was diagnosed with small B-cell lymphoma by bone marrow aspiration. Renal biopsy specimen showed massive periodic acid-Schiff-positive hyaline thrombi in the glomerular capillary lumens and also less mesangial, subendothelial, and subepithelial deposits on light microscopy. Immunofluorescence indicated positive staining for IgM (++) and κ light chain staining in the glomerular capillary lumens, capillary walls, and mesangium in all patients. By electron microscopy, the glomerular capillary lumens were filled with homogeneous high-electron-dense deposits without substructure. Two patients were treated with prednisone combined with cyclophosphamide, and 2 received plasma cell-targeted chemotherapy. One patient achieved partial renal remission.

CONCLUSIONS

Intracapillary monoclonal IgM deposits disease is a rare disease and not always related to WM. Most patients have IgM monoclonal immunoglobulinemia; renal biopsy specimens mainly show a large number of pseudothrombi in the glomerular capillary lumens. Cyclophosphamide is effective in some patients.

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.

Case report: Successful treatment of renal-limited thrombotic microangiopathy secondary to chronic lymphocytic leukemia

Thrombotic microangiopathy (TMA) is a rare renal complication of patients with chronic lymphocytic leukemia (CLL) and is often associated with peripheral features. We present the first case of CLL patients with renal-limited TMA. A 70-year-old female patient with a history of well-controlled type 2 diabetes and baseline albuminuria of 87.2 mg/g 1 year prior and CLL was on active surveillance only. Her baseline white blood cell (WBC) was 202.6 x 103/µl. She presented with nephrotic syndrome with proteinuria of 10 g/g and a subsequent unremarkable serologic work-up. A kidney biopsy revealed diabetic glomerulosclerosis and chronic TMA. Initially, she was treated conservatively with angiotensin receptor blockade and sodium glucose cotransporter-2 inhibition but progressed with increased proteinuria of 17 g/g. Complement functional panel testing was pursued and showed dysregulation of the classical and alternative complement pathways. We decided to treat CLL which was suspected to be the culprit. At 9 months post-ibrutinib initiation, there was a 90% reduction in the WBC as well as a 94% reduction in proteinuria (17 g/g to 0.97 g/g). This case emphasizes the role of complement dysregulation in the pathogenesis of TMA in CLL patients. Treatment of CLL can restore complement dysregulation and improve renal outcomes.

Monoclonal gammopathy of renal significance from the perspective of nephrologists

Kidney disease is a frequent complication of multiple myeloma and other malignancies associated with monoclonal gammopathies. Additionally, dysproteinemia-related kidney disease can occur independently of overt multiple myeloma or hematologic malignancies. Monoclonal gammopathy of renal significance (MGRS) is a spectrum of disorders in which a monoclonal immunoglobulin produced by a benign or premalignant B-cell or plasma cell clone causes kidney damage. MGRS-associated renal disease manifests in various forms, including immunoglobulin-associated amyloidosis, monoclonal immunoglobulin deposition diseases (light chain, heavy chain, and combined light and heavy chain deposition diseases), proliferative glomerulonephritis with monoclonal immunoglobulin deposits, C3 glomerulopathy with monoclonal gammopathy, and light chain proximal tubulopathy. Although MGRS is a nonmalignant or premalignant hematologic condition, it has significant renal implications that often lead to progressive kidney damage and, eventually, end-stage kidney disease. This review discusses the epidemiology, pathogenesis, and management of MGRS and focuses on the perspective of nephrologists.

Paraneoplastic Glomerular Diseases

Paraneoplastic glomerular disease (PGD) develops from tumor cell products, leading to renal dysfunction. Unlike direct tumor effects, PGD illustrates the complex association between cancer and diverse clinical presentations and outcomes. Initially detected in a Hodgkin's disease patient, current research has defined diagnostic criteria based on PGD symptoms and cancer progression. PGDs, although rare (found in <1% of adult cancer patients with overt renal manifestations), are crucial, as they can signal cancer onset and frequently resist standard glomerulonephritis treatments. The emerging field of onconephrology studies this relationship between kidney disorders and cancers. The exact cause of many PGD cases remains unknown. This review examines PGDs, their clinicopathological features, related cancers, and mechanisms, emphasizing the need for early diagnosis and tailored treatment for kidney disease and linked cancer.

Thrombotic Microangiopathies and the Kidney

Thrombotic microangiopathy (TMA) is a pathological lesion that occurs due to endothelial injury. It can be seen in a heterogenous group of disorders, typically characterized by microangiopathic hemolytic anemia, thrombocytopenia, and end-organ ischemia. TMA can also be renal limited with no systemic manifestations. There are multiple etiologies of a TMA with complement activation being a core underlying mechanism, although the nature and extent of complement involvement can vary. A further complicated factor is the cross talk between complement, neutrophils, and coagulation pathways in the pathophysiology of TMAs. Therefore, a thorough and systematic clinical history and laboratory evaluation are critical to establish the cause and pathophysiology of a TMA. Furthermore, TMAs are associated with significant morbidity and mortality, and timely diagnosis is key for appropriate management and to prevent end-stage kidney disease and other associated complications. In this review, we focus on the pathology, mechanisms, diagnostic work up and treatment of TMAs associated with various etiologies. We also define the complement evaluations that should be conducted in these patients and further highlight the currently approved complement therapies as well as others in the pipeline.

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.

Development and validation of a diagnostic nomogram model for predicting monoclonal gammopathy of renal significance

In patients with kidney disease, the presence of monoclonal gammopathy necessitates the exploration of potential causal relationships. Therefore, in this study, we aimed to address this concern by developing a nomogram model for the early diagnosis of monoclonal gammopathy of renal significance (MGRS). Univariate and multivariate logistic regression analyses were employed to identify risk factors for MGRS. Verification and evaluation of the nomogram model's differentiation, calibration, and clinical value were conducted using the receiver operating characteristic (ROC) curve, calibration curve, and decision curve analysis. The study encompassed 347 patients who underwent kidney biopsy, among whom 116 patients (33.4%) were diagnosed with MGRS and 231 (66.6%) with monoclonal gammopathy of undetermined significance. Monoclonal Ig-related amyloidosis (n = 86) and membranous nephropathy (n = 86) was the most common renal pathological type in each group. Notably, older age, abnormal serum-free light chain ratio, and the absence of microscopic hematuria were identified as independent prognostic factors for MGRS. The areas under the ROC curves for the training and verification sets were 0.848 and 0.880, respectively. In conclusion, the nomogram model demonstrated high accuracy and clinical applicability for diagnosing MGRS, potentially serving as a valuable tool for noninvasive early MGRS diagnosis.

The spectrum of thrombotic microangiopathy related to monoclonal gammopathy

Background

Recent studies showed a high prevalence of monoclonal gammopathy (MG) in patients with thrombotic microangiopathy (TMA) aged over 50 years and suggested that complement dysregulation is pivotal for the disease to develop. Here, we studied this premise in seven patients with TMA and coexisting MG.

Methods

Patients with TMA on kidney biopsy and/or peripheral blood were recruited from the prospective COMPETE cohort (NCT04745195) and Limburg Renal Registry. Patients were screened for complement dysregulation, including genetics/factor H autoantibodies (FHAA) and functional ex vivo testing on microvascular endothelial cells.

Results

Seven (8%) out of 84 patients with TMA presented with a coexisting MG. MG clustered in patients aged over 50 years (n/N = 6/32, 19%). C4 and/or C3 levels were low in three patients, while four patients presented with normal complement levels. None of the patients carried rare variants in complement genes. Massive ex vivo C5b9 formation on the endothelium was noted in one patient; purified IgG from this patient caused massive ex vivo C5b9 formation via the alternative pathway of complement activation, pointing to complement dysregulation in the fluid phase. Kidney biopsies from other nephropathies linked to MG rarely exhibited concurrent TMA (n/N = 1/27, 4%).

Conclusions

MG clustered in patients with TMA aged over 50 years. TMA and coexisting MG represents a heterogeneous disease spectrum, including a small subset of patients who may present with complement dysregulation.

KDOQI US Commentary on the 2021 KDIGO Clinical Practice Guideline for the Management of Glomerular Diseases

The KDIGO 2021 Clinical Practice Guideline for the Management of Glomerular Diseases represents the first update to this set of recommendations since the initial set of KDIGO guideline recommendations was published in 2012. The pace of growth in our molecular understanding of glomerular disease has quickened and a number of newer immunosuppressive and targeted therapies have been introduced since the original set of guideline recommendations, making such an update necessary. Despite these updates, many areas of controversy remain. In addition, further updates since the publication of KDIGO 2021 have occurred which this guideline does not encompass. With this commentary, the KDOQI work group has generated a chapter-by-chapter companion opinion article that provides commentary specific to the implementation of the KDIGO 2021 guideline in the United States.

Microangiopathy in multiple myeloma: a case of carfilzomib-induced secondary thrombotic microangiopathy successfully treated with plasma exchange and complement inhibition

BACKGROUND

Thrombotic microangiopathy (TMA) is a potentially organ and life-threatening condition affecting patients with multiple myeloma (MM). Cases of proteasome inhibitor-induced TMA and specifically carfilzomib-induced TMA have been rarely reported and standards for diagnostic workup and treatment are not available.

CASE PRESENTATION

We describe a case of a male MM patient under salvage therapy including proteasome inhibitor carfilzomib following chemotherapy and autologous stem cell transplantation. The patient then developed acute kidney injury with clinical and laboratory signs of TMA. Hemodialysis became necessary and treatment with plasma exchange was initiated followed by therapy with C5 complement inhibitor eculizumab which led to amelioration of kidney function and hemolysis parameters.

CONCLUSION

We report a patient with suspected proteasome inhibitor-induced secondary thrombotic microangiopathy that has been successfully treated with plasma exchange and eculizumab, a monoclonal antibody targeting complement factor C5.

Onconephrology and Thrombotic Microangiopathy: Looking Beyond the Horizon

Thrombotic microangiopathies (TMAs) represent a complex interaction of endothelial and podocyte biology, nephron physiology, complement genetics, and oncologic therapies with host immunology. The complexity of various factors, such as molecular causes, genetic expressions, and immune system mimicking, along with incomplete penetrance, make it difficult to find a straightforward solution. As a result, there may be variations in diagnosis, study, and treatment approaches, and achieving a consensus can be challenging. Here, we review the molecular biology, pharmacology, immunology, molecular genetics, and pathology of the various TMA syndromes in the setting of cancer. Controversies in etiology, nomenclature, and points requiring further clinical, translational, and bench research are discussed. Complement-mediated TMAs, chemotherapy drug-mediated TMAs, TMAs in monoclonal gammopathy, and other TMAs central to onconephrology practice are reviewed in detail. In addition, established and emerging therapies within the US Food and Drug Administration pipeline subsequently are discussed. Finally, a comprehensive review of critical areas of onconephrology clinical practice is presented as practical value to the clinical practitioner and seeds of investigation to be sown among the community of atypical hemolytic uremic syndrome researchers.

Proteinuria in thrombotic microangiopathy is associated with partial podocytopathy

BACKGROUND

Thrombotic microangiopathy (TMA) results in acute kidney injury, but the cause of heavy proteinuria in this disorder is puzzling. The goal of this study was to determine if there were significant effacement of foot processes and CD133-positive hyperplastic podocytes in TMA to explain the proteinuria.

METHODS

The study included 12 negative controls (renal parenchyma removed from renal cell carcinoma) and 28 thrombotic microangiopathy due to different etiologies. The percent of foot process effacement was estimated, and proteinuria level was obtained for each TMA case. Both groups of cases were stained for CD133 by immunohistochemical method, and the number of positive CD133 in hyperplastic podocytes was counted and analyzed.

RESULTS

Nineteen (19) of 28 (68%) TMA cases had nephrotic range proteinuria (urine protein/creatinine >3). Twenty-one (21) of 28 (75%) TMA cases showed positive CD133 staining in scattered hyperplastic podocytes within Bowman's space but was absent in control cases. The percent of foot process effacement (56 ± 4%) correlated with proteinuria (protein/creatinine ratio 4.4 ± 0.6) (r = 0.46, p = .0237) in TMA group.

CONCLUSION

Our data indicate that the proteinuria in TMA can be associated with significant effacement of foot processes. CD133-positive hyperplastic podocytes can be seen in the majority of TMA cases of this cohort, indicating a partial podocytopathy.

How I diagnose and treat atypical hemolytic uremic syndrome

Our understanding and management of atypical hemolytic uremic syndrome (aHUS) have dramatically improved in the last decade. aHUS has been established as a prototypic disease resulting from a dysregulation of the complement alternative C3 convertase. Subsequently, prospective nonrandomized studies and retrospective series have shown the efficacy of C5 blockade in the treatment of this devastating disease. C5 blockade has become the cornerstone of the treatment of aHUS. This therapeutic breakthrough has been dulled by persistent difficulties in the positive diagnosis of aHUS, and the latter remains, to date, a diagnosis by exclusion. Furthermore, the precise spectrum of complement-mediated renal thrombotic microangiopathy is still a matter of debate. Nevertheless, long-term management of aHUS is increasingly individualized and lifelong C5 blockade is no longer a paradigm that applies to all patients with this disease. The potential benefit of complement blockade in other forms of HUS, notably secondary HUS, remains uncertain.

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.

Overlap of C3 Glomerulopathy and Thrombotic Microangiopathy: A Case Series

Introduction

Dysregulation of alternative complement pathway underlies the pathogenesis of both C3 glomerulopathy (C3G) and thrombotic microangiopathy (TMA). In this study, we describe both disease entities occurring in 5 patients.

Methods

We identified 114 patients at our institution from 2007 to 2016 with C3G in native kidney biopsies and those with concurrent TMA were included.

Results

The median age at diagnosis was 58 years (range: 28-69); all were male. Median serum creatinine and proteinuria at presentation were 2.3 mg/dl and 2089 mg/d, respectively. Three cases presented with TMA-predominant phenotype and 2 with C3G-predominant phenotype. Immunofluorescence (IF) showed bright C3 staining in mesangium and/or capillary walls. Electron microscopy showed marked subendothelial expansion by fluffy material in the capillary loops without associated deposits. However, capillary wall deposits were present in other loops in 4 cases. Mesangial deposits were present in all cases. Four cases showed low C3, of which 2 showed low C4. Complement evaluation in 3 cases showed pathogenic CFH mutation in 1 case, and multiple variant of unknown significance along with factor B autoantibody and C4 nephritic factor in 1 case. One patient negative for complement abnormalities had a monoclonal gammopathy. Three cases were treated with steroids and/or immunosuppressants. One case progressed to end-stage renal disease (ESRD) at 38.3 months; the remaining showed median serum creatinine and proteinuria of 2.5 mg/dl and 1169 mg/d, respectively at median follow-up of 17.5 months.

Conclusion

Overlap of C3G and TMA is rare and can clinically present as C3G-predominant or TMA-predominant phenotype. The significance of concurrent C3G/TMA findings on long-term renal survival remains to be explored.

Mutations in the alternative complement pathway in multiple myeloma patients with carfilzomib-induced thrombotic microangiopathy

Thrombotic microangiopathy (TMA) has been reported to occur in multiple myeloma (MM) patients in association with treatment with carfilzomib, an irreversible proteasome inhibitor (PI). The hallmark of TMA is vascular endothelial damage leading to microangiopathic hemolytic anemia, platelet consumption, fibrin deposition and small-vessel thrombosis with resultant tissue ischemia. The molecular mechanisms underlying carfilzomib-associated TMA are not known. Germline mutations in the complement alternative pathway have been recently shown to portend increased risk for the development of atypical hemolytic uremic syndrome (aHUS) and TMA in the setting of allogeneic stem cell transplant in pediatric patients. We hypothesized that germline mutations in the complement alternative pathway may similarly predispose MM patients to carfilzomib-associated TMA. We identified 10 MM patients with a clinical diagnosis of TMA in the context of carfilzomib treatment and assessed for the presence of germline mutations in the complement alternative pathway. Ten, matched MM patients exposed to carfilzomib but without clinical TMA were used as negative controls. We identified a frequency of deletions in the complement Factor H genes 3 and 1 (delCFHR3-CFHR1) and genes 1 and 4 (delCFHR1-CFHR4) in MM patients with carfilzomib-associated TMA that was higher as compared to the general population and matched controls. Our data suggest that complement alternative pathway dysregulation may confer susceptibility to vascular endothelial injury in MM patients and predispose to development of carfilzomib-associated TMA. Larger, retrospective studies are needed to evaluate whether screening for complement mutations may be indicated to properly counsel patients about TMA risk with carfilzomib use.

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.

A Rare Case of Renal Thrombotic Microangiopathy and Focal Segmental Glomerulosclerosis Secondary to Plasma Cell Leukemia

Plasma cell dyscrasias are a subset of hematological malignancies involving the production of monoclonal immunoglobulins. This spectrum of disorders includes asymptomatic conditions such as monoclonal gammopathy of unknown significance as well as extremely aggressive malignancies such as plasma cell leukemia. Monoclonal gammopathies are occasionally associated with renal failure, which can occur via many pathophysiological processes. The most common of these is light chain cast nephropathy, but many rare renal complications exist, including thrombotic microangiopathy (TMA) and focal segmental glomerulosclerosis (FSGS). Here, we report a patient with new renal failure with features of TMA and FSGS on biopsy and found to be secondary to plasma cell leukemia.

Monoclonal Gammopathy of Thrombotic Significance

The current review provides an overview of the thrombotic risk observed in patients with MG who do not otherwise require treatment. We discuss clinical and biomarker studies that highlight the heterogenous hemostatic profile observed in these patients and how knowledge has evolved over the past 20 years. Biomarker studies suggest shared biologic features between multiple myeloma and monoclonal gammopathy of undetermined significance (MGUS), which involves both hypercoagulability and platelet activation. Hemostatic abnormalities identified in MGUS patients cannot be translated into clinical practice as they lack correlation to clinical events. The prothrombotic phenotype of MGUS patients has not been ascertained yet, but novel data on coagulation markers are promising. We also review rare conditions associated with the thrombogenic properties of the monoclonal protein that predispose to arterial, venous or microthrombotic events and demonstrate that the M-protein can be linked to clinically significant thrombotic events. Cryoglobulinemia, cryofibrinogenemia, cryo-crystaloglobulinemia and MG-related antiphospholipid syndrome are reviewed. We propose the new umbrella term "monoclonal gammopathy of thrombotic significance" (MGTS) to refer to significant, recurrent thrombotic events in patients with MGUS that provide a rationale for targeting the underlying plasma cell clone. Identifying MGUS patients at high risk for thrombotic events is currently a challenge.

Renal Thrombotic Microangiopathy: A Review

Thrombotic microangiopathy (TMA), a pathological lesion observed in a wide spectrum of diseases, is triggered by endothelial injury and/or dysfunction. Although TMA lesions are often accompanied by clinical features of microangiopathic hemolytic anemia, thrombocytopenia, and ischemic end-organ injury, renal-limited forms of TMA are not infrequently encountered in clinical practice. The presence of renal-limited manifestations can be diagnostically challenging, often delaying the initiation of targeted therapy. Prompt investigation and empirical treatment of TMA is warranted to reduce associated morbidity and mortality. Major advances have been made with respect to the pathophysiology of primary TMA entities, with the subsequent development of novel diagnostic tools and lifesaving therapies for diseases like thrombotic thrombocytopenic purpura and complement-mediated TMA. This article will review the clinical presentation and pathologic hallmarks of TMA involving the kidney, and the disease-specific mechanisms that contribute to the endothelial injury that characterizes TMA lesions. Diagnostic approach and both empirical and disease-specific treatment strategies will be discussed, along with the potential role for emerging targeted disease-specific therapies.

Santos M, Esteves J. Monoclonal Gammopathy of Renal Significance and Thrombotic Microangiopathy: A Case Report

Monoclonal gammopathy of renal significance (MGRS) is a group of pathologies that includes all kidney disorders related to a monoclonal protein in patients without diagnostic criteria for B-cell malignancies. There are multiple MGRS-associated kidney disorders, and more are still being discovered, which makes this diagnosis challenging. The relationship between monoclonal gammopathies and thrombotic microangiopathy (TMA) is of growing interest in literature. This article describes the case of a patient with newly diagnosed MGRS, presenting with rapidly progressing kidney failure and with histologic characteristics of TMA. The patient progressed to end-stage renal disease (ESRD) despite treatment with plasmapheresis and clone-directed therapy, as is currently advised in the literature. Although rare, the association between these two entities should not be unnoticed because of patients' renal and vital prognosis.

[Nephropathy associated with monoclonal immunoglobulins: From clonal expansion B to renal toxicity of pathological immunoglobulins]

Germinal center regulation pathways are often involved in lymphomagenesis and myelomagenesis. Most of the lymphomas (and multiple myeloma) derive from post-germinal center B-cells that have undergone somatic hypermutation and class switch recombination. Hence, B-cell clonal expansion can be responsible for the presence of a monoclonal component (immunoglobulin) of variable titer which, owing to physicochemical properties, can provoke pathologically defined entities of diseases. These diseases can affect any functional part of the kidney, by multiple mechanisms, either well known or not. The presence of renal deposition is influenced by germinal gene involved, immunoglobulin primary structure, post-translational modifications and microenvironmental interactions. The two ways immunoglobulin can cause kidney toxicity are (i) an excess of production (overcoming catabolism power by proximal tubule epithelial cells) with an excess of free light chains within the distal tubules and a subsequent risk of precipitation due to local physicochemical properties; (ii) by structural characteristics that predispose immunoglobulin to a renal disease (whatever their titer). The purpose of this manuscript is to review literature concerning the pathophysiology of renal toxicities of clonal immunoglobulin, from molecular B-cell expansion mechanisms to immunoglobulin renal toxicity.

Overexpression of Plasmalemmal Vesicle-Associated Protein-1 Reflects Glomerular Endothelial Injury in Cases of Proliferative Glomerulonephritis with Monoclonal IgG Deposits

Introduction

Proliferative glomerulonephritis with monoclonal IgG deposits (PGNMID) occasionally presents refractory nephrotic syndrome resulting in poor renal prognosis, but its etiology is not fully elucidated. Given that glomerular endothelial cell (GEC) stress or damage may lead to podocytopathy and subsequent proteinuria, as in thrombotic microangiopathy (TMA), diabetic kidney disease, and focal segmental glomerulosclerosis, we investigated the evidence of glomerular endothelial injury by evaluating the expression of plasmalemmal vesicle-associated protein-1 (PV-1), a component of caveolae in the cases of PGNMID.

Methods

We measured the immunofluorescent PV-1 intensities of 23 PGNMID cases and compared with those of primary membranoproliferative glomerulonephritis (MPGN) (n = 5) and IgA nephropathy (IgAN) (n = 54) cases. PV-1 localization was evaluated with Caveolin-1, and CD31 staining, and the ultrastructural analysis was performed using a low-vacuum scanning electron microscope (LVSEM). To check the association of podocyte injury, we also conducted 8-oxoguanine and Wilms tumor 1 (WT1) double stain. We then evaluated PV-1 expression in other glomerulitis and glomerulopathy such as lupus nephritis and minimal change disease.

Results

The intensity of glomerular PV-1 expression in PGNMID is significantly higher than that in the other glomerular diseases, although the intensity is not associated with clinical outcomes such as urinary protein levels or renal prognosis. Immunostaining and LVSEM analysis revealed that glomerular PV-1 expression is localized in GECs in PGNMID. 8-oxoguanine accumulation was detected in WT1-positive podocytes but not in PV-1-expressing GECs, suggesting GEC-derived podocyte injury in PGNMID.

Conclusion

PV-1 overexpression reflects glomerular endothelial injury, which could be associated with podocyte oxidative stress in PGNMID cases.

Clinicopathological features and individualized treatment of kidney involvement in B-cell lymphoproliferative disorder

Background

Due to the various clinical and pathological manifestations of kidney involvement in lymphoproliferative disorder (LPD), the whole spectrum of kidney disease in LPD is still unclear, and data on kidney prognosis is scarce.

Methods

We retrospectively reviewed the renal pathology profiles from January 2010 to December 2021, and 28 patients with B-cell LPD combined with intact renal biopsy data were included.

Results

There were 20 men and eight women aging 41 to 79 years at the time of renal biopsy (median age 62 years). According to hematological diagnosis, patients were classified into four groups: chronic lymphocytic leukemia (CLL) (group1, n=7), Waldenström macroglobulinemia/lymphoplasmacytic lymphoma (WM/LPL) (group 2, n=8; WM, n=6; LPL, n=2), Other non-Hodgkin’s lymphomas (NHL) (group3, n=7; diffuse large B-cell lymphoma (DLBCL), n=2; mucosa-associated lymphoid tissue (MALT) lymphoma, n=4; Low grade B-cell lymphoma, n=1), and monoclonal gammopathy of undetermined significance/monoclonal gammopathy of renal significance (MGUS/MGRS) (group 4, n=6). Median serum creatinine (Scr) level was 129 (range,59-956) umol/L. Eight patients (29%) were presented with acute kidney injury (AKI), and five patients (18%) required hemodialysis upon admission. Twenty-three patients (82%) presented with proteinuria (median protein excretion, 2.14 g/d), 11(39%) of whom had the nephrotic syndrome. Interstitial malignant infiltration was the most frequent renal lesion (n=6). Eight patients underwent immunohistochemistry of renal tissues, of which three patients (CLL, n=1; LPL, n=1; WM, n=1) had confirmed lymphoma infiltrates, and the infiltrating cells in the remaining five patients (CLL, n=1; MALT lymphoma, n=2; MGUS, n=2) were considered unrelated to lymphoma. The most common glomerular diseases were renal amyloidosis (n=4) and membranous nephropathy (n=4). Only 20 patients were treated, 13 of whom were treated with rituximab separately or in combination. The median follow-up time was 11 months. Of these, six had achieved hematological response, complete response in five cases. Eight had achieved renal response. At the end-of-study visit, four patients died and two progressed to end stage kidney disease (ESKD).

Conclusion

In conclusion, the clinicopathological spectrum of renal involvement in BLPD is diverse. Renal biopsy and immunohistochemistry are required for early diagnosis and prognostic assessment.

Complement Activation and Thrombotic Microangiopathy Associated With Monoclonal Gammopathy: A National French Case Series

RATIONALE & OBJECTIVE

Hemolytic uremic syndrome (HUS), a thrombotic microangiopathy (TMA) with kidney involvement, is a rare condition in patients with monoclonal gammopathy. In the absence of known causes of TMA, the role of complement activation in endothelial injury in patients with monoclonal gammopathy remains unknown and was the focus of this investigation.

STUDY DESIGN

Case series.

SETTING & PARTICIPANTS

We studied the 24 patients in the French national registry of HUS between 2000 and 2020 who had monoclonal gammopathy without other causes of secondary TMA. We provide the clinical histories and complement studies of these patients.

FINDINGS

Monoclonal gammopathy-associated TMA with kidney involvement is estimated to be 10 times less frequent than adult atypical HUS (aHUS) in the French national registry. It is characterized by severe clinical features, with 17 of 24 patients requiring dialysis at disease onset, and with median renal survival of only 20 months. TMA-mediated extrarenal manifestations, particularly cutaneous and neurological involvement, were common and associated with poor overall prognosis. Complement studies identified low C3, normal C4, and high soluble C5b-9 levels in 33%, 100%, and 77% of tested patients, respectively, indicating a contribution of the alternative and terminal complement pathways in the pathophysiology of the disease. Genetic abnormalities in complement genes known to be associated with aHUS were found in only 3 of 17 (17%) who were tested.

LIMITATIONS

Retrospective study without comparison group; limited number of patients, limited available blood samples.

CONCLUSIONS

Within the spectrum of TMA, TMA associated with monoclonal gammopathy represents a distinct subset. Our findings suggest that HUS associated with monoclonal immunoglobulin is a complement-mediated disease akin to aHUS.

Vascular Occlusion in Kidney Biopsy Is Characteristic of Clinically Manifesting Thrombotic Microangiopathy

Thrombotic microangiopathy (TMA) can sometimes manifest only histologically. Our aim was to retrospectively compare biopsy-proven adult TMA patients showing only histological (h-TMA) or both histological and clinical (c-TMA) TMA in 2006–2017. All native kidney biopsies with TMA were included. Biopsies were re-evaluated by light and electron microscopy, and immunofluorescence. Clinical characteristics, laboratory variables, and treatments were recorded from the electronic medical database. Patients were categorized into h-TMA and c-TMA and these groups were compared. In total, 30 biopsy-proven cases among 7943 kidney biopsies were identified and, of these, 15 had h-TMA and 15 c-TMA. Mean follow-up was 6.3 y, and 73.3% had secondary hemolytic uremic syndrome (HUS) and the rest were atypical HUS. Patient characteristics, treatments, and kidney, and patient survival in the groups were similar. Statistically significant differences were found in histological variables. Vascular myxoid swelling and vascular onion-skinning were almost exclusively detected in c-TMA and, thus, vascular occlusive changes indicate clinically apparent rather than merely histological TMA. In addition, regardless of clinical presentation, kidney and patient survival times were similar in the patient groups highlighting the importance of a kidney biopsy in the case of any kidney-related symptoms.

Acute glomerulonephritis

Glomerulonephritis is a heterogeneous group of disorders that present with a combination of haematuria, proteinuria, hypertension, and reduction in kidney function to a variable degree. Acute presentation with full blown nephritic syndrome or rapidly progressive glomerulonephritis is uncommon and is mainly restricted to patients with post-infectious glomerulonephritis, anti-neutrophil cytoplasmic antibodies-associated vasculitis, and anti-glomerular basement membrane disease. Most frequently, patients present with asymptomatic haematuria and proteinuria with or without reduced kidney function. All glomerulonephritis disorders can show periods of exacerbation, but disease flairs characteristically occur in patients with IgA nephropathy or C3 glomerulopathy. The gold standard for the diagnosis of a glomerulonephritis is a kidney biopsy, with a hallmark glomerular inflammation that translates into various histopathological patterns depending on the location and severity of the glomerular injury. Traditionally, glomerulonephritis was classified on the basis of the different histopathological patterns of injury. In the last few years, substantial progress has been made in unravelling the underlying causes and pathogenetic mechanisms of glomerulonephritis and a causal approach to the classification of glomerulonephritis is now favoured over a pattern-based approach. As such, glomerulonephritis can be broadly classified as immune-complex glomerulonephritis (including infection-related glomerulonephritis, IgA nephropathy, lupus nephritis, and cryoglobulinaemic glomerulonephritis), anti-neutrophil cytoplasmic antibodies-associated (pauci-immune) glomerulonephritis, anti-glomerular basement membrane glomerulonephritis, C3 glomerulopathy, and monoclonal immunoglobulin-associated glomerulonephritis. We provide an overview of the clinical presentation, pathology, and the current therapeutic approach of the main representative disorders in the spectrum of glomerulonephritis.

Light chain deposition disease masquerading as smoking-associated nodular glomerulosclerosis with deposits identified by electron microscopy only

Light chain deposition disease (LCDD) is a form of monoclonal gammopathy of renal significance. The diagnosis is based on the immunofluorescence (IF) findings of linear monoclonal light chain staining of basement membranes throughout the kidney, which appear as non-organized, granular punctate to powdery electron dense deposits by electron microscopy (EM). Although "LCDD by IF only" without EM deposits has been well-described, LCDD identified by EM with negative IF is very rare and hardly mentioned in the literature. Herein we describe a case of lambda-type LCDD that appeared negative by IF and showed light microscopic findings of nodular glomerulosclerosis, which was initially attributed to the patient's history of significant tobacco use and uncontrolled hypertension. However, EM later showed powdery electron dense material in focal glomerular and tubular basement membranes and mesangium. Subsequent bone marrow analysis revealed greater than 60% lambda-restricted plasma cells. We report this case to illustrate that within the differential diagnosis of nodular sclerosis, monoclonal immunoglobulin deposition disease (MIDD) should remain in the differential even if immunofluorescence appears negative as EM can prove to be crucial in identifying cases of MIDD.

The Intriguing Connections between von Willebrand Factor, ADAMTS13 and Cancer

von Willebrand factor (VWF) is a complex and large protein that is cleaved by ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin type 1 motif, member 13), and together they serve important roles in normal hemostasis. Malignancy can result in both a deficiency or excess of VWF, leading to aberrant hemostasis with either increased bleeding or thrombotic complications, as respectively seen with acquired von Willebrand syndrome and cancer-associated venous thromboembolism. There is emerging evidence to suggest VWF also plays a role in inflammation, angiogenesis and tumor biology, and it is likely that VWF promotes tumor metastasis. High VWF levels have been documented in a number of malignancies and in some cases correlate with more advanced disease and poor prognosis. Tumor cells can induce endothelial cells to release VWF and certain tumor cells have the capacity for de novo expression of VWF, leading to a proinflammatory microenvironment that is likely conducive to tumor progression, metastasis and micro-thrombosis. VWF can facilitate tumor cell adhesion to endothelial cells and aids with the recruitment of platelets into the tumor microenvironment, where tumor/platelet aggregates are able to form and facilitate hematogenous spread of cancer. As ADAMTS13 moderates VWF level and activity, it too is potentially involved in the pathophysiology of these events. VWF and ADAMTS13 have been explored as tumor biomarkers for the detection and prognostication of certain malignancies; however, the results are underdeveloped and so currently not utilized for clinical use. Further studies addressing the basic science mechanisms and real word epidemiology are required to better appreciate the intriguing connections between VWF, ADAMTS13 and malignancy. A better understanding of the role VWF and ADAMTS13 play in the promotion and inhibition of cancer and its metastasis will help direct further translational studies to aid with the development of novel cancer prognostic tools and treatment modalities.

Monoclonal gammopathy of renal significance presenting with cryoglobulinemia type I associated severe thrombotic microangiopathy

We report a 53-year-old man who presented with acute renal failure. His medical history revealed a spondyloarthropathy, for which secukinumab was started recently, and a monoclonal gammopathy of unknown significance. Kidney function deteriorated despite the withdrawal of secukinumab and dialysis was started. In the serum, type 1 cryoglobulins were present and a kidney biopsy showed ischaemic glomeruli, with thrombosis of the larger interlobular arteries. Other causes of thrombotic microangiopathy were excluded. Bone marrow immunophenotyping showed 1% monoclonal plasma cells. A diagnosis of monoclonal gammopathy of renal significance was made. Haematological treatment resulted in haematological and renal response.

Hematological Malignancies and the Kidney

The incidence of hematologic malignancies is on the rise worldwide. Kidney disease is ubiquitous in patients with hematologic malignancies, encompassing a wide spectrum of disorders involving each kidney compartment, including the vasculature, tubules, interstitium, and glomerulus, and there is significant overlap of kidney involvement with each hematologic malignancy. Vascular disorders include both microvascular and macrovascular damage, via thrombotic microangiopathy, hyperleukocytosis, hyperviscosity, and cryoglobulinemia. The tubulointerstitial compartment may be affected by prerenal azotemia and acute tubular injury, but malignant infiltration, tumor lysis syndrome, extramedullary hematopoiesis, cast nephropathy, granulomatous interstitial nephritis, and lysozymuria should be considered in certain populations. Obstructive uropathy may occur due to nephrolithiasis or retroperitoneal fibrosis. Glomerular disorders, including membranoproliferative, membranous, minimal change, and focal segmental glomerulosclerosis, can rarely occur. By understanding how each compartment may be affected, care can best be optimized for these patients. In this review, we summarize the widely varied etiologies of kidney diseases stratified by kidney compartment and hematologic malignancy, focusing on demographics, pathology, pathophysiology, mechanism, and outcomes. We conclude with common electrolyte abnormalities associated with hematologic malignancies.

A Diverse Spectrum of Immune Complex- and Complement-Mediated Kidney Diseases Is Associated With Mantle Cell Lymphoma

Introduction

There are limited reports on kidney biopsy findings in patients with mantle cell lymphoma (MCL).

Methods

We initiated a multi-institutional, retrospective review of kidney biopsy findings in patients with active and treated MCL.

Results

A total of 30 patients with MCL and kidney biopsies were identified, with a median age of 67 (range 48-87) years, 73% of whom were men. A total of 20 patients had active MCL at the time of biopsy, of whom 14 (70%) presented with acute kidney injury (AKI), proteinuria and/or hematuria, and biopsy findings potentially attributable to lymphoma. Of the 14, 11 had immune complex (IC) or complement-mediated (C3) disease including proliferative glomerulonephritis (GN) with monotypic Ig deposits (PGNMID [2]), C3GN, (2), secondary membranous nephropathy (MN [3]), tubular basement membrane (TBM) deposits (2), and modest lupus-like GN (2). Lymphomatous infiltration was present in 8 of the 20 patients, 5 with coincident IC or C3 lesions. A total of 6 patients with available follow-up were treated for MCL, all with clinical remission of GN (2 PGNMID, 2 C3GN, and 2 MN).

Conclusion

MCL is associated with diverse monoclonal and polyclonal glomerular and extra-glomerular IC and C3 disease. For patients with active MCL and kidney dysfunction requiring biopsy, 70% had findings due or potentially due to lymphoma, including 55% with IC or C3 disease and 40% had lymphomatous kidney infiltration. IC and C3GN in the setting of active MCL was responsive to lymphoma-directed therapy.

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.

Kidney Histopathologic Spectrum and Clinical Indicators Associated with MGRS

BACKGROUND AND OBJECTIVES

Patients with monoclonal gammopathy and concomitant kidney diseases are frequently found in clinical practice. Some of them are diagnosed with monoclonal gammopathy of renal significance (MGRS) due to the presence of monoclonal Ig-related kidney injuries. This study aimed to investigate the histopathologic spectrum and clinical characteristics associated with MGRS in a large cohort of patients with monoclonal gammopathy and biopsy-proven kidney diseases from a single Chinese nephrology referral center.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients who presented with monoclonal gammopathy (monoclonal spike on serum and/or urine immunofixation tests) and underwent kidney biopsy in the Peking University First Hospital from January 1, 1999 to December 31, 2020 were enrolled in this retrospective study. Patients with malignant hematologic diseases were excluded. Clinical and laboratory data were collected from the electronic medical record system. Comparisons of patients with and without MGRS and with and without amyloidosis were performed. The clinical characteristics associated with MGRS were identified using multivariable logistic regression.

RESULTS

A total of 700 patients with monoclonal gammopathy and kidney biopsy were identified. Thirteen patients with repeat kidney biopsies were analyzed separately. For the remaining 687 patients with one kidney biopsy, 261 patients (38%) had MGRS lesions, and the rest (426 patients, 62%) had non-MGRS kidney diseases. Ig-related amyloidosis accounted for the most MGRS cases (n=164, 63%), followed by monoclonal Ig deposition disease (n=23, 9%) and thrombotic microangiopathy (n=22, 8%). In the non-MGRS group, membranous nephropathy was the most common diagnosis (n=171, 40%). In the multivariable logistic regression model, the presence of abnormal serum free light chain ratio, older age, and greater proteinuria were independently associated with MGRS.

CONCLUSIONS

Monoclonal Ig amyloidosis is the leading cause of MGRS in Chinese patients with monoclonal gammopathy. The presence of abnormal free light chain ratio, older age, and greater proteinuria were associated with MGRS.

Scleroderma Renal Crisis Associated With Microangiopathic Hemolytic Anemia in a Patient With Seronegative Scleroderma and Monoclonal Gammopathy

Systemic sclerosis with negative serology, particularly that complicated by scleroderma renal crisis (SRC), is rarely encountered. We describe a patient with seronegative systemic sclerosis who developed acute kidney injury, proteinuria, and hypertensive emergency following motor vehicle-related trauma and in the setting of nonsteroidal anti-inflammatory drug use. Findings on physical examination, imaging, and skin biopsy led to a clinical diagnosis of scleroderma, despite the lack of supportive laboratory data. IgG lambda paraproteinemia was detected on workup. Bone marrow biopsy showed plasmacytosis and trace lambda-restricted plasma cells consistent with monoclonal gammopathy of undetermined significance. Chemotherapy was initially started given concern for myeloma with cast nephropathy but was later stopped after a kidney biopsy revealed thrombotic microangiopathy (TMA). The SRC associated with TMA was ultimately diagnosed, though atypical hemolytic uremic syndrome (aHUS) induced perhaps by monoclonal gammopathy or hypertension was also possible. Captopril and eculizumab were initiated for SRC and aHUS, respectively. Despite therapy, renal function did not recover, and the patient required hemodialysis indefinitely. This case highlights clinical features common to both SRC and aHUS as well as points out a few ways to differentiate between them.

Thrombotic Microangiopathy, an Unusual Form of Monoclonal Gammopathy of Renal Significance: Report of 3 Cases and Literature Review

Monoclonal gammopathies result from neoplastic clones of the B-cell lineage and may cause kidney disease by various mechanisms. When the underlying clone does not meet criteria for a malignancy requiring treatment, the paraprotein is called a monoclonal gammopathy of renal significance (MGRS). One rarely reported kidney lesion associated with benign paraproteins is thrombotic microangiopathy (TMA), provisionally considered as a combination signifying MGRS. Such cases may lack systemic features of TMA, such as a microangiopathic hemolytic anemia, and the disease may be kidney limited. There is no direct deposition of the paraprotein in the kidney, and the presumed mechanism is disordered complement regulation. We report three cases of kidney limited TMA associated with benign paraproteins that had no other detectable cause for the TMA, representing cases of MGRS. Two of the cases are receiving clone directed therapy, and none are receiving eculizumab. We discuss in detail the pathophysiological basis for this possible association. Our approach to therapy involves first ruling out other causes of TMA as well as an underlying B-cell malignancy that would necessitate direct treatment. Otherwise, clone directed therapy should be considered. If refractory to such therapy or the disease is severe and multisystemic, C5 inhibition (eculizumab or ravulizumab) may be indicated as well.

The Syndromes of Thrombotic Microangiopathy: A Critical Appraisal on Complement Dysregulation

Thrombotic microangiopathy (TMA) is a rare and potentially life-threatening condition that can be caused by a heterogeneous group of diseases, often affecting the brain and kidneys. TMAs should be classified according to etiology to indicate targets for treatment. Complement dysregulation is an important cause of TMA that defines cases not related to coexisting conditions, that is, primary atypical hemolytic uremic syndrome (HUS). Ever since the approval of therapeutic complement inhibition, the approach of TMA has focused on the recognition of primary atypical HUS. Recent advances, however, demonstrated the pivotal role of complement dysregulation in specific subtypes of patients considered to have secondary atypical HUS. This is particularly the case in patients presenting with coexisting hypertensive emergency, pregnancy, and kidney transplantation, shifting the paradigm of disease. In contrast, complement dysregulation is uncommon in patients with other coexisting conditions, such as bacterial infection, drug use, cancer, and autoimmunity, among other disorders. In this review, we performed a critical appraisal on complement dysregulation and the use of therapeutic complement inhibition in TMAs associated with coexisting conditions and outline a pragmatic approach to diagnosis and treatment. For future studies, we advocate the term complement-mediated TMA as opposed to the traditional atypical HUS-type classification.

Continuous plasma exchange with dialysis for thrombotic microangiopathy in intensive care unit: Retrospective observational study

Continuous plasma exchange with dialysis is a novel method of blood purification and is a modification of the plasma exchange. Technically, this process suggests a reduction in adverse events, cost-effectiveness, and compatibility with hemodynamic instability. The therapeutic effect of plasma exchange on thrombotic microangiopathies has been established. We present three clinical cases in the intensive care unit that illustrate continuous plasma exchange with dialysis as a flexible blood purification therapy for critically ill patients; a radical treatment, thrombotic microangiopathies; supportive therapy, multiple organ failure; and fluid balance regulator. The retrospective analysis of 13 continuous plasma exchange with dialysis sessions showed that the platelet count increased significantly (p = 0.0096) after its administration. The total protein, albumin, fibrinogen, or calcium did not decrease significantly after continuous plasma exchange with dialysis, suggesting therapeutic efficacy and fewer adverse events. A prospective study on thrombotic microangiopathies for continuous plasma exchange with dialysis is currently underway.

Thrombotic microangiopathy in oncology - a review

Thrombotic microangiopathy is a syndrome triggered by a wide spectrum of situations, some of which are specific to the Oncology setting. It is characterized by a Coombs-negative microangiopathic haemolytic anemia, thrombocytopenia and organ injury, with characteristic pathological features, resulting from platelet microvascular occlusion.

TMA is rare and its cancer-related subset even more so. TMA triggered by drugs is the most common within this group, including classic chemotherapy and the latest targeted therapies. The neoplastic disease itself and hematopoietic stem-cell transplantation could also be potential triggers.

Evidence-based medical guidance in the management of cancer-related TMA is scarce and the previous knowledge about primary TMA is valuable to understand the disease mechanisms and the potential treatments.

Given the wide spectrum of potential causes for TMA in cancer patients, the aim of this review is to gather the vast information available. For each entity, pathophysiology, clinical features, therapeutic approaches and prognosis will be covered.

The Clone Wars: Diagnosing and Treating Dysproteinemic Kidney Disease in the Modern Era

Dysproteinemic kidney diseases are disorders that occur as the result of lymphoproliferative (B cell or plasma cell) disorders that cause kidney damage via production of nephrotoxic monoclonal immunoglobulins or their components. These monoclonal immunoglobulins have individual physiochemical characteristics that confer specific nephrotoxic properties. There has been increased recognition and revised characterization of these disorders in the last decade, and in some cases, there have been substantial advances in disease understanding and treatments, which has translated to improved patient outcomes. These disorders still present challenges to nephrologists and patients, since they are rare, and the field of hematology is rapidly changing with the introduction of novel testing and treatment strategies. In this review, we will discuss the clinical presentation, kidney biopsy features, hematologic characteristics and treatment of dysproteinemic kidney diseases.

Kidney injury and disease in patients with haematological malignancies

Acute kidney injury (AKI) is common in patients with cancer, especially in those with haematological malignancies. Kidney injury might be a direct consequence of the underlying haematological condition. For example, in the case of lymphoma infiltration or extramedullary haematopoiesis, it might be caused by a tumour product; in the case of cast nephropathy it might be due to the presence of monoclonal immunoglobulin; or it might result from tumour complications, such as hypercalcaemia. Kidney injury might also be caused by cancer treatment, as many chemotherapeutic agents are nephrotoxic. High-intensity treatments, such as high-dose chemotherapy followed by haematopoietic stem cell transplantation, not only increase the risk of infection but can also cause AKI through various mechanisms, including viral nephropathies, engraftment syndrome and sinusoidal obstruction syndrome. Some conditions, such as thrombotic microangiopathy, might also result directly from the haematological condition or the treatment. Novel immunotherapies, such as immune checkpoint inhibitors and chimeric antigen receptor T cell therapy, can also be nephrotoxic. As new therapies for haematological malignancies with increased anti-tumour efficacy and reduced toxicity are developed, the number of patients receiving these treatments will increase. Clinicians must gain a good understanding of the different mechanisms of kidney injury associated with cancer to better care for these patients.

Management of acute kidney injury in symptomatic multiple myeloma

Symptomatic multiple myeloma is commonly complicated by acute kidney injury through various mechanisms. The most frequent is the precipitation of monoclonal free light chains with uromodulin in the distal tubules, defining light chain cast nephropathy. Early diagnosis and identification of the cause of acute kidney injury are required for optimizing management and avoiding chronic kidney injury that strongly affects quality of life and patient survival. In light chain cast nephropathy, often manifesting with severe acute kidney injury, renal recovery requires urgent intervention based on vigorous rehydration, correction of precipitating factors, and efficient anti-plasma cell chemotherapy to rapidly reduce the secretion of nephrotoxic free light chains. Currently, the association of the proteasome inhibitor bortezomib with high-dose dexamethasone is the standard regimen in newly diagnosed patients. The addition of another drug such as cyclophosphamide or an immunodulatory agent may improve free light chain response but raises tolerance concerns in frail patients. Further studies are warranted to confirm the role of anti-CD38 monoclonal antibodies, whose efficacy and tolerance have been documented in patients without renal impairment. Despite controversial results from randomized studies, recent data suggest that in patients with light chain cast nephropathy and acute kidney injury requiring dialysis, the combination of chemotherapy with free light chain removal through high-cutoff hemodialysis may increase renal response recovery rates. Kidney biopsy may be helpful in guiding management and assessing renal prognosis that appears to depend on the extent of cast formation and interstitial fibrosis/tubular atrophy. Because of continuous improvement in life expectancy of patients with multiple myeloma, renal transplantation is likely to be increasingly considered in selected candidates.