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Kidney international 100(4), 753-779 (2021). doi:10.1016/j.kint.2021.05.015, Published by Elsevier, New York, NY

There is increasing recognition of monoclonal gammopathy as a cause of proliferative glomerulonephritis (GN), including cases in which glomerular deposition of monoclonal immunoglobulin is demonstrated. Recently, proliferative GN with monoclonal immunoglobulin deposits (PGNMID) has incorporated a light chain variant of the disease (termed PGNMID-LC). Intriguingly, glomerular co-deposition of C3 is found in addition to monotypic light chain, implying complement activation via the alternative pathway (AP). We present a unique case of proliferative GN in a 42-year-old man who presented with nephrotic syndrome and was found to have κ light chain multiple myeloma. Immune staining of the glomerulus was positive only for κ light chain and C3, with the striking appearance of nonamyloid fibrils on electron microscopy. Following clonally targeted therapy for myeloma, the renal clinical abnormalities resolved completely. We present detailed molecular studies for light chain and complement and consider local mechanisms whereby monoclonal κ light chain fibrils may have triggered AP activation within the glomerulus.

Monoclonal Gammopathy of Renal Significance Monoclonal gammopathy of renal significance is a B-cell or plasma-cell clonal disorder that does not meet the criteria for cancer but produces a monoclon...

Daratumumab is a human monoclonal antibody targeting CD38, an antigen uniformly expressed by plasma cells in multiple myeloma and light-chain amyloidosis (AL). We report the results of a prospective multicenter phase 2 study of daratumumab monotherapy in AL (NCT02816476). Forty previously treated AL patients with a difference between involved and uninvolved free light chains (dFLC) >50 mg/L were included in 15 centers between September of 2016 and April of 2018. Patients received 6 28-day cycles of IV daratumumab, every week for cycles 1 and 2 and every 2 weeks for cycles 3 through 6. Median age was 69 years (range, 45-83). Twenty-six patients had ≥2 organs involved, with heart in 24 and kidney in 26. Median time from diagnosis to enrollment was 23 months (interquartile range, 4-122), with a median of 3 prior therapies (range, 1-5). At data cutoff (September of 2019), all patients discontinued therapy; 33 received the planned 6 cycles. Overall, 22 patients had hematological response, and 19 patients (47.5%) achieved very good partial response (dFLC

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.

Kidney international 100(4, Supplement) S1-S276 (2021). doi:10.1016/j.kint.2021.05.021 special issue: "KDIGO 2021 Clinical Practice Guideline for the Management of Glomerular Diseases", Published by Elsevier, New York, NY

International audience; The diagnostic approach of monoclonal gammopathy of renal significance is based on the detection of a monoclonal immunoglobulin in the blood and urine, and the identification of the underlying clone through bone marrow and/or peripheral blood cytologic and flow cytometry analysis. However, the monoclonal component and its corresponding clone may be undetectable using these routine techniques. Since clone identification is the cornerstone for guiding therapy and assessing disease response, more sensitive methods are required. We recently developed a high-throughput sequencing assay from bone marrow mRNA encoding immunoglobulins (RACE-RepSeq). This technique provides both full-length V(D)J region (variable, diversity and joining genes that generate unique receptors as antigen receptors) of the monoclonal immunoglobulin and the dominant immunoglobulin repertoire. This allows analysis of mutational patterns, immunoglobulin variable gene frequencies and diversity due to somatic hypermutation. Here, we evaluated the diagnostic performance of RACE-RepSeq in 16 patients with monoclonal-associated kidney lesions, and low serum monoclonal immunoglobulin and free light chain levels at diagnosis. Bone marrow immunohistochemical analysis was negative in all 11 patients so tested and 7 of 12 patients had no detectable clone matching the kidney deposits using flow cytometry analysis. By contrast, RACE-RepSeq detected a dominant clonal light chain sequence of matched isotype with respect to kidney deposits in all patients. Thus, high throughput mRNA sequencing appears highly sensitive to detect subtle clonal disorders in monoclonal gammopathy of renal significance and suggest this novel approach could help improve the management of this kidney disease.

Proliferative glomerulonephritis (GN) with monoclonal immunoglobulin deposits (PGNMIDs) is a recently described entity among the spectrum of monoclonal gammopathy of renal significance (MGRS). The disease is renal limited and manifests with chronic glomerular disease, altered renal function and albuminuria, sometimes in the nephrotic range. Acute nephritic syndrome is rare. PGNMID occurs mostly in the sixth decade, but it may affect young adults. Histologically, PGNMID is characterized predominantly by membranoproliferative GN and less frequently by diffuse endocapillary GN, mesangioproliferative GN or atypical membranous GN. Immunofluorescence and electron microscopic studies are the cornerstone of diagnosis, showing granular deposits involving glomeruli only, and composed of monotypic immunoglobulin G (IgG), with a single heavy chain subclass (most commonly IgG3) and light chain (LC) restriction (usually κ), admixed with complement deposits. PGNMID variants with monotypic LC-only, IgA or IgM deposits are uncommon. Ultrastructurally, deposits are amorphous with predominant subendothelial and mesangial distribution. PGNMID should be distinguished from type 1 cryoglobulinemic GN and immunotactoid GN, which share some common pathological features. Contrary to other MGRS lesions, the rate of detection of the nephrotoxic monoclonal Ig in the serum or urine, and of an abnormal bone marrow B-cell clone, is only ∼30%. Renal prognosis is poor, with progression to end-stage renal disease in 25% of patients within 30 months and frequent early recurrence on the renal allograft. The pathophysiology of PGNMID is unclear and its treatment remains challenging. However, recent studies indicate that clone-targeted chemotherapy may significantly improve renal outcomes, opening future perspectives for the management of this rare disease.

Heavy chain amyloidosis and heavy chain deposition disease are the only known kidney diseases caused by the deposition of truncated immunoglobulin heavy chains. Fibrillary glomerulonephritis typically results from deposition of DNAJB9 (DnaJ heat shock protein family [Hsp40] member B9) and polytypic immunoglobulin G (IgG). We describe a patient with monoclonal gammopathy (IgG with λ light chain) who developed DNAJB9-negative fibrillary glomerulonephritis leading to end-stage kidney disease, with recurrence in 2 kidney allografts. Pre- and postmortem examination showed glomerular deposition of Congo red-negative fibrillar material that was determined to be immunoglobulin heavy chain. We propose the term "heavy chain fibrillary glomerulonephritis" to describe this lesion, which appears to be a rare kidney complication of monoclonal gammopathy. The diagnosis should be suspected when the kidney biopsy shows fibrillary glomerulonephritis with negative staining for immunoglobulin light chains and DNAJB9; the diagnosis can be confirmed using immunochemical and molecular studies.

The type of monoclonal light chain nephropathy is thought to be largely a function of the structural and physiochemical properties of light chains; hence most affected patients have only one light chain kidney disease type. Here, we report the first series of kidney light chain deposition disease (LCDD) concomitant with light chain amyloidosis (LCDD+AL), with or without light chain cast nephropathy (LCCN). Our LCDD+AL cohort consisted of 37 patients (54% females, median age 70 years (range 40-86)). All cases showed Congo red-positive amyloid deposits staining for one light chain isotype on immunofluorescence (62% lambda), and LCDD with diffuse linear staining of glomerular and tubular basement membranes for one light chain isotype (97% same isotype as the amyloidogenic light chain) and ultrastructural non-fibrillar punctate deposits. Twelve of 37 cases (about 1/3 of patients) had concomitant LCCN of same light chain isotype. Proteomic analysis of amyloid and/or LCDD deposits in eight revealed a single light chain variable domain mutable subgroup in all cases (including three with separate microdissections of LCDD and amyloid light chain deposits). Clinical data on 21 patients showed proteinuria (100%), hematuria (75%), kidney insufficiency and nephrotic syndrome (55%). Extra-kidney involvement was present in 43% of the patients. Multiple myeloma occurred in 68% (about 2/3) of these patients; none had lymphoma. On follow up (median 16 months), 63% developed kidney failure and 56% died. The median kidney and patient survivals were 12 and 32 months, respectively. LCDD+AL mainly affected patients 60 years of age or older. Thus, LCDD+AL could be caused by two pathological light chains produced by subclones stemming from one immunoglobulin light chain lambda or kappa rearrangement, with a distinct mutated complementary determining region.

Randall-type monoclonal immunoglobulin deposition disease (MIDD) is a rare disease that belongs to the spectrum of monoclonal gammopathy of renal significance (MGRS). Renal involvement is prominent in MIDD, but extra-renal manifestations can be present and may affect global prognosis. Recent data highlighted the central role of molecular characteristics of nephrotoxic monoclonal immunoglobulins in the pathophysiology of MIDD, and the importance of serum free light chain monitoring in the diagnosis and follow-up disease. Clone-targeted therapy is required to improve the overall and renal survival, and the achievement of a rapid and deep hematological response is the goal of therapy. This review will focus on the recent progress in the pathogenesis and management of this rare disease.

Research on AL amyloidosis suffers from the lack of a reliable animal model to better understand the pathophysiology of the disease and to design novel therapeutic strategies. Even if few mouse mod...

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.

PURPOSE We report a multicenter controlled trial comparing renal recovery and tolerance profile of doublet versus triplet bortezomib-based regimens in patients with initial myeloma cast nephropathy (CN) and acute kidney injury (AKI) without need for dialysis. METHODS After symptomatic measures and high-dose dexamethasone, patients were randomly assigned to receive bortezomib plus dexamethasone (BD), or BD plus cyclophosphamide (C-BD). In patients with < 50% reduction of serum free light chains (sFLCs) after 3 cycles, chemotherapy was reinforced with either cyclophosphamide (BD group) or thalidomide (C-BD group). RESULTS Ninety-two patients were enrolled in each group. At random assignment, characteristics of the 2 groups were similar, including median age (68 years) and serum creatinine level (305.5 and 273.5 µmol/L in BD and C-BD group, respectively). At 3 months, renal response rate (primary end point) was not different (41 v 47 responders in the BD and C-BD groups, respectively; relative risk [RR], 0.87; P = .46). Very good partial response (free light chain reduction ≥ 90%) or more was achieved in 36 and 47 patients, respectively (RR, 0.76; P = .10). After 1 cycle of chemotherapy, 69 in the BD group and 67 patients in the C-BD group had achieved sFLC level ≤ 500 mg/L. Serious adverse events were recorded in 30 and 40 patients, respectively. At 12 months, 19 patients had died (9 in the BD group v 10 in the C-BD group), including 10 (6 in the BD group and 4 in the C-BD group) from myeloma progression and 3 (0 in the BD group and 3 in the C-BD group) from infection. Within median follow-up of 27 months, 43 and 42 patients switched to new therapy, respectively. Overall, 50 patients (24 in the BD group and 26 in the C-BD group) had died. CONCLUSION This randomized study did not show any benefit of C-BD compared with BD on renal recovery of patients with initial CN not requiring dialysis. Adding cyclophosphamide did not sufficiently improve the efficacy-toxicity balance. Patients with myeloma with AKI are fragile, and indication for doublet or triplet regimen should be adapted to frailty.

Light chain deposition disease (LCDD) is a rare disorder characterized by glomerular and peritubular amorphous deposits of a monoclonal immunoglobulin (Ig) light chain (LC), leading to nodular glomerulosclerosis and nephrotic syndrome. We developed a transgenic model using site-directed insertion of the variable domain of a pathogenic human LC gene into the mouse Ig kappa locus, ensuring its production by all plasma cells (PCs). High free LC levels were achieved after backcrossing with mice presenting increased PC differentiation and no Ig heavy chain (HC) production. Our mouse model recapitulates the characteristic features of LCDD, including progressive glomerulosclerosis, nephrotic-range proteinuria and finally, kidney failure. The variable domain of the LC bears alone the structural properties involved in its pathogenicity. RNA sequencing conducted on PCs demonstrated that LCDD LC induces endoplasmic reticulum stress, likely accounting for the high efficiency of proteasome inhibitor-based therapy. Accordingly, reduction of circulating pathogenic LC was efficiently achieved and not only preserved renal function, but partially reversed kidney lesions. Finally, transcriptome analysis of pre-sclerotic glomeruli revealed that proliferation and extracellular matrix remodelling represented the first steps of glomerulosclerosis, paving the way for future therapeutic strategies in LCDD and other kidney diseases featuring diffuse glomerulosclerosis, particularly diabetic nephropathy.

The term monoclonal gammopathy of renal significance (MGRS) was introduced by the International Kidney and Monoclonal Gammopathy Research Group (IKMG) in 2012. The IKMG met in April 2017 to refine the definition of MGRS and to update the diagnostic criteria for MGRS-related diseases. Accordingly, in this Expert Consensus Document, the IKMG redefines MGRS as a clonal proliferative disorder that produces a nephrotoxic monoclonal immunoglobulin and does not meet previously defined haematological criteria for treatment of a specific malignancy. The diagnosis of MGRS-related disease is established by kidney biopsy and immunofluorescence studies to identify the monotypic immunoglobulin deposits (although these deposits are minimal in patients with either C3 glomerulopathy or thrombotic microangiopathy). Accordingly, the IKMG recommends a kidney biopsy in patients suspected of having MGRS to maximize the chance of correct diagnosis. Serum and urine protein electrophoresis and immunofixation, as well as analyses of serum free light chains, should also be performed to identify the monoclonal immunoglobulin, which helps to establish the diagnosis of MGRS and might also be useful for assessing responses to treatment. Finally, bone marrow aspiration and biopsy should be conducted to identify the lymphoproliferative clone. Flow cytometry can be helpful in identifying small clones. Additional genetic tests and fluorescent in situ hybridization studies are helpful for clonal identification and for generating treatment recommendations. Treatment of MGRS was not addressed at the 2017 IKMG meeting; consequently, this Expert Consensus Document does not include any recommendations for the treatment of patients with MGRS., This Expert Consensus Document from the International Kidney and Monoclonal Gammopathy Research Group includes an updated definition of monoclonal gammopathy of renal significance (MGRS) and recommendations for the use of kidney biopsy and other modalities for evaluating suspected MGRS

We herein report the complete characterization of the monoclonal Ig fragments produced by the plasma cell clone in a 65-year-old patient with a typical heavy chain deposition disease (HCDD).[1][1]–[3][2] The patient was referred for nephrotic syndrome and the main biological parameters are

Two categories of renal disorders associated with monoclonal gammopathies are to be distinguished, according to the characteristics of the underlying B-cell clone. The first group of renal diseases always occurs in the setting of high tumor mass with production of large amounts of monoclonal immunoglobulins. The main complication is the so-called myeloma cast nephropathy, which almost invariably complicates high tumor mass myeloma. The second group includes all renal disorders caused by a monoclonal immunoglobulin secreted by a nonmalignant B-cell clone, and currently referred as a "monoclonal gammopathy of renal significance (MGRS)". This term was introduced to distinguish monoclonal gammopathies that are responsible for the development of kidney damage from those that are truly benign. The spectrum of renal diseases in MGRS is wide and its classification relies on the localization of renal lesions, either glomerular or tubular, and on the pattern of ultrastructural organization of immunoglobulin deposits. Physicochemical characteristics of the pathogenic monoclonal immunoglobulin are probably involved in their propensity to deposit or precipitate in the kidney, as illustrated by the high rate of recurrence of each specific type after kidney transplantation. Early diagnosis and efficient chemotherapy targeting the causal B-cell clone are mandatory to improve renal prognosis and patient survival.

Background: AL amyloidosis is the most frequent type of amyloidosis caused by the deposition in tissues of fibrillar aggregates composed of an abnormal immunoglobulin (Ig) light chain (LC) and leading to organ dysfunction. The most frequent and severe forms involve kidney and heart. Research on this disease suffers from the lack of reliable animal models, that could allow a better understanding of the disease and the design of new therapeutic strategies. In the present study, we aimed at reproducing AL amyloidosis in a mouse model. Methods: We developed an original transgenic approach using an insertion of a human pathogenic LC gene in the endogenous mouse kappa locus, such as the LC is produced by the naturally Ig producing B and plasma cells. Then, to avoid the association of human LCs with endogenous murine HCs, we backcrossed this strain with the DH-LMP2A mice, characterized by a high number of plasma cells devoid of endogenous HC. This strategy leads to a production of the human free LC similar or higher than in patients and proved efficient to reproduce in mice several monoclonal gammopathies of clinical significance (MGCS) (Fig.1A). Results: Despite strong LC production (Fig.1B), mice did not naturally develop AL amyloidosis. In vitro, the full length LC was resistant to amyloid formation at physiological conditions but the variable domain (IGLV6) showed high propensity to form fibrils. A single injection of amyloid fibrils and/or seeds, obtained from the variable domain (VL) of the human LC gene, led to amyloid deposits starting at 1 month post-injection, especially in the heart, spleen, liver and, to a lesser extent, in the kidney (Fig.1C). We confirmed that the deposits contain the full-length human LCs, which elongate VL fibrils in vivo (Fig.1D). Conclusions: This is, to our knowledge, the first transgenic mouse model of AL amyloidosis closely reproducing human lesions, especially in heart. Further studies are needed to better understand the early biochemical events leading to AL amyloidosis in vivo, but this model already shows that a partial degradation of the LC is likely required to initiate amyloid fibrils and that once seeded, the full length LC can elongate these fibrils. This mouse model opens new perspectives to better understand the toxicity of amyloid LC, their involvements in different biological processes and organ dysfunction and of course, to test new therapeutic approaches. Figure 1 Figure 1. Disclosures Roussel: Takeda: Consultancy; Janssen: Membership on an entity's Board of Directors or advisory committees; GSK: Honoraria; BMS: Honoraria; Amgen: Consultancy. Jaccard: Janssen: Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria; Abbvie: Honoraria. Bridoux: Janssen: Consultancy; AstraZeneca: Consultancy, Speakers Bureau. Sirac: Attralus, Inc: Patents & Royalties, Research Funding.

Introduction Fibrillary glomerulonephritis (FGN) is a rare disease with unknown pathogenesis and a poor prognosis. Until now, the diagnosis of this disease has required demonstration of glomerular deposition of randomly oriented fibrils by electron microscopy that are Congo red negative and stain with antisera to Igs. We recently discovered a novel proteomic tissue biomarker for FGN, namely, DNAJB9. Methods In this work, we developed DNAJB9 immunohistochemistry and tested its sensitivity and specificity for the diagnosis of FGN. This testing was performed on renal biopsy samples from patients with FGN (n = 84), amyloidosis (n = 21), a wide variety of non-FGN glomerular diseases (n = 98), and healthy subjects (n = 11). We also performed immunoelectron microscopy to determine whether DNAJB9 is localized to FGN fibrils. Results Strong, homogeneous, smudgy DNAJB9 staining of glomerular deposits was seen in all but 2 cases of FGN. The 2 cases that did not stain for DNAJB9 were unique, as they had glomerular staining for IgG only (without κ or λ) on immunofluorescence. DNAJB9 staining was not observed in cases of amyloidosis, in healthy subjects, or in non-FGN glomerular diseases (with the exception of very focal staining in 1 case of smoking-related glomerulopathy), indicating 98% sensitivity and > 99% specificity. Immunoelectron microscopy showed localization of DNAJB9 to FGN fibrils but not to amyloid fibrils or immunotactoid glomerulopathy microtubules. Conclusion DNAJB9 immunohistochemistry is sensitive and specific for FGN. Incorporation of this novel immunohistochemical biomarker into clinical practice will now allow more rapid and accurate diagnosis of this disease.

Introduction Low molecular weight heparins (LMWH) are widely used for preventing clotting during hemodialysis (HD). Although injection in venous bloodline (VBL) is recommended to avoid initial loss of LMWH through the dialyzer, LMWH is still frequently administered in the arterial blood line (ABL) at the start of dialysis. Description The aim of this study was to compare the efficacy and safety of same enoxaparin dose administered through VBL or ABL. We also evaluated antifactor Xa (aXa) activity according to the injection route and dialysis modalities: high-flux (HF) HD, medium cut-off (MCO) HD and on-line hemodiafiltration (OL-HDF). Methods This open, single-center prospective study was conducted at the Poitiers university Hospital HD unit. Forty-three patients were studied over 18 consecutive dialysis sessions using a fixed enoxaparin dose (20 or 40 mg) first administered through ABL bolus and then through VBL for another 18 sessions. Results Compared to ABL, VBL bolus resulted in significant increase in median post-dialysis aXa activity: 0.16 (0.1–0.6) IU/mL vs. 0.31 (0.1–1.3) IU/mL, respectively, P = 0.006. After ABL bolus of enoxaparin 40 mg, median post-dialysis aXa activity was significantly lower with OL-HDF compared to HF-HD: 0.14 (0.1–0.35) vs. 0.32 (0.15–0.49), P = 0.02. A trend for lower clotting within lines and bubble trap using VBL bolus was observed. Conclusion In conclusion, VBL enoxaparin injection is safe in OL-HDF patients. However, in HF-HD and MCO-HD, VBL injection of enoxaparin 40 mg may increase overdosing risk. Thus, aXa activity should be monitored in HF-HD and MCO-HD patients at risk of bleeding and/or on vitamin K antagonists, and careful surveillance is required when administering enoxaparin dose 40 mg through the VBL route.

International audience; Background - Intensive haemodialysis (IHD) in addition to bortezomib-based chemotherapy might be efficient to rapidly decrease serum immunoglobulin-free light chains removal in patients with multiple myeloma (MM) and to improve renal prognosis and survival. Methods - The aim of this retrospective multi-centre study was to compare the efficacy (renal recovery rate) of IHD and of standard haemodialysis (SHD) in patients with MM and dialysis-dependent acute kidney injury (AKI), concomitantly treated with bortezomib-based chemotherapy. Results - We selected 41 patients with MM and dialysis-dependent AKI, most likely due to myeloma cast nephropathy (MCN), and who were treated in eight French hospitals between January 2007 and June 2011. Patients were classified in two groups according to dialysis regimen: IHD [ = 21, with a mean of 11.3 dialysis sessions all with poly(methyl methacrylate) (PMMA) membranes for 13.2 days] and SHD ( = 20 patients, mostly three times per week, 31% with PMMA membrane). The main outcome was dialysis-independence at 3 months. At 3 months, 15 patients could stop dialysis: 8 (38.1%) in the IHD and 7 (35%) in the SHD group (P = 1). Moreover, 14 (56%) of the 25 patients who did show haematological response and only one of the 16 patients who did not were dialysis-independent (P = 0.002) at 3 months.Conclusions - The results of this retrospective study did not show any clear renal benefit of IHD in patients with MM and MCN compared with SHD. Conversely, they underline the importance of the haematological response to chemotherapy for the renal response and patient prognosis.

Introduction: Systemic light chain (AL) amyloidosis is a plasma cell dyscrasia in which a toxic plasma cell clone causes devastating multiorgan complications and death, and substantially affects the quality of life of patients (pts). Current therapeutic options are not regulatory approved and are typically based on modified treatments that are used for multiple myeloma. The aim of EMN23 study is to thoroughly describe patterns of AL amyloidosis management in a large-scale real-world evidence (RWE) setting throughout Europe, to understand different treatment strategies and their evolution, and evaluate resource utilization. Methods: EMN23 is an ongoing, retrospective, observational, multicenter study aiming to enroll 5000 pts in 10 countries (13 Sites) across Europe; Austria, Czech Republic, France, Germany, Greece, Italy, the Netherlands, Portugal, Spain, and UK. Pts must have documented systemic AL amyloidosis, and a first-line treatment start date between 2004 and 2018. Results are presented in 2 chronological cohorts, 2004-2010, and 2011-2018, with 2010 being an important landmark, since bortezomib, cyclophosphamide, dexamethasone (CyBorD) regimen was introduced in clinical practice. Pts who received treatment in the context of an interventional clinical trial were not analyzed for treatment and efficacy results. The current analysis presents baseline disease characteristics, treatment patterns and efficacy outcomes. Informed consent or a non-opposition letter was collected for all alive pts, depending on the regulatory environment of each country, and a waiver of consent was obtained for the deceased. Results: In total, 2031 pts from Austria (1.9%), Czech Republic (0.9%), France (9.2%), Germany (3.6%), Greece (12.6%), Italy (58.7%), the Netherlands (7.2%), Portugal (1.0%), and Spain (4.9%) have been analyzed; 67.9% of pts started treatment after 2010. Median age at diagnosis was 66 years and 54.5% were males, while 48.2% had ECOG performance status ≤1. Heart (71.9%), kidney (67.2%), soft tissue (19.7%) and nervous system (18.5%) were most often involved at diagnosis, and 17.2%, 36.2%, 21.1% and 15.2% of pts were at cardiac stage I, II, IIIA and IIIB, according to Mayo staging system, respectively, while for 10.3% of pts staging was not reported. There was a slight increase of pts with stage III in the more recent era. In the period 2004-2010, 52.8% of the pts had at least 2 lines of therapy, which dropped to 35.2% in the period 2011-2018. A 6.4% of pts received autologous stem cell transplant at first line. The prevailing first-line regimen in 2004-2010 was melphalan with dexamethasone (MDex; 50.6% of the pts), replaced by CyBorD (46.1%) in the post-2010 period. The predominant first-line regimens were different in various countries in 2004-2010, but in general CyBorD was the most extensively used regimen after 2010. Overall, the most frequent second-line regimen was BorD (29.8%), which was also the treatment of choice for 15.7% of the pts who had frontline therapy with MDex in the pre-2010 period; and lenalidomide dexamethasone (RD, 25.5%) which was also favored following frontline treatment with CyBorD for 10.6% of the pts in the post-2010 period. In the 2004-2010 era, 31.7% of the pts achieved a hematologic VGPR or CR at first line, which was slightly improved to 37.2% in the post-2010 period. Notably, 29.9% and 23% of pts did not achieve a hematologic response (no response or disease progression) in the two periods, respectively (p=0.001). Mortality in the first months of treatment remained roughly at the same level, with the 3-month overall survival (OS) rate at 82.3% for both cohorts, whereas the median OS increased from 43.5 months in the pre-2010 period to 50.1 months in the post-2010 period (p=0.525). There was a trend towards an improvement in the median OS of stage IIIA pts from 9.5 to 25.9 months, pre- and post-2010, respectively, however, no change was observed for stage IIIB pts (2.7 to 3.5 months). Conclusions: Therapeutic options for AL amyloidosis have changed considerably over time. After 2010 CyBorD became the prominent first-line treatment; the proportion of pts not achieving a response was reduced by 23% and a trend towards improvement of OS for stage IIIA disease was observed, but the prognosis of stage IIIB pts remained dismal and early mortality remained unchanged. Early diagnosis is still an unmet need, and improved therapies are essential. Figure 1 Disclosures Palladini: Celgene: Other: Travel support; Jannsen Cilag: Honoraria, Other. Schönland:Janssen, Prothena, Takeda: Honoraria, Other: travel support to meetings, Research Funding. Milani:Celgene: Other: Travel support; Pfizer: Other: Speaker honoraria; Janssen: Other: Speaker honoraria. Jaccard:Janssen: Consultancy, Honoraria, Other: A.J. has served in a consulting or advisory role for Janssen and has received honoraria from, received research funding from, and had travel, accommodations, or other expenses paid for or reimbursed by Janssen., Research Funding; Celgene: Honoraria, Other: A.J. has served in a consulting or advisory role for Janssen and has received honoraria from, received research funding from, and had travel, accommodations, or other expenses paid for or reimbursed by Celgene., Research Funding. Bridoux:Celgene: Honoraria; Baxter: Consultancy; Janssen: Honoraria. Cibeira:Amgen: Honoraria, Other: Educational lectures; Celgene: Honoraria, Other: Educational lectures; Akcea Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Educational lectures. Agis:Janssen: Honoraria, Research Funding; Amgen: Honoraria; BMS: Honoraria; Celgene: Honoraria; Takeda: Honoraria. Minnema:Amgen: Honoraria; Servier: Honoraria; Janssen Cilag: Honoraria; Celgene Corporation: Honoraria, Research Funding; Gilead: Honoraria. Bergantim:AMGEN, Celgene, Janssen, Takeda: Membership on an entity's Board of Directors or advisory committees, Other: Speaker honoraria; Celgene, AMGEN/SPH/APCL: Other: Grants, Research Funding. Hajek:Oncopeptides: Consultancy; Janssen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Research Funding; BMS: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; PharmaMar: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria. João:Takeda: Consultancy, Research Funding; Amgen: Consultancy; Janssen: Consultancy; BMS: Consultancy. Wechalekar:Celgene: Honoraria; Janssen: Honoraria, Other: Advisory; Caelum: Other: Advisory; Takeda: Honoraria, Other: Travel. Sonneveld:Karyopharm: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Sanofi: Consultancy; Skyline Dx: Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding. Kastritis:Amgen: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Genesis Pharma: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria. OffLabel Disclosure: This is a RWE study on AL amyloidosis, and currently there are no regulatory approved therapeutic options for the disease.

International audience; Apolipoprotein A1 amyloidosis (ApoAI) results from specific mutations in the APOA1 gene causing abnormal accumulation of amyloid fibrils in diverse tissues. The kidney is a prominent target tissue in ApoAI amyloidosis with a remarkable selectivity for the renal medulla. Here, we investigated six French families with ApoAI Glu34Lys, p.His179Profs*47, and a novel p.Thr185Alafs*41 variant revealing unprecedented clinical association of a glomerular with a retinal disease. Comprehensive clinicopathological, molecular and proteomics studies of numerous affected tissues ensured the correlation between clinical manifestations, including novel unrecognized phenotypes, and apoA-I amyloid deposition. These ophthalmic manifestations stemmed from apoA-I amyloid deposition, highlighting that the retina is a previously unrecognized tissue affected by ApoAI amyloidosis. Our study provides the first molecular evidence that a significant fraction of ApoAI amyloidosis cases with no family history result from spontaneous neomutations rather than variable disease penetrance. Finally, successful hepatorenal transplantation resulted in a life- and visionsaving measure for a 32-year-old man with a hitherto unreported severe ApoAI amyloidosis caused by the very rare Glu34Lys variant. Our findings reveal new modes of occurrence and expand the clinical spectrum of ApoAI amyloidosis. The awareness of glomerular and ocular manifestations in ApoAI amyloidosis should enable earlier diagnosis and avoid misdiagnosis with other forms of renal amyloidosis. Thus, documented apoA-I amyloid deposition in the retina offers new biological information about this disease and may change organ transplantation practice to reduce retinal damage in patients with ApoAI amyloidosis.

Light chain cast nephropathy (LCCN) in multiple myeloma often leads to severe and poorly reversible acute kidney injury. Severe renal impairment influences the allocation of chemotherapy and its tolerability; it also affects patient survival. Whether renal biopsy findings add to the clinical assessment in predicting renal and patient outcomes in LCCN is uncertain. We retrospectively reviewed clinical presentation, chemotherapy regimens, hematologic response, and renal and patient outcomes in 178 patients with biopsy-proven LCCN from 10 centers in Europe and North America. A detailed pathology review, including assessment of the extent of cast formation, was performed to study correlations with initial presentation and outcomes. Patients presented with a mean estimated glomerular filtration rate (eGFR) of 13 ± 11 mL/min/1.73 m2, and 82% had stage 3 acute kidney injury. The mean number of casts was 3.2/mm2 in the cortex. Tubulointerstitial lesions were frequent: acute tubular injury (94%), tubulitis (82%), tubular rupture (62%), giant cell reaction (60%), and cortical and medullary inflammation (95% and 75%, respectively). Medullary inflammation, giant cell reaction, and the extent of cast formation correlated with eGFR value at LCCN diagnosis. During a median follow-up of 22 months, mean eGFR increased to 43 ± 30 mL/min/1.73 m2. Age, β2-microglobulin, best hematologic response, number of cortical casts per square millimeter, and degree of interstitial fibrosis/tubular atrophy (IFTA) were independently associated with a higher eGFR during follow-up. This eGFR value correlated with overall survival, independently of the hematologic response. This study shows that extent of cast formation and IFTA in LCCN predicts the quality of renal response, which, in turn, is associated with overall survival.

POEMS syndrome is a rare multisystem disease due to an underlying plasma cell (PC) dyscrasia. The pathophysiology of the disease remains unclear but the role of the monoclonal immunoglobulin (Ig) light chain (LC) is strongly suspected, due to the highly restrictive usage of two λ variable (V) domains (IGLV1-40 and IGLV1-44) and the general improvement of clinical manifestations following PC clone-targeted treatment. However, the diagnostic value of Ig LC sequencing, especially in case of incomplete forms of the disease, remains to be determined. Using a sensitive high-throughput Ig repertoire sequencing on RNA (RACE-RepSeq), we detected a λ LC monoclonal expansion in the bone marrow (BM) of 85% of patients with POEMS syndrome, including some in whom bone marrow tests routinely performed to diagnose plasma cell dyscrasia failed to detect λ+monoclonal PCs. Twenty-four of the 30 LC clonal sequences found (80%) were derived from the IGLV1-40 and IGLV1-44 germline genes, two from the closely related IGLV1-36 gene, and all were associated with an IGLJ3*02 junction (J) gene, confirming the high restriction of VJ region usage in POEMS syndrome. RACE-RepSeq VJ full-length sequencing additionally revealed original mutational patterns, the strong specificity of which might crucially help establish or eliminate the diagnosis of POEMS syndrome in uncertain cases. Thus, RACE-RepSeq appears as a sensitive, rapid and specific tool to detect low-abundance PC clones in BM, and assign them to POEMS syndrome, with all the consequences for therapeutic options hereby.

BackgroundAccumulation of middle-weight uraemic toxins in haemodialysis (HD) patients results in increased morbidity and mortality. Whether medium cut-off HD (MCO-HD) improves removal of middle-weight uraemic toxins remains to be demonstrated.MethodsThis cross-over prospective study included 40 patients randomly assigned to receive either 3 months of MCO-HD followed by 3 months of high-flux HD (HF-HD), or vice versa. The primary endpoint was myoglobin reduction ratio (RR) after 3 months of MCO-HD. Secondary endpoints were the effect of MCO-HD on other middle-weight toxins and protein-bound toxins, and on parameters of nutrition, inflammation, anaemia and oxidative stress.ResultsCompared with HF-HD, MCO-HD provided higher mean RR of myoglobin (36 ± 8 versus 57 ± 13%, P ConclusionsCompared with HF-HD, MCO-HD provides higher myoglobin and other middle molecules RR and is associated with moderate hypoalbuminemia. The potential benefits of this strategy on long-term clinical outcomes deserve further evaluation.

Light chain deposition disease (LCDD) is a rare disorder characterized by glomerular and peritubular amorphous deposits of a monoclonal immunoglobulin (Ig) light chain (LC), leading to nodular glomerulosclerosis and nephrotic syndrome. We developed a transgenic model using site-directed insertion of the variable domain of a pathogenic human LC gene into the mouse Ig kappa locus, ensuring its production by all plasma cells. High free LC levels were achieved after backcrossing with mice presenting increased plasma cell differentiation and no Ig heavy chain (HC) production. Our mouse model recapitulates the characteristic features of LCDD, including progressive glomerulosclerosis, nephrotic-range proteinuria and finally, kidney failure. The variable domain of the LC bears alone the structural properties involved in its pathogenicity. RNA sequencing conducted on plasma cells demonstrated that LCDD LC induces endoplasmic reticulum stress, likely accounting for the high efficiency of proteasome inhibitor-based therapy. Accordingly, reduction of circulating pathogenic LC was efficiently achieved and not only preserved renal function, but partially reversed kidney lesions. Finally, transcriptome analysis of pre-sclerotic glomeruli revealed that proliferation and extracellular matrix remodelling represented the first steps of glomerulosclerosis, paving the way for future therapeutic strategies in LCDD and other kidney diseases featuring diffuse glomerulosclerosis, particularly diabetic nephropathy.

International audience; The clinicopathological characteristics of kidney infiltration in B-cell lymphoproliferative disorders remain poorly described. We retrospectively studied 52 adults with biopsy-proven malignant B-cell kidney infiltration, including Waldenström's macroglobulinemia (n=21), chronic lymphocytic leukemia (n=11), diffuse large B-cell lymphoma (DLBCL) (n=8), other lymphoma (n=11), and multiple myeloma (n=1). Kidney disease varied according to the underlying lymphoproliferative disorder. In DLBCL, malignant kidney infiltration was prominent, resulting in acute kidney injury (AKI, 75%) and kidney enlargement (88%). In the other types, associated immunoglobulin-related nephropathy (most commonly AL amyloidosis) was more common (45%), and chronic kidney disease with proteinuria was the primary presentation. All patients received chemotherapy. Over a median follow-up of 31 months, 20 patients died and 21 reached end-stage kidney disease. Renal response, achieved in 25 patients (48%), was associated with higher overall survival (97 vs. 37 months in non-renal responders). In univariate analysis, percentage of sclerotic glomeruli, kidney enlargement, and complete hematological response at 6 months were predictive of renal response. In multivariate analysis, concomitant immunoglobulin-related nephropathy was the sole independent predictor of poor renal outcome. In conclusion, clinical presentation of renal lymphomatous infiltration depends on the nature of the underlying lymphoproliferative disorder. In DLBCL, massive renal infiltration manifests with enlarged kidneys and AKI, and the diagnosis primarily relies on lymph node biopsy. In other B-cell lymphoproliferative disorders, the clinicopathological spectrum is more heterogeneous, with a high frequency of immunoglobulin-related nephropathy that may affect renal outcome; thus kidney biopsy is required for early diagnosis and prognostic assessment. © 2019 International Society of Nephrology

Monoclonal immunoglobulin deposition disease (MIDD) is a rare complication of B-cell clonal disorders, defined by Congo red negative–deposits of monoclonal light chain (LCDD), heavy chain (HCDD), or both (LHCDD). MIDD is a systemic disorder with prominent renal involvement, but little attention has been paid to the description of extrarenal manifestations. Moreover, mechanisms of pathogenic immunoglobulin deposition and factors associated with renal and patient survival are ill defined. We retrospectively studied a nationwide cohort of 255 patients, with biopsy-proven LCDD (n = 212) (including pure LCDD [n = 154], LCDD with cast nephropathy (CN) [n = 58]), HCDD (n = 23), or LHCDD (n = 20). Hematological diagnosis was monoclonal gammopathy of renal significance in 64% and symptomatic myeloma in 34%. Renal presentation was acute kidney injury in patients with LCCD and CN, and chronic glomerular disease in the other types, 35% of whom had symptomatic extrarenal (mostly hepatic and cardiac) involvement. Sequencing of 18 pathogenic LC showed high isoelectric point values of variable domain complementarity determining regions, possibly accounting for tissue deposition. Among 169 patients who received chemotherapy (bortezomib-based in 58%), 67% achieved serum free light chain (FLC) response, including very good partial response (VGPR) or above in 52%. Renal response occurred in 62 patients (36%), all of whom had achieved hematological response. FLC response ≥ VGPR and absence of severe interstitial fibrosis were independent predictors of renal response. This study highlights an unexpected frequency of extrarenal manifestations in MIDD. Rapid diagnosis and achievement of deep FLC response are key factors of prognosis.

Background: In patients with cast nephropathy and acute kidney injury (AKI) requiring dialysis, the reduction of serum free light chains (FLC) using chemotherapy and intensive hemodialysis (IHD) with a high cut-off filter may improve renal and patient outcomes. We evaluated the effectiveness of a combination of chemotherapy and IHD with an adsorbent polymethylmethacrylate membrane (IHD-PMMA) on renal recovery and survival. Methods: A single-center retrospective cohort-study was conducted. Between 2007 and 2014, patients with dialysis-dependent acute cast nephropathy treated with chemotherapy and IHD-PMMA were included. Patients had six 6-h hemodialysis sessions a week, until predialysis serum FLC fell below 200 mg/L, for a maximum of 3 weeks. Primary outcomes were renal recovery, defined as dialysis independence, and survival. Results: Seventeen patients were included, all with stage 3 AKI. All received chemotherapy, mostly based on bortezomib and steroids (88%). Twelve patients (71%) achieved renal recovery, usually within 60 days (92%). At 3 months, the overall hematological response rate was 57%; hematological response was maintained for at least 2 years in 86% of responders. At 6, 12, and 24 months, 76, 75, and 62% of patients were alive, respectively. Higher reduction in involved FLC by day 12 (p = 0.022) and day 21 (p = 0.003) was associated with renal recovery. Patients with FLC reduction rate >50% by day 21 experienced a lower mortality (hazard ratio 0.10, 95% CI 0.02–0.63). Conclusion: In patients with dialysis-dependent myeloma cast nephropathy, early FLC removal by IHD-PMMA combined with chemotherapy was associated with high rates of renal recovery and survival.

Renal impairment (RI) is a common comorbidity in multiple myeloma (MM). Current dose adjustments recommended for renally excreted lenalidomide are based on data from noncancer patients. This study evaluated the pharmacokinetics, safety, efficacy, and exposure–response for lenalidomide plus dexamethasone in patients with relapsed/refractory MM and stable RI using the recommended dose adjustments. This phase 2 multicenter, open-label study stratified patients into 5 groups based on creatinine clearance (CrCl) calculated by Cockcroft–Gault equation: normal renal function (CrCl > 80 mL/min), mild RI (50 ≤ CrCl ≤ 80 mL/min), moderate RI (30 ≤ CrCl

Cryoglobulins are circulating immunoglobulins that precipitate with cold temperature and dissolve with rewarming. Type 1 cryoglobulinemia is composed of a single monoclonal immunoglobulin and is associated with renal involvement in up to 40% of cases. Type 1 cryoglobulinemia is related to an underlying B-cell haematological malignancy in 60% of patients. In the remaining cases, in the absence of criteria for malignancy, the diagnosis of monoclonal gammopathy of renal significance should be established. The clinical and biological setting and histological features of type 1 cryoglobulinemia are globally similar to those of mixed cryoglobulinemia. In case of haematological malignancy, the treatment is guided by the nature of the underlying disease, and aims at inducing haematological remission, which is necessary for the renal response. The management of monoclonal gammopathy of renal significance has been clarified by an international consensus group and is based on the nature of the underlying clone. In case of monoclonal cryoglobulinemia associated with a plasma-cell clone (IgG or IgA), the treatment is based on the combination of bortezomib, cyclophosphamide and dexamethasone. In case of IgM monoclonal cryoglobulinemia, the treatment is similar to that of Waldenstrom macroglobulinemia, and is based on rituximab. The clinical course of renal monoclonal cryoglobulinemia is intimately associated with the haematological response, and is usually favourable.

Supported by a travel grant to JD from the Association pour la Recherche et l'Enseignement en Nephrologie Poitou-Charentes, which had no role in study design; collection, analysis, and interpretation of data; writing the report; and the decision to submit the report for publication.

Monoclonal gammopathy is a common condition, particularly in the elderly. It can indicate symptomatic multiple myeloma or another overt malignant lymphoid disorder requiring immediate chemotherapy. More frequently, it results from a small and/or quiescent secreting B-cell clone, is completely asymptomatic, and requires regular monitoring only, defining a monoclonal gammopathy of unknown significance (MGUS). Sometimes, although quiescent and not requiring any treatment per se, the clone is associated with potentially severe organ damage due to the toxicity of the monoclonal immunoglobulin or to other mechanisms. The latter situation is increasingly observed but still poorly recognized and frequently undertreated, although it often requires rapid specific intervention to preserve involved organ function. To improve early recognition and management of these small B-cell clone–related disorders, we propose to introduce the concept of monoclonal gammopathy of clinical significance (MGCS). This report identifies the spectrum of MGCSs that are classified according to mechanisms of tissue injury. It highlights the diversity of these disorders for which diagnosis and treatment are often challenging in clinical practice and require a multidisciplinary approach. Principles of management, including main diagnostic and therapeutic procedures, are also described. Importantly, efficient control of the underlying B-cell clone usually results in organ improvement. Currently, it relies mainly on chemotherapy and other anti–B-cell/plasma cell agents, which should aim at rapidly producing the best hematological response.

The renal deposition of monoclonal immunoglobulins can cause severe renal complications in patients with B cell and plasma cell lymphoproliferative disorders. The overproduction of a structurally unique immunoglobulin can contribute to the abnormal propensity of monoclonal immunoglobulins to aggregate and deposit in specific organs. A wide range of renal diseases can occur in multiple myeloma or monoclonal gammopathy of renal significance, including tubular and glomerular disorders with organized or unorganized immunoglobulin deposits. The development of reliable experimental models is challenging owing to the inherent variability of immunoglobulins and the heterogeneity of the pathologies they produce. However, although imperfect, animal models are invaluable tools to understand the molecular pathogenesis of these diseases, and advances in creating genetically modified animals might provide novel approaches to evaluate innovative therapeutic interventions. We discuss the strategies employed to reproduce human monoclonal immunoglobulin-induced kidney lesions in animal models, and we highlight their advantages and shortcomings. We also discuss how these models have affected the management of these deposition diseases and might do so in the future. Finally, we discuss hypotheses that explain some limitations of the various models, and how these models might improve our understanding of other nephropathies without immunoglobulin involvement that have similar pathogenic mechanisms.

International audience; B-cell clones can produce a monoclonal immunoglobulin, which may be responsible for visceral involvements. Kidney involvement is frequent, affecting 20 to 50% of patients with multiple myeloma. One mechanism underlying this involvement is a dysregulation of the complement alternative pathway, leading to C3 glomerulopathies. We report a patient who had a multiple myeloma, C3 glomerulopathy related to factor H autoantibody, and digital ischemia, who was treated successfully with eculizumab, an anti-complement therapy, without any relapse in 2 years of follow-up.

BACKGROUND Light chain myeloma cast nephropathy (MCN) is the major cause of renal failure in multiple myeloma and strongly impacts patient survival. The role of kidney biopsy in the management of MCN is unclear. METHODS Renal pathological findings were retrospectively studied in 70 patients with multiple myeloma and MCN. Patients were categorized according to the achievement or not of renal response, as defined by estimated glomerular filtration rate (eGFR) ≥ 30 mL/min/1.73 m(2) and/or dialysis independence at 3 months. RESULTS Thirty-two patients (46%) achieved a renal response. In the whole study population, the following parameters differed significantly between patients with and without renal response, respectively: baseline median eGFR (13.3 versus 9.3 mL/min/1.73 m(2), P = 0.017), Acute Kidney Injury Network Stage 3 (68.8 versus 92.1%, P = 0.019), haematological response rate (94 versus 34%, P < 0.0001), median percentage of free light chain (FLC) reduction at Day 21 (92 versus 24%, P = 0.006) and median number of casts/10 fields (14 versus 25, P = 0.005). The extent of interstitial fibrosis and tubular atrophy was similar. In multivariate analysis, only FLC reduction at Day 21 was significantly associated with renal response. However, when considering only the subgroup of haematological responders, both median number of casts [odds ratio (OR) = 0.93, 95% confidence interval (95% CI): 0.88-0.98, P = 0.01] and extent of tubular atrophy (OR = 0.03, 95% CI: 0.00-0.52, P = 0.02) were independent predictors of renal response. CONCLUSIONS In MCN, the presence of numerous casts and diffuse tubular atrophy is associated with poor renal prognosis. These data suggest that additional strategies to reduce FLC burden should be considered in patients with extensive cast formation.

Abnormal regulation of the alternative pathway of the complement system is a well-described trigger of microangiopathy leading to atypical hemolytic uremic syndrome (aHUS). However, the involvement of complement dysregulation in distal angiopathy has not been reported in adults. We describe the clinical course of a patient with severe distal angiopathy (amputation of all fingers and toes) followed 3 years later by aHUS with end-stage renal disease. This course was attributed to a circulating monoclonal immunoglobulin A λ light chain (IgAλ) with unusual properties: it bound complement factor H (CFH) and impaired CFH-glycosaminoglycan interaction and cell-surface protection. Local complement activation with distal angiopathy and microvascular injury was suggested by deposition of IgA, C4d, and C5b-9 in limb and preglomerular arteries. We therefore postulated that the monoclonal IgAλ inhibited activity of endothelial cell-bound CFH, which led to local activation of complement, vasoconstriction (distal angiopathy), and aHUS. While the patient was dependent on dialysis and plasma exchange, treatment with the anti-C5 antibody eculizumab induced remission of distal angiopathy and aHUS. During eculizumab treatment, kidney transplantation was performed. The patient had normal kidney function at the 3-year follow-up. We suggest that the association of distal angiopathy and aHUS in this patient is clearly linked to anti-CFH properties of the monoclonal IgAλ.

Summary Background Localised immunoglobulin light-chain amyloidosis, involving one type of tissue, is rare. Little systematic data exists regarding clinical presentations, course or outcomes, or risk of progression to systemic amyloidosis. We aimed to report clinical features and outcomes of a large series of patients with localised light-chain amyloidosis. Methods We examined data for all patients with localised amyloidosis who were diagnosed, assessed, and followed at the UK National Amyloidosis Centre (NAC) between Jan 2, 1980, and Dec 15, 2011, from the NAC database and written records. The inclusion criteria was the presence of biopsy sample proven localised amyloidosis classified as biopsy proven amyloid deposition confined to one site or tissue proven by histology of the tissue examined), without any evidence of vital organ involvement, which was defined as cardiac, renal, or liver involvement or peripheral or autonomic neuropathy and treatment naive. Findings We identified 606 patients with biopsy proven localised amyloidosis (likely light-chain type in 98%) from 5050 newly diagnosed patients with all types of amyloidosis. Median age was 59·5 years (IQR 50·2–74·5). The most common sites included bladder (95; 16%), laryngeal or tonsillar (92; 15%), cutaneous (84; 14%), and pulmonary nodular (47; 8%). 121 (20%) had a monoclonal immunoglobulin or abnormal circulating free light chains. At median follow-up of 74·4 months (IQR 37·2–132·0), seven (1%) patients progressed to systemic immunoglobin light-chain amyloidosis. 270 (51%) patients had one repeated treatment intervention and 112 (21%) had more than one repeated treatment interventions (predominantly localised debulking). The estimated 5-year overall survival was 90·6% (95% CI 87·7–92·9) and 10-year overall survival was 80·3% (75·1–84·1). In patients aged 70 years or older, median overall survival was 12·1 years (95% CI 10·5–13·7). Interpretation Localised immunoglobulin light-chain amyloidosis has an excellent prognosis with no apparent effect on life expectancy. Evolution into systemic immunoglobulin light chain amyloidosis is very rare. Funding None.

Monoclonal gammopathy of renal significance (MGRS) regroups all renal disorders caused by a monoclonal immunoglobulin (MIg) secreted by a nonmalignant B-cell clone. By definition, patients with MGRS do not meet the criteria for overt multiple myeloma/B-cell proliferation, and the hematologic disorder is generally consistent with monoclonal gammopathy of undetermined significance (MGUS). However, MGRS is associated with high morbidity due to the severity of renal and sometimes systemic lesions induced by the MIg. Early recognition is crucial, as suppression of MIg secretion by chemotherapy often improves outcomes. The spectrum of renal diseases in MGRS is wide, including old entities such as AL amyloidosis and newly described lesions, particularly proliferative glomerulonephritis with monoclonal Ig deposits and C3 glomerulopathy with monoclonal gammopathy. Kidney biopsy is indicated in most cases to determine the exact lesion associated with MGRS and evaluate its severity. Diagnosis requires integration of morphologic alterations by light microscopy, immunofluorescence (IF), electron microscopy, and in some cases by IF staining for Ig isotypes, immunoelectron microscopy, and proteomic analysis. Complete hematologic workup with serum and urine protein electrophoresis, immunofixation, and serum-free light-chain assay is required. This review addresses the pathologic and clinical features of MGRS lesions, indications of renal biopsy, and a proposed algorithm for the hematologic workup.

Patients with Gitelman syndrome (GS), an inherited salt-losing tubulopathy, are usually treated with potassium-sparing diuretics or nonsteroidal anti-inflammatory drugs and oral potassium and magnesium supplementations. However, evidence supporting these treatment options is limited to case series studies. We designed an open-label, randomized, crossover study with blind end point evaluation to compare the efficacy and safety of 6-week treatments with one time daily 75 mg slow-release indomethacin, 150 mg eplerenone, or 20 mg amiloride added to constant potassium and magnesium supplementation in 30 patients with GS (individual participation: 48 weeks). Baseline plasma potassium concentration was 2.8±0.4 mmol/L and increased by 0.38 mmol/L (95% confidence interval [95% CI], 0.23 to 0.53; P