Diagnosis of monoclonal gammopathy of renal significance. Kidney Int. 2015;87:698-711. [PMID: 25607108 DOI: 10.1038/ki.2014.408]

Tubular Injury and Dendritic Cell Activation Are Integral Components of Light Chain-Associated Acute Tubulointerstitial Nephritis

CONTEXT.—

Light chain-associated acute tubulointerstitial nephritis (LC-ATIN) is a variant of light chain proximal tubulopathy (LCPT). It is characterized by interstitial inflammation with tubulitis and deposition of monoclonal light chains in the tubulointerstitium. LC-ATIN is a rather poorly recognized pattern of LCPT and not much is known about this entity.

OBJECTIVE.—

To determine the clinicopathologic features of patients with LC-ATIN and investigate the proximal tubular injury and mechanism of interstitial inflammation in LC-ATIN.

DESIGN.—

A total of 38 cases of LC-ATIN were identified from the archives of 5043 renal biopsy specimens. In all cases, routine light microscopic examination, immunofluorescence, and electron microscopic examination were performed. In selected cases, immunofluorescent staining of dendritic cells and immunohistochemical staining for 4 tubular injury markers-KIM-1, p53, bcl-2, and Ki-67-were performed.

RESULTS.—

A characteristic finding in LC-ATIN cases was immunofluorescence staining of monoclonal light chains along tubular basement membranes in linear fashion and inside proximal tubular cells with a granular pattern. No monoclonal light chains were present in glomerular or vascular compartments confirmed with immunofluorescence, electron microscopy, and ultrastructural gold labeling. Ten of 15 LC-ATIN cases (67%) were concurrently positive for the 4 tubular injury markers. Dendritic cells were identified within the tubulointerstitium in the renal biopsy specimens, interacting with surrounding tubules with light-chain deposits and inflammatory cells.

CONCLUSIONS.—

Significant proximal tubular injury occurs associated with LC-ATIN, and the monoclonal light chains accumulated in proximal tubular cells contribute to the injury. Dendritic cells are involved in the pathogenesis of interstitial inflammation in LC-ATIN.

New developments in the diagnosis of fibrillary glomerulonephritis

Fibrillary glomerulonephritis is a glomerular disease historically defined by glomerular deposition of Congo red-negative, randomly oriented straight fibrils that lack a hollow center and stain with antisera to immunoglobulins. It was initially considered to be an idiopathic disease, but recent studies highlighted association in some cases with autoimmune disease, malignant neoplasm, or hepatitis C viral infection. Prognosis is poor with nearly half of patients progressing to end-stage renal disease within 4 years. There is currently no effective therapy, aside from kidney transplantation, which is associated with disease recurrence in a third of cases. The diagnosis has been hampered by the lack of biomarkers for the disease and the necessity of electron microscopy for diagnosis, which is not widely available. Recently, through the use of laser microdissection-assisted liquid chromatography-tandem mass spectrometry, a novel biomarker of fibrillary glomerulonephritis, DnaJ homolog subfamily B member 9, has been identified. Immunohistochemical studies confirmed the high sensitivity and specificity of DnaJ homolog subfamily B member 9 for this disease; dual immunofluorescence showed its colocalization with IgG in glomeruli; and immunoelectron microscopy revealed its localization to individual fibrils of fibrillary glomerulonephritis. The identification of this tissue biomarker has already entered clinical practice and undoubtingly will improve the diagnosis of this rare disease, particularly in developing countries where electron microscopy is less available. Future research is needed to determine whether DnaJ homolog subfamily B member 9 is an autoantigen or just an associated protein in fibrillary glomerulonephritis, whether it can serve as a noninvasive biomarker, and whether therapies that target this protein are effective in improving prognosis.

Clinicopathological spectrum of renal parenchymal involvement in B-cell lymphoproliferative disorders

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.

Monoclonal gammopathy of renal significance: clinical manifestation, pathogenic characteristic and treatment

Monoclonal gammopathy of renal significance (MGRS) is a group of renal disorders caused by a monoclonal immunoglobulin (MIg) secreted by a dangerous plasmatic/B-cell clone hyperplasia through MIg deposition or dysfunction of complement pathway, with increasing risk of progress to end stage renal disease (ESRD) and the underlying hematologic malignancy. The combination of renal biopsy, complete laboratory examination and bone marrow biopsy is an indispensable diagnostic tool for MGRS to identify accurately and unequivocally the pathogenic monoclonal MIg and provide guidance to treatment. Treatment of MGRS is composed of conventional therapy, chemotherapy, and stem cell transplantation to target the underlying clone and eliminate the noxious MIg on the basis of clinical data of some retrospective studies and a small amount of prospective trial. In addition, it is worthwhile point out assessment of therapeutic effect is significantly relevant for renal and overall prognosis. Thus, by comprehensively analyzing the clinical manifestations and pathogenic characteristic of MGRS, early recognition and prompt treatment can improve the prognosis and prevent post-translation recurrence with multidisciplinary cooperation.

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

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

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

Background

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

Case presentation

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

Conclusions

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

Randall-type monoclonal immunoglobulin deposition disease: novel insights from a nationwide cohort study

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.

A case report of crystalline light chain inclusion-associated kidney disease affecting podocytes but without Fanconi syndrome: A clonal analysis of pathological monoclonal light chain

RATIONALE

Crystalline light chain inclusion-associated kidney disease affects mainly tubular epithelial cells and is often clinically manifested as Fanconi syndrome. However, only very few case reports about the crystalline deposits within the podocytes are available, and the nature of the pathogenic monoclonal light chain implicated in these cases is still unknown. We report a case of crystalline inclusion-associated kidney disease manifested as crystalline podocytopathy in which we identified the complete structure of the pathogenic monoclonal light chain as belonging to the germ-line gene of Vκ1-39.

PATIENT CONCERNS

We describe a 65-year-old woman with crystalline light chain inclusion-associated kidney disease showing mild proteinuria and renal insufficiency with monoclonal gammopathy of undetermined significance without Fanconi syndrome. She had crystalline inclusions mainly within podocytes, tubular epithelial cells and histiocytes in the kidney. Light microscopy showed vacuolation of podocytes and tubular epithelial cells, while eosin negative pale needle-like crystals were present within these cells. Electron microscopy showed accumulation of club-like crystals with high electron density in podocytes, proximal tubular epithelial cells and interstitial histiocytes. Clonal analysis revealed that a pathogenic monoclonal light chain was derived from germline gene, Vκ1-39.

DIAGNOSES

The diagnosis of crystalline light chain inclusion-associated kidney disease was made.

INTERVENTIONS AND OUTCOMES

Bortezomib and dexamethasone were started and her renal function improved to eGFR 36 mL/min/1.73 m after 9 courses of therapy.

LESSONS

Patients with light chain crystalline podocytopathy may have a similar pathogenic monoclonal light chain derived from the same germline gene, Vκ1-39, to that of patients with light chain proximal tubulopathy.

KIDNEY DISEASE ASSOCIATED WITH MONOCLONAL GAMMOPATHIES: SINGLE-CENTER STUDY

INTRODUCTION:Renal injury associated with monoclonal gammopathies (MG) is an area of interest of practical onconephrology. Prevalence, spectrum and renal outcome as far as approaches to treatment in this pathological entity, particularly in Russian population, still remain unclear and need refinement. AIM: Analysis of the prevalence, spectrum, treatment approaches and renal outcome in kidney injury associated with monoclonal gammopathies (MG).

PATIENTS AND METHODS:Patients with MG and renal injury proven by kidney biopsies from 01.01.2011 till 01.05.2018 were enrolled into this one-center prospective study (n=119). Cases of MG of undetermined significance and non-amyloid kidney lesions were estimated as MG of renal significance (MGRS). Treatment approaches, haematological and renal responses were analysed. Worsening of kidney function was estimated as eGFR decrease >25 % from initial value or initiation of renal replacement treatment (RRT), improving – as eGFR increase >25 % from the initial value or the discontinuation of RRT. Other cases were determined as stable kidney function. Kidney outcome was determined in RRT initiation or eGFR<15 ml/min/1,73m2 at the end of follow-up. Long-term kidney outcome was estimated by Kaplan-Meier survival analysis. The median follow-up period was 12 (2; 27) months.

RESULTS.Prevalence of kidney injury associated with MG among all performed kidney biopsies was 7,5 %, MGRS – 0,94 %. Multiple myeloma (MM), AL-amyloidosis and lymphoproliferative disorder (LPD) were diagnosed in 39, 55 and 10 patients, respectively. Prevalence of kidney injury types was the following: Al-amyloidosis (53 %); cast nephropathy (12 %); light chain deposition disease (12 %); C3-glomerulopathy (3 %); proliferative glomerulonephritis (GN) with monoclonal immunoglobulin deposits (3 %); cryoglobulinemic GN (2 %); thrombotic microangiopathy (2 %); podocytopathy (2 %); acute tubular necrosis – 2 %; immunotactoid GN (1 %); fibrillary GN (1 %); proximal tubulopathy (1 %), combination of different types (6 %). Patients mostly were treated with bortezomib and dexamethasone. Autologous stem cell transplantation was performed in 13 patients. Haematological response was achieved in 48,8 %, 45,4 % and 46,7 % of patients with MM, AL-amyloidosis and MGRS, respectively. Worsening of kidney function was registered in 11,1 % of MM and in 37,2 % of AL-amyloidosis; improving or stable kidney function was in 88,9 % and 62,7 % MM and AL-amyloidosis patients, respectively. In MGRS improving (20 %) and stable kidney function (80 %) were detected. Four-years cumulative renal survival in MM, AL-amyloidosis, MGRS and LPD groups was 63 %, 54 %, 80 % and 39 %, respectively, and does not differ between 4 groups.

CONCLUSION:MG-associated kidney disease represented by diverse clinical and morphological patterns is standard problem in routine clinical practice. It is associated with inferior renal outcome and requires a practical implementation of highly-specialized interdisciplinary approach to diagnostics and treatment.

Monoclonal gammopathies of unknown significance and smoldering myeloma: Assessment and management of the elderly patients

Monoclonal gammopathy of unknown significance (MGUS) is the most frequent plasma cell disorder that commonly affects elderly patients. Although it is an asymptomatic condition, as well as smoldering myeloma (SMM), the risk of progression to multiple myeloma requiring therapy or other B-cell disorders varies greatly for individual patients, remaining low for MGUS (1% per year), while higher and not uniform for SMM patients (10% per year). This scenario implies some special considerations regarding assessment and follow-up, especially in the elderly. In this review, we provide the updated diagnostic criteria of monoclonal gammopathies proposed by the International Myeloma Working Group (IMGW); the current recommendations for the assessment of asymptomatic plasma cell disorders, with some concerns about the need of geriatric evaluation in the elderly population, the importance of distinguishing myeloma-related symptomatology from signs or symptoms caused by multiple chronic conditions typically found in the elderly. Finally, the identification of predictor markers of progression has enabled a proposal of risk-adapted follow-up strategies in MGUS and SMM that should be implemented in clinical practice. Although the standard of care is observation for MGUS and SMM patients as well, a recent randomized trial targeting high-risk SMM showed the clinical benefit of early intervention. The change of the treatment paradigm is also very promising and feasible for elderly patients, as long as a comprehensive geriatric assessment is conducted to optimize early treatment and reach maximum benefit with minimum toxicity, in other words, to ensure a better quality of life for these patients.

AL amyloidosis with non-amyloid forming monoclonal immunoglobulin deposition; a case mimicking AHL amyloidosis

BACKGROUND

Immunoglobulin heavy-and-light-chain amyloidosis (AHL amyloidosis) is a newly established disease entity where both the immunoglobulin heavy-chain and light-chain compose amyloid fibrils. The immunoglobulins responsible for the amyloid fibrils are generally identified by immunostaining and/or laser microdissection-liquid chromatography-tandem mass spectrometry (LMD-LC-MS/MS). However, both techniques do not biochemically differentiate immunoglobulins that formed amyloid fibrils from non-responsible immunoglobulins.

CASE PRESENTATION

We herein report a case of 67-year-old female patient with renal amyloidosis due to lymphoplasmacytic lymphoma secreting monoclonal immunoglobulin M (IgM)-kappa. Renal immunostaining monotypically positive for IgM-kappa and LMD-LC-MS/MS identification of mu heavy-chain and kappa light-chain were consistent with the diagnosis of AHL amyloidosis. In order to confirm that both the immunoglobulin heavy-chain and light-chain were forming amyloid fibrils, we performed LC-MS/MS of renal amyloid fibrils isolated by the traditional amyloid purification method. The additional LC-MS/MS identified kappa light-chain only without any heavy-chain component. These results were suggestive that amyloid fibrils were composed by kappa light-chain only and that the mu heavy-chain identified by immunostaining and LMD-LC-MS/MS was derived from the non-specific co-deposition of monoclonal IgM-kappa.

CONCLUSION

The case was AL amyloidosis with non-amyloid forming monoclonal immunoglobulin deposition. While immunostaining and LMD-LC-MS/MS are irreplaceable techniques to classify amyloidosis, confident exclusion of the present condition should be required to diagnose AHL amyloidosis.

Monoclonal light chain crystalline podocytopathy and tubulopathy associated with monoclonal gammopathy of renal significance: a case report and literature review

Background

Monoclonal gammopathy of renal significance (MGRS) is a recently defined group of renal diseases caused by monoclonal immunoglobulin secreted by nonmalignant proliferative B cell or plasma cell. Monoclonal immunoglobulin can form different types of structures deposited in renal tissue, including fibrils, granules, microtubules, crystals and casts, and has mostly been reported in multiple myeloma patients. Here we report a rare case with κ light chain crystals in both podocytes and tubular epithelial cells associated with MGRS, which adds more information to the spectrum of MGRS-related renal diseases.

Case presentation

A 53-year old woman presented with albumin–predominant moderate proteinuria and renal failure. She had monoclonal IgGκ in the serum and monoclonal IgGκ plus free κ in the urine. Multiple myeloma and lymphoproliferative disorders were excluded. Renal biopsy confirmed κ-restricted crystal-storing renal disease involving the podocytes and proximal tubular epithelial cells. The patient was treated with bortezomib followed by lenalidomide-based chemotherapy, and renal function was stable after 1 year of follow-up.

Conclusions

This is a rare case of combined crystalline podocytopathy and tubulopathy associated with MGRS, in which diagnosis was dependent on electron and immuno-electron microscopy.

Exploring Protein⁻Protein Interaction in the Study of Hormone-Dependent Cancers

Estrogen receptors promote target gene transcription when they form a dimer, in which two identical (homodimer) or different (heterodimer) proteins are bound to each other. In hormone-dependent cancers, hormone receptor dimerization plays pivotal roles, not only in the pathogenesis or development of the tumors, but also in the development of therapeutic resistance. Protein–protein interactions (PPIs), including dimerization and complex formation, have been also well-known to be required for proteins to exert their functions. The methods which could detect PPIs are genetic engineering (i.e., resonance energy transfer) and/or antibody technology (i.e., co-immunoprecipitation) using cultured cells. In addition, visualization of the target proteins in tissues can be performed using antigen–antibody reactions, as in immunohistochemistry. Furthermore, development of microscopic techniques (i.e., electron microscopy and confocal laser microscopy) has made it possible to visualize intracellular and/or intranuclear organelles. We have recently reported the visualization of estrogen receptor dimers in breast cancer tissues by using the in situ proximity ligation assay (PLA). PLA was developed along the lines of antibody technology development, and this assay has made it possible to visualize PPIs in archival tissue specimens. Localization of PPI in organelles has also become possible using super-resolution microscopes exceeding the resolution limit of conventional microscopes. Therefore, in this review, we summarize the methodologies used for studying PPIs in both cells and tissues, and review the recently reported studies on PPIs of hormones.

Monoclonal gammopathy of clinical significance: a novel concept with therapeutic implications

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.

GFR estimation in lenalidomide treatment of multiple myeloma patients: a prospective cohort study

BACKGROUND

The estimated glomerular filtration rate (eGFR) is clinically used to approximate renal function and adapt drug dosage. Multiple myeloma is a hematological disease; its prognosis is largely influenced by renal function. We evaluated two commonly used GFR estimations, CKD-EPI and MDRD (CKD Epidemiology Collaboration; Modification of Diet in Renal Disease) in myeloma patients undergoing treatment with lenalidomide, a renally excreted immunomodulatory drug.

METHODS

We prospectively studied 130 myeloma patients receiving lenalidomide treatment at our institution. At baseline and after 3 months, GFR estimations were performed based on the CKD-EPI and MDRD equations. We compared eGFR-dependent CKD staging and lenalidomide dosage assignments.

RESULTS

Initially, most patients were classified as CKD stage I/II, using both equations. Comparison of baseline renal function via CKD-EPI and MDRD induced concordance of CKD staging in 83% of patients, while CKD-EPI improved CKD staging in 16% of patients (p = 0.11). CKD-EPI assigned 3% of patients to higher lenalidomide dosing as opposed to MDRD. Both equations showed improved eGFR after 3 months of lenalidomide treatment.

CONCLUSIONS

In our multiple myeloma patient cohort, CKD-EPI and MDRD led to similar CKD staging with minor differences in lenalidomide dosage assignment. Consistent with previous studies, eGFR improved under lenalidomide treatment. To standardize GFR estimation in myeloma patients, we suggest using the CKD-EPI equation.

Proliferative glomerulonephritis with unusual microlamellar organized deposits related to monoclonal immunoglobulin G3 (IgG3) kappa

A 71-year-old woman presented with massive proteinuria and microhematuria. Renal biopsy showed diffuse global membranoproliferative and endocapillary proliferative lesions with leukocytic infiltration and an irregular duplication of the glomerular basement membrane on light microscopy. Immunofluorescence study showed granular deposits of monoclonal immunoglobulin G3 (IgG3) kappa, C3, and C1q in the glomeruli. Electron microscopy revealed unique structurally organized microlamellar electron-dense deposits. There was no evidence of systemic diseases such as paraproteinemia, cryoglobulinemia, or systemic lupus erythematosus. Following renal biopsy, the oral administration of mizoribine in addition to predonisolone gradually improved the patient's clinical status. So far, partial remission has continued for a year, and she has not been affected with hematopoietic or lymphoproliferative disorders. We report a case of proliferative glomerulonephritis with unusual microlamellar organized deposits related to monoclonal IgG3 kappa. Our case was immunologically identical to proliferative glomerulonephritis with monoclonal IgG deposits (PGNMID). Therefore, we concluded that our case should be categorized as an atypical form of PGNMID, though it was difficult to diagnose using the usual diagnostic approach to glomerular diseases with organized deposits.

Paraffin Immunofluorescence: A Valuable Ancillary Technique in Renal Pathology

Immunofluorescence on frozen tissue is the gold standard immunohistochemical technique for evaluation of immune deposits in the kidney. When frozen tissue is not available or lacks glomeruli, immunofluorescence can be performed on paraffin tissue after antigen retrieval (paraffin immunofluorescence). Excellent results can be obtained by paraffin immunofluorescence in most immune complex-mediated glomerulonephritides and dysproteinemia-associated kidney lesions, and thus this technique has become a valuable salvage technique in renal pathology. Furthermore, new data have emerged suggesting that paraffin immunofluorescence can be used as an unmasking technique, as it is more sensitive than frozen tissue immunofluorescence in some kidney lesions, such as crystalline light chain proximal tubulopathy and is needed to establish the diagnosis of certain unique lesions, such as membranous-like glomerulopathy with masked IgG kappa deposits and membranoproliferative glomerulonephritis with masked monotypic Ig deposits. However, it is important to recognize and be aware of the limitations and pitfalls associated with paraffin immunofluorescence. These include poor sensitivity for detection of C3 deposits and for the diagnosis of primary membranous nephropathy. Here, we summarize the available techniques of paraffin immunofluorescence, review its role and performance as a salvage and unmasking technique in renal pathology, address its limitations and pitfalls, and highlight unusual forms of glomerulopathy that require paraffin immunofluorescence for diagnosis.

Monoclonal Gammopathy of Renal Significance Presenting as Cryoglobulinemic Glomerulonephritis: A Case Report and Review of Literature

Monoclonal gammopathy of renal significance (MGRS) can present with myriad of morphological features. We report a case of MGRS in a 46-year-old man who presented with nephrotic-range proteinuria and renal insufficiency. Renal biopsy showed amorphous eosinophilic periodic acid–Schiff positive deposits in capillary loops and lamda light chain positivity on immunofluorescence, suggestive of cyoglobulinemic glomerulonephritis. Serum cryoglobulins were positive. Serum immunoelectrophoresis and immunofixation showed a M band of 0.5 g/dl of IgG lambda type. Bone marrow showed 8% of plasma cells which confirmed the diagnosis of MGRS.

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

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

A case of immunotactoid glomerulopathy with false-negative IgG staining

BACKGROUND

Immunotactoid glomerulopathy (ITG) is a rare glomerulonephritis characterized by microtubular deposits. Immunofluorescence findings are necessary to differentiate ITG from other proliferative glomerular diseases. The characteristic tubular structure on electron microscopy is essential for a definitive diagnosis, and the diameter of the structure has been traditionally used for differentiating between ITG and other types of glomerulonephritis with organized deposits. In recent years, the disease concept of monoclonal gammopathy of renal significance, which is associated with M protein produced by plasma cell tumors, has been proposed.

CASE PRESENTATION

This was a peculiar case of ITG with underlying monoclonal gammopathy in which IgG showed a false-negative result with immunofluorescence using frozen sections. Additional examinations using a different clone of the anti-IgG antibody revealed typical IgG staining. C4d was strongly positive, consistent with immune complex type glomerulonephritis.

CONCLUSIONS

This case highlights unusual features of ITG, and provides a practical hint to avoid a diagnostic pitfall.

C3 glomerulonephritis associated with monoclonal gammopathy of renal significance: case report

Background

Morbidity associated with monoclonal gammopathy of renal significance is high due to the severe renal lesions and the associated systemic alterations. Accordingly, early diagnosis is fundamental, as is stopping the clonal production of immunoglobulins using specific chemotherapy.

Case presentation

A 75-year-old man with chronic renal disease of unknown origin since 2010 experienced rapid worsening of renal function over a period of 6 mos. Bone marrow biopsy showed monoclonal gammopathy of undetermined significance. Kidney biopsy showed the presence of C3 glomerulonephritis, with exclusive deposits of C3 visible on immunofluorescence and a membranoproliferative pattern on light microscopy. Skin biopsy showed endothelial deposition of complement. Given both the renal and cutaneous involvement the patient was considered to have monoclonal gammopathy of renal significance. We considered an underlying pathogenic mechanism for the renal alteration secondary to activation of the alternative complement pathway by the anomalous immunoglobulin. Despite treatment with plasmapheresis, bortezomib and steroids, advanced chronic kidney disease developed.

Conclusions

The possible underlying cause of the monoclonal gammopathy of renal significance suggests that monoclonal gammopathy should be considered in adult patients with membranoproliferative glomerulonephritis.

[Chronic lymphoid leukemia and renal complication: Report on 10 cases from Marseille over 16 years]

INTRODUCTION

Chronic lymphoid leukemia (CLL) is a hematological malignant disease, associated with a clonal B cell proliferation. The incidence is 4400 new cases per year in France. The prevalence increases with age with a median age at diagnostic of 65 years. Renal involvement is rare and estimated at 1.2% of patients with CLL. Renal pathological diagnoses associated with CLL are variable and are not always related to the hematological disease. We report here on cases of patients with CLL who underwent a renal biopsy over the past 16 years in Marseille.

METHODS

All cases of renal biopsies performed in patients with CLL between2000 and 2016 in Marseille were included. Pathological analysis was performed by the same experimented pathologist. Data were collected at the time of biopsy and after treatment.

RESULTS

Ten patients were included in this study. The reason for renal biopsy was acute kidney injury or the onset of nephrotic syndrome. We report on 4 cases of membranous nephropathy, 1 minimal change disease, 1 cryglobulinemia-related membrano-proliferative glomerulonephritis, 1 light chain amyloidosis, 1 fibrillary glomerulonephritis, 1 interstitial monoclonal infiltration and one case of non-specific tubular lesions. Only one patient was treated before the biopsy, 7 patients received a specific hematological treatment of CLL because of its renal involvement. Renal and hematological responses were variable.

CONCLUSION

Renal involvement of CLL is rare and is not mentioned in the Binet classification. Yet, it can be severe, with acute kidney injury or nephrotic syndrome, and can lead to the initiation of a specific treatment. The most frequent presentation this series was secondary MN, which differs from previous series.

Frequent premature atrial complexes as a predictor of atrial fibrillation: Systematic review and meta-analysis

BACKGROUND

Frequent premature atrial complexes (PACs) are associated with higher morbidity and mortality. Recent studies suggest that frequent PACs are associated with new onset atrial fibrillation (AF). However, a systematic review and meta-analysis of the literature has not been done. We assessed the association between frequent PACs and new onset AF by a systematic review and a meta-analysis.

METHODS

We comprehensively searched the databases of MEDLINE and EMBASE from inception to September 2017. Included studies were published cohort (prospective or retrospective) that compared new onset AF among patients with and without frequent PACs documented by Holter monitoring or 12-lead electrocardiogram. Data from each study were combined using the random-effects, generic inverse variance method of DerSimonian and Laird to calculate risk ratios and 95% confidence intervals.

RESULTS

Twelve studies from 2009 to 2017 were included in this meta-analysis involving 109,689 subjects (9217frequent and 100,472 non-frequent PACs). Frequent PACs were associated with increased risk of new onset AF (pooled risk ratio = 2.76, 95% confidence interval: 2.05-3.73, p < 0.000, I² = 90.6%).

CONCLUSION

Frequent PACs are associated with up to three-fold increased risk of new onset AF. Our study suggests that frequent PACs in general population is an independent predictor of new onset AF.

Myeloma light chain cast nephropathy, a review

Multiple Myeloma is a plasma cell proliferative disorder that commonly involves the kidney. Renal impairment is a serious complication during the course of the disease that is associated with increased morbidity and mortality. Light chain cast nephropathy is the predominant pattern of renal injury in Multiple Myeloma. This review article focuses on the pathophysiology and diagnostic approach of myeloma cast nephropathy. The management of precipitating factors as well as anti-plasma cell treatment modalities in the context of renal impairment are also discussed.

C3 glomerulopathy associated with monoclonal Ig is a distinct subtype

Monoclonal immunoglobulins (MIg) may play a causal role in C3 glomerulopathy (C3G) by impairing regulation of the alternative pathway of complement. Ninety-five patients with C3G were tested for MIg of which 36 were positive. Their mean age at diagnosis was 60 years and among patient 50 years and older, 65.1% had a MIg. At presentation, median serum creatinine and proteinuria were 1.9 mg/dL and 3.0 g/24 hours. Hematuria was present in 32 (88.9%) patients. Twelve (34.3%) patients had low C3 levels. C3 nephritic factor was detected in 45.8% patients; pathogenic variants in complement protein genes were rare. Hematologic evaluation revealed monoclonal gammopathy of renal significance in 26 patients, multiple myeloma in five, smoldering multiple myeloma in two, and chronic lymphocytic leukemia, lymphoma, or type I cryoglobulin each in one patient. After a median follow-up of 43.6 months, the median serum creatinine and proteinuria were 1.4 mg/dL and 0.8g/24 hours. Nine patients developed ESRD. Sixteen patients received MIg-targeted treatment, 17 patients received non-targeted treatment while three patients were managed conservatively. Of the 16 patients receiving MIg-targeted treatment, ten achieved complete/very good/partial hematologic response. Of these, seven achieved a complete/partial/stable renal response. Five patients receiving targeted treatment did not achieve hematologic response, none had a renal response. Patients receiving targeted treatment were more likely to have multiple myeloma/smoldering multiple myeloma. Patients receiving non-targeted treatment were more likely to have monoclonal gammopathy of renal significance. Thus, C3G with MIg is seen in older patients, C3 nephritic factor is the most common autoantibody detected, and MIg-targeted treatment may result in remission and stabilization of kidney function in a subset of these patients.

Favorable effect of bortezomib in dense deposit disease associated with monoclonal gammopathy: a case report

Background

Complement component 3 (C3) glomerulopathy, which includes dense deposit disease (DDD) and C3 glomerulonephritis, is caused by dysregulation of the alternative complement pathway. In most cases, C3 glomerulopathy manifests pathologically with membranoproliferative glomerulonephritis-like features. An association between C3 glomerulopathy and monoclonal gammopathy was recently reported in several cases, raising the possibility that C3 glomerulopathy is the underlying pathological process in monoclonal gammopathy of renal significance.

Case presentation

We herein report a case of monoclonal gammopathy-induced DDD that improved histologically and clinically with chemotherapy including bortezomib. Our case is the first in which treatment response can be linked to the histological response. Potential pathological insights are also discussed.

Conclusions

Rapid and efficient chemotherapy has the potential to limit renal damage in monoclonal gammopathy-associated DDD.

The treatment of paraprotein-related kidney disease

PURPOSE OF REVIEW

Myeloma kidney and amyloid light-chain (AL) amyloidosis remain the principal kidney complications of paraproteins. In this review, we update readers to many of the recent advances which have occurred in the care and outcomes for patients with these presentations.

RECENT FINDINGS

Myeloma kidney has historically caused a severe acute kidney injury with very poor outcomes. The combination of new diagnostic techniques, enabling a rapid diagnosis and novel chemotherapy agents has transformed these poor outcomes for the better. Two multicentre randomized controlled trials have recently evaluated if the removal of free light chains by high cut-off haemodialysis improves renal outcomes beyond effective chemotherapy alone. Although we await the full articles of these studies to be published, abstracts suggested the studies will have contradictory primary results. In the field of AL amyloidosis, there are now novel criteria for the risk stratification of kidney outcomes which can be used in combination with markers of early kidney response to provide clinicians with powerful tools to guide patient discussions.

SUMMARY

Across both AL amyloidosis and myeloma kidney patient outcomes continue to improve. Principally this improvement has been driven by the continuing development of novel chemotherapy agents in this field.

Proliferative glomerulonephritis with monoclonal immunoglobulin G deposits is associated with high rate of early recurrence in the allograft

The characteristics of allograft proliferative glomerulonephritis with monoclonal immunoglobulin G deposits (PGNMID) are not well defined. To better characterize this disease we retrospectively identified 26 patients with allograft PGNMID, including 16 followed with early protocol biopsies. PGNMID was found to be a recurrent disease in most (89%) patients. A diagnostic biopsy was done for proteinuria and/or increased creatinine in most patients. Median time from transplant to diagnostic biopsy was 5.5 months, with detection within three to four months post-transplant in 86% of patients. Mesangial proliferative glomerulonephritis was the most common pattern on the diagnostic biopsy with 89% of cases showing immunoglobulin G3 subtype restriction. A detectable serum paraprotein was present in 20% of patients. During a mean follow up of 87 months from implantation, 11 of 25 patients lost their allograft largely due to PGNMID within a mean of 36 months from diagnosis. Median graft survival was 92 months. Independent predictors of graft loss were a higher degree of peak proteinuria and longer time from implantation to diagnosis. Sixteen patients were treated with immunosuppressive therapy which resulted in over 50% reduction in proteinuria in 60%, and improvement of glomerular pathology in nine of 13 patients. However, 44% of responders subsequently relapsed. Thus, PGNMID has a high recurrence rate in renal allografts occurring early with detection enhanced by protocol biopsies. Graft outcome is guarded as nearly half of patients lose their graft within three years from diagnosis. Hence, there is a need for better treatment strategies for this disease.

The Complexity and Heterogeneity of Monoclonal Immunoglobulin-Associated Renal Diseases

Monoclonal gammopathies are characterized by the overproduction of monoclonal Ig (MIg) detectable in the serum or urine resulting from a clonal proliferation of plasma cells or B lymphocytes. The underlying hematologic conditions range from malignant neoplasms of plasma cells or B lymphocytes, including multiple myeloma and B-cell lymphoproliferative disorders, to nonmalignant small clonal proliferations. The term MGUS implies presence of an MIg in the setting of a "benign" hematologic condition without renal or other end organ damage. The term MGRS was recently introduced to indicate monoclonal gammopathy with MIg-associated renal disease in the absence of hematologic malignancy. Most MIg-associated renal diseases result from the direct deposition of nephrotoxic MIg or its light- or heavy-chain fragments in various renal tissue compartments. Immunofluorescence microscopy is essential to identify the offending MIg and define its tissue distribution. Mass spectrometry is helpful in difficult cases. Conditions caused by direct tissue deposition of MIg include common disorders, such as cast nephropathy, amyloidosis, and MIg deposition diseases, as well as uncommon disorders, such as immunotactoid glomerulopathy, proliferative GN with MIg deposits, light-chain proximal tubulopathy, and the rare entities of crystal-storing histiocytosis and crystalglobulinemia. Indirect mechanisms of MIg-induced renal disease can cause C3 glomerulopathy or thrombotic microangiopathy without tissue MIg deposits. Treatment of MIg-associated renal disease is aimed at eliminating the clonal plasma cell or B-cell population as appropriate. Both the renal and the underlying hematologic disorders influence the management and prognosis of MIg-associated renal diseases.

Proliferative Glomerulonephritis with Monoclonal Immunoglobulin G Lambda Deposits: Report of the First Pediatric Case

Proliferative glomerulonephritis with monoclonal immunoglobulin G deposits (PGNMID) is a recently described, uncommon renal disorder which is considered a monoclonal gammopathy of renal significance. Although some patients will have a detectable monoclonal spike, overt hematologic malignancy is found in only a minority. Most patients with PGNMID are over the age of 50 years, and to our knowledge no cases have been reported in children or adolescents. Renal biopsy shows variable histologic patterns by light microscopy, with membranoproliferative and membranous patterns being most common. Immunofluorescence microscopy demonstrates restriction to a single immunoglobulin G heavy chain isotype and a single light chain subtype. Electron microscopy reveals granular, unorganized deposits. We report a rare pediatric case which occurred in a 17-year-old female. The rarity of this entity in the adult population has not permitted a standard treatment regimen to be established. Our adolescent patient was treated with multiple treatment regimens including prednisone, mycophenolate mofetil, rituximab, bortezomib, and daratumumab. Our case demonstrates that awareness of this disorder by pediatric nephrologists and pathologists is vital to guide accurate disease classification, prognosis, and treatment.

[IgA nephropathy: Unusual forms]

IgA nephropathy can have various initial presentation and evolutive characteristics. In this article, specific forms of IgA nephropathy are described, such as hypertensive emergency, nephrotic syndrome, rapidly progressive glomerulonephritis, monotypic IgA deposits, or IgA nephropathy associated with inflammatory diseases. Identification of these specific forms is needed to better characterize and treat these rare pathologies.

The role of the immune system in kidney disease

The immune system and the kidneys are closely linked. In health the kidneys contribute to immune homeostasis, while components of the immune system mediate many acute forms of renal disease and play a central role in progression of chronic kidney disease. A dysregulated immune system can have either direct or indirect renal effects. Direct immune-mediated kidney diseases are usually a consequence of autoantibodies directed against a constituent renal antigen, such as collagen IV in anti-glomerular basement membrane disease. Indirect immune-mediated renal disease often follows systemic autoimmunity with immune complex formation, but can also be due to uncontrolled activation of the complement pathways. Although the range of mechanisms of immune dysregulation leading to renal disease is broad, the pathways leading to injury are similar. Loss of immune homeostasis in renal disease results in perpetual immune cell recruitment and worsening damage to the kidney. Uncoordinated attempts at tissue repair, after immune-mediated disease or non-immune mediated injury, result in fibrosis of structures important for renal function, leading eventually to kidney failure. As renal disease often manifests clinically only when substantial damage has already occurred, new diagnostic methods and indeed treatments must be identified to inhibit further progression and promote appropriate tissue repair. Studying cases in which immune homeostasis is re-established may reveal new treatment possibilities.

Monoclonal gammopathy in rheumatic diseases

To analyze the clinical spectrum, laboratory characteristics, and outcomes of monoclonal gammopathy (MG) in patients with rheumatic diseases. Screening for the presence of MG was performed in 872 inpatients with rheumatic diseases from January 2010 to July 2017. A total of 41 patients were enrolled. Their clinical and biological features in addition to outcomes were described. For each patient with primary Sjögren syndrome (pSS), 2 age- and sex-matched pSS patients without MG were selected as controls. Risk factors for the presence of MG and malignant hematological neoplasias were assessed. MG was observed in patients with SS, rheumatoid arthritis, systemic lupus erythematosus, ankylosing spondylitis, primary biliary cirrhosis, polymyositis, hypomyopathic dermatomyositis, psoriatic arthritis, ANCA-associated vasculitis, polyarteritis nodosa, and polymyalgia rheumatic, with SS the most frequent type. Serum M protein was detected in 37 patients. The monoclonal bands identified in serum were 16 IgG (5 κ, 11 λ), 11 IgA (6 κ, 5 λ), 6 IgM (5 κ, 1 λ), and 4 free λ chains. M components were observed in urine in the other 4 patients. High ESR, albumin/globulin inversion, rheumatoid factor positivity, hypergammaglobulinemia, and hypocomplementemia were common features, presented in more than half of the 41 patients. Patients with pSS, when complicated with MG, showed a higher rate of abnormal urine NAG (71.4 vs 15.8%, P = 0.025), higher levels of ESR [55.0 (53.5) mm/h vs 21.0 (31.8) mm/h, P = 0.001], ESSDAI [26.0 (25.0) vs 12.0 (9.0), P = 0.006], and ClinESSDAI scores [24.0 (25.0) vs 10.5 (10.0), P = 0.011]. Multivariate analysis revealed that the disease activity, assessed by either ESSDAI [adjusted OR 1.127 (95%CI 1.015-1.251), P = 0.025] or ClinESSDAI [adjusted OR 1.121 (95%CI 1.011-1.242), P = 0.030], was the only independent risk factor for the presence of MG. During the follow-up, 2 patients had transient serum M protein, 2 had isotype switch, 1 progressed to multiple myeloma (MM), and another 2 experienced renal injuries attributed by monoclonal or polyclonal plasma cell interstitial infiltration. Seven (17.1%) of the 41 MG patients presented hematological neoplasias, 4 with MM, 2 with smoldering multiple myeloma, and 1 with B cell lymphoma of mucosa-associated lymphoid tissue (MALT) type. The presence of light-chain MG was associated with the development of MM [OR 17.5 (95%CI 1.551-197.435), P = 0.041], but not with an increased risk of lymphoma or SMM. MG was observed in patients with various rheumatic disorders, with SS being the most common type. The presence of MG might be associated with higher disease activity. The development of hematological neoplasias including MM and lymphoma was seen in this setting. Therefore, we recommend the screening for MG and close monitoring for potential malignant transformation in patients with rheumatic diseases as needed.

Proliferative glomerulonephritis with monoclonal immunoglobulin deposits of lambda chains

Increasingly, monoclonal gammopathies of renal significance (MGRS) are being described as unique, distinct disease states. We describe a type of MGRS with proliferative glomerular lesions with monoclonal immunoglobulin deposits of rarely reported IgG2 lambda chains.

Eculizumab reversed severe distal ischemic syndrome and glomerulonephritis with isolated C3 deposits associated with anti-factor H autoantibodies: a case report

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.