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

Phospholipidosis is a rare disorder which consists of an excessive intracellular accumulation of phospholipids and the appearance of zebra bodies or lamellar bodies when looking at them using electron microscopy. This disease is associated with certain genetic diseases or is secondary to drugs or toxins. Drug-induced phospholipidosis encompasses many types of pharmaceuticals, most notably chloroquine, amiodarone or ciprofloxacin. Clinically and histologically, renal involvement can be highly variable, with the diagnosis not being made until the zebra bodies are seen under an electron microscope. These findings may require genetic testing to discount Fabry disease, as its histological findings are indistinguishable. Most of the chemicals responsible are cationic amphiphilic drugs, and several mechanisms have been hypothesized for the formation of zebra bodies and their pathogenic significance. However, the relationship between drug toxicity and phospholipid accumulation, zebra bodies and organ dysfunction remains enigmatic, as do the renal consequences of drug withdrawal. We present, to our knowledge, the first case report of acute renal injury with a monoclonal gammopathy of renal significance, lesions, and sclerodermiform syndrome, with zebra bodies that were associated with the initiation of a hydroxychloroquine and amiodarone treatment, as an example of drug-induced-phospholipidosis. [ABSTRACT FROM AUTHOR]

Introduction: Monoclonal gammopathy of renal significance (MGRS) disorders are indolent B-cell or plasma cell lymphoproliferative neoplasms which do not meet the hematological criteria for malignancy, however they cause renal dysfunction as a result of production of nephrotoxic monoclonal immunoglobulin (MIg). Objectives: To study the clinical presentation, laboratory features, light microscopy and immunofluorescence (IF) characteristics of all cases of MGRS diagnosed at our hospital over a period of five years. Patients and Methods: A record of all renal biopsies performed at our hospital between 2014-2019 was accessed from the database. Out of 1356 kidney biopsies, 68 had evidence of MIg deposition on immunofluorescence. Only six cases met the criteria of MGRS. Histopathological and immunofluorescence characteristics were studied to classify the lesions as per International Kidney and Monoclonal Gammopathy (IKMG) Research Group classification. Results: All six cases presented with deranged renal function. Four had sub-nephrotic and one had nephrotic range proteinuria. MIg was identified in only one case on serum protein electrophoresis and free light chain assay. Using a conjunction of histomorphology of renal lesions, special stains and immunofluorescence all six cases of MGRS were categorized as per IKMG classification into monoclonal immunoglobulin deposition disease (two cases), AL amyloidosis, light chain cast nephropathy, proliferative glomerulonephritis with monoclonal immunoglobulin deposits (PGNMID) and light chain proximal tubulopathy (LCPT). Conclusion: MGRS presents as renal failure and proteinuria. MIg may not be detected on protein electrophoresis due to low-secretion in serum. A kidney biopsy is essential to study the morphology of renal lesions and identify MIg deposition. [ABSTRACT FROM AUTHOR]

Background Recent studies showed a high prevalence of monoclonal gammopathy (MG) in patients with thrombotic microangiopathy (TMA) aged over 50 years and suggested that complement dysregulation is pivotal for the disease to develop. Here, we studied this premise in seven patients with TMA and coexisting MG. Methods Patients with TMA on kidney biopsy and/or peripheral blood were recruited from the prospective COMPETE cohort (NCT04745195) and Limburg Renal Registry. Patients were screened for complement dysregulation, including genetics/factor H autoantibodies (FHAA) and functional ex vivo testing on microvascular endothelial cells. Results Seven (8%) out of 84 patients with TMA presented with a coexisting MG. MG clustered in patients aged over 50 years (n/N  = 6/32, 19%). C4 and/or C3 levels were low in three patients, while four patients presented with normal complement levels. None of the patients carried rare variants in complement genes. Massive ex vivo C5b9 formation on the endothelium was noted in one patient; purified IgG from this patient caused massive ex vivo C5b9 formation via the alternative pathway of complement activation, pointing to complement dysregulation in the fluid phase. Kidney biopsies from other nephropathies linked to MG rarely exhibited concurrent TMA (n/ N = 1/27, 4%). Conclusions MG clustered in patients with TMA aged over 50 years. TMA and coexisting MG represents a heterogeneous disease spectrum, including a small subset of patients who may present with complement dysregulation. [ABSTRACT FROM AUTHOR]

Introduction: Monoclonal gammopathy of renal significance (MGRS) disorders are indolent B-cell or plasma cell lymphoproliferative neoplasms which do not meet the hematological criteria for malignancy, however they cause renal dysfunction as a result of production of nephrotoxic monoclonal immunoglobulin (MIg). Objectives: To study the clinical presentation, laboratory features, light microscopy and immunofluorescence (IF) characteristics of all cases of MGRS diagnosed at our hospital over a period of five years. Patients and Methods: A record of all renal biopsies performed at our hospital between 2014-2019 was accessed from the database. Out of 1356 kidney biopsies, 68 had evidence of MIg deposition on immunofluorescence. Only six cases met the criteria of MGRS. Histopathological and immunofluorescence characteristics were studied to classify the lesions as per International Kidney and Monoclonal Gammopathy (IKMG) Research Group classification. Results: All six cases presented with deranged renal function. Four had sub-nephrotic and one had nephrotic range proteinuria. MIg was identified in only one case on serum protein electrophoresis and free light chain assay. Using a conjunction of histomorphology of renal lesions, special stains and immunofluorescence all six cases of MGRS were categorized as per IKMG classification into monoclonal immunoglobulin deposition disease (two cases), AL amyloidosis, light chain cast nephropathy, proliferative glomerulonephritis with monoclonal immunoglobulin deposits (PGNMID) and light chain proximal tubulopathy (LCPT). Conclusion: MGRS presents as renal failure and proteinuria. MIg may not be detected on protein electrophoresis due to low-secretion in serum. A kidney biopsy is essential to study the morphology of renal lesions and identify MIg deposition.

Monoclonal gammopathy of renal significance (MGRS) represents a group of disorders, characterized by paraproteinemia which causes renal damage. These disorders never meet the diagnostic criteria for multiple myeloma (MM) or lymphoproliferative disease. Crystal-storing histiocytosis is one of the rarest patterns of MGRS, characterized by an accumulation of light chains of crystals within histiocyte’s cytoplasm, located in bone marrow or other extramedullary sites such as the kidney, cornea, or thyme. A very few cases have been described as immunoglobulin-storing histiocytosis (IgSH) without evidence of crystals. In the recent literature, only 3 cases of IgSH have been described so far, none renal. In all cases, these very peculiar histopathological patterns are associated with lymphoproliferative or plasma cellular disorders. Here, we report a very unusual IgSH pattern in a kidney biopsy, which led to prompt detection and early therapeutic intervention, in a patient with otherwise misdiagnosed MGRS.

In light chain amyloidosis (LA), the massive glomerular and vascular amyloid deposition leading to interstitial fibrosis/tubular atrophy (IFTA) is thought to be responsible for renal failure. The amyloid deposition in the interstitium and the tubular basement membrane (TBM) has received less attention in the study of LA. We, therefore, collected clinical and laboratory data on patients diagnosed with LA in our Nephrology Department and studied amyloid deposition in the TBM. Twelve LA patients were diagnosed by renal biopsy during a seven-year period. In 4 of the 12, amyloid deposition could also be detected in the TBM. In our first case of a patient with diabetes mellitus, non-amyloid fibrils resembling 'diabetic fibrillosis' were also seen by electron microscopy. Despite the double damage, IFTA was negligible, blood vessels were unaffected, and the glomerular deposition was segmental. In the other three cases, significant (>50%) IFTA and a severely reduced estimated glomerular filtration rate were already detected at the time of diagnosis and amyloid deposition was also observed in the blood vessels. These findings indicate the importance of TBM amyloid deposition in the progression of renal disease. This may represent a late-stage presentation of the disease with a heavy LC burden. [ABSTRACT FROM AUTHOR]

Cryoglobulins are immunoglobulins that precipitate at temperatures below 37 °C and dissolve upon reheating. They can induce small-vessel vasculitis with renal involvement. Cryoglobulinemic glomerulonephritis is a rare manifestation that occurs in patients with monoclonal gammopathy, specifically Waldenström's macroglobulinemia. We present the case of a 52-year-old patient with a history of cutaneous vasculitis and hypothyroidism, who presented with generalized edema, moderate anemia, hypercholesterolemia, nephrotic range proteinuria of 12.69 g/day, microhematuria, arterial hypertension, and hypocomplementemia via the classical pathway, without acute kidney injury and with negative serological studies and positive cryoglobulins in the second determination. Serum and urine protein electrophoresis and immunofixation studies showed a monoclonal band of IgM and kappa light chain. Renal biopsy was consistent with cryoglobulinemic glomerulonephritis. In the context of dysproteinemia and cryoglobulinemic glomerulonephritis, bone-marrow aspiration and biopsy were performed, leading to the diagnosis of Waldenström's macroglobulinemia. Monoclonal gammopathies have been described in association with type I cryoglobulinemias. This described association is uncommon, which is why we present this case, along with a review of the literature. [ABSTRACT FROM AUTHOR]

Background Light chain proximal tubulopathy (LCPT) is a rare form of paraprotein-related disease, occurring in two main histopathological forms: crystalline and non-crystalline. The clinicopathological features, treatment strategies and outcomes, especially of the non-crystalline form, are not well described. Methods We conducted a single-centre retrospective case series of 12 LCPT patients, 5 crystalline and 7 non-crystalline, between 2005 and 2021. Results The median age was 69.5 years (range 47–80). Ten patients presented with CKD and significant proteinuria (median estimated glomerular filtration rate of 43.5 ml/min/1.73 m2; urine protein:creatinine ratio 328 mg/mmol). Only six patients had known haematological disease at the time of renal biopsy. Multiple myeloma (MM) was diagnosed in seven patients cases and monoclonal gammopathy of renal significance (MGRS) in five patients. A clone was detected in all cases combining serum/urine electrophoresis and free light chain (LC) assays. Crystalline and non-crystalline variants had similar clinical presentations. For the non-crystalline variant, a diagnosis was reached based on a combination of CKD without another cause, haematological workup, LC restriction on immunofluorescence and abnormalities on electron microscopy (EM). Nine of 12 patients received clone-directed treatment. Patients who achieved haematological response (including all non-crystalline LCPT) had improved renal outcomes over a median follow-up of 79 months. Conclusions The non-crystalline variant may go unrecognised because of its subtle histopathological features and requires EM to distinguish it from 'excessive LC resorption without tubular injury'. Clone-directed treatment with good haematological response improves renal outcomes in both variants but limited data exist in MGRS. Multicentre prospective studies are needed to better define the clinicopathological characteristics associated with poor outcomes and optimize treatment strategies in patients with MGRS. [ABSTRACT FROM AUTHOR]

Background: Monoclonal immunoglobulin deposition disease (MIDD) includes three entities: light chain deposition disease (LCDD), heavy chain deposition disease (HCDD) and light and heavy chain deposition disease (LHCDD). The renal presentation can manifest with varying degrees of proteinuria and/or nephrotic syndrome, microhematuria, and often leads to end-stage renal disease. Given the rarity of LHCDD, therapeutic approaches for this condition remain inconclusive, as clinical trials are limited. Case presentation: We report two male patients with underlying monoclonal gammopathy of renal significance (MGRS) associated with LHCDD lesions. Both cases had non-nephrotic proteinuria, moderately impaired renal function, and normal levels of C3 and C4. Light microscopy of the renal biopsies in both patients did not show lesions of nodular glomerulosclerosis. Immunofluorescence showed a staining pattern with interrupted linear IgA-κ in patient #1 and IgA-λ in patient #2 only along the glomerular basement membrane (GBM). Electron microscopy of patient #1 revealed electrodense deposits in the subendothelial and mesangial areas only along the GBM. Discussion: In this case series, we discuss the clinical, analytical, and histopathological findings of two rare cases of LHCDD. Both patients exhibited IgA monoclonality and were diagnosed with monoclonal gammopathy of undetermined significance (MGUS) by the hematology department at the time of renal biopsy. Treatment with steroids and cytotoxic agents targeting the clone cells responsible for the deposition disease resulted in a favorable renal and hematologic response. [ABSTRACT FROM AUTHOR]

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

Phospholipidosis is a rare disorder which consists of an excessive intracellular accumulation of phospholipids and the appearance of zebra bodies or lamellar bodies when looking at them using electron microscopy. This disease is associated with certain genetic diseases or is secondary to drugs or toxins. Drug-induced phospholipidosis encompasses many types of pharmaceuticals, most notably chloroquine, amiodarone or ciprofloxacin. Clinically and histologically, renal involvement can be highly variable, with the diagnosis not being made until the zebra bodies are seen under an electron microscope. These findings may require genetic testing to discount Fabry disease, as its histological findings are indistinguishable. Most of the chemicals responsible are cationic amphiphilic drugs, and several mechanisms have been hypothesized for the formation of zebra bodies and their pathogenic significance. However, the relationship between drug toxicity and phospholipid accumulation, zebra bodies and organ dysfunction remains enigmatic, as do the renal consequences of drug withdrawal. We present, to our knowledge, the first case report of acute renal injury with a monoclonal gammopathy of renal significance, lesions, and sclerodermiform syndrome, with zebra bodies that were associated with the initiation of a hydroxychloroquine and amiodarone treatment, as an example of drug-induced-phospholipidosis.

AbstractIn light chain amyloidosis (LA), the massive glomerular and vascular amyloid deposition leading to interstitial fibrosis/tubular atrophy (IFTA) is thought to be responsible for renal failure. The amyloid deposition in the interstitium and the tubular basement membrane (TBM) has received less attention in the study of LA. We, therefore, collected clinical and laboratory data on patients diagnosed with LA in our Nephrology Department and studied amyloid deposition in the TBM. Twelve LA patients were diagnosed by renal biopsy during a seven-year period. In 4 of the 12, amyloid deposition could also be detected in the TBM. In our first case of a patient with diabetes mellitus, non-amyloid fibrils resembling ‘diabetic fibrillosis’ were also seen by electron microscopy. Despite the double damage, IFTA was negligible, blood vessels were unaffected, and the glomerular deposition was segmental. In the other three cases, significant (>50%) IFTA and a severely reduced estimated glomerular filtration rate were already detected at the time of diagnosis and amyloid deposition was also observed in the blood vessels. These findings indicate the importance of TBM amyloid deposition in the progression of renal disease. This may represent a late-stage presentation of the disease with a heavy LC burden.

Abstract Due to differences in the protein folding mechanisms, it is exceedingly rare for amyloid light chain (AL) amyloidosis and monoclonal gammopathy of renal significance (MGRS) to coexist. We herein report the first case of concurrent AL amyloidosis and a subclass of MGRS, light chain proximal tubulopathy (LCPT). The 53‐year‐old female was diagnosed with smoldering myeloma immunoglobulin G kappa and AL amyloidosis with deposits in fat and gastrointestinal tissue. The kidney biopsy did not show amyloid deposits but electron microscopy revealed the presence of LCPT with crystal formation in proximal tubular epithelial cells. This case illustrates the complex pathophysiology of protein deposition in monoclonal gammopathies.

Background: The renal biopsy represents a cornerstone in the definition of monoclonal gammopathy of renal significance (MGRS), helping in identifying patients with sub-detectable neoplastic clones (MGUS) that would deserve aggressive chemotherapies. However, the rising complexity of this onco-nephrology field is significantly challenging the daily work of nephrologists and nephropathologists, leading to the formation of ultra-specialized international centers with dedicated personnel/instrumentation and stressing the need for a better understanding of the underlying molecular landscape of these entities. Summary: In this setting, the application of proteomic techniques, some with in situ capabilities (e.g., MALDI-MS imaging), for the investigation of the most challenging MGRS is progressively shedding light on the pathobiology of these diseases, providing new insights in the diagnosis and prognosis of these cases. This transformation is further enhanced by the application of next-generation digital pathology platforms, leading to a significant improvement of the cultural background for physicians thanks to second opinions, database and atlas creation, enhancement of diagnostic reports, with obvious repercussions for patients both in terms of turnaround time and appropriateness. Key Messages: The present review is aimed at bridging the gap between clinical questions (i.e., a better characterization of MGRS) and the molecular landscape of onco-nephrology entities.

Summary: Background and objectives: Monoclonal gammopathy of renal significance (MGRS) includes smoldering B cell or plasma cell clones causing renal disease. Our understanding of MGRS is still evolving and through our study we intend to analyze the spectrum of renal involvement in patients with MGRS in our institution in the last 6 years. Materials and methods: All patients admitted to our hospital with a diagnosis of MGRS from November 2015 to October 2021 were reviewed. It was a retrospective observational study. History, physical examination, and laboratory investigations were meticulously documented. Results: During the 6 year study period, 108 patients with monoclonal gammopathy of unknown significance (MGUS) were diagnosed, with 29 (26.85%) of them developing MGRS. Median age of the patients was 55 years with majority being men. On light microscopy, the most common renal biopsy patterns were AL amyloidosis (11 patients), monoclonal immunoglobulin deposition disease (6 patients) followed by proliferative glomerulonephritis with monoclonal IgG deposits in 5 patients. Conclusions: During the 6 year study period, 108 patients with MGUS were diagnosed, with 29 (26.85%) of them developing MGRS. Serum immunoelectrophoresis was the most sensitive test for paraprotein detection in our study. IgG kappa and IgG lambda were the most common paraprotein patterns on serum immunofixation. On renal biopsy, AL amyloidosis-lambda was the most common, followed by monoclonal immunoglobulin deposition disease and proliferative glomerulonephritis with monoclonal IgG deposition. Serum creatinine and paraprotein measured by the serum-free light chain (SFLC) ratio had a positive correlation (statistically significant). There was no correlation between urine protein creatinine ratio and M protein measured by serum protein electrophoresis (SPEP) or SFLC ratio in MGRS patients. We conclude by saying that in case of suspicion of MGRS, renal biopsy should be considered. [ABSTRACT FROM AUTHOR]

Adult-onset hypophosphatemic osteomalacia is rare and diagnosis is frequently delayed. Fanconi syndrome (FS) due to monoclonal gammopathy is a well-recognized, but rare cause of hypophosphatemia. The relatively young age of patients and normal routine hematological parameters often results in late recognition of this treatable disease entity. Low phosphorus, elevated alkaline phosphatase, mildly impaired renal function and hypokalemia are often the only abnormalities on routine evaluation. We summarize the clinico-pathological features of two cases who initially presented with fractures and proximal myopathy and were subsequently found to have FS secondary to light chain proximal tubulopathy. Atypical features like absence of hypokalemia at presentation and elevated fibroblast growth factor 23 (FGF 23), a marker of oncogenic osteomalacia were noted. Marked clinical improvement and recovery of renal parameters were evident with phosphate supplements and chemotherapy for the plasma cell disorder. FS due to monoclonal gammopathy may present with atypical features and diagnosis may be challenging. [ABSTRACT FROM AUTHOR]

Abstract Background Monoclonal gammopathy of renal significance (MGRS) encompasses a heterogeneous group of kidney diseases in which a monoclonal immunoglobulin secreted by a clone of B cells or plasma cells causes kidney damage without meeting the hematological criteria for malignancy. Among the various forms of involvement, MGRS can manifest as a proximal tubule disorder, such as Fanconi syndrome (FS), characterized by urinary loss of phosphate, glucose, amino acids, uric acid and bicarbonate. Few cases of MGRS have been described in the literature, manifesting as FS and monoclonal production of lambda light chains, almost all of which are secondary to the production of kappa light chains. Case presentation Here we report a clinical case of a 45-year-old Brazilian male, African descent, with proximal weakness of the lower limbs, whose initial assessment showed a urine summary with the presence of proteinuria and glycosuria without hyperglycemia, associated with mild worsening of renal function, hypouricemia, hypocalcemia and phosphaturia. Evolution was characterized by a MGRS manifesting as FS and osteomalacia. Conclusion The diagnosis of MGRS is not always easy, it requires knowledge of the clinical characteristics, diagnostic criteria and prognosis of each case. Therefore, all possible efforts should be made for multidisciplinary diagnosis.

Monoclonal gammopathy of renal significance (MGRS) represents a group of disorders, characterized by paraproteinemia which causes renal damage. These disorders never meet the diagnostic criteria for multiple myeloma (MM) or lymphoproliferative disease. Crystal-storing histiocytosis is one of the rarest patterns of MGRS, characterized by an accumulation of light chains of crystals within histiocyte's cytoplasm, located in bone marrow or other extramedullary sites such as the kidney, cornea, or thyme. A very few cases have been described as immunoglobulin-storing histiocytosis (IgSH) without evidence of crystals. In the recent literature, only 3 cases of IgSH have been described so far, none renal. In all cases, these very peculiar histopathological patterns are associated with lymphoproliferative or plasma cellular disorders. Here, we report a very unusual IgSH pattern in a kidney biopsy, which led to prompt detection and early therapeutic intervention, in a patient with otherwise misdiagnosed MGRS. [ABSTRACT FROM AUTHOR]

Cryoglobulins are immunoglobulins that precipitate at temperatures below 37 °C and dissolve upon reheating. They can induce small-vessel vasculitis with renal involvement. Cryoglobulinemic glomerulonephritis is a rare manifestation that occurs in patients with monoclonal gammopathy, specifically Waldenström’s macroglobulinemia. We present the case of a 52-year-old patient with a history of cutaneous vasculitis and hypothyroidism, who presented with generalized edema, moderate anemia, hypercholesterolemia, nephrotic range proteinuria of 12.69 g/day, microhematuria, arterial hypertension, and hypocomplementemia via the classical pathway, without acute kidney injury and with negative serological studies and positive cryoglobulins in the second determination. Serum and urine protein electrophoresis and immunofixation studies showed a monoclonal band of IgM and kappa light chain. Renal biopsy was consistent with cryoglobulinemic glomerulonephritis. In the context of dysproteinemia and cryoglobulinemic glomerulonephritis, bone-marrow aspiration and biopsy were performed, leading to the diagnosis of Waldenström’s macroglobulinemia. Monoclonal gammopathies have been described in association with type I cryoglobulinemias. This described association is uncommon, which is why we present this case, along with a review of the literature.

Background: Monoclonal immunoglobulin deposition disease (MIDD) includes three entities: light chain deposition disease (LCDD), heavy chain deposition disease (HCDD) and light and heavy chain deposition disease (LHCDD). The renal presentation can manifest with varying degrees of proteinuria and/or nephrotic syndrome, microhematuria, and often leads to end-stage renal disease. Given the rarity of LHCDD, therapeutic approaches for this condition remain inconclusive, as clinical trials are limited. Case presentation: We report two male patients with underlying monoclonal gammopathy of renal significance (MGRS) associated with LHCDD lesions. Both cases had non-nephrotic proteinuria, moderately impaired renal function, and normal levels of C3 and C4. Light microscopy of the renal biopsies in both patients did not show lesions of nodular glomerulosclerosis. Immunofluorescence showed a staining pattern with interrupted linear IgA-κ in patient #1 and IgA-λ in patient #2 only along the glomerular basement membrane (GBM). Electron microscopy of patient #1 revealed electrodense deposits in the subendothelial and mesangial areas only along the GBM. Discussion: In this case series, we discuss the clinical, analytical, and histopathological findings of two rare cases of LHCDD. Both patients exhibited IgA monoclonality and were diagnosed with monoclonal gammopathy of undetermined significance (MGUS) by the hematology department at the time of renal biopsy. Treatment with steroids and cytotoxic agents targeting the clone cells responsible for the deposition disease resulted in a favorable renal and hematologic response.

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 in chronic glomerular disease, altered renal function and albumi­nuria, sometimes in the nephrotic range. Acute nephritic syndrome is rare. Until recently, in the absence of criteria for symptomatic haematological disease, patients with monoclonal Ig-related nephropathies often experienced difficulties in getting appropriate chemotherapy. Noticeable progress in management was achieved with the introduction of the concept of monoclonal gammopathy of renal significance, which distinguishes the situation of nephropathies induced by dangerous small B-cell clones from that of monoclonal gammopathy of undetermined significance (MGUS) that does not feature any end-organ damage. Monoclonal gammapathy of renal significance is not an independent kidney disease, not “chronic glomerulonephritis”, but a condition in which kidney damage is secondary to clonal B-cell proliferation. In other words, MGRS is a precancerous disease combined with chronic kidney disease that requires immediate treatment. 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. However, recent studies indicate that clone-targeted chemotherapy may significantly improve renal outcomes, opening future perspectives for the management of this rare disease.

A toxic monoclonal protein typically results in a single kidney pathology due to the specific biophysical characteristics of monoclonal proteins. Multiple monoclonal protein lesions are rarely reported and often portend a poor prognosis. We present a 57-year-old male who developed rapidly progressive glomerulonephritis after concealed ruptured diverticulitis. A kidney biopsy showed light chain cast nephropathy, light chain proximal tubulopathy, and thrombotic microangiopathy. Laboratories showed IgG kappa with an M-spike of 0.2 g/dl and a kappa light chain of 16 mg/dl. A bone marrow biopsy showed 3% kappa-restricted plasma cells. The dramatic renal presentation despite the minimal hematological burden is suggestive of a highly toxic light chain, which is consistent with monoclonal gammopathy of renal significance (MGRS). Clone-directed therapy and a complement blockade were initiated. The patient remained dialysis-dependent despite a hematological response. This case highlights the importance of considering the toxic properties of monoclonal proteins in causing kidney diseases. Our case is the first report of an MGRS patient with three distinct kidney lesions. Triple monoclonal protein-related kidney lesions are very rare and are usually associated with multiple myeloma. Light chain cast nephropathy (LCCN) is a myeloma-defining event but his light chain (LC) (<50 mg/dl) and plasma cell (<10%) burdens were low which makes this case very unusual. Sepsis-induced low-flow stage and the toxic properties of LC may induce LCCN in this patient. Aggressive therapy is likely needed to eradicate the clone in order to achieve an organ response., Competing Interests: NK is on the Calliditas advisory board. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Alvi, Gallan and Klomjit.)

Objectives: Intracapillary monoclonal IgM deposits disease (ICMDD) has long been considered a hallmark of Waldenström macroglobulinemia (WM) nephropathy. Intracapillary immunoglobulin thrombi are the characteristic features of cryoglobulinemic glomerulonephritis. Here, we reported 4 cases of ICMDD with massive pseudothrombi but without WM or cryoglobulinemia., Methods: We retrospectively analyzed the clinical and pathologic features of patients diagnosed with ICMDD with massive pseudothrombi., Results: A total of 4 patients (2 men and 2 women) aged 62 to 73 years were enrolled in this study. Microscopic hematuria, edema, and renal insufficiency were present in all patients, along with low serum C3 and C4 in 2 patients. Hematologic examination showed abnormal serum free light chain ratios in all patients and high levels of serum IgM in 3 patients. IgM-κ monoclonal band was identified by serum immunofixation electrophoresis in 3 patients. One patient was diagnosed with small B-cell lymphoma by bone marrow aspiration. Renal biopsy specimen showed massive periodic acid-Schiff-positive hyaline thrombi in the glomerular capillary lumens and also less mesangial, subendothelial, and subepithelial deposits on light microscopy. Immunofluorescence indicated positive staining for IgM (++) and κ light chain staining in the glomerular capillary lumens, capillary walls, and mesangium in all patients. By electron microscopy, the glomerular capillary lumens were filled with homogeneous high-electron-dense deposits without substructure. Two patients were treated with prednisone combined with cyclophosphamide, and 2 received plasma cell-targeted chemotherapy. One patient achieved partial renal remission., Conclusions: Intracapillary monoclonal IgM deposits disease is a rare disease and not always related to WM. Most patients have IgM monoclonal immunoglobulinemia; renal biopsy specimens mainly show a large number of pseudothrombi in the glomerular capillary lumens. Cyclophosphamide is effective in some patients., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Society for Clinical Pathology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

C3 glomerulonephritis (C3GN) is rare. It is a proliferative glomerulonephritis resulting from glomerular deposition of complement factors due to dysregulation of the alternative pathway of complement. The association between monoclonal protein production and development of C3GN was described. We report a 74-year-old man with rapid worsening of kidney function and dialysis needed due to C3GN. In this case, serum protein electrophoresis showed no monoclonal spike but serum immunoelectrophoresis showed a lambda light chain monoclonal gammopathy. Once the diagnosis was made, the patient was treated with immunosuppression with complete kidney recovery. This case shows the importance of accurate and prompt diagnosis and appropriate treatment., Competing Interests: There are no conflicts of interest., (© 2024 Indian Journal of Nephrology | Published by Scientific Scholar.)

Rationale & Objective: Light and heavy chain deposition disease (LHCDD) is a rare form of monoclonal immunoglobulin (Ig) deposition disease, and limited clinical data are available characterizing this condition. Here we describe the clinicopathological characteristics and outcomes of LHCDD., Study Design: Case series., Setting & Participants: 13 patients with biopsy-proven LHCDD diagnosed between January 2008 and December 2022 at one of 2 Chinese medical centers., Findings: Among the 13 patients described, 6 were men and 7 were women, with a mean age of 52.6±8.0 years. Patients presented with hypertension (76.9%), anemia (84.6%), increased serum creatinine concentrations (84.6%; median, 1.7mg/dL), proteinuria (100%; average urine protein, 3.0g/24h), nephrotic syndrome (30.8%), and microscopic hematuria (76.9%). Serum immunofixation electrophoresis showed monoclonal Ig for 11 patients (84.6%). Serum free light chain ratios were abnormal in 11 patients (84.6%), and heavy/light chain ratios were abnormal in 9 of 10 patients (90%) with available data. Five patients were diagnosed with multiple myeloma. A histological diagnosis of nodular mesangial sclerosis was made in 10 patients (76.9%). Immunofluorescence demonstrated deposits of IgG subclass in 7 patients (γ-κ, n=4; γ-λ, n=3) and IgA in 5 patients (α-κ, n=2; α-λ, n=3). Six patients underwent IgG subclass staining (γ1, n=3; γ2, n=2; γ3, n=1). The deposits of IgD-κ were confirmed by mass spectrometry in 1 patient. Among 12 patients for whom data were available during a median of 26.5 months, 11 received chemotherapy and 1 received conservative treatment. One patient died, and disease progressed to kidney failure in 3 (25%). Among the 9 patients evaluable for hematological and kidney disease progression, 5 (56%) had a hematologic response and 1 (11%) exhibited improvement in kidney disease., Limitations: Retrospective descriptive study, limited number of patients, urine protein electrophoresis or immunofixation electrophoresis test results missing for most patients., Conclusions: In this case series of LHCDD, light and heavy chain deposition in kidney tissues were most frequent with monoclonal IgG1-κ. Among patients with evaluable data, more than half had a hematologic response, but a kidney response was uncommon., (Copyright © 2024 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.)

Background Glomerulonephritis (GN) with non-Randall-type, non-cryoglobulinaemic monoclonal immunoglobulin G deposits encompasses rare diseases [proliferative GN with non-organized deposits (PGNMID) and immunotactoid GN] that cannot be distinguished without ultrastructural analysis by electron microscopy (EM). Methods Here, we report and analyse the prognosis of 41 EM-proven (PGNMID for 39/41) and 22 non-EM-proven/DNAJB9-negative cases, diagnosed between 2001 and 2019 in 12 French nephrology centres. Results Median (interquartile range) serum creatinine (SCr) at presentation was 150 (92–256) µmol/L. The predominant histological pattern was membranoproliferative GN (79%), with IgG3 (74%) kappa (78%) deposits the most frequently observed. Disease presentation and patient management were similar between EM-proven and non-EM-proven cases. A serum monoclonal spike was detected for 21 patients and 10 had an underlying haematological malignancy. First-line therapy was mixed between clone-targeted therapy (n = 33), corticosteroids (n = 9) and RAAS inhibitors (n = 19). After 6 months, nine patients achieved complete and 23 partial renal recovery. In univariate analysis, renal recovery was associated with baseline SCr (odds ratio 0.70, P = 0.07). After a median follow-up of 52 (35–74) months, 38% of patients had progressed to end-stage kidney disease independently associated with baseline SCr [hazard ratio (HR) 1.41, P = 0.003] and glomerular crescentic proliferation (HR 4.38, P = 0.004). Conclusions Our results confirm that non-cryoglobulinaemic and non-Randall GN with monoclonal IgG deposits are rarely associated with haematological malignancy. The prognosis is uncertain but may be improved by early introduction of a specific therapy. [ABSTRACT FROM AUTHOR]

Background: Monoclonal gammopathy of renal significance (MGRS) encompasses a heterogeneous group of kidney diseases in which a monoclonal immunoglobulin secreted by a clone of B cells or plasma cells causes kidney damage without meeting the hematological criteria for malignancy. Among the various forms of involvement, MGRS can manifest as a proximal tubule disorder, such as Fanconi syndrome (FS), characterized by urinary loss of phosphate, glucose, amino acids, uric acid and bicarbonate. Few cases of MGRS have been described in the literature, manifesting as FS and monoclonal production of lambda light chains, almost all of which are secondary to the production of kappa light chains.Case Presentation: Here we report a clinical case of a 45-year-old Brazilian male, African descent, with proximal weakness of the lower limbs, whose initial assessment showed a urine summary with the presence of proteinuria and glycosuria without hyperglycemia, associated with mild worsening of renal function, hypouricemia, hypocalcemia and phosphaturia. Evolution was characterized by a MGRS manifesting as FS and osteomalacia.Conclusion: The diagnosis of MGRS is not always easy, it requires knowledge of the clinical characteristics, diagnostic criteria and prognosis of each case. Therefore, all possible efforts should be made for multidisciplinary diagnosis. [ABSTRACT FROM AUTHOR]

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

The article discusses the concept of monoclonal renal gammopathy, which combines various renal diseases caused by the deposition of monoclonal immunoglobulin and / or their components in the glomeruli and tubulointerstitium. This nosological group was identified within the group of monoclonal gammopathies of undetermined significance (in 2012). The data on the study of morphological kidney damage associated with monoclonal renal gammopathy are presented. The spectrum of renal diseases in monoclonal renal gammopathy is diverse, and its classification is based on the localization of renal lesions in the glomeruli, tubules, vascular interstitium and stroma, as well as the peculiarity of the deposition of immunoglobulins (organized and unorganized). Kidney biopsy is required in most cases to locate the lesion, assess its severity, and predict patient survival. Diagnostics requires the integration of morphological changes using light microscopy, immunofluorescence, electron microscopy, and in some cases, staining of monoclonal protein for Ig isotypes is used (staining with hematoxylin / eosin, Schiff stain (PAS reaction), Jones stain, Congo Red stain, Masson’s trichromal stain). Early diagnosis and timely prescription of clone-oriented therapy by a hematologist and / or a hematooncologist can stop the progression of the malignant process and kidney malfunction. A nephrologist should monitor the patient, interacting with the hematologist.

Abstract Background This study aimed to analyze the clinicopathological characteristics of patients with paraproteinemia and renal damage. Methods Ninety-six patients from 2014 to 2018 with paraproteinemia and renal damage were enrolled and the clinical data, renal pathology, treatment and prognosis data were collected. Results A total of 96 patients (54 male and 42 female), accounting for 2.7% of all renal biopsies, were enrolled in this study. Among them, 42 were monoclonal gammopathy of renal significance (MGRS), 21 were renal monotypic immunoglobulin alone (renal monoIg), and 19 were monoclonal gammopathy of undetermined significance (MGUS). Individuals with multiple myeloma (MM) accounted for the fewest number of patients (n = 14). In the MGRS group, the main diseases were amyloidosis (n = 25) and cryoglobulinemic glomerulonephritis (n = 7), while in the MM group, the main diseases were cast nephropathy (n = 9) and light chain deposit disease (n = 3). In the MGUS group, it was mainly IgA nephropathy (IgAN, n = 10) and idiopathic membranous nephropathy (n = 5); while in the renal monoIg group, most of the cases were IgAN (n = 19). Chemotherapy was mainly administered to patients in the MM group, while immunosuppression therapy was mostly administered to patients in the renal monoIg group. Most patients with renal monoIg exhibited a major response, followed by the patients with MGUS and MGRS, while most of the patients with MM had a partial response but none had a major response. Approximately more than half (57.1%) of the patients with MM progressed to end-stage renal disease (ESRD), followed by MGRS (33.3%); however, the mortality rate was low in both the MGRS and MM groups. The survival analysis reviewed that serum creatinine, hemoglobin levels, and the serum κ/λ ratio were independent risk factors for ESRD in patients with MGRS. Conclusions The clinicopathological changes in patients with MGRS were between those in patients with MM and MGUS. The treatment for MGRS and MM was more intensive, and the overall mortality rate was low. Both MGUS and renal monoIg alone exhibited slighter clinicopathological features than MGRS and MM, and the treatment was focused mostly on primary renal diseases.

Abstract Background Plasma cell dyscrasias (PCD) are characterized by an abnormal production of intact monoclonal immunoglobulins or parts such as heavy or light chains. In most cases, the monoclonal protein (also termed paraprotein) is produced by a clonal plasma cell population. The production of monoclonal proteins can result in deposits of various types and localization depending on the type, amount, and electrochemical properties of the paraprotein. One histopathologic presentation, albeit rare, are crystalline deposits. They can form in various organs and hence cause a wide spectrum of symptoms. Case presentation A 49-year-old man presented to the emergency department with eyestrain and foreign body sensation after overhead drilling. Examination of the eyes revealed crystalline deposits in the cornea of both eyes. After additional diagnostic testing, deposits were attributed to free light chains. Monoclonal gammopathy of undetermined significance (MGUS) was diagnosed according to serum electrophoresis and immunofixation. Four years later, new onset of proteinuria was detected. A percutaneous biopsy of the kidney showed severe light chain podocytopathy with secondary focal segmental glomerulosclerosis (FSGS) and light chain proximal tubulopathy (LCPT). In these lesions, crystalline deposits identical to the corneal deposits were found in ultrastructural and immunofluorescent analysis. The patient was diagnosed with monoclonal gammopathy of renal significance (MGRS), and a plasma cell directed therapy was initiated. Conclusions PCD can present with a wide array of symptoms and are notoriously difficult to diagnose. Extrarenal manifestations such as crystalline deposits in the cornea are one possible manifestation. The case presented herein emphasizes the notion that extrarenal paraprotein deposits warrant a thorough search for the underlying clonal disease.

Background: Glomerular diseases (GDs) and other renal immunologic diseases are an important cause of morbidity and mortality. Providing a single point of service in collaboration with various specialists at a renal immunology clinic for such patients is not novel, but outcomes have not been reported. Here, we report the short-term outcome of Indian patients attending our clinic. Methods: This single-center prospective cohort study enrolled biopsy-proven immunologically-mediated adults with renal diseases between April 2018 and December 2019, and followed them for six months. The primary end point for the analysis was an incidence of end-stage renal disease (ESRD) or loss of >50% estimated glomerular filtration rate (eGFR) and patient survival at six months. Secondary endpoints were the rate of complete or partial remission, and impact of demographic factors. Results: Ninety two patients underwent renal biopsy for suspected immunological renal diseases. Fourteen (15.2%) cases were excluded for nonimmune etiologies, whereas 78 (84.7%) confirmed cases of immune etiology were included. Most common primary GD (n = 51) (93.5%) was membranous nephropathy (n = 20) (25.6%), whereas lupus nephritis was the most common (n = 8) (29.6%) secondary GD. Overall, 10 (12.8%) patients reached renal endpoint of ESRD or >50% fall in eGFR. Focal segmental glomerulosclerosis (FSGS) (27%) patients had worst renal outcome. Patient survival was 94.8%. Thirty patients (38.4%) achieved complete, whereas 24 each (30.7%) achieved partial remission and remained resistant to disease specific therapies, respectively. Univariate analysis identified hypertension, severity of hypertension, and resistance to achieve proteinuria remission as significantly associated (P < 0.001) factors with poor renal outcome. Conclusions: The present study shows that short term renal outcome of Indian patients with renal immune diseases remains poor. FSGS remains the GD with the worst renal outcome. Hypertension, its severity, failure to achieve proteinuria remission were significantly associated with poor renal outcomes. [ABSTRACT FROM AUTHOR]

Abstract Background Lately, monoclonal gammopathy of renal significance (MGRS) has been defined as a group of renal disorders that are strongly associated with monoclonal protein, including amyloid immunoglobulin light chain (AL) amyloidosis. Amyloid myopathy is rare (1.5% of all patients with amyloidosis) and the prognosis is poor. Furthermore, only approximately 20% of patients with amyloid myopathy are reported to have renal involvement, indicating a lack of data in the literature. Case presentation Here, we report a rare case of MGRS-related AL amyloidosis complicated by amyloid myopathy that presented with muscle weakness in the upper and lower limbs, neck and fingers, and nephrotic syndrome. Blood, urine, and bone marrow examination revealed monoclonal gammopathy of undetermined significance (MGUS) (Bence Jones protein-lambda). Muscle biopsy of the vastus lateralis muscle demonstrated amyloid proteins in the sarcolemma and in the blood vessel walls on Congo red staining, suggesting amyloid myopathy, and tiny inclusions in fibers on modified Gomori trichrome stain. Although we thought they were reminiscent of nemaline bodies, we could not confirm the nature of this structure. Renal biopsy demonstrated amyloid proteins in the mesangial region, part of the capillary walls, and the blood vessel walls on direct fast scarlet staining. As these amyloid proteins were positive for p-component staining and negative for amyloid A staining, β2-microglobulin, and pre-albumin, and as lambda light chains were positive in the mesangial region, we diagnosed the patient with MGRS-related AL amyloidosis. Although he was treated with melphalan and dexamethasone, his symptoms did not improve. Conclusions AL amyloidosis involving the kidneys and muscles has a poor prognosis, and a delayed diagnosis of amyloid myopathy is common because of its rarity and frequent misdiagnosis, which increases organ function deterioration. Therefore, early detection, therapeutic intervention, and careful follow-up are crucial.

Monoclonal gammopathy of renal significance is a relatively new diagnosis that attributes kidney disease to damage caused by a monoclonal protein. There is growing recognition of this disease in patients previously diagnosed with monoclonal gammopathy of undetermined significance, as they increasingly develop clinically significant renal impairment requiring treatment. We outline a case of a patient presenting with worsening renal function, found to have a circulating monoclonal protein and ultimately diagnosed with a subtype of monoclonal gammopathy of renal significance referred to as immunotactoid glomerulopathy. Abbreviations: MGUS: Monoclonal gammopathy of undetermined significance; M-protein: Monoclonal protein; MM: Multiple myeloma; MGRS: Monoclonal gammopathy of renal significance; MGCS: Monoclonal gammopathy of clinical significance; CKD: Chronic kidney disease; C3 and C4: Complement 3 and complement 4, respectively; EF: Ejection fraction; CT: Computed tomography; IgG: Immunoglobulin G; GFR: Glomerular filtration rate; PET: Positron emission tomography; MRI: Magnetic Resonance Imaging.

The kidney is commonly involved in multiple myeloma and other disorders producing monoclonal immunoglobulins. Crystalglobulinemia is a rare condition characterized by spontaneous crystallization and deposition of monoclonal immunoglobulins within the microvasculature of the kidney and other organs, leading to inflammation, ischemia, and end-organ damage. The present case and literature review highlight the clinical spectrum, diagnostic challenges, management, and outcomes of this underrecognized complication of monoclonal gammopathy. Crystalglobulin-associated kidney disease should be suspected in patients with rapidly progressive kidney disease associated with hematuria, proteinuria, extrarenal lesions (ie, skin and joints), and monoclonal gammopathy. Kidney biopsy is critical to the diagnosis, which relies on the identification by ultrastructural analysis of electron-dense crystalline structures composed of a monoclonal immunoglobulin within the kidney microvasculature. Conventional immunofluorescence on frozen tissue frequently fails to detect monoclonal protein deposits, and pronase-based antigen retrieval on paraffin-embedded material or immunoelectron microscopy is required to unmask antigenic epitopes located within crystalline inclusions. Early intervention combining treatment of clonal cell proliferation and plasma exchanges is warranted to reduce the burden of this rare but dramatic complication of monoclonal gammopathy.

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 in chronic glomerular disease, altered renal function and albuminuria, sometimes in the nephrotic range. Acute nephritic syndrome is rare. Until recently, in the absence of criteria for symptomatic haematological disease, patients with monoclonal Ig-related nephropathies often experienced difficulties in getting appropriate chemotherapy. Noticeable progress in management was achieved with the introduction of the concept of monoclonal gammopathy of renal significance, which distinguishes the situation of nephropathies induced by dangerous small B-cell clones from that of monoclonal gammopathy of undetermined significance (MGUS) that does not feature any end-organ damage. Monoclonal gammapathy of renal significance is not an independent kidney disease, not “chronic glomerulonephritis”, but a condition in which kidney damage is secondary to clonal B-cell proliferation. In other words, MGRS is a precancerous disease combined with chronic kidney disease that requires immediate treatment. 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. However, recent studies indicate that clone-targeted chemotherapy may significantly improve renal outcomes, opening future perspectives for the management of this rare disease. [ABSTRACT FROM AUTHOR]

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

Abstract Patients with monoclonal gammopathy of renal significance should be treated with clone‐directed therapy against sources of monoclonal proteins in order to prevent progression to more advanced monoclonal gammopathies and renal failure.

Monoclonal gammopathy of renal significance (MGRS) is a new nosology in modern nephrology and oncohematology. MGRS is defined as kidney injury due to nephrotoxic monoclonal immunoglobulin produced by the B-cell line clone which does not reach the hematological criteria for specific treatment initiation. Monoclonal proteins pathological effects on kidney parenchyma result in irreversible decline of kidney function till the end stage renal disease that in line with the position of International Consensus of hematologists and nephrologists determinates critical necessity for clone specific treatment in patients with MGRS despite the absence of hematological indications for treatment initiation. Main challenge of MGRS in Russian Federation is an inaccessibility of an in-time diagnostic and appropriate treatment for the great majority of patients due to the following reasons: 1) limited knowledge about the MGRS among hematologists and nephrologists; 2) lack of necessary diagnostic resources in most health-care facilities; 3) lack of approved clinical recommendations and medical economic standards for treatment of this pathological entity. Consensus document comprises the opinion of experts leading nephrologists and hematologists of Russian Federation on the problem of MGRS including the incoherence in nosology classification, diagnostics approach and rationale for clone specific treatment. Consensus document is based on conclusions and agreements reached during the conference of leading nephrologists and hematologists of Russia which was held in the framework of symposia Plasma cell dyscrasias and lymphoproliferative diseases: modern approaches to therapy, 1516 of March 2019, Pavlov First Saint Petersburg State Medical University. The present Consensus is intended to define the principal practical steps to resolve the problem of MGRS in Russian Federation that are summarized as final clauses.

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

Abstract Background Cryoglobulins are cold-precipitable immunoglobulins that may cause systemic vasculitis including cryoglobulinaemic glomerulonephritis (CGN). Type 1 cryoglobulins consist of isolated monoclonal immunoglobulin (mIg), whereas mixed cryoglobulins are typically immune complexes comprising either monoclonal (type 2) or polyclonal (type 3) Ig with rheumatoid activity against polyclonal IgG. Only CGN related to type 1 cryoglobulins has been clearly associated with monoclonal gammopathy of undetermined significance (MGUS) using the conventional serum-, urine- or tissue-based methods of paraprotein detection. Case presentation We present four patients with noninfectious mixed (type 2 or 3) CGN and MGUS. Two patients had type 2 cryoglobulinaemia, one had type 3 cryoglobulinaemia, and one lacked definitive typing of the serum cryoprecipitate. The serum monoclonal band was IgM-κ in all four cases. Treatments included corticosteroids, cyclophosphamide, plasma exchange, and rituximab. At median 3.5 years’ follow-up, no patient had developed a haematological malignancy or advanced chronic kidney disease. Other potential causes of mixed cryoglobulinaemia were also present in our cohort, notably primary Sjögren’s syndrome in three cases. Conclusion Our study raises questions regarding the current designation of type 2 CGN as a monoclonal gammopathy of renal significance, and the role of clonally directed therapies for noninfectious mixed CGN outside the setting of haematological malignancy.

The pathogenetic relationship of kidney damage and an aberrant clone of the B-cell line producing nephrotoxic monoclonal immunoglobulin underlies the concept of “monoclonal gammopathy of renal significance” (MGRS). Herein the aberrant clone does not reach the criteria necessary for initiating antitumor therapy according to oncohematological indications. MGRS is a new nosology in modern nephrology and oncohematology. Monoclonal protein’s pathological effects on kidney parenchyma result in irreversible decline of kidney function till the end stage renal disease that in line with the position of International Consensus of hematologists and nephrologists determinates critical necessity for clone specific treatment in patients with MGRS despite the absence of hematological indications for treatment initiation. Main challenge of MGRS in Russian Federation is an inaccessibility of an in-time diagnostic and appropriate treatment for the great majority of patients due to the following reasons: i) limited knowledge about the MGRS among hematologists and nephrologists; ii) lack of necessary diagnostic resources in most health-care facilities; iii) lack of approved clinical recommendations and medical economic standards for treatment of this pathological entity. In order to overcome these limitations, leading oncohematologists and nephrologists of the Russian Federation on behalf of professional communities at the end of 2019 published a conciliation document: “Monoclonal gammopathy of renal significance: Consensus of hematologists and nephrologists of Russia on the establishment of nosology, diagnostic approach and rationale for clone specific treatment”. Consensus document comprises the opinion of experts – leading nephrologists and hematologists of Russian Federation – on the problem of MGRS including the incoherence in nosology classification, diagnostics approach and rationale for clone specific treatment. Consensus document is based on conclusions and agreements reached during the conference of leading nephrologists and hematologists of Russia which was held in the framework of symposia “Plasma cell dyscrasias and lymphoproliferative diseases: modern approaches to therapy”, 15–16 of March 2019, Pavlov First Saint Petersburg State Medical University, Saint Petersburg, Russia. Consensus is intended to define the principal practical steps to resolve the problem of MGRS in Russian Federation that are summarized as final clauses which we present here.