Epidemiological and clinical characteristics and outcome of monoclonal gammopathy of renal significance‐related lesions in Latin America

IgM Variant of Proliferative Glomerulonephritis With Monoclonal Immunoglobulin Deposits: A Case Series

RATIONALE & OBJECTIVE

Most deposits in proliferative glomerulonephritis with monoclonal immunoglobulin deposits (PGNMID) are of the IgG class. The IgM variant (PGNMID-IgM) is very rare, and data are mostly derived from single case reports or cases associated with B-cell lymphoproliferative disorders. We describe the clinicopathologic characteristics and outcomes among cases of PGNMID-IgM.

STUDY DESIGN

Case series.

SETTING & PARTICIPANTS

23 PGNMID-IgM cases identified from kidney pathology archives. PGNMID-IgM was defined by glomerulonephritis with glomerular granular monotypic IgM deposits after excluding cryoglobulinemic glomerulonephritis and intracapillary monoclonal deposits disease.

FINDINGS

Seventy-eight percent of the cases were male, they had a median age of 72 years, and they had presented with proteinuria (median, 3.1g/day), hematuria (91%), and reduced estimated glomerular filtration rate (median serum creatinine, 1.9mg/dL). Hypocomplementemia was present in 31% of cases. The underlying hematologic condition for all cases was monoclonal gammopathy of renal significance (MGRS). Serum protein electrophoresis/serum immunofixation (SPEP/SIF) detected the nephropathic monoclonal immunoglobulin (MIg) in 27% of cases whereas matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) detected the nephropathic IgM in 4 of 7 tested patients. Kidney biopsy revealed membranoproliferative glomerulonephritis (83%) with nonorganized glomerular monotypic IgM (100%) and C3 deposition (96%), but C1q deposition was rare. Seventeen percent received symptomatic treatment alone, 17% received steroids alone, and 65% received other immunosuppressive therapy (mostly rituximab-based therapy). Follow-up (median, 40 months) was available for all patients. The median kidney and patient survivals were 44 and 158 months, respectively. Three patients underwent kidney transplantation, and all had recurrence, in 2 cases within a month.

LIMITATIONS

Small sample size, retrospective design, nonstandardized clinical management.

CONCLUSIONS

PGNMID-IgM mostly affects elderly men and is associated with MGRS with a low detection rate of the circulating nephropathic MIg on SPEP/SIF, which may be improved by MALDI-TOF. Kidney survival is guarded, with a high rate of early recurrence after transplant although overall survival is favorable. The pathogenesis remains unknown, but it likely involves local activation of alternative or lectin pathways of complement system by the monotypic IgM.

PLAIN-LANGUAGE SUMMARY

The IgM variant of proliferative glomerulonephritis with monoclonal immunoglobulin deposits (PGNMID-IgM) is very rare, and data on its clinicopathologic and outcome characteristics are scanty. This study of 23 patients with PGNMID-IgM identified in the Mayo Clinic pathology archives revealed that most patients were elderly White males who presented with proteinuria, hematuria, and reduced kidney function. The underlying hematologic condition was monoclonal gammopathy of renal significance in all cases, and the detection rate of the circulating nephropathic monoclonal immunoglobulin with serum protein electrophoresis/serum immunofixation was low but was increased using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Pathologically, all cases exhibited nonorganized glomerular monotypic IgM, most with a membranoproliferative glomerulonephritis pattern. Outcome analysis revealed a guarded kidney survival (median, 44 months), a high rate of early recurrence after transplant, and favorable patient survival (158 months).

Clinical characteristics of monoclonal immunoglobulin-associated renal disease: a retrospective cohort study

INTRODUCTION

Clinical epidemiological data on monoclonal gammopathy of renal significance (MGRS) are lacking. In this retrospective observational study, MGRS was compared with B-cell or plasma cell malignancies (BCM/PCM) with renal involvement to clarify differences in their clinical features.

METHODS

Among the 1408 renal biopsies performed at our hospital, 25 MGRS and 18 BCM/PCM patients were identified. We investigated baseline characteristics and hematologic parameters of MGRS in reference to BCM/PCM using multivariable analysis. Cox proportional hazards analysis was performed for end-stage kidney disease (ESKD) and all-cause mortality.

RESULTS

Comparing the MGRS with the BCM/PCM, mean differences in creatinine level, estimated glomerular filtration rate, and clonal bone marrow plasma cell percentage were - 2.76 mg/dL, 27.72 mL/min/1.73 m2, and - 18.86%, respectively (all P < 0.001). MGRS group had a predominance of glomerular lesions such as immunoglobulin-associated amyloidosis, cryoglobulinemic GN, and MIDD, and a lower risk of acute kidney injury/acute renal disease compared to BCM/PCM. During a median observation period of 23.7 months, clone-directed therapy was performed in 32.0% of patients in the MGRS group, compared to 83.3% of patients in the BCM/PCM group. Compared with BCM/PCM, MGRS had a hazard ratio of 0.66 (95% confidence interval (CI) 0.23-1.92, P = 0.45) for ESKD and 0.33 (95% CI 0.11-1.03, P = 0.06) for death in multivariate logistic regression analysis.

CONCLUSIONS

The clinical characteristics of MGRS and BCM/PCM with monoclonal immunoglobulin-associated renal disease are disparate. Understanding these differences is crucial for developing tailored clinical approaches and therapeutic strategies to improve patient outcome.

Diagnosis and management of monoclonal gammopathy of renal significance: A British Society for Haematology good practice paper

This guideline provides consensus opinion on the investigations required for people presenting with suspected monoclonal gammopathy of renal significance to both nephrology and haematology physicians. The guideline discusses the principles of treating a patient with MGRS and provides recommendations for both supportive management and haematological therapy. It details the recommended on-going monitoring required for both specialty areas.

[Renal involvement in monoclonal gammopathies]

INTRODUCTION

The kidney is one of the organs most frequently affected by disease processes which produce monoclonal immunoglobins, therefore renal morphological and immunopathological alterations should be clearly recognized.

OBJECTIVE

To describe the pathological features of renal involvement in monoclonal gammopathies.

MATERIAL AND METHODS

A descriptive, retrospective and cross-sectional study of renal biopsies studied in a single center during a period of 14 years was carried out.

RESULTS

102 cases were included, of which 53% were male patients and the median age was 62.5 years (range 34 - 79). 97% of the biopsies were from native kidneys. The most frequent histopathological diagnosis (31.4%) was myeloma kidney, with kappa being the light chain most frequently deposited (65.6% of cases). AL amyloidosis was the second most common (29.4%) where the lambda chain predominated in 86.6%, followed by light chain deposition disease (20.6%) with the predominance of the kappa chain in 66.6%.

CONCLUSIONS

The most frequent renal involvement due to monoclonal gammopathies was myeloma kidney with deposition of kappa light chains, followed by AL lambda amyloidosis; these diseases were found more frequently in patients over 50 years of age.

Monoclonal Gammopathy of Renal Significance (MGRS): Prospects for Treatment in Integrated Chinese and Western Medicine

Monoclonal gammopathy of renal significance (MGRS) is a pathological state which presents with a spectrum of renal lesions. MGRS is characterized by pathogenic monoclonal immunoglobulins or light chains produced by a premalignant plasma cell or B cell clone. In view of inadequate understanding in the past, the low detection rate of MGRS often results in poor outcomes and reduces quality of life of patients. Thus, MGRS stands for a group of clinical refractory renal diseases. To date, no standard treatment strategy for MGRS is available. Current consensus suggests a clone-directed approach that aims to eradicate the offending clone, but its long-term prognosis is not clear. In this article, we discuss the diagnostic methods, highlight treatment advances, and introduce integrated Chinese and Western medicine in the management of MGRS.