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Monoclonal immunoglobulin (MIg) related kidney disease with various patterns of damage can present as a renal manifestation of B-cell malignancies and of the non-malignant monoclonal gammopathies, the latter merged under the umbrella of monoclonal gammopathy of renal significance (MGRS). We aimed to compare clinical presentation and pathology patterns of MIg-related kidney damage in B-cell malignancies and in the MGRS setting.
A single center non-interventional retrospective study included 197 patients with pathology-proven MIg-related kidney disease, followed in the nephrology unit 2010-2021. For the purpose of the study we analyzed main diagnosis, clinical presentation, proteinuria, serum albumin and creatinine, need for dialysis at the time of kidney biopsy, and kidney pathology findings.
Study group included 93 (47.7%) males and 104 (52.8%) females, aged from 28 to 82 (mean 59.41±10.44) years. About a half of patients (45.2%) presented with multi-organ damage, while another half (54.8%) had kidney damage only. MGRS sub-group included 168 (85.2%) cases, and B-cell malignancies sub-group - 29 (14.7%) patients. In the MGRS sub-group general weakness, arterial hypotension and nephrotic syndrome were significantly more often than in B-cell malignancies sub-group (p=0.012, p=0.028, and p=0.025 respectively). We did not find significant differences in the mean age, other clinical features and presentation of kidney disease, including need for dialysis, between the sub-groups. Pathology findings included AL amyloidosis, MIg deposition disease (MIDD), proliferative glomerulonephritis with MIg deposits (PGNMID), cryoglobulinemic glomerulonephritis, glomerulonephritis with intracapillary deposition of MIgM, atypical membranous nephropathy, C3 glomerulonephritis, light chain proximal tubulopathy (LCPT) and cast-nephropathy (CN). AL amyloidosis dominated in both sub-groups, and presented almost 2.5 times more often in MGRS than in B-cell malignancies setting (72.6% vs 31.0% respectively). In contrast MIDD was twice more often in B-cell malignancies sub-group than in MGRS (24.1% vs 11.3% respectively), while cast-nephropathy in B-cell malignancies (in cases of multiple myeloma only) was ten times more often than in MGRS (in cases of smoldering myeloma only) (13.8% vs 1.2% respectively). PGNMID was found in MGRS sub-group only. (Figures 1 and 2) Other patterns, including various combinations of two types of damage, ex. AL amyloidosis and MIDD, LCPT and CN, or MIDD and LCPT were rare in both sub-groups.
AL amyloidosis, presenting with general weakness, arterial hypotension and nephrotic syndrome is the most often pattern of MIg-related kidney damage, regardless malignant or non-malignant nature of secreting clone; however, in MGRS setting it is more than twice prevalent than in B-cell malignancies. Cast-nephropathy is ten times more often in multiple myeloma than in smoldering myeloma. MIDD constitutes about a quarter of MIg-related kidney damage in B-cell malignancies, and just one tenth of the MGRS spectrum. In contrast, PGNMID is most typical in the MGRS setting. Other variants, including various combinations of organized and non-organized MIg deposits, are rare both in B-cell malignancies and in MGRS.