Crystalloid glomerulopathy in monoclonal gammopathy of renal significance (MGRS)

Abstract

We report a case of monoclonal gammopathy of renal significance in a 63-year-old man who presented with nephrotic-range proteinuria and renal insufficiency. The kidney biopsy showed a membranoproliferative glomerulonephritis pattern with extensive crystalloid deposits in the glomerular capillary endothelial cells and very few in the tubular epithelial cells. The immunoperoxidase staining showed kappa light chain restriction. Subsequently, the bone marrow showed 6% plasma cells which confirmed the diagnosis of monoclonal gammopathy of renal significance. He responded well to bortezomib treatment with resolution of the nephrotic syndrome and normalization of renal function after 7 months.

An Unusual Case of Lysosomal Paraprotein Accumulation in Glomerular Endothelial Cells

“…5 Vankalakunti et al reported a rare case of monoclonal gammopathy of renal significance, which had similarities with our case; their case presented monoclonal LC inclusions predominantly in the glomerular endothelial cells and showed a good response to bortezomib. 6 However, their case demonstrated heavy proteinuria with renal insufficiency, and their renal biopsy revealed a membranoproliferative glomerulonephritis with crystalloid formation in glomerular endothelial cells, 6 which were different from ours. Although considered an atypical finding in MM, this presentation was considered to be associated with MM in the current patient because the urinary abnormalities improved after the treatment for MM.…”

The Complexity and Heterogeneity of Monoclonal Immunoglobulin–Associated Renal Diseases

“…Both CSH and crystalglobulinemia are most frequently seen in the setting of MM and lymphoproliferative disorders, and they are only rarely seen in MGRS. 48,[50][51][52][53][54][55]…”

“…61 A subset of patients with C3 glomerulopathy have an associated MIg. [62][63][64] MIgs in the setting of C3 glomerulopathy likely act as autoantibodies to complement regulatory proteins, such as factor H or the C3 convertase (i.e., behaving as a C3 nephritic factor), thereby increasing the t 1/2 of the C3 convertase, [52][53][54] resulting in DDD, C3GN, or rarely, atypical hemolytic uremic syndrome. 65 Indeed, in a recent large study, complement evaluation revealed C3 nephritic factor in 45.8% of patients with MIg-associated C3 glomerulopathy, whereas pathogenic variants in complement genes were rare.…”

Light Chain Podocytopathy Mimicking Recurrent Focal Segmental Glomerulosclerosis

“…Crystals are located within the cytoplasm of proximal tubular epithelial cells, although occasional intraluminal crystalline casts can also be seen . Other cell types within the kidney can accumulate light chain crystals including podocytes, endothelial cells, and histiocytes . Light chain podocytopathy is particularly uncommon and was present in only 3 of 46 cases reported by Stokes et al .…”