An update to the pathogenesis for monoclonal gammopathy of renal significance

Monoclonal gammopathy of renal significance (MGRS) is characterized by the nephrotoxic monoclonal immunoglobulin (MIg) secreted by an otherwise asymptomatic or indolent B-cell or plasma cell clone, without hematologic criteria for treatment. The spectrum of MGRS-associated disorders is wide, including non-organized deposits or inclusions such as C3 glomerulopathy with monoclonal glomerulopathy (MIg-C3G), monoclonal immunoglobulin deposition disease, proliferative glomerulonephritis with monoclonal immunoglobulin deposits and organized deposits like immunoglobulin related amyloidosis, type I and type II cryoglobulinaemic glomerulonephritis, light chain proximal tubulopathy, and so on. Kidney biopsy should be conducted to identify the exact disease associated with MGRS. These MGRS-associated diseases can involve one or more renal compartments, including glomeruli, tubules and vessels. Hydrophobic residues replacement, N-glycosylated, increase in isoelectric point in MIg causes it to transform from soluble form to tissue deposition, causing glomerular damage. Complement deposition is found in MIg-C3G, which is caused by an abnormality of the alternative pathway and may involve multiple factors including complement component 3 nephritic factor, anti-complement factor auto-antibodies or MIg which directly cleaves C3. The effect of transforming growth factor beta and platelet-derived growth factor-β on mesangial extracellular matrix is associated with glomerular and tubular basement membrane thickening, nodular glomerulosclerosis, and interstitial fibrosis. Furthermore, inflammatory factors, growth factors and virus infection may play an important role in the development of the diseases. In this review, for the first time, we discussed current highlights in the mechanism of MGRS-related lesions.