An advanced approach toward an etiology-based diagnosis of this disease arose from the more recent immunofluorescence (IF)-based classification that distinguishes between immune-complex-mediated MPGN (IC-MPGN), with glomerular IgG and C3 deposits, and C3 glomerulopathy (C3G) with predominant C3 deposits (8, 9). Here, C3 is linked to primary membranoproliferative glomerulonephritis.