Membranoproliferative glomerulonephritis (MPGN) is a pathological diagnosis characterized by mesangial proliferation, thickening of the glomerular basement membrane, and “tram-track” or double-contour appearance of glomerular capillary walls on light microscopy [
1]. Historically, MPGN was divided into three types based on the location of immune deposits on electron microscopy: type I (subendothelial/mesangial), type II (intramembranous or dense deposits), and type III (subepithelial/subendothelial, some variants with mesangial/intramembranous). With increasing use of immunofluorescence in biopsies and a greater understanding of the role of complement in kidney disease, it became apparent that a subset of MPGN biopsies showed predominant C3 staining pattern, highlighting dysregulation of the alternative pathway of complement as the pathogenic cause for a subset of MPGN. From this, a reclassification of MPGN arose, discriminating between C3-predominant and immune-complex-initiated forms of MPGN, with this new category of complement-driven MPGN being termed C3 glomerulopathy (C3G) [
2]. C3G encompasses a group of kidney diseases characterized by predominant deposition of C3 in the glomeruli, with further sub-grouping defined by the location of deposits; either intramembranous for dense deposit disease (DDD) or more widely and variably distributed in C3 glomerulonephritis (C3GN) [
3]. …
