C3 and primary membranoproliferative glomerulonephritis: More recently, MPGN has been reclassified into two diseases: immune-complex MPGN (IC-MPGN) and C3 glomerulopathy (C3G) based on immunofluorescence findings in kidney biopsies: predominant or exclusive C3 deposits in C3G and combined immunoglobulins and complement deposits in IC-MPGN [1].