C3 Glomerulopathy (C3G) and Immune Complex-Mediated Membranoproliferative glomerulonephritis (IC-MPGN) are rare diseases characterized by glomerular deposition of C3 caused by dysregulation of the alternative pathway (AP) of complement. The gene discussed is C3; the disease is immunoglobulin-mediated membranoproliferative glomerulonephritis.