C3 and monoclonal gammopathy: Based on the positivity of immunoglobulin (Ig) staining, MGPN now are divided into Ig (+) C3 (+)-MPGN such as infection, autoimmune/rheumatological diseases, or monoclonal gammopathy-mediated GN, and Ig (−) but C3 (+)-MPGN including C3 glomerulonephritis (C3GN) and dense-deposit disease (DDD) (5).