In patients with membranous nephropathy (MN) that is accompanied by multi-system damage, impaired renal function, elevated IgG4 levels (absolute or relative value), negative PLA2R, and/or renal interstitial plasma cell infiltration, the possibility of IgG4-related kidney disease (IgG4-RKD) should be carefully assessed. This evidence concerns the gene PLA2R1 and membranous glomerulonephritis.