A 65‐year‐old female with a past medical history of monoclonal gammopathy of undetermined significance (MGUS, with IgM Kappa monoclonal protein in Gamma region), type II CG vasculitis (monoclonal IgM and polyclonal IgG positive), and membranoproliferative glomerulonephritis (MPGN) confirmed with biopsy presented with severe fatigue. The gene discussed is CD40LG; the disease is primary membranoproliferative glomerulonephritis.