A 68-year-old-male who was diagnosed as having rheumatoid arthritis (RA) 7 years previously was admitted the Chiba Social Insurance Hospital due to general fatigue, spiking fever, and appetite loss. Blood tests showed extremely high levels of C-reactive protein (CRP, 318.5 mg/dL), and hypergammapathy (IgG 3228 mg/dL, IgA 905 mg/dL, IgM 2537 mg/dL) and high titers of rheumatoid factor (RAPA 40960X). He was diagnosed as having RA with vasculitis, according to interstitial pneumonitis, cutaneous nodules and polyneuropathy. Prednisolone (30 mg/day) was prescribed, however, myeloperoxidase-antineutrophil cytoplasmic antibody proved to be positive (86EU) and cyclophosphamide (50 mg/day) was added one week later. Additionally, IgM K-chain M-protein was revealed and the differentiation between auto-immune and hematologic diseases was required for further drug prescriptions. Therefore, double filtration plasmapheresis (DFPP) was initiated weekly. Hematologic diseases were negated and the hypergammapathy was improved. C-reactive protein and MPOANCA decreased to the normal level after three sessions (IgG 1064 mg/dL, IgA 331 mg/dL, IgM 94 mg/dL, CRP 0.04 mg/dL) and the patients symptoms improved. Prednisolone was tapered and he was discharged. It was suggested that the case presented here was quite rare, having an extremely high level of CRP which was successfully managed by DFPP.