For all MS patients the content of IgG3 (range 6.8–10.0%; average value 8.2±0.6% or (0.49±0.04)×10−2 mg/ml) and IgG4 (range 1.8–3.5%; average value 2.5±0.4% or (0.15±0.02)×10−2 mg/ml) in CSF was different. Here, IGHG3 is linked to myeloid sarcoma.