All IgM-positive serum samples from MS patients (n = 9) were obtained from individuals with IMD treatment (interferon beta n = 5; dimethyl fumarate n = 2; glatiramer acetate n = 1; teriflunomide n = 1) whereas no specific IgM antibodies in non-treated patients were noted (χ21 = 4.04, p = 0.044). Here, IFNB1 is linked to myeloid sarcoma.