Anti-IFN-β neutralizing antibodies are reported to develop for IFN-β-1a in approximately 5% and for IFN-β-1b in approximately 25% of MS patients [47]; therefore, two to three patients on IFN-β in our cohort may have had anti-IFN-β neutralizing antibodies. This evidence concerns the gene IFNB1 and myeloid sarcoma.