Recently, an observational study of MS patients suggested that serum 25-hydroxy-vitamin D (25-OH-D) level was associated with a reduced relapse risk only among patients treated with IFN-β [8], while in another patient cohort no association between 25-OH-D and disease activity was detected among IFN-β -treated MS patients [9]. Here, IFNB1 is linked to myeloid sarcoma.