Interestingly, a previous study demonstrated that MS patients with intrathecal IgG synthesis had a higher risk and shorter time to EDSS worsening during follow-up19 and patients with IRLs ultimately showed more severe clinical disability and a progressive disease course.5, , –8 Of note, some studies also reported that intrathecal IgM synthesis is associated with a more severe disease course,25,26 whereas in this study, intrathecal IgM synthesis did not statistically differ between both groups. This evidence concerns the gene CD40LG and myeloid sarcoma.