Since another anti-CD20-antibody (rituximab) is EMA- and FDA-approved for the treatment of RA and has shown beneficial treatment results in patients with MS, and ocrelizumab as well as ofatumumab showed beneficial treatment effects in phase III studies, anti-CD20-therapies seem to be a valuable treatment option on people with MS and comorbid RA. Here, MS4A1 is linked to myeloid sarcoma.