For several of the main disease‐modifying drug makers in the field of MS, slowly expanding PRL and the activity state of microglia/macrophages have become a major focus in their argument underpinning the efficacy of Bruton tyrosine kinase (BTK) inhibitors in MS, a number of which are going to report phase III clinical trial data in the near future [10]. Here, BTK is linked to myeloid sarcoma.