We evaluated i) the impact of the BTK inhibitor (BTKi) evobrutinib on monocyte markers for activation, costimulation, adhesion and phagocytosis in peripheral blood mononuclear cell (PBMC) cultures from healthy and MS subjects; ii) the therapeutic effects and the action of evobrutinib on myeloid cell phenotype in the experimental autoimmune encephalomyelitis (EAE) model of MS; iii) the contribution of BTK in short-lived vs. long-lived myeloid cells to EAE expression via experiments with double transgenic mice allowing inducible inactivation of BTK in CX3CR1 expressing cells. The gene discussed is BTK; the disease is myeloid sarcoma.