BTK and myeloid sarcoma: Inhibition of Bruton’s tyrosine kinase (BTK) has been shown to alter B cell activation, decrease phagocytosis, prevent microglial activation, and reduce the secretion of pro-inflammatory cytokines, and the inhibition of microglial activation may promote remyelination (10); since BTK inhibitors may act on both B cells and microglia, use of BTK inhibitors may have benefits in both RMS and progressive MS (10).