We, and others, have demonstrated that there are differences in the global methylation profiles of immune cell subtypes of cases with MS compared with non-MS controls.4, -, 7 Most differences were observed in CD19+ B cells and monocytes, with less occurring in T cells.4,7, -, 9 Furthermore, there have been distinct differences observed due to treatment, particularly after dimethyl fumarate use in both CD4+ T cells and monocytes.10,11. The gene discussed is CD19; the disease is myeloid sarcoma.