IL17A and myeloid sarcoma: Chronic inflammation in MS is driven by production of pro-inflammatory cytokines, such as interferon gamma (IFN γ) and interleukin (IL)-17 by CD4+ T cells [22], which promote the disruption of blood–brain barrier integrity, allowing egress of activated T cells into the central nervous system (CNS), targeting of CNS-resident cells and resulting in demyelination [23].