We also found abundance of myeloid activation markers34–36, specifically CHIT1 (chitotriosidase) and TREM2 (triggering receptor expressed on myeloid cells 2), in MS CSF, consistent with prior studies showing enrichment of CHIT1 and TREM2 in CSF of patients with a chronic neuroinflammatory and neurodegenerative disease state37,38. This evidence concerns the gene TREM2 and myeloid sarcoma.