The available evidence points strongly to the root cause of MS being the overexpression of human endogenous retrovirus W (HERV-W) ENV coding for the syncytin-1 protein consequent to a complex immunological background centered on a past infection with Epstein-Barr virus (EBV) 005B [11,14] ●●●. Here, ERVW-1 is linked to myeloid sarcoma.