A decreased immune control of EBV could be particularly pronounced in the context of the main genetic risk factor for MS, HLA-DRB1*1501, and both IM as well as elevated EBNA1 specific antibody titers have been shown to interact with HLA-DRB1*1501 for additive MS risk [34,36,72,73]. The gene discussed is HLA-DRB1; the disease is myeloid sarcoma.