When comparing HLA-DRB1 allele frequencies in OCB negative and OCB positive MS patients, HLA-DRB1*15 conferred relative protection for OCB negative MS (p-value = 1.28×10−7, OR 0.59, 95% CI 0.48–0.73) and HLA-DRB1*04 increased risk of OCB negative MS compared with OCB positive MS (p-value = 1.46×10−7, OR 1.80, 95% CI = 1.44–2.25) (data not shown). This evidence concerns the gene HLA-DRB1 and myeloid sarcoma.