HLA-DRB1 and myeloid sarcoma: More recent genome-wide-association studies (GWASs), which identified several MHC genes and over 100 non-MHC genetic variants/genes associated with MS susceptibility (4) have localized the greatest effect on MS risk to the HLA-DRB1 locus, with the DRB1*15:01 allele within the HLA-DR15 haplotype bearing the strongest association with MS.