In addition to HLA-DRB1*15:01, there are other HLA-DRB1 alleles that can also increase MS risk [such as HLA-DRB1*17:03 allele in the Swedish and Canadian MS populations (21)], albeit to a lesser extent, while other HLA-DRB1 alleles, particularly HLA-DRB1*14 can abrogate the risk associated with HLA-DRB1*15 when they are inherited together (22), apparently via functional epistasis. This evidence concerns the gene HLA-DRB1 and myeloid sarcoma.