HLA-DRB1 and myeloid sarcoma: For example, human leukocyte antigen (HLA)-DRB1*15:01 is the strongest genetic susceptibility factor for MS in Europeans, while both HLA-DRB1*15:01 and DRB1*04:05, which is a rare allele in Northern Europeans, are frequent susceptibility alleles in Japanese MS patients9–13.