HLA-DRB1 and myeloid sarcoma: Whilst it is well established that MS is polygenically inherited, specific human leukocyte antigen (HLA) class II alleles, including HLA-DRB1*15:01, HLA-DRB1*13:03, HLA-DRB1*03:01, HLA-DRB1*08:01 and HLA-DQB1*03:02 are associated with increased risk, particularly amongst MS patients and their relatives (5, 10).