HLA-DRB1 and myeloid sarcoma: In MS per se, there is well-documented evidence for a genetic association with MS involving the major histocompatibility complex (MHC), in particular the human leukocyte antigen (HLA) with the strongest risks associating to carriage of the disease-predisposing HLA-DRB1*15:01 class II allele and to non-carriage of the protective HLA-A*02:01 class I allele (3).