In Caucasians, the ethnic group with the highest prevalence of MS, it is particularly the HLA-class II genes, HLA-DRB1*1501, -DRB5*0101, -DQA1*0102, -DQB1*0602, that are associated with MS [3], [4]. The gene discussed is HLA-DRB1; the disease is myeloid sarcoma.