Although HLA-DRB1*15 is a common susceptibility gene for MS in Caucasians and Japanese, the phenotype frequency of DRB1*15:01 ranges between 45% and 60% in European MS patients (10–30% in the general population) but is only approximately 30% in Japanese patients (16–17% in the general population) [26, 27, 29, 37–39]. This evidence concerns the gene HLA-DRB1 and myeloid sarcoma.