The best evidence for a second HLA-DRB1 risk allele in MS probably lies with HLA-DRB1*03 (DR3) [19],[22],[23], although HLA-DRB1*0103 and HLA-DR4 alleles may also increase disease risk (reviewed in [13]) [19], [24]–[26]. The gene discussed is HLA-DRB1; the disease is myeloid sarcoma.