Genome-wide association studies have found that loci in the human leukocyte antigen (HLA) region, such as HLA-DRB1 and HLA-DQA1 genes, are associated with both MS risk and elevated anti-EBNA IgG levels.4,5,6 The possibility of confounding is suggested by studies showing that the increased MS risk associated with IM decreased in magnitude7 or became statistically nonsignificant8 after controlling for potential confounders, including genetic ancestry and HLA-DRB1*1501 carrier status. The gene discussed is HLA-DRB1; the disease is myeloid sarcoma.