Quintile analyses confirmed this pattern, with individuals in the top quintile of the whole-genome EBV DNA positivity PRS showing 43% higher odds of MS compared with the bottom quintile (OR=1.43, 95% CI=1.26–1.61, p<0.0001), an effect entirely attributable to MHC variants (MHC-only Q5 vs Q1: OR=1.45, 95% CI=1.28–1.64, p<0.0001; non-MHC Q5 vs Q1: OR=1.01, 95% CI=0.89–1.14, p=0.91). Here, HLA-C is linked to myeloid sarcoma.