HLA-DRB1 and myeloid sarcoma: In those who developed MS, HLA-DRB1*1501 remained associated with faster increase in WM lesion number [+2.23 lesions/year, 95% CI: (0.72, 3.73), P = 3.9 × 10−3] and greater annualized change in WM lesion volume [+0.30 ml/year, 95% CI: (0.02, 0.58), P = 0.035].