We studied the risk conferred by the different DRB1*03:01-containing haplotypes (AH 18.2, AH 8.1 and non-conserved haplotypes) in relation to MS susceptibility and, specifically, to the presence of intrathecal IgM against myelin lipids restricted to CSF in MS patients. Here, HLA-DRB1 is linked to myeloid sarcoma.