HLA-DRB1 and primary progressive multiple sclerosis: Confronted to MS clinical forms, we remarkably noted that the DRB1*13:03 allele was found only among relapsing–remitting MS (RRMS) patients (6%, p = 0.003), while DQB1*02:01 was significantly associated with RRMS (42.1%) and primary progressive MS (41%, p = 0.001), with an intermediate Expanded Disability Status Scale (EDSS) score, which may indicate a possible link with disease progression and severity.