HLA-DRB1 allele heterogeneity influences multiple sclerosis severity as well as risk in Western Australia

Susceptibility to multiple sclerosis (MS) has been consistently associated with the Human Leukocyte Antigen (HLA)-DRB11501 genotype, however effects on disease severity and clinical outcome have varied in different populations. We present the results of a high-resolution HLA-DRB1 genotyping and genotype-phenotype correlation study in a large West Australian MS cohort. Our findings indicate that in this population, which is of largely Anglo-Celtic and Northern European origin, HLA-DRB11501 is not only a strong determinant of disease risk but may also be associated with disease severity as measured by the Multiple Sclerosis Severity Score (MSSS), with the MSSS increasing by an estimated 0.51 per DRB11501 allele. We also found evidence that the HLA-DRB11201 allele is associated with less severe disease.