Conventional MS in Japanese people is, like MS in white people, associated with HLA-DRB1*1501, whereas opticospinal MS is associated with HLA-DPB1*0501.
Our results indicate that OS-MS is a DPB 1*0501-associated subgroup of MS, and that DPB1*0501 is also correlated with risk of conventional MS in Japanese.
The marked differences in the clinical and MRI findings as well as in the immunogenetic backgrounds between the opticospinal multiple sclerosis and Western-type multiple sclerosis together suggest that HLA-DPB1*0501-associated opticospinal multiple sclerosis is a distinct subtype of multiple sclerosis.