HLA-DRB1 and neuromyelitis optica: In that population, conventional MS was associated with HLA-DRB1*1501 whereas OSMS/NMO was associated with HLA DPB1*0501.33 Other population studies of HLA in NMO indicate that the DRB1*030134, –36 and DRB1*1037 alleles are associated with increased risk.