One GWAS study analyzing exclusively NMO genetic risk factors in Caucasians showed an association with the DRB1*03:01–DQA1*05:01/3/5–DQB1*02:01 haplotype and the class I, HLA-B*08:01 and HLA-C*07:01alleles in NMO subgroup positive for the NMO-IgG. Here, HLA-C is linked to neuromyelitis optica.