In our study, with a model adjusting by the most significant HLA allele (HLA-DRB1*03:01), the most significant HLA allele was HLA-DRB1:15:01 (OR = 1.79, P = 3.9 × 10−3; OR = 2.08, P = 5.8 × 10−4; OR = 1.96, P = 2.96 × 10−5 for NMO, NMO-IgG+ and NMO-IgG−, respectively) (Table 2). This evidence concerns the gene HLA-DRB1 and neuromyelitis optica.