With respect to protective alleles, HLA-DRB1*09:01-positive NMOSD patients had co-existing autoimmune diseases, especially Sjögren syndrome, more frequently than DRB1*09:01-netagive patients (p = 0.030 and 0.034, respectively) (Supplementary Table S13). This evidence concerns the gene HLA-DRB1 and autoimmune disease.