We recently reported that the GRP78 autoantibodies in NMO‐IgG were associated with the breakdown of the BBB in NMO.10 The aim of this study was to address the next question; whether BBB‐endothelial cell activation and GRP78 antibodies are correlated with the clinical phenotype and disease activity, and whether it is a clinical marker of the breakdown of the BBB in NMOSD. This evidence concerns the gene HSPA5 and neuromyelitis optica.