Elevated plasma high-mobility group box 1 protein is a potential marker for neuromyelitis optica

High-mobility group box 1 protein (HMGB1) has cytokine activities and mediates systemic inflammation as well as immune responses. The aim of this study was to determine if plasma HMGB1 level can be used as a marker for neuromyelitis optica (NMO) and to differentiate NMO from multiple sclerosis (MS). We measured plasma levels of HMGB1, tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), and interleukin 17 (IL-17) in 29 patients with NMO and 20 patients with MS at enrollment and at 2years follow-up (at the time of definitive diagnosis) by enzyme-linked immunosorbent assay. Plasma HMGB1 level was significantly greater in the NMO group compared to the MS group (P<0.001). Plasma levels of TNF-α, IFN-γ, and IL-17 were significantly greater in the NMO group compared to the MS group, and HMGB1 level was positively correlated with TNF-α, IFN-γ, and IL-17 levels. Univariate logistic regression analysis showed a significant association of HMGB1 level, and IFN-γ level with NMO diagnosis. Although this study included a limited sample size, we attempted to determine an optimized cutoff point for HMGB1 (≥2 ng/ml), which provided 89.7% sensitivity and 95.0% specificity for the diagnosis of NMO. These results indicate that plasma HMGB1 level might serve as a surrogate marker for NMO disease activity and aid in the differentiation of NMO from MS at the early disease stage.