The etiology of HSES is still unknown. It has been reported that cytokine storm may be associated with the progress of acute encephalopathy including HSES [22] [23] [24] as septic shock, and levels of some cytokines were useful markers for HSES [25, 26] . The serum levels of IL-6 and soluble IL-2 receptors were increased in our patients, however, the degree of the increase varied in each patient. These results suggest that the increase in cytokines may be associated with HSES. As septic shock is characterized by severe vascular leakage, this is the reason that large amounts of fluids and/or norepinephrine infusions were needed for the patients in this study.