HMGB1 and Feingold syndrome: Furthermore, a combined analysis of the 6 included studies (including 773 patients with FS and 266 healthy controls) showed that the concentration levels of HMGB1 in the serum of children with FS were higher than that of healthy controls [SMD = 2.37, 95% CI  1.42–3.31; P< 0.001] (Fig. 2).