KLB and Dravet syndrome: The serum concentration of FGF21 in the group with DS was significantly greater than that observed in the group with NDS (p = 0.039), while the serum concentrations of β-klotho, mBDNF, and mBDNF/proBDNF were significantly lower (p = 0.041, p = 0.021, and p = 0.029, respectively).