PLCB1 and early-infantile DEE: Six of the genes contributing to the enriched gene sets in exceptional responders (STXBP1, DNM1, SYNJ1, KCNB1, PLCB1, and CACNA1A) are among a group of genes that have been implicated in early infantile epileptic encephalopathy (EIEE) [25], an extremely debilitating disorder characterized by uncontrollable seizures and severe mental retardation [26].