GABBR2 and Epileptic encephalopathy: Previous studies on GABBR2 missense variants have revealed a correlation between the phenotype, such as epileptic encephalopathy vs. Rett-like phenotype without seizures, and the type of the variant (gain or loss-of-function), as well as the severity of the dysfunction (Yoo et al., 2017; Vuillaume et al., 2018; Samanta and Zarate, 2019).