SCN1A and developmental and epileptic encephalopathy: The phenotype of SCN1A variant is a continuous disease spectrum ranging from the mild self-limited and drug-reactive diseases, such as GEFS+, FS, and FS+ to the severe drug-refractory developmental epileptic encephalopathies (DEE), including DS and other rare phenotypes such as myoclonic-atonic epilepsy (MAE), epilepsy of infancy with migrating focal seizures (EIMFS), and early onset SCN1A- related DEE, which have been reported in rare cases (Wallace et al., 2001; Carranza Rojo et al., 2011; Freilich et al., 2011).