This group of EE etiologically includes channelopathies (e.g., KCNQ2/3, KCNT1, SCN2A), cell signaling disorders including developmental transcription factor and RNA processing disorders (e.g., FOXG1, GNAO1, BRAT1, CDKL5), synaptopathies and synaptic transmission disorders (STXBP1, DNM1, SPTAN1) and mitochondrial disorders (e.g., PDHA1, PDHB, PDHX, POLG1) (11, 71, 75). Here, SCN2A is linked to ethylmalonic encephalopathy.