Analysis of two previous Drosophila knock-in models of SCN1A missense mutations, one causing Dravet syndrome (S1231R) and one causing GEFS+ (K1270T) exhibited alterations in sodium current and firing properties only in animals homozygous for the mutations (Schutte et al., 2016). Here, SCN1A is linked to encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.