SCN1A and encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy: A different percentage of the mutant allele in brain tissues might explain the different phenotypes, similarly to what has been postulated regarding X-inactivation in female carriers, and as previously described in other epilepsy disorders like SCN1A-related Dravet syndrome (Depienne et al. 2010).