For example, multiple deleterious poison exons have been found in SCN1A, leading to Dravet Syndrome (DRVT [MIM: 607208]), a severe neurodevelopmental disorder marked by epileptic encephalopathies [96, 101, 102]. This evidence concerns the gene SCN1A and encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.