Among patients harbouring SCN1A LP/P variants, although the largest group was composed of patients with Dravet syndrome followed by those with a GEFS plus phenotype [57,58,59], we also reported on one patient [12] with the recently defined phenotype of neonatal developmental and epileptic encephalopathy with movement disorders and arthrogryposis, associated with gain-of-function SCN1A variants [60]. This evidence concerns the gene SCN1A and encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.