SCN1A and encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy: In a study by Xu et al., approximately 10% of variants in the sodium channel gene SCN1A (which cause Dravet syndrome), initially considered de novo, were identified by deep amplicon resequencing to have resulted from either maternal or paternal mosaicism at allele frequencies ranging from 1.1 to 32.6% [62].