The c.5797del variant in SCN1A is a single nucleotide deletion predicted to cause a frameshift at amino acid position 1933 leading to a premature stop codon (p.Arg1933Glufs*3). The variant is located within the last exon and thus predicted to escape nonsense mediated decay. The truncated region is not known to be important for protein function, as missense variants reported in the region do not meet PLP per these criteria. Furthermore, LOF variants within this exon are relatively common in gnomAD v4.1. As such, this variant does not meet criteria to apply PVS1. This variant has been identified in a family in which 2 affected siblings with developmental and epileptic encephalopathy (DEE) harbored the variant, in addition to an unaffected parent and 2 unaffected siblings (LabCorp Genetics, Inc. internal data). Given the severity of the phenotype and presence in multiple unaffected family members, this case was not included as evidence for PS4. The variant is absent from the population database, gnomAD v4.1 (PM2_Supporting). In summary, this variant meets the criteria to be classified as Variant of Uncertain Significance for autosomal dominant SCN1A-related disorder, based on the ACMG/AMP criteria applied, as specified by the ClinGen Epilepsy Sodium Channel VCEP: PM2_Supporting. (version 1.0, approved September 24, 2024).