SCN1B encodes the voltage-gated sodium channel β1 subunit, a multifunctional protein essential for neuronal and cardiac excitability 1. Beyond its canonical role as a sodium channel regulator, SCN1B functions as a cell adhesion molecule stimulating neurite outgrowth and regulating gene transcription through regulated intramembrane proteolysis 1. The protein modulates both sodium and potassium currents with subtype-specific effects on different sodium channel α subunits 1. SCN1B is expressed in both brain and heart, where it interacts with other regulatory proteins like FGF13A and LRRC37B to fine-tune neuronal excitability 2. Biallelic SCN1B pathogenic variants cause developmental and epileptic encephalopathy 52 (DEE52), clinically overlapping Dravet syndrome 1. SCN1B-linked disease mechanisms involve variable loss-of-function effects; the recessive variant SCN1B-c.265C>T produces incomplete loss-of-function with altered sodium channel regulation, distinct from complete null effects 1. Beyond seizures, DEE52 patients exhibit high sudden unexpected death in epilepsy (SUDEP) risk, potentially involving cardiac arrhythmias: patient-derived cardiomyocytes show increased sodium and potassium currents with altered electrophysiology 3. SCN1B variants are also associated with Brugada syndrome, atrial fibrillation, and generalized epilepsy with febrile seizures plus 1 1. Phenotypic severity varies substantially even within families carrying identical variants, influenced by polygenic background 4.