SCN11A encodes Nav1.9, a tetrodotoxin-resistant voltage-gated sodium channel predominantly expressed in nociceptive sensory neurons of dorsal root ganglia and trigeminal ganglia. The channel mediates sodium ion influx in response to membrane voltage changes, enabling neuronal depolarization during action potentials that relay pain signals from peripheral tissues to the central nervous system 1. SCN11A is also involved in rapid brain-derived neurotrophic factor-evoked neuronal depolarization 2. Pathogenic variants in SCN11A cause familial episodic pain syndrome, a childhood-onset neuropathic disorder characterized by severe episodic limb pain; in a Japanese cohort, SCN11A variants accounted for 19.8% of genetically confirmed cases 3. Gain-of-function mutations predominantly cause painful conditions, though a subset produce pain insensitivity, whereas only gain-of-function mutations have been reported in SCN11A 4. SCN11A variants also associate with erythromelalgia and small fiber neuropathy 56. The channel's restricted neuronal expression and critical role in pain signaling make it a therapeutic target; approved analgesics including carbamazepine and cenobamate modulate sodium channel activity to reduce neuropathic pain.