SCN4A encodes Nav1.4, the pore-forming subunit of voltage-gated sodium channels specifically expressed in skeletal muscle 1. This channel is essential for generating action potentials that initiate muscle contraction by allowing selective passage of Na+ ions across the membrane in response to voltage changes 1. The channel operates through voltage-dependent conformational switching between closed and open states, with structural studies revealing molecular mechanisms underlying Na+ permeation and channel inactivation 1. SCN4A mutations cause a broad spectrum of skeletal muscle channelopathies including periodic paralysis (hyperkalemic, hypokalemic, and normokalemic variants), non-dystrophic myotonias, paramyotonia congenita, and congenital myasthenic syndromes 2345. These disorders typically result from gain-of-function mutations that destabilize muscle fiber resting potential rather than complete loss-of-function 3. Clinically, patients present with episodic muscle weakness, delayed muscle relaxation (myotonia), muscle stiffness, and pain 24. Diagnosis requires electromyography demonstrating myotonic discharges and genetic confirmation 24. Treatment primarily involves sodium channel blockers like mexiletine 24. The significant clinical overlap between different SCN4A-related conditions necessitates comprehensive genetic testing for precise subtype identification and optimal therapeutic management 4.