Mutations of the CaV1.1 or NaV1.4 channels are associated with hypokalemic periodic paralysis, a neurologic condition presenting with hypotonia and transient intervals of local or generalized paresis or paralysis [44] due to long-lasting membrane depolarization leading to NaV channel inactivation and loss of muscle excitability. The gene discussed is SCN4A; the disease is periodic paralysis.