Unlike SCN1A, where epilepsy stems almost exclusively from loss-of-function variants that impair channel function, which is caused by deficits in circuit disinhibition and inhibitory interneuron excitability [100–102], the SCN2A gene which encodes Nav1.2 is associated with seizures through both gain-of function and loss-of-function mutations. The gene discussed is SCN2A; the disease is epilepsy.