Developmental and epileptic encephalopathies (DEEs) are a phenotypically and genetically heterogeneous group of severe epilepsy accompanied by intellectual disability. Mutations in the KCNA2 gene have been identified as a potential cause of DEE.1 The KCNA2 gene encodes the Kv1.2 channel, which plays a critical role in the initiation and propagation of action potentials, thereby influencing firing patterns and regulating neuronal excitability.2 KCNA2-DEE has a broad spectrum of diseases, including drug-resistant seizures, cognitive impairment, and ataxia. Encouragingly, treatments for KCNA2-DEE have evolved from traditional anti-epileptic seizure therapies to gene-targeted strategies. 4-Aminopyridine (4-AP), a non-specific inhibitor of voltage-gated potassium channels, was reported to be effective in treating KCNA2-DEE in 2021.3 To date, 9 of 11 patients have benefited from treatment with 4-AP.3 However, further clinical evidence is necessary to determine the generalizability of these effects, particularly in adult patients with a long course beginning in childhood. Here, we report an adult patient with a 30-year history of epileptic encephalopathy beginning in infancy, carrying the KCNA2 gain-of-function variant p.(Arg297Gln), who benefited from treatment with 4-AP.