Background <p>Anti-AK5 encephalitis is a rare, non-paraneoplastic autoimmune disorder, typically characterized by anterograde amnesia as a core clinical manifestation. Although seizures are infrequent in the early disease phase, some patients may develop seizures as the condition progresses.</p> Case presentation <p>We report a rare case of anti–adenylate kinase 5 (AK5) autoimmune encephalitis following surgical resection and radiotherapy for craniopharyngioma. After cranial radiotherapy, the patient exhibited clinical manifestations such as personality changes and a decline in recent memory. However, the diagnosis was not made until several years later when the patient presented with the onset of epilepsy. By that time, imaging already showed abnormal signals and atrophy in the hippocampus.</p> Conclusion <p>This case highlights the distinct clinical features of AK5 encephalitis and raises the potential association between brain radiotherapy and the development of autoimmune inflammation within the central nervous system.</p>