Background A 56-year-old man presented to hospital with a 6-month history of recurrent episodes of altered behavior and 'odd' episodes. He had become apathetic and uninterested in his family. He had no relevant past medical or family history. General and physical neurological examinations were unremarkable, as was bedside cognitive testing. Investigations Brain MRI scan, 24-h electroencephalogram, serum and cerebrospinal fluid testing for voltage-gated potassium channel antibodies, blood screening for tumors, CT scans of the chest, abdomen and pelvis, whole-body PET scan, neuropsychological examination, brain F-18-fluorodeoxyglucose-PET scan. Diagnosis Voltage-gated potassium channel antibody-related limbic encephalitis. Management Antiepileptic drugs, immunomodulatory therapy, oral steroids, plasma exchange.