Varley, James

AbstractBackground and purposeDespite it being an immunotherapy‐responsive neurological syndrome, patients with autoimmune encephalitis (AE) frequently exhibit residual neurobehavioural features. Here, we report criminal behaviours as a serious and novel postencephalitic association.MethodsThis retrospective cohort study included 301 AE patients. Five of who committed crimes underwent direct assessments and records review alongside autoantibody studies.ResultsFive of 301 patients (1.7%) with AE exhibited criminal behaviours, which included viewing child pornography (n = 3), repeated shoplifting, and conspiracy to commit murder. All five were adult males, with LGI1 autoantibodies (n = 3), CASPR2 autoantibodies, or seronegative AE. None had evidence of premorbid antisocial personality traits or psychiatric disorders. Criminal behaviours began a median of 18 months (range = 15 months–12 years) after encephalitis onset. At the time of crimes, two patients were immunotherapy‐naïve, three had been administered late immunotherapies (at 5 weeks–4 months), many neurobehavioural features persisted, and new obsessive behaviours had appeared. However, cognition, seizure, and disability measures had improved, alongside reduced autoantibody levels.ConclusionsCriminal behaviours are a rare, novel, and stigmatizing residual neurobehavioural phenotype in AE, with significant social and legal implications. With caution towards overattribution, we suggest they occur as part of a postencephalitis limbic neurobehavioural syndrome.