There is considerable interest in the role of neuroimmune processes in neuropsychiatric presentations among young people seeking mental health, neurological, paediatric and rheumatological services. The increasing availability of new immunotherapies, particularly monoclonal antibodies, introduces challenges in effectively and appropriately selecting candidates for immunotherapies. Neuroimmune-mediated neuropsychiatric syndromes (NIMNPS) typically include two broad types: i) ‘autoimmune encephalitis’, characterised by acute or subacute onset, neurological signs such as seizures, delirium or motor features and severe psychotic or major mood phenomena. Anti-N-methyl-D-aspartate receptor encephalitis was a pioneering clinical example, but various other autoantibodies have since been associated with this phenotype; and ii) atypical mood or psychotic syndromes with sub-acute or insidious onset, moderately severe atypical mood or psychotic symptoms, autonomic dysregulation, narcolepsy-like features, poor response to conventional treatments and adverse (notably motor) effects from psychotropic medications. Diagnosis of NIMNPS requires clinical or laboratory evidence of direct brain involvement, though autoantibodies are not always detectable. Given the broad and controversial diagnostic criteria for NIMNPS, we propose standardised clinical criteria for identifying ‘possible cases’, followed by laboratory, neuropsychological and brain imaging tests to confirm ‘probable’ cases suitable for immunotherapy. We emphasise rapid clinical and informed co-decision-making with young people and their families and loved ones. While immunotherapy holds promise for symptom alleviation, highly-personalised approaches and long-term management are essential. Future research should validate our proposed criteria, establish optimal, standardised yet personalised immunotherapy strategies that balance between clinical benefit and risks, and identify predictive markers of treatment response.
