Introduction: Autoimmune encephalitis against N-methyl-D-aspartate (NMDA) receptors is being diagnosed more and more frequently in the paediatric age. It should be suspected in children with psychiatric symptoms, encephalopathy, abnormal movements or epileptic seizures. Paraneoplastic cases are less frequent than in adults.
Case report: We report the case of a boy, 2.5 years of age, with subacute encephalopathic signs and symptoms and epileptic seizures followed by behaviour disorders, neurological regression, dyskinesias and insomnia. Results of a cerebrospinal fluid study were normal, the magnetic resonance scan of the head revealed a focal periventricular lesion and diffuse leptomeningeal uptake; moreover, the serial electroencephalograms showed high-amplitude delta activity interspersed with generalised intercritical epileptiform activity. The patient was given empirical treatment with high doses of corticoids and intravenous immunoglobulins with no response. After showing up positive for antibodies against the NMDA receptor, plasmapheresis was begun, which led to his swift and spectacular recovery. After more than 18 months' follow-up, his sequelae are limited to mild behavioural and language alterations. He has had no relapses and has not needed any kind of maintenance treatment.
Conclusions: Anti-NMDA encephalitis is a treatable disorder and, sometimes, the first evidence of an underlying neoplasia, which makes its early recognition and treatment essential. Treatment of the non-paraneoplastic forms are based on immunotherapy: glucocorticoids, intravenous immunoglobulins, plasmapheresis and immunosuppressants. Plasmapheresis can bring about a fast, spectacular improvement.