2026 ECNP Congress

PS02-2079

Anti N-methyl-D-aspartate receptor encephalitis: a diagnosis to consider for first-episode psychosis: a case report

Catarina Alvarez Loureiro — J.A. Campos Pérez · Hospital Álvaro Cunqueiro. Instituto de Investigación Biomédica Galicia Sur., Psychiatry. Neuroscience, Vigo, Spain

2026 ECNP Congress

1. INTRODUCTION

Encephalitis are an inflammatory brain disorder that are secondary to different pathological processes that include infectious and autoimmune causes. Anti-NMDA receptor encephalitis was first described in 2007 by Dalmau and colleagues in a cohort of twelve women presenting with a severe neuropsychiatric syndrome [1]. Since then, there has been a growing body of literature and nowadays it is among the most common encephalitis.

2. OBJECTIVE

To present a case report that exemplifies the importance of considering anti-NMDA-receptor encephalitis in the differential diagnosis in young people with a first psychotic episode.

3.METHODS

An observationally, retrospective, descriptive case review was conducted for a 23-year-old male presenting with an anti-NMDA-receptor encephalitis with psychotic symptoms .

Case analysis included comprehensive review of medical history, head CT scan, brain MRI, EEG and autoimmune antibodies.

4. CLINICAL CASE

A 23-year-old healthy man with no psychiatric history was brought to a general hospital with a one-week history of confusion, disorganized speech and altered behaviour. Only diaphoresis was reported as a physical symptom. He was admitted to the Neurology service with suspected encephalitis and numerous tests were performed (lumbar puncture with negative autoimmune antibodies, head CT scan, brain MRI and EEG) without relevant results. As organic causes were ruled out, he was transferred to the psychiatric service, being treated as a first psychotic episode.

He presented a rapid worsening within a few days with psychomotor agitation and self mutilation requiring intensive care to secure the airway. During his stay in the ICU, a new lumbar puncture was performed, and in this case the result was positive for anti-NMDA receptor antibody in CSF. The study was completed with a brain PET scan, which showed a predominantly posterior right cerebral pattern of hypometabolism.

He was then diagnosed with anti-NMDA receptor encephalitis and started on immunotherapy, with improvement of the symptoms with second-line rituximab after the poor response to corticosteroids and intravenous immunoglobulins. Antipsychotics were useful in the initial management of behavioural-psychotic symptoms. No evidence of oncological disease was found in the other tests performed.

4. RESULTS

The classic presentation of Anti-NMDA receptor encephalitis involves a confluence of psychiatric, neurologic and autonomic symptoms, often with a non-specific viral prodrome (subfebrile temperature, headache and fatigue) [2]. Although it is frequently associated with underlying oncological disease, the presence of a paraneoplastic syndrome is not essential and it can occur in the absence of tumours.

Diagnosis is based on the clinical symptoms and requires a positive serum or CSF sample screening for antibodies to the NMDA receptor subunit, supported by other complementary studies, such as brain magnetic resonance imaging scans, brain PET scan and EEGs [3]. It is potentially reversible, and treatment must target both the cause (if identified) and the clinical consequences of the encephalitis with immunotherapy as first-line treatment.

Clinicians need to be highly aware of this disorder in patients presenting acute psychiatric symptomatology in association with neurological and autonomic symptoms since the prognosis crucially depends on early recognition and prompt therapy.

References

  1. Dalmau J, Bataller L. Limbic encephalitis: the new cell membrane antigens and a proposal of clinical-immunological classification with therapeutic implications. Neurologia 2007; 22: 526–37
  2. Barry H, Byrne S, Barrett E, Murphy KC, Cotter DR. Anti-N-methyl-d-aspartate receptor encephalitis: review of clinical presentation, diagnosis and treatment. BJPsych Bull. 2015;39(1):19-23. doi:10.1192/pb.bp.113.045518
  3. Pădureanu V, Dop D, Pădureanu R, Pîrșcoveanu DFV, Olaru G, Streata I, Bugă AM. Anti-NMDA Receptor Encephalitis: A Narrative Review. Brain Sciences. 2025; 15(5):518.