A 25-year-old woman develops sudden-onset psychosis, seizures, and autonomic instability. CSF shows mild lymphocytosis. MRI shows bilateral mesiotemporal signal change. Anti-NMDAR antibodies are detected. What is the pathological target of these antibodies?

• A AMPA receptor GluA1 subunit
• B GluN1 subunit of the NMDA receptor on hippocampal neurons ✓
• C GABA-B receptor on inhibitory interneurons
• D LGI1 protein of the voltage-gated potassium channel complex

Explanation

Anti-NMDA receptor encephalitis is the most common autoimmune encephalitis, caused by IgG antibodies targeting the GluN1 (NR1) subunit of the NMDA receptor. Antibody binding causes receptor internalisation and reduction in synaptic NMDAR density, disinhibiting dopaminergic pathways (explaining psychosis) and impairing hippocampal function (memory, seizures). It is strongly associated with ovarian teratoma in young women. LGI1 antibodies cause limbic encephalitis with faciobrachial dystonic seizures; GABA-B antibodies cause limbic encephalitis with early seizures.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.