A 25-year-old immunocompetent man develops fever, confusion, and seizures. CSF shows lymphocytic pleocytosis, elevated protein, normal glucose. Brain MRI shows bilateral temporal lobe and insular signal abnormality on FLAIR. Serum and CSF anti-NMDAR (anti-GluN1) antibody is positive. This condition is most commonly associated with which underlying neoplasm in women?
- A Thymoma — associated with anti-CASPR2 and anti-LGI1 encephalitis
- B Small cell lung carcinoma — associated with anti-Hu (ANNA-1) encephalitis
- C Breast carcinoma — associated with anti-amphiphysin encephalitis
- D Ovarian teratoma — contains neural tissue expressing NMDAR serving as the inciting antigen ✓
Explanation
Anti-NMDAR encephalitis is the most common autoimmune encephalitis. In women, it is associated with ovarian teratoma (mature cystic teratoma) in approximately 50% of cases. The teratoma contains neural tissue expressing NR1 subunit of the NMDA receptor; ectopic expression leads to immune activation, antibody generation against NR1 subunits, and cross-reactive attack on hippocampal and limbic neurons. Clinically: psychiatric prodrome → seizures → autonomic instability → coma. Treatment: ovarian teratoma removal + immunotherapy (steroids, IVIG, rituximab). Anti-Hu is associated with SCLC; anti-amphiphysin with breast carcinoma; anti-CASPR2/LGI1 with thymoma.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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