2026 American Academy of Neurology Autoimmune Abstract Website

Objective:

To report a case of paraneoplastic aquaporin-4 (AQP4)-IgG-seropositive neuromyelitis optica spectrum disorder (NMOSD) associated with a pathology-confirmed AQP4-positive ovarian teratoma.

Background:

NMOSD is a relapsing autoimmune CNS disease characterized by optic neuritis, transverse myelitis, and brainstem syndromes, driven by AQP4-IgG targeting astrocytic water channels. Approximately 3–5% of AQP4-IgG-seropositive cases may have a paraneoplastic etiology, with tumors ectopically expressing AQP4 hypothesized to break immune tolerance. Ovarian teratoma-associated NMOSD is exceedingly rare, with approximately nine prior reported cases.

Design/Methods:

Retrospective chart review.

Results:

Case: A 33-year-old woman with a known left ovarian mass presented with acute bilateral vision loss. Visual acuity (VA) was 20/50 (right eye) and counting fingers (left eye) with bilateral color desaturation. Orbital MRI showed enhancement of bilateral optic nerves, chiasm, and optic tracts. AQP4-IgG was positive at 1:1000 titer. During hospitalization, she developed acute abdominal pain; CT revealed a 12 cm left ovarian teratoma. Emergent surgical resection was performed. Histopathology confirmed AQP4 immunoreactivity in a focal cluster of epithelial cells. She received IV high-dose steroids (5 days) and plasmapheresis (4.5 days), with VA improving to 20/20 (right eye) at discharge. At 2-month follow-up, VA remained stable. Inebilizumab was initiated, and the patient has remained relapse-free.

Conclusions:

This case is notable for isolated bilateral optic neuritis without the brainstem involvement typical of teratoma-associated NMOSD (83% in prior series), AQP4 expression in epithelial rather than neural tissue, and concurrent ovarian torsion. A systematic review of 72 paraneoplastic NMOSD cases demonstrated heterogeneous phenotypes, supporting cancer screening in all newly diagnosed AQP4-IgG NMOSD regardless of age.

This case reinforces the importance of considering paraneoplastic etiology in young women with NMOSD and supports pelvic imaging in newly diagnosed AQP4-IgG-seropositive patients.