AQP4-IgG-Seropositive Patient Who Silently Carried Anti-NMDAR Antibodies Developed Encephalitis During A Relapse

The association of autoimmune diseases is relatively common. Comorbidity anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis and Neuromyelitis Optica Spectrum Disorder (NMOSD) is an unusual and rare overlapping syndrome. We report the case of an AQP4-IgG-seropositive NMOSD patient who developed anti-NMDAR encephalitis during corticosteroid treatment for a relapse of Longitudinal Extensive Transverse Myelitis (LETM), with the presence of anti-NMDAR antibodies in the serum two years earlier. The patient showed significant improvement in both clinical syndromes with a good response to steroid and immunosuppressive therapy. Conclusion Early diagnosis and treatment of overlapping autoimmune syndromes, such as AQP4+IgG seropositive NMOSD with anti-NMDAR encephalitis, are key factors for ensuring early and better recovery outcomes.