Overlapping demyelinating syndrome (Neuromyelitis optica spectrum disorders NMOSD with anti-NMDA receptor encephalitis); A case report.

Neuromyelitis optica spectrum disorder (NMOSD) represents an evolving spectrum of inflammatory demyelinating central nervous system-based autoimmune diseases; while anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is another severe immune-mediated syndrome that occurs in association with IgG antibodies against the GluN1 subunit of the NMDAR and has been predominantly reported in young females (Dalmau et al., 2008 Dec). Although It has been recognized that anti-NMDAR encephalitis can coexist in the same patient who has serological markers of another autoimmune disease (e.g. neuronal autoantibodies and demyelination AQP4 or MOG antibodies) (Titulaer et al., 2014), rare cases are reported with anti-NMDAR encephalitis that overlap with a demyelinating syndrome; such as neuromyelitis optica spectrum disorders associated with Anti- Aquaporin 4 (AQP4) antibodies (Titulaer et al., 2013). We report here an unusual and rare overlapping autoimmune syndrome in a young Omani female who first presented in 2011 with the clinical and radiological presentations of neuromyelitis optica spectrum disorder (NMOSD) and had a complete recovery. Five years later, she was admitted with the diagnosis of anti-NMDAR encephalitis and was found to have positive serum as well as CSF analyses results for AQP4 and anti-NMDAR antibodies. The patient showed significant improvement, for both clinical syndromes with good response to steroid and immunomodulating therapy.