Overlapping anti- N -methyl- d -aspartate receptor (NMDAR) encephalitis with neuromyelitis optica spectrum disorders: a case report

Background Anti- N -methyl- d -aspartate receptor (NMDAR) encephalitis can coexist with neuromyelitis optica spectrum disorder (NMOSD). Patients with overlapping anti-NMDAR encephalitis with positive NMDAR antibodies and aquaporin 4 immunoglobulin G (AQP4-IgG)-seropositive NMOSD are rare but should not be ignored. Case presentation This report describes a unique case of anti-NMDAR encephalitis coexisting with NMOSD. A 27-year-old male presented with blurred vision, cognitive impairment, psychosis, dysphagia, gait instability and urinary incontinence. Brain magnetic resonance imaging (MRI) showed abnormal signals in the right cerebellar hemisphere, temporal lobe, and corpus callosum. NMDAR antibodies were positive in the CSF. AQP4-IgG antibodies were positive in the serum. The patient's condition was stable following intravenous gamma globulin, corticosteroids, immunosuppressants and symptomatic treatments. Conclusions This case provides further evidence for the occurrence of anti-NMDAR encephalitis overlapping NMOSD with AQP4-IgG-seropositive in a Chinese patient. However, the mechanisms underlying the occurrence of double-positive antibodies remain elusive.