The patient was a previously healthy middle-aged female. Two months ago, on the 3rd day after receiving the first dose of inactivated virus vaccine, she developed mild fever, vomiting, diarrhea, and cough. At that time, CT scan of the chest and abdomen showed no obvious abnormalities. After symptomatic and nutritional support treatment, diarrhea was relieved, but nausea and vomiting persisted. Five days ago, she experienced dizziness and unsteady walking. Nausea and vomiting also worsened. Neurological examination revealed weakened pharyngeal reflex, limb muscle strength of grade 4, and unstable tandem walking. MRI scanning of the brain revealed area postrema and bilateral hypothalamus lesions without Gd enhancement (Fig. 1). Optic nerves and the cervical spinal cord were unremarkable on MRI. Electromyography revealed F-wave abnormalities in bilateral median and posterior tibial nerves. Laboratory tests included blood routine, liver and kidney function, cortisol and thyroid hormones, vitamin B1 and B12 levels, tumor markers, erythrocyte sedimentation rate, antinuclear antibody profiles, C-reactive protein, immunoglobulins and complements, rheumatoid factor, ANCA, antiphospholipid antibodies, anti-AQP4, MOG and GFAP IgG (CBA assay), autoimmune encephalitis antibodies, paraneoplastic antibodies, and serum cytokines (IFN-γ, IL-6, IL-4, IL-2, IL-10, IL-21, TNF-ɑ). Abnormal results were leucopenia of 2.36 × 109/L and positive antibodies for AQP4, ANA, SSA, SSB, Ro-52, and p-ANCA. Cerebrospinal fluid (CSF) leukocyte count was 31 × 106/L, all of which were mononuclear cells. CSF glucose and protein were normal, and no oligoclonal bands were found. The patient was diagnosed as AQP4-positive NMOSD with coexisting systemic autoimmunity. After treatment with methylprednisolone (500 mg for 5 days), the patient’s symptoms were greatly relieved.