AQP4 and neuromyelitis optica: And the improvement of the patient's clinical manifestations, laboratory examinations results, auxiliary examinations results and histopathological examination results related to NMO and AHRU including gastrointestinal bleeding, nausea, dizziness, visual impairment, and limb weakness, disappearance of AQP4 antibodies in the blood and CMV genes in the CSF, the healing of rectal ulcer on colonoscopy and shrinkage of lesions on brain MRI, clearance of CMV in rectal pathological biopsy tissues, indicating a causal role of CMV infection in NMO and AHRU.