Infectious disease was excluded through the clinical course and negative CSF cultures and PCR, while MS and neuromyelitis optica spectrum disorder (NMOSD) were ruled out by means of laboratory and radiological findings: CSF oligoclonal bands and anti-aquaporin-4 IgG antibodies were negative, OCT was normal, and MRI of the brain and the spinal cord revealed neither white matter lesions suggestive of MS, nor lesions of the optic nerves, the area postrema, the medulla, or the spinal cord [9]. Here, AQP4 is linked to infectious disease.