Once patients with syphilis and HIV experience neurological symptoms, central nervous system damage caused by neurosyphilis and AIDS should be considered, and MOG/AQP4/GFAP antibodies and oligoclonal bands should be tested to exclude central nervous system demyelinating diseases such as MOGAD, NMOSD, GFAP astrocytopathy, and MS. Here, AQP4 is linked to demyelinating disease of central nervous system.