Blood tests for endocrinopathies, autoimmune diseases (neuromyelitis optica [NMO] antibodies [anti-aquaporin-4], anti-double-stranded DNA [anti-dsDNA] antibodies, antinuclear antibodies, anti-myelin oligodendrocyte [MOG] antibodies, and an autoimmune panel for encephalitis) were also performed and all the results were negative. Here, AQP4 is linked to viral encephalitis.