Diagnosis for NMOSD without AQP4-IgG is met with two core clinical characteristics, one of them being optic neuritis, acute myelitis with longitudinally extensive transverse myelitis lesions, or area postrema syndrome with dissemination in space as well as the absence of a positive AQP4-IgG test [45]. The gene discussed is AQP4; the disease is optic neuritis.