Seronegative Neuromyelitis Optica Spectrum Disorder

Abstract

NMOSD is an inflammatory, antibody-mediated, immunological disease of the central nervous system that causes demyelination of the optic nerve and the spinal cord. It is commonly associated with Serum Anti-Aquaporin 4 Antibody (Anti-AQP4 Ab). We report a case of seronegative NMOSD. A 24-year-old man with no known comorbidities presented with bilateral eye blurred vision which was preceded by fever, associated with frontal headache and numbness over the upper trunk and bilateral lower limbs. Right eye(OD) vision was 6/38 and left eye(OS) vision was counting finger(CF). Ocular examination revealed a positive left relative afferent pupillary defect. Anterior segment examination was unremarkable. Fundus examination noted the presence of bilateral swollen optic disc (worse over OS). Neurological examination revealed a patchy hypoesthesia up to T1 with bilateral lower limb hyperreflexia. MRI brain, orbit and spine showed features of longitudinally extensive transverse myelitis and optic neuritis with the laboratory confirmation of negative Anti-AQ4 Ab and MOG Ab status. He was diagnosed with seronegative NMOSD. Intravenous methylprednisolone was commenced for a 5-day course and subsequently switched to oral steroid with a tapering dose. He was started with Azathioprine and responded well to the treatment with clinical improvement. Seronegative NMOSD was classified by diagnostic criteria with strict clinical presentations, neuroimaging findings and exclusions of differentials. The mainstay treatment includes immunosuppressants for both acute attacks and prevention of recurrence.