Seronegative Neuromyelitis Optica Spectrum Disorder in a Six-Year-Old Patient: A Case Report.

Neuromyelitis optica spectrum disorder (NMOSD) is a rare demyelinating disease of the central nervous system (CNS) in children. Its main clinical manifestations are optic neuritis and myelitis. In most cases, it is associated with suggestive magnetic resonance imaging (MRI) and positive serology (AQP4-IgG). We report a six-year-old girl with acute asymmetric quadriparesis, bilateral decreased visual acuity, and sudden loss of sphincter control. Although AQP4-IgG testing was negative, MRI demonstrated findings consistent with NMOSD. Consequently, she received high-dose methylprednisolone, intravenous immunoglobulin, and early rehabilitation, resulting in substantial neurological recovery. High clinical suspicion for NMOSD in children, particularly in the presence of bilateral optic neuritis and longitudinally extensive transverse myelitis (LETM), should prompt early treatment, even in seronegative cases, to prevent permanent neurological deficits.