Neuromyelitis optica spectrum disorder in an 11-year-old: a case report in a pediatric patient from Nepal.

Introduction and importance: Neuromyelitis optica spectrum disorder (NMOSD) is an auto-immune inflammatory disorder of the central nervous system mediated by auto-antibodies against Aquaporin-4 (AQP4). It causes vision impairment, vomiting, and paralysis. Case presentation: We report a case of an 11-year-old Nepalese girl who initially presented with persistent vomiting for 2 months, followed by progressive limb weakness and facial asymmetry. She was initially misdiagnosed as gastroduodenitis with mesenteric lymphadenitis and later with major depressive illness and dissociative motor disorder. Neurological examination revealed multiple cranial nerve palsies and upper motor neuron signs. Magnetic resonance imaging (MRI) of the brain and cervical spine demonstrated long segment T2 hyper-intensities involving the medulla, cervicomedullary junction, and cervical spinal cord which was highly suggestive of transverse myelitis with postrema lesions. Serum anti-AQP4 antibody testing done by indirect immunofluorescence assay was positive which confirmed NMOSD. The patient was treated with intravenous methylprednisolone pulse therapy followed by intravenous immunoglobulin and transitioned to oral prednisolone with gradual improvement in neurological function. Clinical discussion: This case highlights diagnostic challenge of NMOSD, particularly when presented with area postrema syndrome without early neurological findings. Such atypical presentations are frequently mistaken for gastrointestinal or psychiatric conditions, delaying appropriate diagnosis and management. MRI findings and a positive anti-AQP-4 antibody remain key to confirming the diagnosis. Early initiation of immunotherapy is essential to prevent irreversible neurological deficits. Conclusion: NMOSD should be considered in children presenting with unexplained persistent vomiting and subsequent neurological deficits. A high index of suspicion, prompt antibody testing, and timely immunotherapy are vital for favorable outcomes.