MOG Antibody-Associated Disease With Bilateral Deep Gray Matter Involvement in a Child: Unique MRI Findings and Therapeutic Response.

Myelin oligodendrocyte glycoprotein antibody-associated disease is an autoimmune inflammatory demyelinating disorder of the central nervous system with diverse clinical and radiological manifestations; however, bilateral symmetric deep gray matter involvement is an exceptionally uncommon presentation in children. We report a previously healthy 3-year-old boy who presented with fever, encephalopathy, and focal seizures following a viral illness. Brain magnetic resonance imaging (MRI) demonstrated bilateral symmetric T2/FLAIR hyperintensities involving the basal ganglia, thalami, external capsules, subcortical white matter, and brainstem. Cerebrospinal fluid analysis revealed lymphocytic pleocytosis, and MOG-IgG antibodies were detected using a cell-based assay. Extensive infectious, metabolic, mitochondrial, and genetic investigations were unrevealing. Despite treatment with high-dose intravenous methylprednisolone and intravenous immunoglobulin, the patient showed minimal clinical improvement; however, six sessions of plasmapheresis resulted in marked neurological recovery, with complete clinical and radiological resolution by Day 24. This case expands the recognized neuroimaging spectrum of pediatric MOGAD and highlights the importance of considering MOGAD in children presenting with encephalopathy and atypical bilateral deep gray matter lesions after exclusion of alternative etiologies. It also underscores the potential role of plasmapheresis in severe or steroid-refractory cases, emphasizing the importance of early diagnosis and prompt immunomodulatory treatment for favorable outcomes.