Delayed Myelin Oligodendrocyte Glycoprotein Antibody-Associated Demyelination Five Years After an Acute Disseminated Encephalomyelitis-Like Episode in an Adolescent: A Case Report.

Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is an immune-mediated inflammatory demyelinating disorder of the central nervous system with a broad pediatric clinical spectrum. Acute disseminated encephalomyelitis (ADEM)-like presentations are more frequent in younger children, whereas older children and adolescents may present with optic neuritis, transverse myelitis, or multifocal central nervous system involvement. We report the case of a 14-year-old male adolescent who developed a severe MOG-IgG-positive demyelinating event five years after an initial ADEM-like episode. At nine years of age, he presented with back pain, gait disturbance, urinary incontinence, mild drowsiness, fever, cerebrospinal fluid pleocytosis, subcortical and medullary brain lesions, and longitudinally extensive myelitis. MOG-IgG testing was not available at that time, and the episode was diagnosed as ADEM based on the overall clinico-radiological presentation, with complete recovery after corticosteroid therapy. Five years later, he presented with fever, acute quadriparesis predominating in the lower limbs, pyramidal signs, and sphincter dysfunction. Brain MRI showed multiple ill-defined subcortical T2-weighted/fluid-attenuated inversion recovery (T2/FLAIR) hyperintense lesions, and spinal MRI demonstrated longitudinally extensive cervical myelitis from the cervicomedullary junction to C6. Cerebrospinal fluid analysis showed marked pleocytosis, elevated protein, absence of oligoclonal bands, and negative infectious studies. Serum MOG-IgG was positive at a titer of 1:100 using a fixed cell-based assay, while AQP4-IgG was negative. He received intravenous methylprednisolone followed by intravenous immunoglobulin because of insufficient initial improvement, with complete clinical recovery at one month and marked radiological regression at six months. This case emphasizes that a confirmed MOG-IgG-positive demyelinating event may occur after a prolonged relapse-free interval following an earlier ADEM-like demyelinating episode, while also underscoring that the first episode should be interpreted cautiously because MOG-IgG testing was unavailable. Long-term follow-up remains essential because short-term clinical and radiological improvement does not establish durable disease control.