Pediatric Unilateral Optic Neuritis Associated with Double-Positive Anti-Myelin Oligodendrocyte Glycoprotein and Anti-N-Methyl-D-Aspartate Receptor Antibodies: A Case Report and Literature Review

A 13-year-old Japanese boy was admitted to hospital with tonic-clonic seizures. Brain magnetic resonance imaging (MRI) showed diffuse swelling of the gray matter and obscured cerebral sulci in the lateral part of the right cortex. He was treated with intravenous midazolam, diazepam, fosphenytoin sodium hydrate, edaravone and mannitol infusion due to suspicion of acute encephalopathy. Five days after discharge, he noticed blurred vision in his left eye. Worsening of visual acuity (6/60), optic disc swelling and left optic nerve enhancement on head MRI suggested the presence of optic neuritis. His visual acuity and optic disc appearance recovered to normal after treatment with intravenous high-dose methylprednisolone. Optical coherence tomography (OCT) detected thinning of the ganglion cell complex in the peri-macular region of the left eye but no thinning of the peripapillary retinal nerve fiber layer. Antibodies against myelin oligodendrocyte glycoprotein (MOG) in the serum and cerebrospinal fluid (CSF) and antibodies against N-methyl-D-aspartate receptor (NMDAR) in the CSF were simultaneously detected from specimens obtained during the initial visit. These findings suggested a diagnosis of MOG-associated disease and anti-NMDAR encephalitis overlapping syndrome (MNOS). MNOS is a rare condition, and its visual symptoms are infrequent. Our report adds to the ophthalmologic knowledge of MNOS.