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Myelin Oligodendrocyte Glycoprotein antibody associated disease (MOGAD) is an autoimmune disorder characterized by antibodies against Myelin Oligodendrocyte Glycoprotein (MOG) on the surface of cells (1). The condition is more prevalent in children but has increased in adults. MOG autoantibodies lead to an inflammatory response with heterogenous clinical manifestations. (1) Optic neuritis is most common (3). We present a case of MOGAD leading to a lesion in the optic chiasm presenting with bitemporal hemianopia. 

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A 60-year-old man presented with progressive bilateral vision loss over one month. Initially, he had intermittent spinning sensations for 3 days, then an intense bitemporal frontal headache and a spot in his left eye. Eventually, he developed complete right eye vision loss. Further inquiry revealed constant nausea and "possible" narcoleptic episodes. Neuro-ophthalmologic examination revealed visual acuity (VA) right eye 20/800 and left eye 20/100 with optic neuropathy signs, including right relative afferent pupilar defect (rAPD), asymmetric visual field defects and right eye painful extra ocular movements. MRI brain showed bilateral optic nerve involvement (R> L) and chiasmal involvement. MRI cervical and thoracic spine were negative for demyelination. Lumbar puncture showed elevated protein without leukocytosis. After ruling out infectious etiologies, he started high dose IV methylprednisolone for 5 days. His positive MOGAD live cell-based assay showed 1:1000 titers. He responded to the steroid treatment with improvement of the right eye VA to 20/100 and left 20/70. He started outpatient monthly IVIG treatment and responded well. His vision continues to improve with ongoing treatment.  

 MOGAD is uncommon, but advances in diagnostic tools and increased awareness in the neurology community have increased its identification. This case report highlights the diagnostic complexity associated with MOGAD in older patients. The initial complexity of the presentation to a broader differential diagnosis, ultimately guiding the correct diagnosis and appropriate treatment.