5 year old patient with 1 week of right eye blurry vision, then several days of right eye pain. Physical exam notable for right papilledema and progressively worsening vision.

MRI postcontrast through the orbits shows an enlarged, hyperenhancing right optic nerve (red arrow) compared to the normal left side (green arrow), compatible with optic neuritis.

A lumbar puncture was performed: no oligoclonal bands, no aquaporin 4 IgG, positive anti-MOG. The patient was treated with prednisone with return to normal vision a few months later.

Final diagnosis: optic neuritis from myelin oligodendrocyte glycoprotein​ antibody-associated disease (MOGAD).