To report on a 9-year-old girl who developed headache and esotropia and was found to have an infiltrative pontine lesion though had low positive MOG IgG. She was treated with corticosteroids with improvement, and 7 months later, developed left optic neuritis consistent with MOG antibody disease.

MOG antibody disease (MOGAD) is an autoimmune condition commonly manifesting as acute disseminated encephalomyelitis (ADEM), optic neuritis, and/or myelitis. The significance of low titer MOG IgG (i.e. 1:20-1:40) has been questioned, particularly if multiple sclerosis is suspected. The presented case was challenging due to atypical finding of isolated brainstem lesion and initial low level MOG titers.

Case report discussing clinical presentation, laboratory and neuroimaging results, and medical decision-making.

A 9-year-old girl presented with headache, esotropia, and gait abnormality and was found to have an enhancing, infiltrative pontine lesion concerning for a high-grade glioma.  She was treated with corticosteroids with improvement in symptoms. CSF evaluation demonstrated 4 nucleated cells/mm3, normal protein and glucose, and 3 unmatched oligoclonal bands. She had a low positive MOG IgG of 1:40.

Seven months later, she developed left eye pain and blurry vision. MRI orbits demonstrated left optic neuritis. MOG IgG returned 1:100 and she was started on monthly IVIG for the diagnosis of relapsing MOG antibody disease.

This case highlights an atypical presentation of MOG antibody disease due isolated pontine involvement at onset. Her initial low titer of MOG IgG at 1:40 led to diagnostic uncertainty. The patient later developed left optic neuritis, a well known manifestation of MOG antibody disease, and she had a higher MOG IgG of 1:100. She responded well to treatment with IV high dose steroids and IVIG. Less common manifestations of MOG antibody disease and the predictive value of MOG IgG titers warrant further study.