MOG-IgG Optic Neuritis: Key Insights

Case Study

A 29-year-old female presented with acute onset of blurred vision and periocular pain in her right eye, worsened by eye movement.

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She reported that symptoms developed over 48 hours, with a rapid decline in visual acuity. She had no history of multiple sclerosis or autoimmune disease.

Examination Results

Visual Acuity: 20/200 (right eye), 20/20 (left eye)
Pupils: Right relative afferent pupillary defect (RAPD)
Color Vision: Impaired in the right eye
Fundus: Mild optic disc swelling in the right eye
MRI Orbit: T2 hyperintensity and contrast enhancement of the right optic nerve
Serum MOG-IgG: Positive by cell-based assay

A diagnosis of Myelin Oligodendrocyte Glycoprotein MOG-IgG Associated Optic Neuritis was established.

Disease Entity

Myelin Oligodendrocyte Glycoprotein (MOG)-IgG Associated Optic Neuritis is an inflammatory demyelinating condition of the optic nerve linked to antibodies against the MOG protein, located on the surface of myelin sheaths in the CNS.

Unlike optic neuritis in multiple sclerosis or neuromyelitis optica spectrum disorder (NMOSD), MOG-IgG-associated optic neuritis presents unique clinical and radiologic features, necessitating specific diagnosis and tailored treatment.

Pathophysiology

MOG is a CNS-specific glycoprotein expressed on the surface of oligodendrocytes and outermost myelin sheaths.

In MOG-IgG disease, circulating antibodies target MOG, leading to immune-mediated demyelination and inflammation.

Unlike multiple sclerosis, which involves T-cell-mediated mechanisms and CNS plaques, MOG-IgG optic neuritis is more often antibody-mediated and monophasic or relapsing in pattern.

The inflammatory response affects the optic nerve, resulting in visual loss and optic disc edema.

Epidemiology

MOG-IgG-associated optic neuritis can occur in both children and adults. It is slightly more common in females and can present as a monophasic illness or part of a relapsing disease.

Unlike MS-associated optic neuritis, MOG-related ON often involves bilateral presentation, optic disc edema, and poorer visual acuity at onset.

However, visual recovery is often better with appropriate therapy. The prevalence of MOG-IgG positivity in ON patients is estimated to be 5–25% depending on the population and diagnostic methods.

Clinical Features

Rapid onset of visual loss, often severe
Periocular pain, particularly with eye movement
Optic disc swelling, frequently bilateral
Color vision deficiency and central visual field defects
Positive MOG-IgG serology
May be recurrent or relapsing
In children, it may be associated with ADEM-like presentations

Examination Findings

Decreased visual acuity, often ≤20/200 at nadir
RAPD in unilateral cases
Optic disc edema on fundoscopy (frequent)
Visual field defects (central or altitudinal scotomas)
MRI: Optic nerve swelling and enhancement, often long-segment and anterior
CSF: May show mild pleocytosis, rarely oligoclonal bands
Serum: MOG-IgG positive by live cell-based assay

Differential Diagnosis

Multiple Sclerosis (MS)-related optic neuritis
Neuromyelitis Optica Spectrum Disorder (AQP4-IgG positive)
Infectious optic neuritis (e.g., syphilis, Lyme disease)
Sarcoidosis-associated optic neuropathy
Ischemic optic neuropathy (AION/NAION)

Diagnosis

Clinical presentation: acute, painful visual loss
MRI brain and orbit with contrast
Serum MOG-IgG testing by live cell-based assay
Lumbar puncture may help rule out other demyelinating or infectious causes
Visual evoked potentials (VEP) and OCT may be supportive

Management

Acute Phase:
- High-dose IV methylprednisolone (1g/day for 3–5 days)
- Consider plasma exchange (PLEX) if poor response
Long-term management (for relapsing disease):
- Oral immunosuppressants (e.g., azathioprine, mycophenolate mofetil)
- Rituximab or IVIG in some cases
Avoid MS-specific drugs like interferon-beta, which may worsen MOG disease

Prognosis

Visual recovery is generally good if treated early
Relapses are common; up to 50% of patients may experience recurrence
Long-term monitoring and serologic testing may be needed
Recurrence can be minimized with appropriate maintenance immunotherapy

Prevention

No known way to prevent the onset of MOG-IgG disease
Early recognition and prompt treatment of relapses
Maintenance immunosuppression in relapsing cases
Regular ophthalmologic follow-up with OCT and visual field testing

Conclusion

MOG-IgG-associated optic neuritis is a distinct clinical entity with unique immunopathological features.

Differentiating it from MS and NMOSD is crucial, as management strategies and prognosis differ significantly.

Prompt diagnosis using serological and radiologic tools, combined with early initiation of therapy, offers the best chance for visual recovery and long-term disease control.

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References

Jarius S, et al. MOG encephalomyelitis: international recommendations on diagnosis and antibody testing. J Neuroinflammation.
Chen JJ, et al. Distinguishing MOG-IgG from AQP4-IgG optic neuritis. Neurology.
Hacohen Y, et al. MOG antibody-associated demyelinating disease in children. Neurology.
Narayan R, et al. MOG antibody disease: A review of clinical spectrum. Ann Indian Acad Neurol.
Reindl M, et al. Myelin oligodendrocyte glycoprotein antibodies: How clinical presentations differ. Curr Opin Neurol.