How should Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease (MOGAD) be evaluated and managed?

How to Evaluate and Manage MOGAD

MOGAD should be diagnosed when a patient presents with acute optic neuritis, myelitis, brainstem encephalitis, or ADEM-like presentations, has MRI/VEP findings compatible with CNS demyelination, and tests positive for serum MOG-IgG using a cell-based assay—with acute treatment consisting of high-dose IV methylprednisolone followed by plasma exchange if recovery is incomplete, and long-term immunosuppression reserved for relapsing patients. 1

Diagnostic Evaluation

When to Test for MOG-IgG

Test for MOG-IgG antibodies when patients present with acute CNS demyelination AND at least one of these features 1:

Clinical presentations:

• Optic neuritis (especially bilateral, recurrent, or with severe visual deficit)
• Acute transverse myelitis
• Brainstem encephalitis
• ADEM-like encephalitis
• Any combination of the above

MRI features that increase pre-test probability:

• Longitudinally extensive transverse myelitis (≥3 vertebral segments, contiguous) 1
• Longitudinally extensive optic nerve lesions (>1/2 length of pre-chiasmal nerve) 1
• Perioptic gadolinium enhancement during acute ON 1
• Conus medullaris lesions 1
• Large, confluent T2 brain lesions suggestive of ADEM 1
• Absence of MS-typical features: no ovoid periventricular lesions, no Dawson's fingers, no juxtacortical U-fiber lesions 1

CSF findings:

• Neutrophilic pleocytosis or WCC >50/μL 1
• Absence of CSF-restricted oligoclonal bands (in continental European patients) 1

Clinical features:

• Prominent papilledema/optic disc swelling during acute ON 1
• Particularly good response to plasma exchange or B-cell depletion 1

Laboratory Testing Protocol

Antibody testing requirements 1:

• Use cell-based assays employing full-length human MOG as target antigen (NOT ELISA)
• Test serum (MOG-IgG is produced extrathecally, not intrathecally)
• If initial test is negative but suspicion remains high, retest during acute attacks or treatment-free intervals
• MOG-IgG concentrations are higher during relapses than remission 1

Timing considerations 1:

• Antibody levels may be transiently suppressed by plasma exchange—retest 1-3 months after PLEX if initially negative
• Levels may be lower during immunosuppression
• Consider retesting 6-12 months after first attack for prognostic purposes 1

Diagnostic Criteria

Definite MOGAD requires all three 1:

1. Monophasic or relapsing acute ON, myelitis, brainstem encephalitis, or encephalitis (or combinations)
2. MRI or VEP findings compatible with CNS demyelination
3. Seropositivity for MOG-IgG via cell-based assay

Red Flags That Should Challenge a Positive MOG-IgG Result

Immediately reconsider diagnosis and retest with alternative assay if 1:

• Disease course: Chronic progressive disease (SPMS, PPMS), sudden onset <4 hours, or continuous worsening over weeks
• MRI: Ovoid periventricular lesions, Dawson's fingers, inferior temporal lobe lesions, or silent lesion accumulation between relapses
• CSF: Bi- or trispecific MRZ reaction (suggests MS)
• Serology: MOG-IgG barely above cut-off with atypical clinical picture, positive MOG-IgM/IgA with negative IgG, CSF-positive but serum-negative, or double-positive AQP4-IgG/MOG-IgG
• Other: Combined central and peripheral demyelination (MOG not expressed peripherally), or features suggesting alternative diagnoses (infection, sarcoidosis, vasculitis, lymphoma)

Management

Acute Attack Treatment

First-line therapy 2:

• High-dose IV methylprednisolone (typically 1g daily for 3-5 days)
• Follow with oral steroid taper (do not stop abruptly)

Second-line for incomplete recovery 2:

• Plasma exchange (rapid escalation if inadequate response to steroids) 1
• IVIG can be considered as alternative 1

The evidence shows particularly good responses to antibody-depleting therapies in MOGAD compared to MS 1, making aggressive acute treatment critical for preventing permanent disability.

Long-Term Management

Indications for chronic immunosuppression 2:

• Relapsing disease course (40-80% of patients relapse)
• Incomplete recovery from presenting attack

Treatment options with evidence of efficacy 1:

• B-cell depleting therapies (rituximab, ocrelizumab, ofatumumab)—particularly good response noted
• IVIG
• Oral steroids (maintenance low-dose)
• Other immunosuppressants

Critical pitfall: Some MS disease-modifying therapies may be ineffective or harmful in MOGAD due to different immunopathogenesis 1. Avoid treating as MS without confirming diagnosis.

Monitoring and Prognosis

Antibody monitoring 1:

• MOG-IgG may disappear in monophasic cases (often pediatric ADEM)
• Persistent seropositivity suggests relapsing course
• Regular titer monitoring for relapse prediction is not currently recommended due to lack of validated cut-offs and timing protocols
• If antibodies disappear and treatment is stopped, close monitoring is essential as transient seroreversion can occur

Follow-up imaging:

• Serial MRI to assess for lesion normalization (T2 lesions often normalize in MOGAD, unlike MS) 3
• Lack of normalization should prompt reconsideration of diagnosis

Special Considerations

Pediatric patients 1:

• MOG-IgG testing indications can be less rigorous (higher prevalence in children)
• ADEM presentation more common
• Higher likelihood of monophasic course

Differential diagnosis challenges 3:

• 4% of MOG-IgG positive patients may also meet McDonald MS criteria
• Distinguish based on: severity of initial event, lesion characteristics, degree of T2 lesion normalization on serial imaging, and response to therapy
• Low-titer MOG-IgG (barely above cut-off) with MS-like features may represent false positives 4