MOG-EM Diagnosis and Treatment

Disease Definition and Pathophysiology

MOG-EM is a distinct autoimmune inflammatory demyelinating disease of the central nervous system, characterized by antibodies against full-length MOG protein, presenting most commonly with optic neuritis, myelitis, brainstem encephalitis, or ADEM-like presentations, and is immunopathogenetically distinct from both multiple sclerosis and aquaporin-4-positive neuromyelitis optica spectrum disorders, as stated by the Journal of Neuroinflammation 1, 2
Immunological studies demonstrate direct pathogenic impact of MOG-IgG antibodies, according to the Journal of Neuroinflammation 1, 3
Neuropathological studies reveal discrete histopathological features distinct from MS, as reported by the Journal of Neuroinflammation 1
Serological studies show lack of aquaporin-4 (AQP4)-IgG in almost all MOG-IgG-positive patients, as found by the Journal of Neuroinflammation 1
Cohort studies demonstrate differences in clinical presentation, treatment response, and prognosis compared to MS and NMOSD, according to the Journal of Neuroinflammation 1

Optic neuritis is the most frequent presenting phenotype in adults, often presenting with severe visual deficit or blindness during acute episodes, as stated by the Journal of Neuroinflammation is not the source, however, 4
Transverse myelitis can manifest as longitudinally extensive transverse myelitis (LETM) affecting ≥3 vertebral segments, with permanent sphincter and/or erectile disorders, and conus medullaris lesions are particularly characteristic, as reported by Praxis Medical Insights: Practical Summaries of Clinical Guidelines 4
Acute disseminated encephalomyelitis (ADEM) is the most common presentation in children, with large, confluent T2 brain lesions, disturbance of consciousness, behavioral changes, or epileptic seizures, as stated by Praxis Medical Insights: Practical Summaries of Clinical Guidelines 4

Adults typically experience a relapsing course in at least 80% of cases, with 33% of adult patients meeting McDonald's criteria for MS at some point, and 15% meeting Barkhof's criteria for MS, as reported by the Journal of Neuroinflammation 5, 6
Children more commonly have monophasic disease, particularly with ADEM presentations, as stated by the Journal of Neuroinflammation 7

Neutrophilic pleocytosis or white cell count >50/μl is common, usually lacks CSF-restricted oligoclonal bands, particularly in continental European patients, as reported by Praxis Medical Insights: Practical Summaries of Clinical Guidelines 4
White cell counts can range from 6-306 cells/μl (median 33), with neutrophil granulocytes present in 64.3% of patients with pleocytosis, as found by the Journal of Neuroinflammation 7

Cell-based assays (CBA) using full-length human MOG are the only recommended approach, must employ full-length human MOG as target antigen, not peptides or denatured protein, as stated by Praxis Medical Insights: Practical Summaries of Clinical Guidelines 8
Serum is the specimen of choice, not CSF, MOG-IgG is produced mostly extrathecally, resulting in higher serum titers than CSF, as reported by Praxis Medical Insights: Practical Summaries of Clinical Guidelines 8

Misclassification as MS has critical therapeutic consequences, some MS-approved drugs might be ineffective or even harmful in MOG-EM due to differences in immunopathogenesis, as stated by the Journal of Neuroinflammation 5, 6
MOG-EM is associated with high risk of flare-ups after cessation of steroid treatment, requiring close monitoring and careful steroid tapering, as reported by the Journal of Neuroinflammation 6
Patients may be particularly responsive to antibody-depleting treatments (plasma exchange, immunoadsorption), as stated by the Journal of Neuroinflammation 6
B cell-targeted therapies like rituximab may be more appropriate, as reported by the Journal of Neuroinflammation 6
IVIG may be especially effective in children, as stated by the Journal of Neuroinflammation 6