MOG Antibody Disease

Myelin Oligodendrocyte Glycoprotein (MOG) is a glycoprotein expressed selectively at the outermost surface of myelin sheaths and oligodendrocyte membrane. It is found exclusively in the CNS to serve as a necessary adhesion molecule to provide structuralintegrity to the myelin sheath. This glycoprotein has a role in different disease such as multiple sclerosis (MS) and adrenoleukodystrophy. MOG antibody is involved in a clinical spectrum of disease named as MOG antibody disease (MOG-AD). These include neuromyelitis opticaspectrum disorder (NMOSD), acute demyelinating encephalomyelitis (ADEM), focal cortical inflammatory disease, and some conditions such as NMD receptor encephalitis. An ADEM-like presentation is more common in children. MOG antibodies are found in overhalf of these patients and in virtually all patients with multiphasic ADEM. Persistence of MOG antibodies in children with ADEM appears to predict further relapses, particularly of optic neuritis or ADEM. MOG antibody positive ADEM patients do not differ significantly fromMOG antibody-negative patients in terms of clinical presentation or demographics. Focal cerebral cortical inflammatory disease has been recently reported in benign, unilateral, cerebral cortical encephalitis with epilepsy in adult patients with steroid-responsive encephalitis. MOG-AD could be presented with MS/ NMOSD like features. Thirty three percent of adult patients with MOG-AD meet McDonald’s criteriafor MS, but it should be considered that some drugs approved for MS might be ineffective or even harmful in MOG-EM. Isolated optic neuritis is the most common onset presentation (55%–64%) which typically involves the anterior segment (papillitis). Transverse myelitis inMOG-AD typically presents as longitudinal extensive Transverse myelitis (LETM). A LETM lesion in MOGAD disease seen on MR scan of the spinal cord tends to be central and associated with swelling in the acute phase. It involves the conus more often than in the AQP4antibody LETM. MOG antibody disease can be either monophasic or relapsing. Attacks generally recover, but some patients are left with residual disability: mostly sphincter, erectile or visual. MS-typical brain lesions on MRI are very unusual in MOG antibody or AQP4antibody disease, including Dawson’s fingers, inferior temporal lobe lesions and S-shaped/curved juxtacortical lesions. In CSF Around half of the patients have elevated white cell counts, and in 5%–10% the lymphocyte count is as high as 100–300 cells/μL. Similarly around halfhave an elevated CSF protein concentration, which can be above 100 mg/dL in 10%. Oligoclonal bands restricted to the CSF occur in up to 15% of patients. Cell based indirect fluorescence test and employing full length human MOG as the target antigen MOG IgG is necessary for diagnosis. Recommended indications for MOG-IgG testing are: 1. Monophasic or relapsing acute optic neuritis, myelitis, brainstem encephalitis, encephalitis, or any combination. 2. Radiological or, only in patients with a history of optic neuritis, electrophysiological (VEP) findings compatible with CNS demyelination.3. At least one of the following findings including simultaneous bilateral acute ON, prominent papilledema/ papillitis/optic disc swelling during acute ON, unusually high ON frequency, particularly severe visual deficit/ blindness, particularly severe or frequent episodes of acute myelitis or brainstem encephalitis, permanent sphincter and/or erectile disorder after myelitis, patients diagnosed with ADEM , multiphasic ADEM , acute respiratory insufficiency, disturbance of consciousness, behavioral changes, or epileptic seizures (radiologicalsigns of demyelination required), disease started within 4 days to 4 weeks after vaccination, otherwise unexplained intractable nausea and vomiting or intractable hiccups, co-existing teratoma or NMDAR encephalitis. Management is largely adopted from NMOSD.Acute relapses are usually treated immediately With Methylprednisolone, plasma exchange or intravenous immunoglobulin. MOG-EM is associated with a high risk of flare-ups after cessation of steroid treatment for acute attack. In patients with persistent antibodytreatment should be continued for up to 12 months. In relapsing disease a corticosteroid-sparing agent such as Azathioprine, Methotrexate, Mycophenolate mofetil, or Rituximab could be added.