Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease (MOGAD) is a rare autoimmune disorder that primarily affects the central nervous system, including the brain, spinal cord, and optic nerves. It involves the immune system mistakenly targeting and damaging myelin, the protective fatty sheath surrounding nerve fibers. This damage disrupts nerve signal transmission.
Defining MOGAD
MOGAD is an autoimmune condition where the immune system produces antibodies against myelin oligodendrocyte glycoprotein (MOG). MOG is a protein on the surface of myelin-producing cells within the central nervous system. These antibodies lead to inflammation and damage to the myelin sheath.
While MOGAD shares clinical similarities with other demyelinating diseases like Multiple Sclerosis (MS) and Neuromyelitis Optica Spectrum Disorder (NMOSD), it is now recognized as a distinct disease entity. Unlike MS, MOGAD often shows better recovery after attacks and can sometimes be a monophasic (single episode) condition, especially in children. NMOSD is typically associated with antibodies against aquaporin-4 (AQP4), a different protein than MOG, and often results in more severe vision loss and incomplete recovery compared to MOGAD.
Distinguishing MOGAD from MS and NMOSD is important because misdiagnosis can lead to inappropriate treatments. MOGAD affects men and women equally, unlike MS and NMOSD which are more common in women.
How MOGAD Manifests
MOGAD can affect different parts of the central nervous system, leading to a range of symptoms. The most commonly affected areas are the optic nerves, spinal cord, and brain. Symptoms can vary in severity and may occur as single episodes or recurrent relapses.
Optic neuritis, an inflammation of the optic nerve, is a frequent manifestation, causing blurry vision, vision loss, pain with eye movement, and loss of color vision. Spinal cord involvement, known as transverse myelitis, can lead to muscle weakness, numbness, difficulty with sensation, and issues with bladder or bowel control, including bladder retention. Patients may also experience muscle stiffness or spasticity, or sharp, shooting pain in the neck, back, or abdomen.
Brain involvement can manifest as acute disseminated encephalomyelitis (ADEM), especially in children, leading to confusion, behavioral changes, headaches, loss of balance and coordination, or seizures. Adults with MOGAD more commonly experience damage to the eyes and spinal cord, while children often have attacks affecting the brain. MOGAD can also cause cerebral cortical encephalitis, brainstem involvement, or cerebellar deficits.
Identifying MOGAD
Diagnosing MOGAD involves clinical evaluation, specific antibody testing, and imaging studies. A definitive diagnosis relies on detecting MOG antibodies in the blood, primarily through a cell-based assay (CBA), which is considered the gold standard for its reliability. This test looks for antibodies that react with cells engineered to express the MOG protein.
Magnetic Resonance Imaging (MRI) of the brain, spinal cord, and optic nerves provides supporting evidence. Characteristic MRI findings in MOGAD can include inflammation of the optic nerve, often showing an enlarged, tortuous nerve with long segment T2 hyperintensity, frequently affecting both eyes. Spinal cord lesions in MOGAD often appear as longitudinally extensive transverse myelitis, sometimes with a distinctive “H-sign” on axial images, indicating central gray matter involvement. Brain MRI might show diffuse white matter lesions, particularly in children presenting with ADEM, or lesions in the brainstem or deep gray matter in adults.
A lumbar puncture, or spinal tap, may also be performed to analyze cerebrospinal fluid (CSF). While MOG antibodies can sometimes be detected in CSF, serum testing is preferred due to higher antibody concentrations in the blood. Oligoclonal bands, which are common in MS, are usually absent in the CSF of MOGAD patients, helping to differentiate the conditions. Clinical evaluation and ruling out other conditions with similar symptoms are also important steps in the diagnostic process.
Treating MOGAD
Treatment for MOGAD focuses on managing acute attacks and preventing future relapses. For acute attacks, intravenous corticosteroids are the primary treatment to reduce inflammation. High doses of methylprednisolone are commonly administered intravenously for three to five days.
If symptoms are severe or do not improve with corticosteroids, plasma exchange (PLEX) or intravenous immunoglobulin (IVIG) may be used. PLEX involves removing the patient’s plasma and replacing it, while IVIG provides donor antibodies to modulate the immune system. These acute treatments aim to speed recovery and minimize damage from the inflammatory attack.
For long-term management and to prevent recurrent attacks, immunosuppressive therapies are often employed. Common medications include rituximab, azathioprine, and mycophenolate mofetil, which work by suppressing the immune system’s activity. IVIG infusions are also recognized as an effective long-term therapy for preventing relapses.
Rehabilitation is an important part of managing MOGAD, especially for residual deficits after an attack. Physical therapy, occupational therapy, and sometimes speech therapy help patients regain function, improve mobility, and enhance their quality of life. Early initiation of rehabilitation can help prevent complications and address functional impairments.