Seropositive Neuromyelitis Optica Spectrum Disorder (NMOSD) is an autoimmune disease that primarily affects the central nervous system, particularly the optic nerves and spinal cord. It is characterized by recurrent episodes of inflammation and demyelination, leading to various neurological symptoms and disability. The term “seropositive” refers to the presence of a specific autoantibody called aquaporin-4 (AQP4) antibody in the patient's blood serum.
Here are some key points about seropositive NMOSD:
Autoantibody: The majority of patients with NMOSD who are seropositive have antibodies targeting the protein aquaporin-4 (AQP4), which is primarily expressed on astrocytes in the central nervous system. These AQP4 antibodies are thought to contribute to the destruction of astrocytes and trigger an inflammatory response.
Clinical Features: Seropositive NMOSD typically presents with severe attacks of optic neuritis (inflammation of the optic nerves) and longitudinally extensive transverse myelitis (inflammation across a large segment of the spinal cord). These attacks can cause vision loss, weakness or paralysis, sensory disturbances, bladder and bowel dysfunction, and other neurological deficits.
Distinction from Multiple Sclerosis (MS): NMOSD was previously considered a subtype of MS due to similarities in clinical presentation. However, the discovery of AQP4 antibodies and distinctive pathological features led to the recognition of NMOSD as a separate disease entity. Unlike MS, NMOSD primarily affects the optic nerves and spinal cord, and the presence of AQP4 antibodies helps differentiate the two conditions.
Triggers and Relapses: Various triggers, such as infections or stressful events, can precipitate relapses or exacerbations of NMOSD symptoms. Relapses in NMOSD tend to be more severe than those in MS and often result in cumulative disability over time.
Long-Term Prognosis: Seropositive NMOSD has a variable course, with some patients experiencing a relapsing-remitting pattern and others having a more severe and progressive disease course. The presence of AQP4 antibodies is associated with a higher risk of relapses and poorer long-term outcomes. Permanent disability, including visual impairment and motor deficits, can occur due to recurrent attacks and the accumulation of neurological damage.
Treatment: The management of seropositive NMOSD involves a combination of acute attack treatment and long-term immunosuppressive therapy. High-dose corticosteroids are commonly used to treat acute attacks, followed by maintenance therapy with immunosuppressive drugs such as azathioprine, mycophenolate mofetil, rituximab, or eculizumab. Newer treatments targeting AQP4 antibodies, such as inebilizumab, are also being investigated.
It's important to note that NMOSD can also occur in a seronegative form, where patients do not have detectable AQP4 antibodies. The serostatus can influence the clinical presentation, treatment response, and long-term prognosis of NMOSD. A comprehensive evaluation by a neurologist specializing in neuroimmunology is necessary for accurate diagnosis and management of seropositive NMOSD.
Seropositive Neuromyelitis Optica Spectrum Disorder Presenting With Optic Nerve Sheath Enhancement and Optic Disc Edema Resembling Optic Nerve Sheath Meningioma 1)