aquaporin4positive

Aquaporin-4 positive (AQP4-positive) refers to individuals whose serum contains autoantibodies against aquaporin-4, the main water channel located on astrocyte endfeet in the central nervous system. The antibodies, known as AQP4-IgG, are highly specific for a neuromyelitis optica spectrum disorder (NMOSD). AQP4-IgG–mediated injury promotes complement activation and inflammatory cell recruitment, leading to astrocyte damage and secondary demyelination.

Clinically, AQP4-positive NMOSD commonly presents with optic neuritis and longitudinally extensive transverse myelitis, and may include area postrema syndrome (intractable nausea, vomiting, or hiccups). Relapses are a key feature and disability often accumulates with recurrent attacks. The condition is distinct from multiple sclerosis and requires a different treatment approach due to differences in relapse patterns and response to therapies.

Diagnosis relies on serologic testing for AQP4-IgG, typically using a cell-based assay, which has high specificity for NMOSD. A positive result strongly supports the diagnosis, while a negative result does not completely exclude NMOSD—some patients are seronegative, especially early in disease or during immunosuppression. Testing for MOG antibodies may help distinguish MOG-associated disorders, which can resemble NMOSD but have different prognosis and management. MRI findings and clinical history contribute to the diagnostic assessment.

Treatment aims to reduce relapses and disability. Acute attacks are treated with high-dose intravenous corticosteroids and plasmapheresis when needed. Long-term management uses immunosuppressive therapies; agents with evidence in AQP4-positive NMOSD include rituximab, eculizumab, satralizumab, and inebilizumab. Early, targeted therapy improves outcomes and quality of life for many patients.