Aquaporin-4 autoimmunity.

Area of Science:

• Neuroimmunology
• Autoimmune CNS disorders

Background:

• Neuromyelitis optica (NMO) and related disorders share a common biomarker: autoantibodies against the aquaporin-4 (AQP4) water channel.
• AQP4 is predominantly found in astrocytic foot processes within the central nervous system (CNS).
• Classic NMO symptoms include optic neuritis and transverse myelitis, but AQP4 autoimmunity can also affect circumventricular organs and skeletal muscle.

Purpose of the Study:

• To summarize the current understanding of NMO and AQP4 autoimmunity.
• To highlight diagnostic approaches and therapeutic goals for NMO spectrum disorders.
• To discuss emerging serological markers and their implications for disease classification.

Main Methods:

• Review of clinical, immunohistopathologic, and in vitro evidence linking AQP4-IgG to NMO pathogenesis.
• Analysis of diagnostic assay specificity for AQP4-IgG.
• Evaluation of current animal models and their limitations.
• Consideration of recent findings on myelin oligodendrocyte glycoprotein (MOG) autoantibodies.

Main Results:

• Serum autoantibodies against AQP4 are highly specific (approaching 100%) for NMO using optimized assays.
• Evidence strongly supports AQP4-IgG as a central pathogenic factor in NMO.
• Newly identified clinical manifestations and associations, including paraneoplastic contexts, are recognized.
• MOG autoantibodies may define distinct entities within the NMO spectrum in AQP4-IgG-negative patients.

Conclusions:

• AQP4-IgG detection is a definitive diagnostic criterion for NMO spectrum disorders.
• Treatment aims to mitigate acute disability and prevent long-term relapse and accumulation of deficits.
• Further serological characterization, including MOG antibodies, is crucial for refining the classification and understanding of NMO spectrum diseases.