GFAP (glial fibrillary acidic protein) is a class-III intermediate filament protein that serves as a cell-specific marker distinguishing astrocytes from other glial cells during central nervous system development. As an astrocytic cytoskeletal protein, GFAP is a key structural component of the intermediate filament cytoskeleton and organizes glial cell projections. GFAP has emerged as a significant biomarker in neurological disease. Peripheral blood GFAP levels are elevated in Alzheimer's disease (AD) and mild cognitive impairment (MCI) compared to healthy controls, with higher levels in amyloid-β-positive individuals 1. Plasma GFAP increases up to 15 years before dementia diagnosis and is associated with faster cognitive decline and increased dementia risk 2. Notably, plasma GFAP is an early marker of amyloid-β pathology specifically, not tau pathology, suggesting astrocytosis secondary to amyloid aggregation may promote tau accumulation 3. Autoimmune GFAP astrocytopathy, a rare neuroinflammatory disorder defined in 2016, involves pathogenic antibodies targeting GFAP (predominantly GFAPα) detected in cerebrospinal fluid and serum 4. This condition presents acutely or subacutely with encephalomyelitis, meningitis, and movement disorders, often preceded by viral prodrome 5. Characteristic neuroimaging shows perivascular enhancement and T2/FLAIR hyperintensities; most patients respond well to corticosteroid therapy 5. Additionally, pathogenic GFAP gene variants cause Alexander disease, a rare neurodegenerative disorder 6.