GFAP serves as a biomarker of reactive astrogliosis, exhibiting elevated levels in plasma and cerebrospinal fluid (CSF) in neurodegenerative diseases such as Alzheimer’s disease (AD)24,25, dementia with Lewy bodies26, frontotemporal lobar degeneration27, and PD28. Here, GFAP is linked to early-onset autosomal dominant Alzheimer disease.