GFAP levels in bodily fluid, especially blood and cerebrospinal fluid (CSF), have underscored associations with disease progression by robust support in a substantial body of reports encompassing cohorts afflicted with a spectrum of brain and spinal cord disorders, including progressive neurodegenerative diseases such as Alzheimer’s disease (AD), Parkinson’s disease, multiple sclerosis and Lewy body dementia. The gene discussed is GFAP; the disease is early-onset autosomal dominant Alzheimer disease.