GFAP and early-onset autosomal dominant Alzheimer disease: Similarly, glial fibrillary acidic protein (GFAP), released by reactive astrocytes, has been proposed as a more specific marker of central nervous system astrogliosis and neurodegeneration [20,21], with elevated levels reported in Alzheimer’s disease (AD) [22], Parkinson’s disease [23], multiple sclerosis [24], and traumatic brain injury [25].