BDNF and early-onset autosomal dominant Alzheimer disease: Biomarkers of neuroprotection, for e.g., brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1, and neurofilaments (NFs), as well as Alzheimer's disease-related biomarkers, for e.g., amyloid-β 42, phosphorylated tau, and total tau, are gaining ground (17–24).