Literature data indicate circulating BDNF as a potential biomarker of memory and cognitive function in healthy adult subjects [36], but also in individuals with cognitive decline-related diseases, such as mild cognitive impairment [37], Alzheimer’s disease [38] and Huntington’s disease [39], which were characterized with the decreased levels of serum BDNF. Here, BDNF is linked to early-onset autosomal dominant Alzheimer disease.