Taking into account that BDNF is required for survival and function of hippocampal, cortical, basal forebrain, and entorhinal cortex neurons, and that in DS the neuropathological aspects are complex and include development of Alzheimer's disease (AD) in older age, we wanted to evaluate the change in BDNF levels in different age groups of Down's Syndrome patients, compared to the same age range healthy controls. Here, BDNF is linked to early-onset autosomal dominant Alzheimer disease.