The accumulation of toxic proteins transcribed from mutated genes causes inherited forms of Alzheimer's disease (amyloid precursor protein and presenilins), Parkinson's disease (α-synuclein and Parkin), and trinucleotide repeat disorders (huntingtin, androgen receptor, ataxin, and others) by overcoming the endogenous neuroprotective mechanisms. Here, APP is linked to early-onset autosomal dominant Alzheimer disease.