APP and early-onset autosomal dominant Alzheimer disease: In DS individuals, the increased risk of early‐onset Alzheimer's disease is related to the trisomic dosage of the genes for amyloid precursor protein (APP, OMIM #104760) and β secretase 2 (BACE2, OMIM #605668), essential proteins for amyloid‐beta (Aβ) peptide production (Ballard et al., 2016).