MAPT and Cognitive impairment: Adults with Down syndrome (DS) present with a triplication of the amyloid precursor protein (APP) gene, due to the presence of three copies of chromosome 21 (chr21),5 which results in the early accumulation of intracellular amyloid already in childhood,6 eventually leading to extracellular accumulation of amyloid, the formation of solid amyloid‐plaques, and subsequent intracellular tau phosphorylation, ultimately resulting in progressive cognitive impairment.7