MAPT and early-onset autosomal dominant Alzheimer disease: While tau aggregation is prominently associated with Alzheimer's disease (AD), primary tauopathies such as frontotemporal dementia (FTD) are associated with mutations in the microtubule‐associated protein tau (MAPT) gene (Bloom, 2014; Hutton et al., 1998; Spillantini & Goedert, 2013).