PSEN1 and Alzheimer disease: Even dominantly inherited AD (caused by pathogenic variants in APP, PSEN1, and PSEN2 genes), which is generally considered a “pure” form of AD, shows heterogeneity between cases and often includes Lewy body pathology (intraneuronal aggregates of alpha‐synuclein) and TAR DNA binding protein 43 (TDP‐43) pathology (intracellular aggregates of TDP‐43).1, 2