APP and Alzheimer disease: Of note, elevations in Aβ precursor, the APP C-terminal fragment of 99 a.a. (C99), have also been reported in TBI (Chen et al. 2004; Cartagena et al. 2016) as well as in AD (Jiang et al. 2010; Lauritzen et al. 2012, 2016, 2019; Cavanagh et al. 2013; Mondragón-Rodríguez et al. 2018; Bourgeois et al. 2018).