PCSK1N and Alzheimer disease: Eight independent proteomic studies have identified proSAAS as a cerebrospinal fluid candidate biomarker in AD and/or frontotemporal dementia (Abdi et al. 2006; Choi et al. 2013; Davidsson et al. 2002; Finehout et al. 2007; Holtta et al. 2015; Jahn et al. 2011; Spellman et al. 2015; Wang et al. 2016), and recent transcriptomics studies have shown that brain proSAAS expression increases during Alzheimer’s progression (Mathys et al. 2019).