Seven independent proteomics studies have shown that the level of proSAAS in CSF taken from AD and/or FTD patients is reduced as compared to controls, suggesting possible cellular retention within the brain (Davidsson et al., 2002; Abdi et al., 2006; Finehout et al., 2007; Jahn et al., 2011; Choi et al., 2013; Holtta et al., 2015; Spellman et al., 2015; reviewed in Pedrero-Prieto et al., 2020). The gene discussed is PCSK1N; the disease is Alzheimer disease.