PSEN1 and Alzheimer disease: Recently, Johnson et al. and the Dominantly Inherited Alzheimer Network (DIAN) published an excellent paper describing the discovery of new diagnostic and progression biomarkers for Alzheimer’s disease (AD) in cerebrospinal fluid (CSF) of patients with mutant or wild-type genes, namely amyloid precursor protein (APP), Presenilin 1 (PSEN1), and Presenilin 2 (PSEN2) [1].