The cerebrospinal fluid (CSF) biomarkers amyloid β peptide 1–42 (Aβ1–42), which correlates inversely with plaque pathology, total tau (t-tau), which is hypothesized to reflect neuroaxonal degeneration, and phosphorylated tau (p-tau181), which may correlate with tangle pathology, have recently been incorporated into the National Institute on Aging guidelines for AD diagnosis [3]. The gene discussed is MAPT; the disease is Alzheimer disease.