Commercially available tests are AlzheimAlertTM (Nymox Pharmaceutical Corp., Saint Laurent, QC, Canada); Innotest® assays for microtubule-associated protein (T-tau), phosphorylated tau (P-tau), and amyloid β 42 (Aβ42) (Fujirebio Diagnotics, Malvern, PA, USA); AdMark® cerebrospinal fluid (CSF) analysis; DISCERNTM (Neurodiagnostics, Phoenix, AZ, USA) skin sample fibroblast testing; AD-Detect (Quest Diagnostics, Secaucus, NJ, USA); and Lumipulse® G ß-Amyloid Ratio (1–42/1–40) Test (Fujirebio Diagnostics). The gene discussed is MAPT; the disease is Alzheimer disease.