Validated in vivo markers for AD-type neuropathologic change include CSF levels of Aβ42 and phosphorylated tau, increased positron emission tomography (PET) ligand binding for amyloid or tau within the cortex, glucose hypometabolism as measured by fluorodeoxyglucose PET (FDG-PET), and brain atrophy as measured by structural magnetic resonance imaging (MRI) (Tan et al., 2014). The gene discussed is MAPT; the disease is Alzheimer disease.