The diagnosis of AD is based on the detection of the cognitive symptoms with the identification of atrophy of the medial temporal lobe structures (especially the hippocampal formation) using MRI, detecting hypometabolism of the posterior parieto-occipital regions bilaterally with fluoro-deoxy-glucose PET and with the identification of AD biomarkers, such as β-amyloid (Aβ) peptide and hyperphosphorylated tau proteins in the cerebrospinal fluid or using Aβ and tau PET [76]. The gene discussed is MAPT; the disease is Alzheimer disease.