The three established CSF biomarkers based on the core pathological proteins are the 42-amino acid form of the β-amyloid protein (Aβ42), total tau (T-tau), and phosphorylated tau at threonine 181 (P-tau181), which have been used diagnostically to validate AD diagnosis in ambiguous clinical dementia diagnosis cases, atypical presentations, and patients with mixed pathologies [55]. The gene discussed is MAPT; the disease is Alzheimer disease.