“Classical” CSF AD biomarkers include amyloid peptide with 42 amino acids (Aβ42) or, better, the Aβ42/Aβ40 ratio as a marker of amyloid pathology (correlates negatively with amyloid burden), tau protein phosphorylated at threonine 181 (τP-181) as a marker of tau pathology (correlated positively with tangle burden) and total tau protein as a marker of neuronal/axonal degeneration [14]. The gene discussed is MAPT; the disease is Alzheimer disease.