A decrease in cerebrospinal fluid (CSF) amyloid beta with 42 amino acids (Aβ42), combined with an increase in total tau protein (τT) and phosphorylated tau protein in threonine 181 (τP-181) are considered highly diagnostic of an underlying AD pathology, and have, therefore, been included in recent AD diagnostic criteria. The gene discussed is MAPT; the disease is Alzheimer disease.