Alzheimer ́s disease is considered a neurodegenerative disease and is diagnosed by exclusion, while the detection of specific cerebrospinal fluid (CSF) biomarkers, namely amyloid-beta (Aβ) peptides Aβ1–42 (Aß42), phospho-tau (181P; P-tau), and total-tau (T-tau), has been shown to improve diagnostic accuracy. The gene discussed is MAPT; the disease is early-onset autosomal dominant Alzheimer disease.