The two neuropathological hallmarks of Alzheimer’s disease (AD) are the extracellular deposition of amyloid beta (Aβ) plaques and intracellular neurofibrillary tangles (NFTs) which are composed of abnormally phosphorylated tau proteins forming paired helical filaments (PHFs). The gene discussed is MAPT; the disease is early-onset autosomal dominant Alzheimer disease.