MAPT and early-onset autosomal dominant Alzheimer disease: Accumulation of assembled tau protein is the hallmark of multiple neurodegenerative diseases that are collectively known as tauopathies.1 Specific clinical and neuropathological features are used to define and distinguish the tauopathies, that include Alzheimer’s disease (AD), primary age-related tauopathy (PART), chronic traumatic encephalopathy (CTE), progressive supranuclear palsy (PSP), corticobasal degeneration (CBD) and Pick’s disease (PiD).