MAPT and argyrophilic grain disease: The most well-known 4R tauopathies are progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD); however, 4R tau pathology is also observed in conditions such as argyrophilic grain disease (AGD), chronic traumatic encephalopathy (CTE), and Alzheimer’s disease (AD), among others [1].