MAPT and argyrophilic grain disease: Imbalances in the TAU isoform ratio can lead to neurodegenerative diseases: neurofibrillary tangles in AD are composed of both hyperphosphorylated 4R tau and 3R tau inclusions; 3R tau aggregates characterize Pick’s disease in FTLD-tau (which is usually sporadic and more rarely due to MAPT mutations), whereas 4R tauopathies include corticobasal degeneration (CBD), progressive supranuclear palsy (PSP), globular glial tauopathy (GGT), and argyrophilic grain disease (AGD) [4].