The remaining ∼50% of patients with FTD have pathology marked by tau-positive, TDP-43-negative inclusions; this form of FTD comprises the “tauopathies” (e.g., Alzheimer disease, multisystem atrophy, corticobasal degeneration) and appears to be etiologically distinct from ALS. Here, MAPT is linked to frontotemporal dementia.