Some diseases show isoform-specific accumulation of tau: 3R isoforms in Pick’s disease, 4R isoforms in argyrophilic grain disease, corticobasal degeneration, globular glial tauopathy, progressive supranuclear palsy and 3 R + 4R isoforms in Alzheimer’s disease and chronic traumatic encephalopathy. This evidence concerns the gene MAPT and early-onset autosomal dominant Alzheimer disease.