While Alzheimer's disease (AD) is indeed the predominant dementia demonstrating consistent tau pathology, the accumulation of abnormally phosphorylated tau species is also a primary histopathologic hallmark of several other heritable dementias, including corticobasal degeneration (CBD), parasupranuclear palsy (PSP) and frontotemporal dementia (FTD). This evidence concerns the gene MAPT and early-onset autosomal dominant Alzheimer disease.