Pick's complex and FTDP-17.

This essay advances the thesis with a review of the evidence that Pick's disease, frontotemporal dementia, primary progressive aphasia, corticobasal degeneration, and progressive supranuclear palsy should be regarded as a clinically and biologically cohesive spectrum. The historically correct eponymic term Pick's complex, for both the clinical and pathological varieties is preferred. The discovery of tau mutations in frontotemporal dementia and parkinsonism linked to specific mutations in chromosome 17 and their resemblance to the sporadic cases validates the concept of Pick's complex. There are recently discovered overlaps between the three-repeat and four-repeat tauopathies, and the tau-negative varieties with or without motor neuron disease-type inclusions may be deficient in normal tau, therefore may be tauopathies also. Although clinical, pathological, and biochemical distinctions continue to be important, integration promises to be productive in this family of not so rare diseases.