Pathomechanisms of frontotemporal lobar degeneration: from view of clinical neuropathology

Frontotemporal lobar degeneration (FTLD) encompasses frontotemporal dementia and related neurological disorders including motor neuron disease and movement disorders. During the 21th century, analyses of aggregative proteins suggested powerful hypotheses of gain-of-neurotoxicity or loss-of-function for aggregation-related proteins. However, recent translational researches in collaboration of basic studies and human pathology indicate that FTLD arises from more complex molecular mechanisms than dyshomeostasis of single molecules. Additionally, accumulation of clinicopathological evidences from various countries, genetic backgrounds or clinical specialties (e.g. neurology and psychiatry), suggests diverse phenotypes of FTLD, which are indicative of future paradigm-shift in the concept of FTLD. In this paper, we discuss FTLD pathomechanism on the basis of human pathology.