Clinical and genetic aspects of progressive supranuclear palsy.

Progressive supranuclear palsy (PSP) is, after Parkinson's disease, the most common form of degenerative parkinsonism. Several clinical features are used in the recognition of this disorder as well as in the differentiation from related disorders. Clinical criteria that could increase diagnostic accuracy in research studies are also emphasized. Due to a better understanding of the genetic aspects of PSP, recent studies have suggested that it is a recessive disorder in linkage disequilibrium with the tau (tau) gene, rather than a sporadic disorder. In addition, the recent identification of mutations in the tau gene associated with a similar neurodegenerative condition (frontotemporal dementia and parkinsonism linked to chromosome 17) has further strengthened the argument that tau dysfunction is somehow involved in the pathogenesis of PSP. Nongenetic factors that could trigger or perpetuate the cascade of events leading to neuronal degeneration in PSP are also reviewed.