[Dominant forms of Alzheimer's disease: from genotype to phenotype]

This review is devoted to the relationships between phenotype and genotype of the autosomal dominant forms of Alzheimer's disease caused by mutations of presenilins (PSs) and amyloid precursor protein (APP) genes. A first part examines the clinical characteristics mainly the early age of onset and argues about the diversity of age of onset between different mutations and also between patients bearing the same mutation in large families. The second part reports several arguments demonstrating that the main effect of the PSs and APP mutations is the elevation of Ab42 peptide. The pathological and behavioral effects observed in transgenic APP or PSs animals suggest that intra cellular deposits of Ab42 play a role in the pathophysiological process.