[The amyloid and tau hypothesis in degenerative dementia].

Alzheimer's disease is the major cause of dementia. The neuropathological basis for the diagnosis is the presence of senile plaques and neurofibrillary degeneration in brain tissue. Senile plaques consist of a central core of fibrillar amyloid beta-protein and some other proteins, surrounded by swollen neurites. Three genes causing early-onset autosomal dominant Alzheimer have so far been described. Recently, polymorphisms in three other genes have been shown to influence the risk for late-onset Alzheimer's disease. All these genes seem to influence the metabolization of the beta-protein or the precursor for this protein. These findings support the "amyloid hypothesis" which states that toxic effects of beta-protein cause Alzheimer's disease. Frontotemporal dementias are the second most common types of degenerative dementias, and may account for more than 10% of the dementias. A substantial number of these cases are probably caused by a mutation in the gene for tau protein on chromosome 17.