[Cerebral amyloidosis].

Cerebral amyloidoses affects only the central nervous system, with rare exceptions. Most of them are related to A beta deposits. They usually occur in the absence of genetic defect in the precursor of A beta. The prevalence and density of A beta deposits increase during the aging process, and in Alzheimer's disease. This A beta amyloidosis has never been transmitted. In contrast, PrPres occurs as a sporadic or genetic event, and induces transmissible amyloidoses (Creutzfeldt-Jakob's disease and other disorders related to non conventional agents). PrPres may be the infectious agent itself (prion hypothesis). Other proteins are rarely responsible for cerebral amyloidoses. The fascinating hypothesis that a common mechanism would be acting in all cerebral amyloidoses has not yet been confirmed.