[Transmissible and non-transmissible brain amyloidoses: neurodegenerative disorders of different etiologies and the same pathogenesis].

I report here the molecular, ultrastructural and immunohistochemical similarities between transmissible (scrapie, Creutzfeldt-Jakob disease and Gerstmann-Sträussler-Scheinker syndrome) and non-transmissible (Alzheimer's disease, hereditary cerebral hemorrhage with amyloidosis--Dutch (HCHWA-D) and Icelandic (HCHWA-I) types) brain amyloidoses. The central pathogenic event in both types of amyloidoses is a synthesis and a processing of amyloid precursor followed by an accumulation of a final deposit. PrPc and APP are amyloid precursors and PrPsc and beta-A4 are final deposits in transmissible and nontransmissible cerebral amyloidoses of Alzheimer's disease type, respectively. In HCHWA-I, cystatin C serves the role of the amyloid precursor protein. The amyloid plaque composed of a different proportions of amyloid fibers, dystrophic neurites and astrocytes and microglia cells is the crucial neuropathological entity. The role of microglial cell as amyloid producer/processor cell seems to be analogous in both types of amyloidoses. The impairment of slow axoplasmic transport which leads to the accumulation of neurofilament triplet protein in the transmissible and tau protein in the non-transmissible cerebral amyloidoses causes the development of dystrophic neurites and neuropil threads. The other elements of neuropathology like Hirano bodies and granulovacuolar degeneration may be only secondary and non-specific phenomena.