Congophilic microangiopathy in the pathogenesis of Alzheimer's syndrome (presenile dementia).

In a large proportion of cases of Alzheimer's presenile dementia the major causal mechanism is compromise of the blood-brain barrier as the result of Congophilic microangiopathy occurring in a relatively young age group. This allows chronic access of serum proteins, perhaps of a selective neurotoxic type, to the cerebrum. The effect on neuronal cells in specific locations, e.g. hippocampus, is to induce the formation of paired helical filaments, autophagia of filamentous protein (filarin) and neuronal degeneration. The partially digested filarin is further enzymatically cleaved by microglia to produce the amyloid core of the neuritic plaque.