A number of neuritic plaques with Alzheimer's disease are seen here. They have an amyloid core as seen here with Congo red stain. Small peripheral cerebral arteries may also be involved. There appears to be a problem with beta amyloid precursor protein, but the exact pathogenesis is unknown. It is interesting that the gene coding for cerebral amyloid is on chromosome 21--and persons with trisomy 21 living to age 40 invariably develop Alzheimer's disease.