| Abstract: | Four autopsied brains from mentally normal patients aged 43–49 who had cerebral β amyloid deposition were examined. Three patients had breast cancer, and in one of these cases it was associated with brain metastasis and brain radiation therapy. One other case had pulmonary small cell carcinoma. In two patients, small β amyloid deposits were only found in the frontal cortex. In another two patients, β amyloid deposits were found in many cortical areas and the density of plaques was higher than in the former two patients. No β amyloid deposition was found in the cerebella, basal ganglia, or brain stem in any of the four patients. When examined with end-specific antisera for the C-terminal of amyloid β protein (Aβ), Aβ42 was predominant in the diffuse plaques and immunoreactions for Aβ40 varied among the patients. The N-terminal of Aβ was truncated in a subset of plaques. Tau- and phosphorylated tau-reactive fine neurites were only found in the entorhinal cortex of Case 3. The apoE genotype of these four patients were 3/4, 3/4, 4/4 and 3/3, and therefore, the ε4 allele frequency (50%) was as high as that in AD. Three out of four patients had at least one ε4 allele, a risk factor of AD. There is a possibility that these subjects might develop AD when in their seventies. It may take 30 years from the beginning of Aβ deposition to the clinical manifestation of dementia. |
