Senile amyloidosis: principles of localization in a heterogeneous form of amyloidosis.

In order to identify amyloid deposits in patients over 60 years of age (so-called senile amyloid), the following five tissues were investigated under the light and electron microscope: 1. pituitary gland, 2. pancreatic islets of Langerhans, 3. heart, 4. aorta, and 5. brain. In all an increasing incidence of amyloid deposits was found with increasing age, and in the brain a significant quantitative increase in amyloid deposits with increasing age was observed. Despite the biochemical heterogeneity of amyloid found in old age, all the deposits seen in tissues examined were morphologically similar. Typical amyloid fibrils were always found (diameter 60-100 A), and these were invariably deposited extracellularly and primarily on basement membranes. The amyloid-binding basement membranes were in most cases those of myocytic, but were also those of endothelial or epithelial cells. The almost invariable involvement of blood vessels, indicates the importance of these structures in the genesis of the various forms of senile amyloid.