Senile amyloid deposition

Amyloid deposition in the aged was studied in a wide selection of tissues from 194 necropsies of subjects aged over 65 years, there being no clinical manifestation of amyloidosis. We employed conventional Congo red staining with the aid of a polarising filter for the identification of amyloid. We analysed the deposits histochemically for tryptophan content and reaction to oxidation using the potassium permanganate method in 26 subjects aged over 85 years. Both the frequency of amyloid deposition and the number of organs involved tended to increase with advancing age, and both increased after the ninth decade with little sex difference. Amyloid deposition preferentially occurred in the aorta, heart, lung, prostate and pancreas among the organs examined. Visceral involvement tended to be confined to the vasculature except in the prostate and pancreas. In cases associated with predisposing conditions considered to evoke secondary amyloidosis such as tuberculosis, multiple myeloma, and rheumatoid arthritis more amyloid was found but the distribution of the deposits was similar by organ and intravisceral site to that of cases unassociated with predisposing disorders. In both groups of cases amyloid was found to contain tryptophan, indicative of immunoamyloid and, with a few exceptions, to be resistant to oxidation by potassium permanganate indicating an immunoglobulin AL component. It can be concluded that senile amyloid should be classified as a form of so-called primary amyloidosis because of its widespread distribution. Its occurrence independent of predisposing disorders and its chemical composition. Subclinical chronic inflammation of the respiratory, gastrointestinal and urogenital tracts may provide the necessary prolonged immunological stimulus to lead to amyloid deposition in ageing tissues.