MedGen

The presence of amyloid deposition in one or more tissues. Amyloidosis may be defined as the extracellular deposition of amyloid in one or more sites of the body. [from HPO]

Extracellular deposition in cardiac tissue of a proteinaceous material that, when stained with Congo red, demonstrates apple-green birefringence under polarized light and that has a distinct color when stained with sulfated Alcian blue. Viewed with electron microscopy, the amyloid deposits are seen to be composed of a beta-sheet fibrillar material. These nonbranching fibrils have a diameter of 7.5 to 10 nm and are the result of protein misfolding. [from HPO]