A term for a collection of diseases that result in the abnormal deposition of beta-pleated amyloid protein throughout the body. In animals, only reactive amyloidosis has been described and its precursor protein is serum amyloid A protein. It has been demonstrated conclusively that some Shar-Pei have an inherited form of amyloidosis. Amyloid AA composes the fibrils in the amyloid deposits in the body which stain brick red with Congo Red stain (CRS)(see Figure 2) and everything else pink. When examined by a pathologist using a special microscope, they have a characteristic apple green color with birefringence under polarized light (see Figure 3). In severe cases, the amorphous pink amyloid substance may be obvious to the pathologist on microscopic exam even under normal stains without CRS (as in Figure 1) but submitted tissues cannot be said to be negative for amyloidosis unless the special stain is used.
Any time that inflammation occurs, certain chemicals are produced and released into the blood. These chemicals of inflammation are called the Acute Phase Reactant Proteins (APP). After the inflammation has gone away, the APP are broken down by the body and eliminated. Dogs (or people) with amyloidosis can't break these APP down into a form that can be excreted by the body and instead turn it into serum Amyloid AA and dump it outside the cells but still within the body.
We would like to thank Dr. Linda Tintle, DVM for her definitions.