1) A group of sporadic, familial and/or inherited, degenerative, and infectious disease processes, linked by the common theme of abnormal protein folding and deposition. As the amyloid deposits enlarge they displace normal tissue structures, causing disruption of function. Various signs and symptoms depend on the location and size of the deposits.

2) A group of diseases in which protein is deposited in specific organs (localized amyloidosis) or throughout the body (systemic amyloidosis). Amyloidosis may be either primary (with no known cause) or secondary (caused by another disease, including some types of cancer). Generally, primary amyloidosis affects the nerves, skin, tongue, joints, heart, and liver; secondary amyloidosis often affects the spleen, kidneys, liver, and adrenal glands.