A group of diseases that result from the abnormal deposition of a protein, called amy- loid, in various tissues of the body. Amyloid protein can be deposited in a localized area, and it may not be harmful or it may affect only a single tissue of the body. This form of amyloidosis is called localized amyloidosis. Amyloidosis that affects tissues throughout the body is referred to as systemic amy- loidosis. Systemic amyloidosis can cause serious changes in organs throughout the body. Amyloidosis can occur as its own entity or secondarily, as a result of another illness, including multiple myeloma, chronic infections (such as tuberculosis or osteomyelitis), or chronic inflammatory diseases (such as rheumatoid arthritis and ankylosing spondylitis).