Systemic (reactive) AA amyloidosis, also called simply AA amyloidosis, is a form of amyloidosis, i.e., a disease characterized by the abnormal aggregation and deposition of insoluble protein in the extracellular space of various tissues and organs. In AA amyloidosis, the deposited protein is serum amyloid A (SAA), an “acute-phase” protein that is normally soluble and whose plasma concentration is highest during inflammation. AA amyloidosis is a rare disease, which accounts for about 3% of all systemic amyloidosis cases. It is associated with inflammation in a variety of diseases, including rheumatoid arthritis, inflammatory bowel disease, familial Mediterranean fever, tuberculosis, osteomyelitis, and bronchiectasis.