Amyloid A Amyloidosis Secondary to Rheumatoid Arthritis

Amyloids are insoluble fibrous protein aggregates sharing specific structural traits. Abnormal accumulation of amyloid in organs may lead to amyloidosis, and may play a role in various diseases. The name amyloid comes from the early mistaken identification of the substance as starch (amylum in Latin), based on crude iodine-staining techniques. For a period, it was debated whether or not amyloid deposits were fatty or carbohydrate deposits until it was finally found that they were, in fact, deposits of proteinaceous mass. The underlying molecular abnormalities may be either acquired or hereditary and more than 20 different proteins can form clinically or pathologically significant amyloid fibrils in vivo. Current nomenclature lists of amyloid fibril protein have been provided from the nomenclature committee of the International Society of Amyloidosis. Amyloidosis is a disorder of protein conformation and metabolism that results in the deposition of insoluble amyloid fibrils in tissues, which causes organ dysfunction; systemic amyloidosis is characterized by failure of various organs and the presence of amyloid precursor protein in the serum. Reactive amyloid A (AA) amyloidosis is one of the most severe complications of several chronic disorders, particularly rheumatoid arthritis (RA), and indeed, most patients with reactive AA amyloidosis have an underlying rheumatic disease. An extra-articular complication of RA, AA amyloidosis is a serious, potentially lifethreatening disorder caused by deposition in organs of AA amyloid fibrils, which derive from the circulatory acute-phase reactant, serum amyloid A protein (SAA). AA amyloidosis secondary to RA is thus one of the intractable conditions found in patients with collagen vascular diseases and is an uncommon yet important complication of RA.