am·y·loid de·gen·er·a·tion

infiltration of amyloid between cells and fibers of tissues and organs.

Farlex Partner Medical Dictionary © Farlex 2012

amyloidosis

A large group of diseases characterised by misfolding of extracellular protein. Insoluble toxic proteins are deposited as bundles of β-sheet fibrillar protein, either in specific organs (localised amyloidosis) or systemically (systemic amyloidosis). It can be primary or secondary to other conditions (e.g., tuberculosis, cancer, leprosy) and accompanied by immune changes.

Primary amyloidosis (AL amyloidosis, idiopathic amyloidosis)
An uncommon condition associated with plasma cell dyscrasias, where the accumulated amyloid fibres correspond to fragments of Ig light chains.

Tissues involved
Heart, GI tract, nerves, skin, tongue, joints, muscle.

Median survival
20 months with renal or cardiac amyloidosis; 40 months without.

Secondary amyloidosis (AA amyloidosis, reactive amyloidosis)
A group of conditions seen in chronic inflammation and multisystem disease, in which amyloid derives from a circulating acute-phase lipoprotein (serum protein 1).

Tissues involved
Liver, spleen, kidney, endocrine, lymph nodes.

Both types of amyloidosis contain amyloid P component, a non-fibrillary glycoprotein found in the circulation; scintigraphy after injection of 123I-labelled serum amyloid P component can locate tissue deposition of amyloidosis and, if the deposition is active, cytotoxic therapy may be instituted; focal amyloidosis commonly occurs in those organs most susceptible to ageing (e.g., the heart and brain), and is only symptomatic if the amyloid deposition is significant.