About the Disease
The best way to distinguish the different forms of amyloid is by chemical characterization. (Immuno-)histochemical typing of amyloid is readily available, but does require expertise in interpreting the results. Proteomics-based methods are used in some centers to characterize the type of amyloid with confidence. A piece of tissue, a biopsy, can be used for this purpose to reveal the type of amyloid involved. In addition to the typing, a second descriptor is whether the patient’s amyloid is limited (localized) or throughout the whole body (systemic). In systemic amyloidosis, it must also be clear which type of systemic amyloidosis is involved.
Each amyloid syndrome should be named according to the Nomenclature Guidelines of the ISA. Most of the distinct amyloidosis syndromes are named after the fibril forming protein, e.g. AL (amyloid derived from immunoglobulin light chain) amyloidosis (localized or systemic), AA amyloidosis (amyloid derived from SAA – serum amyloid A protein), wild type (wt) ATTR (amyloid derived from TTR [transthyretin]) amyloidosis or hereditary ATTRV30M amyloidosis. However, some amyloid fibril proteins such as Aβ, ATau, Aα-Syn and AIAPP play a pathologic role in neurodegenerative or endocrine diseases that are not clinically classified as amyloidosis. The three most common types of systemic amyloidosis are AL, AA, and ATTR amyloidosis.
After detection of amyloidosis it is important to investigate which organs and tissues have been affected by amyloid deposition. Therapy depends on the type of amyloid, the underlying process that is responsible for the production of precursor proteins, and the severity of organ and tissue disease caused by amyloid deposition.