Amyloid is formed when certain proteins fold in an abnormal way to form fibrils, which have a unique chemical structure. These protein fibrils progressively deposit and accumulate in organs and tissues of the body, disrupting normal function. Without treatment this may lead to organ damage and eventually organ failure. Improved testing methods have increased the ability to identify the proteins which are known to misfold and cause amyloidosis. (as of 2022, 36 proteins have been identified as amyloidogenic in humans).
Amyloid deposits cannot be broken down easily by the body, and as a result, the deposits build up in certain tissues and organs. It is not fully understood what causes some amyloid to form, nor do we know why it occurs so rarely. Amyloidosis is progressively debilitating and ultimately fatal: currently there are treatments available to stabilize or reduce the amount of on-going amyloid accumulation. Early diagnosis allows for appropriate intervention to slow the rate deposition.
How does a person develop Amyloidosis?
Amyloidosis can be
- acquired (not a condition you were born with, but something that develops over time), or
- hereditary, (occurring due to a faulty gene).
What is affected by having Amyloidosis?
Amyloidosis can be
- localized (amyloid protein produced and deposited only in one small area of the body), or
- systemic (amyloid protein circulates in the blood and deposits in one or more organs)
Globally, research is being done to develop new treatments for all types of amyloidosis.
Different types of amyloidosis
Over 20 types of amyloidosis have been identified; each type is different, requiring different treatments. The most common types of Amyloidosis are AL, AA and ATTR:
- AL Amyloidosis is a light chain amyloid caused by a bone marrow disorder. AL Amyloidosis is the most commonly diagnosed systemic amyloidosis in the developed world.
- AA Amyloidosis occurs when the serum amyloid A (SAA) protein increases substantially in response to a long-term inflammatory disorder such as rheumatoid arthritis
- ATTR Amyloidosis involves the protein Transthyretin which is produced in the liver; its function is to transport thyroxin and retinol (Vit A). ATTR Amyloidosis can be Hereditary (hATTR), or Wild Type (ATTRwt). In the hereditary form (hATTR), 136 different variants have been identified; each variant presents its own set of unique symptoms, and age of onset.
Other forms of amyloidosis will be discussed elsewhere on this website.