Amyloidosis: the disease
What is amyloid?    
Types of amyloid    
Movie about amyloidosis    

What is amyloid?

Amyloid fibrils are structures in which misfolded proteins are deposited in tissue and organs. Different proteins can be deposited as amyloid in various sites of the human body. When in a piece of tissue (a so-called biopsy) these deposits are viewed under a microscope in normal light, the material looks amorphous. However, if the same deposits are viewed under an electron microscope with higher magnification, massive amounts of small non-branching amyloid fibrils can be seen. When a biopsy is stained with Congo red dye, the deposits will stain red. A characteristic feature of amyloid is that these red deposits will turn into apple green if viewed in polarized light. When amyloid deposition leads to signs and symptoms of disease it is called amyloidosis.

  

Fat tissue stained with Congo red: apple green birefringence of amyloid deposits

 

Most important and common types of amyloidosis

As stated above, different proteins can be deposited in various sites in tissue as amyloid. These deposits can be strictly localized (such as in the pancreas, the brain, the trachea) or systemically, i.e. in the whole body. Localized forms of amyloid are relatively frequent (such as in the brain in Alzheimer's disease and in the pancreas in maturity onset diabetes mellitus). The incidence of systemic amyloidosis is rare and about 8-12 per million inhabitants per year.

Another way to distinguish different forms of amyloid is whether they are inherited or not (inherited versus acquired). However, nowadays the best way to distinguish the different forms of amyloid is by a chemical characterization. This (immuno-)chemical typing of amyloid is generally accepted and should be done in all patients with amyloid. A piece of tissue, a biopsy, can be used for this purpose to reveal the type of amyloid involved. It must be clear in each patient whether deposition of 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. The three major types of systemic amyloidosis are AL, AA, and ATTR amyloidosis. New proteomics-based methods are currently being developed and evaluated to characterise the type of amyloid with confidence.

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.

 

Movie about amyloidosis: Amyloidosis Awareness (made by Greg Singer)

A film, Amyloidosis Awareness, encourages understanding of the main types of amyloidosis, methods of diagnosis, treatment options, and resources for more information. While the film is primarily targeted to doctors, medical students and other health care providers, it will have a broad appeal such that the patient community can also benefit from its message. Use this link to watch the movie.