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Amyloidosis

What is amyloidosis?

A build-up of amyloid proteins, a type of malformed protein, is responsible for a group of conditions referred to as amyloidosis. Although amyloidosis is rare, for the people who have this disorder it can have serious complications and can sometimes be fatal.

What happens in amyloidosis

Normally a string of amino acids fold into a specific shape to create proteins that can perform certain functions. However, in amyloidosis something goes wrong in how one of the types of protein fold. The malformed amyloid proteins clump together, making it more difficult for them to be broken down, and gradually they build up in the tissues and organs in the body. This is known as amyloidosis.

  • If amyloidosis occurs in only one part of the body, it is referred to as localised amyloidosis. Localised amyloidosis is rare. It may not need treatment, and sometimes surgical removal of the deposits can cure the condition.
  • However, amyloidosis most often occurs as systemic amyloidosis, where the amyloid proteins build up in several areas in the body such as the heart, liver, spleen, kidneys, bladder, digestive tract, bones and joints, skin, nerves or eyes; the build-up affects the organs' ability to function normally and can eventually lead to organ failure.

Amyloidosis is mostly diagnosed in older people, especially men, and around 500 - 1000 new cases are diagnosed in the UK each year.

Most common types of amyloidosis

About 30 different proteins can develop this amyloid malformation, so there are as many types of amyloidosis, along with numerous variants. When the name of an amyloidosis begins with capital letters, these are abbreviations that indicate the type of protein involved - the first A is for 'amyloid'. Three common types are:

  • AA amyloidosis: The main organs affected by this systemic form of amyloidosis are the kidneys, but sometimes also the liver, heart or digestive tract; this type can develop as a long-term complication of a chronic inflammatory disorder such as rheumatoid arthritis, diabetes, ankylosing spondylitis or Crohn's disease. Effective anti-inflammatory and immunosuppressive treatment of the underlying condition, for example rheumatoid arthritis, can reduce the risk of developing AA amyloidosis.
  • AL amyloidosis (previously known as primary amyloidosis): This is the most common type of systemic amyloidosis in the UK, and the amyloid proteins can build up in the heart, kidneys, peripheral nerves (the nerves outside the spinal cord and brain), gastrointestinal tract, respiratory tract - in fact, almost any organ except the brain. In AL amyloidosis the amyloid malformation affects a type of protein referred to as "light chains"; these form part of the plasma cells, a type of white blood cell that produces antibodies to fight off infection. AL (or light chain) amyloidosis is diagnosed in people who are mostly over 45 years old, though it can sometimes be present in younger people. AL amyloidosis has been diagnosed in 12-15% of people who have multiple myeloma. Because of the various parts of the body that can be affected, the symptoms are varied - as is the severity of the condition - but in more than two-thirds of cases the kidneys are involved and in over half of cases the heart is affected; weakness and shortness of breath (dyspnoea) are the most common symptoms. Some people have an enlarged tongue. Chemotherapy is the standard treatment option, with diuretics and a pacemaker used to treat any heart disease.
  • ATTR amyloidosis: This is a common inherited form of systemic amyloidosis, in which the transthyretin protein (responsible for transporting Vitamin A (retinol) and the hormone thyroxine in the body) is affected; however, there are dozens of different mutations, it is not always inherited and each mutation provides a different set of symptoms depending on which organs are involved. The liver, nerves, heart and kidneys may be impaired and it can lead to the need for a liver transplant, where the protein for this type of amyloidosis is formed. People of African ancestry are more likely to develop the cardiac form of ATTR amyloidosis.

WebMD Medical Reference

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