Amyloidosis (Amyloidoses)

Amyloid fibril formation and classic facial features of AL amyloidosis[1]

Amyloidosis refers to a group of diseases resulting from abnormal deposition of amyloids in various tissues.

Presentation

In patients with amyloidosis, symptoms presented are as a result of the abnormality in the function of the particular organs involved [7]. Some of the organs that can be affected include the heart, kidney, liver, bowels, skin, nerves, joints and lungs. This is why symptoms are unclear. Presentations can include fatigue, dyspnea, lack of appetite, tingling, weight loss, numbness, decreased appetite, enlarged tongue and general swelling.

Depending on what organs are affected, amyloidosis can lead to cardiomyopathy, heart failure, peripheral neuropathy, arthritis, malabsorption, diarrhea, liver failure and liver damage. When amyloidosis affects the kidney, the resultant condition is nephrotic syndrome. This characterised by the loss of protein in the urine and swelling of the extremities.

Workup

To diagnosis amyloidosis, the presence of the characteristic amyloid protein needs to be established. A biopsy specimen of the involved tissue is required to establish this. This may be obtained from the mouth, rectum, fat, kidney, heart or liver [8]. The presence of the protein in a biopsy specimen can be examined with a special dye known as the Congo red stain.

Treatment

Normally, treatment of amyloidosis involves correction of organ failure. This ensures the treatment of any underlying illness like multiple myeloma, infection or inflammation [9]. The condition is most of the time, discovered after extensive organ damage has been done. This is why treatment is initially targeted at stabilizing the function of the affected organ. In systemic amyloidosis, kidney failure is the most common cause of death.

Treatment generally includes chemotherapy agents that are used for certain cancers and dexamethasone for its anti-inflammatory actions.

A treatment procedure that is still in its early stages is the combination of melphalan, a cancer chemotherapy medication and bone-marrow stem cell transplant. The results from this treatment method have been promising in patients with uncomplicated underlying medical condition. These aggressive treatment options with stem-cell transplantation and high doses of chemotherapy have been hailed as amazing breakthrough for the treatment of patients with amyloidosis.

Familial amyloidosis can be treated with liver transplantation [10]. This treatment however, requires accurate diagnosis of the specific protein that is guilty of causing the disease.

Dialysis amyloidosis can be treated also with the aid of kidney transplantation.

Prognosis

The prognosis is dependent on the form of amyloidosis as well as general response to treatment. Systemic amyloidosis progresses slowly but if left untreated, it could prove fatal [6]. Some forms of amyloidosis like familial amyloidosis have an average survival span of 15 years while others have a survival span of as short as one year. Generally, outlook is dependent on the vital organ that is involved.

Etiology

Amyloidosis is caused by changes in proteins that make them insoluble. This in turn, makes them to become deposited in organs and tissues. The amyloid proteins build up mostly in the tissue space between cells [3]. Gene mutation is the main reason why proteins change from normal proteins to amyloid proteins.

Epidemiology

The condition is a rare disease with an incidence of 1 to 5 cases per 100,000 people each year around the world [4].

Sex distribution
Age distribution

Pathophysiology

The body’s cells make proteins in different ways. Some of the cells make proteins in one piece while other cells make only protein fragments. The fragments often join together to form the complete protein. However, such protein can sometimes fall apart, going back to just fragments. This is what is seen with proteins that cause amyloidosis [5]. The disintegrated fragment becomes insoluble and gets deposited in unnatural sites.

The full pathophysiological pathway of the amyloidosis is however dependent on the type of amyloidosis.

Prevention

There is no clear method of preventing amyloidosis.

However, secondary forms of amyloidosis can be prevented following treatment of underling diseases that are associated with inflammation. For familial amyloidosis, genetic counselling is very important.

Summary

Amyloidosis refers to a group of diseases which arise following the abnormal deposition of proteins in certain body tissues [1]. The abnormally deposited proteins are referred to as amyloid.

Depending on the structure of the amyloid, the protein can either accumulate in a certain tissue or be widespread therefore affecting different organs and tissues. There are 30 documented amyloid proteins today.

Amyloid proteins can be deposited in a localized area. In this situation, it may not be harmful. If it is deposited in a single tissue, it may impair certain functions in the body. This is known as localised amyloidosis. Systemic amyloidosis is seen when the proteins are deposited all over the body. Systemic amyloidosis can bring about extensive changes in just about any organs of the body including the heart, kidneys and lungs.

There are different kinds of amyloidosis. They include [2]:

Primary amyloidosis (AL)

  • This occurs without any known cause however, it is seen in people affected by multiple myeloma

Dialysis-related amyloidosis (Abeta2M)

  • This kind of amyloidosis is seen in older people who have been on dialysis for at least a period of 5 years. 

Secondary amyloidosis (AA)

Familial or hereditary amyloidosis (ATTR)

  • This type of amyloidosis is rare and it is replicated across families. It is generally caused by an abnormal amyloid protein known as the transethyrin (TTR). This protein is made in the liver. 

Senile systemic amyloidosis (AS)

  • This arises following the deposition of normal TTR in the heart and other tissues. It is seen most commonly in older men. 

Organ-specific amyloidosis

  • This is caused by the deposition of amyloid protein in single organs. The skin is affected the most. 

Patient Information

Amyloidosis is a rare disease that occurs when a substance known as amyloid builds up in any of the body organs. Amyloid is an abnormal protein that is produced in the bone marrow but can get deposited in any tissue or organ.

Amyloidosis can affect different organs in different patients and there are different kinds of amyloid based on the organs affected. However, the common organs affected are the digestive tract, the nervous system, spleen, liver, kidney and heart. Severe cases of amyloidosis can lead to life-threatening organ failure.

There is no known complete cure for amyloidosis rather treatment is focused on helping you manage the symptoms and the limiting of the production of amyloid protein.

Self-assessment

References

  1. Chiti F, Dobson CM. Protein misfolding, functional amyloid, and human disease. Annu Rev Biochem. 2006;75:333-66.
  2. Fandrich M, Meinhardt J, Grigorieff N. Structural polymorphism of Alzheimer Abeta and other amyloid fibrils. Prion. Apr-Jun 2009;3(2):89-93.
  3. Fandrich M. On the structural definition of amyloid fibrils and other polypeptide aggregates. Cell Mol Life Sci. Aug 2007;64(16):2066-78.
  4. Westermark P, Benson MD, Buxbaum JN, Cohen AS, Frangione B, Ikeda S, et al. A primer of amyloid nomenclature. Amyloid. Sep 2007;14(3):179-83.
  5. Buxbaum JN. The systemic amyloidoses. Curr Opin Rheumatol. Jan 2004;16(1):67-75. 
  6. Pavelka, Margit; Roth, Jürgen. Functional Ultrastructure: An Atlas of Tissue Biology and Pathology. Springer. p. 258. ISBN 3-211-83564-4.
  7. Breathnach SM: Amyloid and amyloidosis. J Am Acad Dermatol. 18:1-16 1988 3279077
  8. Buxbaum J: The amyloidoses. Mt Sinai J Med. 63:16-23 1996 8935845
  9. Wong CK: Amyloid. History and modern concepts. Clin Dermatol. 8:1-6 1990 2224728
  10. Falk RH, Comenzo RL, Skinner M: The systemic amyloidoses. N Engl J Med. 337:898-909 1997 9302305



Media References

  1. Amyloid fibril formation and classic facial features of AL amyloidosis, CC BY-SA 3.0

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