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What is amyloidosis?

Amyloidosis refers to a group of diseases characterised by the accumulation of an abnormal protein called amyloid which builds up in tissues and organs. Amyloidosis is a serious condition which can lead to life-threatening organ failures. Amyloidosis is considered a rare disease due to its low incidence.

There are several types of amyloid diseases. AL amyloidosis (also called light chain amyloidosis) is the most prevalent type with an estimated incidence of 9 cases per million inhabitants/year.  However, it is thought that misdiagnosis due to the clinical scenarios that mimic this condition may mean the true figure is higher.

 

What is the relation between amyloidosis and myeloma?

AL amyloidosis is related to multiple myeloma in two ways. Firstly, it is the abnormal cells in the bone marrow called plasma cells (as in myeloma), which are part of the immune system that makes antibodies to fight infections. The plasma cells make certain type of proteins called immunoglobulins act as antibodies, and they are composed of four protein chains, two lights (called kappa and lambda) and two heavies. In AL amyloidosis patients, plasma cells produce an abnormal immunoglobulin light chain, amyloid, which is deposited in tissues and organs, causing them damage and affecting their functions. Amyloidosis is also related to myeloma in the sense that amyloidosis treatment uses the same procedures and drugs as myeloma treatment.

Around 10-15% myeloma patients will develop amyloidosis. This disease is called multiple myeloma associated amyloidosis and it is treated in the same way as amyloidosis.

 

How is amyloidosis diagnosed?

Early diagnosis is key in this disease as it can prevent further organ damage. Different tests may be run to diagnose amyloidosis:

  • Laboratory tests. Blood and urine tests may detect an abnormal amount of protein. Depending on the symptoms, tests may be indicated to investigate kidney, heart, thyroid or liver function.
  • Imaging test. These are scans of different types which will indicate the extent of the diseases. Special testing of specific organs, such as an echocardiogram for heart function, could be indicated.
  • The biopsy consists of taking a small piece of tissue. It is usually taken from the skin of the stomach area (abdominal fat biopsy) or the rectum, or indeed the organ affected by the amyloid deposits.

 

What are the main amyloidosis treatments?

The aim of the therapy is firstly to stop the organ damage and then to allow for improvement in the function of organs such as the heart or kidney. The recovery can be a slow process. At present, there are no specific drugs that can help the body to remove the amyloid deposits. Such drugs are in clinical trials and show great promise. Hence, the main treatment for amyloidosis is very similar to that for myeloma using myeloma drugs. Both diseases have the same origin and several data show that these drugs have even better results in amyloidosis patients than in myeloma patients.

The options are either some form of chemotherapy or consideration of a stem cell transplant using stem cells taken from the patient themselves. For the amyloidosis patient who is relatively young and fit, a stem cell transplant (SCT) would be the most suitable option. However if there is substantial organ function damage, then SCT can have unacceptably high risks. SCT can provide a long remission and very good results.

For most other patients, chemotherapy is the treatment of choice. The most important drugs for these patients are proteasome inhibitors (usually a drug called bortezomib, and more recently newer variants of this called as carfilzomib and ixazomib) that have been extremely useful and powerful in amyloidosis treatment. These drugs have really changed the landscape of this disease. They are used in combination with other agents and provide deep durable responses.

In addition to proteasome inhibitors, the current physician’s choice of treatment consists of chemo drugs such as melphalan, cyclophosphamide and immunomodulators (such as thalidomide, lenalidomide and pomalidomide).

 

References

  • Orphanet Journal of Rare Diseases – AL Amyloidosis, E.Desport et al. – 21 August 2012 -https://ojrd.biomedcentral.com/articles/10.1186/1750-1172-7-54
  • Medscape – Pitfalls in the Diagnosis of Primary Amyloidosis – Cheng E. et al. – Clin Lymphoma Myeloma. 2010;10(3):177-180. – http://www.medscape.com/viewarticle/723576
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