Amyloidosis

What is it?

Amyloid is the term used to describe deposits of fibrils of protein folded in a particular, abnormal way in the cells and tissues. When these misfolded proteins form an insoluble deposit in an organ in the body - for example, the heart, the kidneys or nerves - the condition is called amyloidosis.

The collection of these abnormal proteins interferes with the normal functioning of the organ affected.

Since there are more than 20 different proteins that may form amyloid, there are also many different types of amyloidosis.

The most common in the UK is AL amyloidosis, also known as light chain amyloidosis or primary amyloidosis. In this form, abnormal cells in the bone marrow produce abnormal antibody proteins that form the amyloid. Almost any organ can be affected but often the heart, kidney, nerves and gut.

In AA, or secondary amyloidosis, it occurs as a result of an inflammatory condition, most often rheumatoid arthritis, due to the long-term overproduction of an otherwise normal inflammatory protein called normal-sequence serum amyloid A protein.

There are also some rarer hereditary forms.

Who's affected?

Amyloidosis is rare, being diagnosed in between one and five in every 100,000 people every year. It's more common in older people and is also slightly more common in men than in women.

What are the symptoms?

It's the accumulation of amyloid in an organ that causes the organ to malfunction and symptoms to develop. However, amyloid may accumulate in organs of the body for many years before problems arise and any of the resultant symptoms are noticed.

The symptoms that a person experiences depend on which organ is affected.

If amyloid is deposited in the kidneys, chronic kidney failure may occur. This in turn causes symptoms such as fluid retention, tiredness, lethargy, weakness and loss of appetite.

When amyloid is deposited in the heart it may become enlarged and unable to pump blood effectively around the body. This results in the development of chronic heart failure with symptoms of breathlessness and fluid retention.

How is it diagnosed?

The patient’s symptoms and signs may point to a diagnosis of amyloidosis but it can be difficult to diagnose with certainty. To confirm the diagnosis, a biopsy may be taken from an affected part of the body and the sample of tissue is examined under the microscope. Abnormal protein deposits indicate amyloidosis.

Newer and more sophisticated scans such as serum amyloid P (SAP) scintigraphy may sometimes be done instead of a biopsy.

What's the treatment?

It isn't always easy to treat amyloidosis, and there is no treatment yet that specifically targets the amyloid depositing in the tissues. In cases where it's secondary to another problem (AA amyloidosis), such as rheumatoid arthritis, treating that original problem may stop the progress of amyloidosis or may even reverse it.

In cases of primary amyloidosis (AL amyloidosis), chemotherapy drugs may be given to suppress production of new amyloid and cause regression of existing amyloid deposits.

Occasionally, transplantation of a damaged organ is necessary. However, even after this has been carried out the new organ may become affected by amyloidosis.

Treatment may also be aimed at supporting the function of damaged tissues and treating complications such as heart or kidney failure.

Overall, many types of amyloidosis follow a steadily progressive course and may prove fatal within a year or two.