Amyloidosis is a group of rare but serious conditions caused by deposits of abnormal protein, called amyloid, in tissues and organs throughout the body.
Proteins begin as a string of amino acids that fold themselves into a three-dimensional shape. This 'protein folding' allows them to perform useful functions within our cells.
Amyloid is a description of proteins which have folded abnormally and then collected together. In this form they do not break down as easily as normal proteins and can build up in tissues and organs.
If this build-up causes the tissues or organs to stop working properly, the resulting conditions are called amyloidosis.
The amyloid deposits occasionally only affect one part of the body (localised amyloidosis), but more often several different part of the body are affected (systemic amyloidosis), such as the heart, kidneys, liver, or nerves.
Without treatment to address the underlying cause, the amyloid deposits can eventually lead to organ failure and death – sometimes within only a year or two.
There are around 30 different proteins that can misfold and form amyloid, which is why there are many different types of amyloidosis.
Overall, about 600 new cases of amyloidosis are diagnosed in the UK every year and most occur in older people.
This page will focus on the most common type in the UK, called AL amyloidosis (previously known as primary amyloidosis).
Signs and symptoms of AL amyloidosis
AL amyloidosis can affect any organ, and the symptoms depend on which organs are affected.
Most often amyloid is deposited in the kidneys and may cause kidney failure. Symptoms of kidney failure can include fluid retention (oedema), tiredness, weakness and loss of appetite.
Amyloid deposited in the heart can cause it to become enlarged and impair its ability to pump blood efficiently around the body. This may result in heart failure, which can cause symptoms such as causeshortness of breath and oedema.
Some of the other possible signs and symptoms of AL amyloidosis include:
feeling lightheaded or fainting, particularly after standing or sitting up
numbness or a tingling feeling in the hands and feet (peripheral neuropathy)
an irregular heartbeat (arrhythmia)
chest pain (angina)
in men, erectile dysfunction
diarrhoea or constipation
blood spots on the skin
carpal tunnel syndrome – compression of the nerve in your wrist
an enlarged tongue
AL amyloidosis doesn’t usually cause any problems with memory loss, thinking speed, language, understanding, or judgement.
What causes AL amyloidosis?
AL amyloidosis occurs when an abnormality in the plasma cells found in bone marrow (the spongy tissue at the centre of some bones) results in the excessive production of proteins called 'light chains'.
Normally, light chains form part of antibodies (proteins that help protect the body from illness and infection), but in cases of AL amyloidosis, large numbers of misfolded light chains are produced and these clump together into thread-like fibres that the body cannot clear away easily.
These fibres typically then gradually start to form deposits in the heart, kidneys, nerves, or liver.
The abnormal white blood cells in the bone marrow are usually benign (non-cancerous), but some cases of AL amyloidosis are linked to a type of bone marrow cancer called multiple myeloma.
Unlike some other types of amyloidosis, AL amyloidosis is not inherited, so a person with the condition cannot pass it on to their children.
Diagnosing AL amyloidosis
Diagnosis of AL amyloidosis can be challenging, since the symptoms are often very general.
The diagnosis can be confirmed by removing a biopsy (small tissue sample) from the affected part of the body, and examining this under a microscope in the laboratory, using special stains to check for amyloid proteins.
How the tissue sample is removed will depend on which parts of the body are affected. In some people with suspected anyloidosis, a biopsy of tummy fat (taken using a needle) or a biopsy from the gut (taken during an endoscopy) may give a positive result.
Further diagnostic tests are also available at the National Amyloidosis Centre at the Royal Free Hospital in London.
These include a type of scan called SAP scintigraphy, which involves being injected with a mildly radioactive version of blood protein before being scanned with a gamma camera.
This protein coats any amyloid deposits in your body, which highlights most areas of the body affected by amyloid deposits.
You may also have further tests to assess how the amyloid deposits have affected your individual organs. For example, an echocardiogram (heart ultrasound scan) may be carried out to check the condition of your heart.
Treating AL amyloidosis
There are currently no treatments available that can directly remove the amyloid deposits associated with AL amyloidosis. Treatment aims to prevent the further production of abnormal light chains while monitoring and treating any problems affecting your organs.
This can give your body enough time to gradually clear the deposits before they build up again and can help prevent organ damage.
In most cases, this will involve having chemotherapy to damage the abnormal bone marrow cells and inhibit production of the abnormal proteins.
You will also need treatment for organ failure – for example, you may need diuretic medication to treat heart failure and you may needdialysis if you have kidney failure.
Some people with kidney failure may be suitable to receive a kidney transplant, although the underlying bone marrow disorder will need to be suppressed by chemotherapy to prevent build-up of amyloid in the new kidney.
After chemotherapy, you will need regular check-ups every six to 12 months to look for signs of the condition returning (relapsing). If it does relapse at any stage, chemotherapy may need to be started again.
Before effective treatments for AL amyloidosis were discovered, the outlook for the condition was poor, with many people only living for a few months.
With modern treatments, the outlook varies depending on the extent of the amyloid deposits, your age and general health, and how well you respond to treatment.
Overall, many people with AL amyloidosis now survive for several years after they are diagnosed with the condition and increasing numbers of people are living for a decade or more.Light micrograph of amyloid nodules (blue) in a human spleen
Less common types of amyloidosis
AA amyloidosis – occurs as a result of a long-standing inflammatory condition, such as rheumatoid arthritis. Treating the underlying condition will often stop the amyloidosis getting worse, or may even improve it.
Hereditary amyloidosis – this results from inheriting a mutated (changed) gene from one of your parents, and can sometimes be treated with a liver transplant.
ATTR amyloidosis – types of amyloidosis caused by amyloid deposits made up of a protein called transthyretin (TTR), some of which are inherited and some of which are not. It can sometimes be treated with a liver or heart transplant.