What is amyloidosis?
Amyloidosis is the general term given to a relatively rare and serious group of disorders in which an abnormal protein known as amyloid is produced. Amyloid (the word means “starch like”) is an unusually stable material which has a unique chemical structure formed when certain proteins fold in an abnormal way. These protein fibrils progressively deposit and accumulate in organs and tissues of the body, disrupting normal function. Without treatment this may eventually lead to organ damage and failure. At this time it is not known what triggers the initial formation of the amyloid protein and why this happens in such a small proportion of the population.
Amyloidosis can be:
- acquired - occurs spontaneously
- hereditary - occurs due to a faulty gene.
It can also be:
- localised - amyloid protein produced and deposited only in one small area of the body
- systemic - amyloid protein circulates in the blood and deposits in one or several organs of the body.
Amyloidosis is not a cancer but it is equally as serious.
Amyloidosis is classified according to the main protein trigger that causes that particular type of amyloidosis. Each type is given an abbreviation where the first letter A stands for amyloid and the subsequent initials stand for the amyloid protein. For example, in AL amyloidosis the A stands for amyloid and L for the type of fibril protein, light chain. More than 20 different types of amyloidosis have been identified at this time. Many of these are obscure and cause few problems. Each type of amyloidosis is different, requiring different treatments.
Some amyloidosis types include:
In AL amyloidosis a clone or single population of plasma cells grows excessively and produces an abnormal protein called an immunoglobulin light chain. They build up in the bloodstream and are progressively deposited as amyloid fibres (fibrils) in the tissues and organs of the body. AL amyloidosis can involve the kidney, heart, nervous system, liver and gastrointestinal soft tissues. AL amyloidosis is the most commonly diagnosed form of systemic amyloidosis in the western world.
ATTR and AFib amyloidosis
ATTR also includes senile amyloidosis but this is not an inherited disease. It is caused by overproduction of the normal protein TTR. This condition, which mainly affects the heart, is becoming more common as the average age of the population increases. Senile amyloidosis of the heart often coexists with benign bone marrow disorders creating the false impression that AL amyloidosis is the diagnosis.
Over the past 10 years there has been a much greater understanding of these diseases. With earlier diagnosis, great improvements in assessment and treatment regimes, many patients are now experiencing long remissions and living full lives.
How common is amyloidosis?
Amyloidosis is known as a rare group of diseases. In Australia a diagnosis of amyloidosis is not required to be reported on a state or national register, so we have no accurate way of knowing how many people are diagnosed with the disease each year.
Who gets amyloidosis?
Amyloidosis can occur at any age but it is more common in adults over the age of 50. Amyloidosis occurs more frequently in men than in women.
What causes amyloidosis?
At this time it is not known what triggers the initial formation of the amyloid protein and why this happens in such a small proportion of the population. Amyloidosis can be acquired (occurs spontaneously) or hereditary (occurs due to a faulty gene).
Research is going on all the time into possible causes of amyloidosis and certain factors have been identified that mayput some people at an increased risk. These include:
- patients with myeloma may also develop AL amyloidosis (15-20% of myeloma patients)
- patients with a long-term chronic infectious or inflammatory disease are at risk of developing AA amyloidosis
- people who inherit a certain gene mutation may develop hereditary amyloidosis
- patients who require kidney dialysis for a long period of time may be at increased risk of dialysis-associated amyloidosis, although this is rare with modern dialysis techniques.
What are the symptoms of amyloidosis?
Symptoms of amyloidosis depend on which tissues and organs are affected and to what degree. Symptoms vary greatly from patient to patient and between the different types of amyloidosis.
Symptoms are often vague, mimicking other medical conditions. The most common symptoms are:
- unexplained weight loss
- swelling of the ankles and legs due to fluid accumulation.
Other symptoms vary depending on the organ or tissues most affected and may include:
- shortness of breath
- loss of appetite
- enlarged tongue
- unexplained bruising around the eyes
- numbness or tingling in the hands and feet
- lumps in the soft tissue.
Due to the rarity of the disease and vagueness of symptoms, diagnosis may be difficult or delayed. Some of the symptoms described above may also be seen in other illnesses, including viral infections. So, most people with these symptoms don’t have amyloidosis. However, it is important to see your doctor if you have any unusual symptoms, or symptoms that persist much longer than expected so that you can be examined properly.