Amyloidosis is the term applied to a group of conditions caused by deposits of an abnormal protein called amyloid. This rare but serious condition affects between 1 and 5 people in every 100,000 each year in the UK. The condition is mainly seen among the elderly.
All proteins undergo structural modifications before the final 3-D shape of the protein is reached. This modification is achieved through complex folding of the protein. An amyloid protein is the result of an incorrect folding process that results in an abnormal protein structure. This protein is dysfunctional and starts to build up in different tissues and organs, eventually leading to organ failure. There are nearly twenty different proteins that can fold in an abnormal manner and give rise to amyloid protein.
Types of amyloidosis
If amyloid is deposited in a single part of the body, it is referred to as localised amyloidosis and if it is deposited in more than one site, it is called systemic amyloidosis. Localized amyloidosis is usually less serious than the systemic forms.
The accumulation of one particular protein called amyloid-beta causes Alzheimer’s disease, the most common cause of dementia. Alzheimer’s is an example of localized amyloidosis, where the amyloid-beta deposits accumulate in the brain. Most forms of amyloidosis are systemic and affect the heart, kidneys, nerves and gut, leading to severe organ damage.
Symptoms of amyloidosis
The most common type of amyloidosis found in the UK is primary (AL) amyloidosis. In AL amyloidosis, the amyloid takes years to accumulate before it starts to cause symptoms. These symptoms vary depending on the organ the protein accumulates in. Amyloid that builds up in the kidney causes chronic kidney failure and presents with symptoms such as tiredness, weakness, fluid retention and edema. When amyloid accumulates in the heart, the organ becomes enlarged and fails to pump efficiently, increasing the risk of heart failure.
Diagnosis and treatment
Diagnosis involves taking a biopsy from the affected area of the body which is sent for laboratory analysis. Special staining techniques are used to look for amyloid proteins under the microscope.
Amyloidosis may be treated with chemotherapy to suppress the bone marrow and prevent production of the abnormal protein. This reduces the amount of amyloid present in the body and prevents organ damage. Specific organ damage is treated accordingly. For example, those with chronic renal failure may need dialysis while those with heart failure may need diuretic medications.
Reviewed by Sally Robertson, BSc