What is amyloidosis?
Amyloidosis is a disease in which amyloid proteins are deposited and build up in vital organs. This buildup of proteins causes these organs to thicken and lose function.
Our bodies make several proteins that can cause amyloidosis. In order to treat a patient who has amyloidosis, it is very important to know the exact protein that is causing the disease.
What is AA amyloidosis?
Serum amyloid A protein occurs at high levels when inflammation (irritation and swelling) is present in the body. AA amyloidosis occurs when Serum Protein A levels in the bloodstream remain high for a long period of time. This can be seen in chronic (long-term) inflammatory conditions such as rheumatoid arthritis, inflammatory bowel disease (Crohn’s disease, ulcerative colitis), and chronic infections. It is also seen in inherited periodic fever syndromes such as Familial Mediterranean Fever. Sometimes referred to as secondary amyloidosis due to the underlying inflammatory disease, AA amyloidosis is more common in developing countries. This form rarely significantly affects the heart.
Symptoms and Causes
What causes amyloidosis?
Amyloidosis is a “protein misfolding disorder.” Normally, proteins in the bloodstream are removed and/or recycled once they have completed their job. In amyloidosis, however, a protein can change shape (or “misfold”) and can no longer be cleared. These misfolded proteins clump together and form amyloid fibrils, which are then deposited in the spaces between the cells of vital organs. As amyloid fibrils build up in one or more tissues and organs, the cells can no longer work together and the organ(s) loses function.
What are the signs and symptoms of AA amyloidosis?
AA amyloidosis can affect many organs, resulting in the following signs and symptoms:
Signs and symptoms indicating the kidneys are affected include:
- Swelling of the feet or legs
- Excessive bubbles in the urine (foamy/frothy urine)
- Urinating less
Signs indicating the liver is affected include:
- Enlarged liver (hepatomegaly)
Symptoms indicating the stomach or intestines are affected include:
Symptoms indicating the heart is affected (uncommon) include:
- Swelling of the feet or legs
- Shortness of breath
- Chest pain
Other signs and symptoms:
- Enlarged spleen (splenomegaly)
- Increased level of protein in the urine (proteinuria)
- High cholesterol levels (hypercholesterolemia)
Diagnosis and Tests
How is AA amyloidosis diagnosed?
AA amyloidosis is suspected in patients who have chronic inflammatory or rheumatic disease and begin to show signs and symptoms. The kidney is the most common organ affected in AA amyloidosis.
A biopsy (the removal of cells or tissue) is required to confirm AA amyloidosis. A biopsy of abdominal fat just under the skin, known as a “fat pad biopsy,” is often the first location biopsied. If the fat pad biopsy is negative, the next step is usually to biopsy the affected organ. Sometimes the doctor will choose to start directly with a biopsy of the affected organ.
If the biopsy is positive, the tissue sample undergoes further testing to rule out another type of amyloidosis called AL amyloidosis. AL amyloidosis has some of the same early signs and symptoms as AA amyloidosis but is a more aggressive form of amyloidosis.
Management and Treatment
How is AA amyloidosis treated?
For AA amyloidosis, treating the underlying chronic inflammatory condition is crucial to stop further amyloid deposits. For Familial Mediterranean Fever, the medication colchicine (Colcrys®, Mitigare®) is very effective as a preventative medication. Biologic agents (anti-TNFα, anti-IL-1, anti-IL-6) can be used to reduce the risk and treat active AA amyloidosis related to autoimmune and rheumatic disorders. There are many good treatment options available for other conditions such as Crohn’s disease, ulcerative colitis, and rheumatoid arthritis. As the inflammation associated with these diseases is controlled with medication, the AA amyloidosis slowly regresses.
New therapies in the research and development stage include medications that bind and clear the amyloid fibril building blocks from the blood and antibodies that target and clear amyloid fibrils that have already been deposited.
Outlook / Prognosis
What is the outlook (prognosis) for persons with AA amyloidosis?
Amyloidosis is a long term (chronic) and slowly worsening (progressive) disease. If left untreated, there is significant risk of death.
Early diagnosis is the key to managing the disease before it becomes advanced. Our team at Cleveland Clinic is a leader in research efforts to develop diagnosis and treatment strategies to improve our patients’ outcomes.
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Glossary of Terms
Amyloid Fibril: A rigid stack of amyloid proteins that builds up in the organs.
Amyloidosis: A disease caused by a buildup of abnormally shaped proteins (amyloid proteins) in organs.
Atrial Fibrillation: An irregular heart rhythm.
Biopsy: A small piece of tissue that is removed and examined under a microscope.
Cardiac magnetic resonance imaging (MRI): A scan that creates detailed pictures of the heart and shows how well it is working.
Echocardiogram: An ultrasound of the heart to show how well it is working.
Electrocardiography (EKG): A recording of the heart’s electrical activity.
Proteins: Large molecules that control the structure and function of the body’s tissues and organs.
Technetium-pyrophosphate scan (TcPYP): A bone scan that can tell if there is ATTR in the heart.
Transthyretin: A protein produced by the liver.