Amyloidosis is a condition in which too much of a particular protein (amyloid) collects in the organs, so that they are not able to work normally. Amyloidosis can affect the heart, kidneys, liver, spleen, nervous system, stomach or intestines. The condition is rare (affecting fewer than 4,000 people in the United States each year), but it can be fatal.
Amyloidosis sometimes develops when a person has certain forms of cancer, such as multiple myeloma, Hodgkin's disease or familial Mediterranean fever (an intestinal disorder). It also sometimes occurs in people with kidney disease who have undergone dialysis for a long time.
There are three major forms of amyloidosis:
- Primary amyloidosis, which is the most common. It occurs without another associated disease and most often affects the heart, lungs, skin, tongue, nerves and intestines.
- Secondary or acquired amyloidosis, which is associated with chronic diseases, such as tuberculosis, rheumatoid arthritis or osteomyelitis. It most often affects the kidneys, spleen, liver and intestines. If the underlying disease is treated, this form of amyloidosis will go away.
- Hereditary amyloidosis, which runs in families. This type often affects the nervous and digestive systems.
Symptoms vary widely from person to person and depending on which organs are affected. Some people do not even have symptoms, which makes the condition difficult to diagnose.
When amyloidosis is associated with another disease, symptoms may be masked. The underlying disease may be fatal before amyloidosis is found.
- An enlarged liver
- An enlarged tongue (macroglossia)
- An irregular heartbeat
- Diarrhea alternating with constipation
- Difficulty swallowing
- Dizziness or feeling faint
- Loss of weight
- Numbness or tingling in the hands or feet
- Severe fatigue
- Shortness of breath
- Skin changes
- Swelling of the ankles and legs
The severity of amyloidosis depends on which organs it affects. It can be life threatening if it causes kidney or heart failure.
If the amyloidosis affects the kidneys, their ability to filter the blood becomes impaired. Protein leaks from the blood into the urine. The loss of protein from the blood can cause fluid to leak out of the blood vessels, resulting in swelling in the feet, ankles and calves. Eventually, there is so much damage to the kidneys that they are not able to remove waste products from the body and they fail.
If amyloidosis affects the heart, the first symptom typically is shortness of breath even with only light activity. Climbing a flight of stairs or walking long distances may be difficult without having to stop. The buildup of amyloid in the heart lessens its ability to fill up with blood between heartbeats. As a result, less blood is pumped with each beat, and the heart is not able to keep up with the body's needs. The buildup of amyloid can also cause problems with the electrical system of the heart, resulting in irregular heartbeats (arrhythmia).
Other effects of amyloidosis include:
- A burning sensation as a result of nerves being irritated by the amyloid
- Alternating bouts of constipation and diarrhea, if the protein deposits affect the nerves that control the bowels
- Bowel obstruction
- Carpal tunnel syndrome, which causes pain, numbness or tingling in the fingers. Approximately four out of 10 people with amyloidosis develop this syndrome.
- Disruption of the nervous system
- Dizziness or nearly fainting when standing up too quickly. This can happen if the condition affects the nerves that control blood pressure and a sudden drop in blood pressure occurs when standing up.
- Numbness or lack of feeling in the toes or feet
- Weakness in the legs, which can be a result of nerves irritated by the amyloid
Causes and Risk Factors
The cause for amyloid to be produced and to collect in the tissues is not known. The risk of getting amyloidosis is not connected to what a person eats (including how much protein) or does for a living or to the amount of stress in one's life
The disease starts in the bone marrow. Bone marrow creates red and white blood cells, platelets and antibodies that protect the body against infection. After the antibodies have done their work, the body breaks them down. When the bone marrow cells produce antibodies that cannot be broken down, amyloidosis develops. The antibodies build up in the blood and eventually get deposited in the tissues as amyloid.
The risk of developing amyloidosis is greater in people who:
- Are older than 50
- Have a chronic infection or inflammatory disease
- Have a family history of amyloidosis
- Have multiple myeloma. Between 10 and 15% of people who have multiple myeloma develop amyloidosis.
- Have a kidney disease that has required dialysis for more than five years
Blood and urine tests may reveal an abnormal protein in the body, but the only way to diagnose amyloidosis for certain is to take a sample of tissue for analysis under a microscope. Tissue is usually taken from the fat around the abdomen or the tissues of the rectum, which can be done on an outpatient basis. Samples can also be taken from the skin, nerves, kidneys, liver or gums - in which case, a hospital stay may be required. The samples are stained with a dye that reacts with amyloid and then examined under a microscope.
There is no cure for amyloidosis. Treatment of an underlying illness - if there is one - can cause the amyloidosis to go away. Drugs and diet can help manage symptoms and help prevent the production of more of the protein.
Among the drugs that have been helpful in treating amyloidosis are:
- Melphalan (Alkeran), which is used to treat some types of cancer
- Prednisone, a corticosteroid that reduces inflammation (swelling and tenderness)
- Pain relievers
Several drugs (such as thalidomide, which is being used to treat multiple myeloma) are being studied for their ability to treat amyloidosis.
A nutritionally sound diet provides the body with a good energy supply. Diet may also be helpful to treat the many complications that can arise from amyloidosis. Special diets are usually based on symptoms and which organs have been affected by amyloidosis. For example, a doctor may recommend a low-salt diet or diuretics if the kidneys have been affected.
In secondary amyloidosis, the goal is to treat the underlying condition.
In the case of amyloidosis of the kidney, kidney transplantation may be done. Dialysis may be helpful as well. However, amyloid will eventually appear in the donor kidney. Research is underway to study the effect of stem cell transplantation to treat organs with amyloidosis.
In the case of amyloid heart disease, heart transplantation may also be done. Persons who have amyloid heart disease need to be careful if they are taking digitalis because it can precipitate arrhythmias. Myocardial amyloidosis is the most common cause of death. This is usually due to arrhythmias or intractable heart failure.
In some cases of inherited amyloidosis, liver transplantation can help because it removes the source that produces the mutant protein.
Research is underway to find other treatments for amyloidosis. One area under investigation is stem cell transplantation, which involves using chemotherapy and transfusions of immature blood cells (stem cells) that have been collected to replace diseased or damaged bone marrow. The cells may be collected from a patient's own body (autologous transplant) or from a donor (allogeneic transplant).