Amyloidosis (am-uh-loi-DO-sis) is a rare disease that occurs when a substance called amyloid builds up in your organs. Amyloid is an abnormal protein that is produced in your bone marrow and can be deposited in any tissue or organ.

Amyloidosis frequently affects the heart, kidneys, liver, spleen, nervous system and digestive tract. It is often overlooked because it may cause no symptoms at first. And when there are signs or symptoms, they can look like those of more-common diseases.

There's no cure for amyloidosis and severe amyloidosis can lead to life-threatening organ failure. But treatments can help you manage your symptoms and limit the production of amyloid protein.

Diagnosis as early as possible can help prevent further organ damage caused by the protein buildup. So, it's important to talk with your health care provider if you're experiencing any of these 10 possible signs and symptoms.

• Urine changes and swollen legs. If amyloidosis damages your kidneys, it can cause protein to leak from your blood into your urine. This may cause your urine to be foamy, or you may urinate less.When large amounts of protein leave your bloodstream and enter your urine, water can leak out of the blood vessels into your feet. This can cause your feet, ankles and calves to swell.
• Unintentional, significant weight loss. If you're losing protein from your blood, you may lose your appetite and, as a result, lose weight without trying.If amyloidosis affects your digestive system, it can also affect your ability to digest your food and absorb nutrients. It's common to lose 20 to 25 pounds.
• Severe fatigue. Feeling extremely tired is common with amyloidosis. Even small efforts may feel difficult.
• Shortness of breath. If amyloidosis affects your heart, it can limit your heart's ability to fill with blood between heartbeats. This means less blood is pumped with each beat, which may cause you to feel short of breath. Amyloidosis that affects the lungs also can cause shortness of breath.You may find it difficult to climb a flight of stairs or walk long distances without stopping to rest. You may also feel short of breath with even the slightest activity.
• Numbness, tingling, weakness or pain in your hands or feet. If amyloid proteins collect in and put pressure on the nerves to your fingers, you may have pain and other symptoms in your wrists (carpal tunnel syndrome). If the amyloid proteins collect in the nerves to your feet, you may have numbness, lack of feeling, or a burning sensation in your toes and soles of your feet.
• Diarrhea or constipation. If amyloidosis affects the nerves that control your bowels, you may have diarrhea or constipation.
• An enlarged tongue. Amyloidosis can cause your tongue to become enlarged. It can also cause other muscles, such as in your shoulders, to become enlarged.
• Skin changes. You may notice a waxy thickening of your skin; easy bruising of your face, eyelids or chest; or purplish patches around your eyes.
• Irregular heartbeat. If amyloidosis affects your heart's electrical system, it may disturb your heart's rhythm and cause an irregular heartbeat.
• Dizziness when standing. If the nerves that control your blood pressure are affected, you may feel dizzy or near fainting if you stand up too quickly.

Many of these signs and symptoms may be caused by other conditions. But if you experience any of them, talk with your health care provider about whether they might be caused by amyloidosis. And if you have a family history of the condition, be sure to tell your health care provider. Come to your appointment ready to discuss your symptoms and when they happen.

Causes

In general, amyloidosis is caused by the buildup of an abnormal protein called amyloid. Amyloid is produced in your bone marrow and can be deposited in any tissue or organ. The specific cause of your condition depends on the type of amyloidosis you have.

There are several types of amyloidosis, including:

• AL amyloidosis (immunoglobulin light chain amyloidosis) is the most common type and can affect your heart, kidneys, skin, nerves and liver. Previously known as primary amyloidosis, AL amyloidosis occurs when your bone marrow produces abnormal antibodies that can't be broken down. The antibodies are deposited in your tissues as amyloid, interfering with normal function.
• AA amyloidosis mostly affects your kidneys but occasionally your digestive tract, liver or heart. It was previously known as secondary amyloidosis. It occurs along with chronic infectious or inflammatory diseases, such as rheumatoid arthritis or inflammatory bowel disease.
• Hereditary amyloidosis (familial amyloidosis) is an inherited disorder that often affects the liver, nerves, heart and kidneys. Many different types of gene abnormalities present at birth are associated with an increased risk of amyloid disease. The type and location of an amyloid gene abnormality can affect the risk of certain complications, the age at which symptoms first appear, and the way the disease progresses over time.
• Dialysis-related amyloidosis develops when proteins in blood are deposited in joints and tendons — causing pain, stiffness and fluid in the joints, as well as carpal tunnel syndrome. This type generally affects people on long-term dialysis.

Risk factors

Anyone can develop amyloidosis. Factors that increase your risk include:

• Age. Most people diagnosed with AL amyloidosis, the most common type, are between ages 60 and 70, although earlier onset occurs.
• Sex. Nearly 70 percent of people with AL amyloidosis are men.
• Other diseases. Having a chronic infectious or inflammatory disease increases your risk of AA amyloidosis.
• Family history. Some types of amyloidosis are hereditary.
• Kidney dialysis. Dialysis can't always remove large proteins from the blood. If you're on dialysis, abnormal proteins can build up in your blood and eventually be deposited in tissue. This condition is less common with modern dialysis techniques.
• Race. People of African descent appear to be at higher risk of carrying a genetic mutation associated with the type of amyloidosis that can harm the heart.

This article is written by Mayo Clinic staff. Find more health and medical information on mayoclinic.org.

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