What Is Amyloidosis?

Sometimes a nerve disorder develops because amyloid, an abnormal protein, accumulates in and around nerves and interferes with their functioning. This disorder, called amyloid neuropathy, is a form of amyloidosis. Amyloid can accumulate in almost any tissue or organ, including the heart, lungs, liver, skin, tongue, thyroid gland, intestines, kidneys, spleen, and blood vessels. Amyloidosis is rare but is more common among older people. Amyloidosis is twice as common among men.

What causes amyloid to accumulate is unknown. Amyloid may accumulate in people who have certain disorders, such as arthritis, a kidney disorder, or multiple myeloma (cancer of the bone marrow). It accumulates in the brain of people with Alzheimer's disease and may play a role in causing the disease. Sometimes amyloidosis runs in families.

The symptoms depend on where and how much amyloid accumulates. When amyloid accumulates in and around nerves, it often causes numbness, tingling, and pain in the hands and feet. If amyloidosis affects nerves in the hands and arms, carpal tunnel syndrome may result. Sometimes nerves are damaged. Then, people may lose sensation or become very sensitive to changes in temperature. If enough amyloid accumulates in a vital organ, the consequences may be serious. For example, heart or kidney failure may result. The only way to diagnose amyloidosis is a biopsy. Depending on the symptoms, a sample of nerve tissue, fat in the abdomen, or other tissue is removed and examined under a microscope.

No treatment cures amyloidosis. But treating other disorders the person has may help. For most people, treatments to control symptoms (such as prednisone) are only moderately effective. Sometimes surgery to remove the amyloid is done. The outlook for people with amyloidosis depends on where and how much amyloid accumulates. If amyloid affects only nerves in the arms and legs, life expectancy is not shortened. But if amyloidosis causes heart failure, as many as half of the people die within 6 months. The outlook also depends on other disorders present. Most people with amyloidosis and multiple myeloma die within 1 to 2 years.