Amyloidosis is a progressive, incurable, metabolic disease characterized by abnormal deposits of protein in one or more organs or body systems.
Amyloidosis is a rare disease, occurring in about eight of every one million people. It affects males and females equally and usually develops after the age of 40.
Blood and urine tests can reveal the presence of amyloid protein, but tissue or bone-marrow biopsy is necessary to positively diagnose amyloidosis. Once the diagnosis has been confirmed, additional laboratory tests and imaging procedures are performed to determine:
Amyloid proteins are manufactured by malfunctioning bone marrow. Amyloidosis, which occurs when accumulated amyloid deposits impair normal body function, can cause organ failure or death. At least 15 types of amyloidosis have been identified. Each one is associated with deposits of a different kind of protein.
The major forms of this disease are primary systemic, secondary, and familial or hereditary amyloidosis. Another form of amyloidosis is associated with Alzheimer's disease. Primary systemic amyloidosis usually develops between the ages of 50 and 60. With about 2,000 new cases diagnosed annually, primary systemic amyloidosis is the most common form of this disease in the United States. Also known as light-chain-related amyloidosis, it may also occur in association with multiple myeloma (bone marrow cancer).
Secondary amyloidosis is a result of chronic infection or inflammatory disease. It is often associated with:
Familial or hereditary amyloidosis is the only inherited form of the disease. It occurs in members of most ethnic groups, and each family has a distinctive pattern of symptoms and organ involvement. Hereditary amyloidosis is thought to be autosomal dominant, which means that only one copy of the defective gene is necessary to cause the disease. A child of a parent with familial amyloidosis has a 50-50 chance of developing the disease.
Amyloidosis can involve any organ or system in the body. The heart, kidneys, gastrointestinal system, and nervous system are affected most often. Other common sites of amyloid accumulation include the brain, joints, liver, spleen, pancreas, respiratory system, and skin.
The cause of amyloidosis is unknown. Most patients have gastrointestinal abnormalities, but other symptoms vary according to the organ(s) or system(s) affected by the disease. The affected organs are rubbery, firm, and enlarged.
Because amyloid protein deposits can limit the heart's ability to fill with blood between beats, even the slightest exertion can cause shortness of breath. If the heart's electrical system is affected, the heart's rhythm may become erratic. The heart may also be enlarged and heart murmurs may be present. Congestive heart failure may result.
The feet, ankles, and calves swell when amyloidosis damages the kidneys. The kidneys become small and hard, and kidney failure may result. It is not unusual for a patient to lose 20-25 lb (9-11 kg) and develop a distaste for meat, eggs, and other proteinrich foods. Cholesterol elevations that do not respond to medication and protein in the urine (proteinuria) are common.
Nervous system symptoms often appear in patients with familial amyloidosis. Inflammation and degeneration of the peripheral nerves (peripheral neuropathy) may be present. One in four patients with amyloidosis has carpal tunnel syndrome, a painful disorder that causes numbness or tingling in response to pressure on nerves around the wrist. Amyloidosis that affects nerves to the feet can cause burning or numbness in the toes and soles and eventually weaken the legs. If nerves controlling bowel function are involved, bouts of diarrhea alternate with periods of constipation. If the disease affects nerves that regulate blood pressure, patients may feel dizzy or faint when they stand up suddenly.
The most common symptoms are enlargement of the liver and spleen. Liver function is not usually affected until quite late in the course of the disease. Protein accumulation in the spleen can increase the risk of rupture of this organ due to trauma.
When amyloidosis affects the gastrointestinal system, there may be bleeding, abdominal pain, constipation, and diarrhea. Intestinal movement (motility) may be reduced, and absorption of food and other nutrients may be impaired (leading to malnutrition). The tongue may become inflamed, enlarged, and stiff.
Skin symptoms occur in about half of all cases of primary and secondary amyloidosis and in all cases where there is inflammation or degeneration of the peripheral nerves. Waxy-looking raised bumps (papules) appear on the face and neck, in the groin, armpits, or anal area, and on the tongue or in the ear canals. Swelling, hemorrhage beneath the skin (purpura), hair loss, and dry mouth may occur.
Airways may be obstructed by amyloid deposits in the nasal sinus, larynx and trachea (windpipe).
The goal of treatment is to slow down or stop production of amyloid protein, eliminate existing amyloid deposits, alleviate underlying disorders (that give rise to secondary amyloidosis), and relieve symptoms caused by heart or kidney damage. Specialists in cardiology, hematology (the study of blood and the tissues that form it), nephrology (the study of kidney function and abnormalities), neurology (the study of the nervous system), and rheumatology (the study of disorders characterized by inflammation or degeneration of connective tissue) work together to assess a patient's medical status and evaluate the effects of amyloidosis on every part of the body.
Colchicine (Colebenemid, Probeneaid), prednisone, (Prodium), and other anti-inflammatory drugs can slow or stop disease progression. Bone-marrow and stem-cell transplants can enable patients to tolerate higher and more effective doses of melphalan (Alkeran) and other chemotherapy drugs prescribed to combat this non-malignant disease. Surgery can relieve nerve pressure and may be performed to correct other symptom-producing conditions. Localized amyloid deposits can also be removed surgically. Dialysis or kidney transplantation can lengthen and improve the quality of life for patients whose amyloidosis results in kidney failure. Heart transplants are rarely performed.
Although no link has been established between diet and development of amyloid proteins, a patient whose heart or kidneys have been affected by the disease may be advised to use a diuretic or follow a low-salt diet.
Most cases of amyloidosis are diagnosed after the disease has reached an advanced stage. The course of each patient's illness is unique, but death resulting from heart disease or kidney failure generally occurs within a few years. Amyloidosis associated by multiple myeloma usually has a poor prognosis. Most patients with both diseases die within one to two years.
Genetic counseling may be helpful for patients with hereditary amyloidosis and their families. Use of Cholchicine in patients with familial Mediterranean fever has successfully prevented amyloidosis.