MEDICAL CONDITIONS
Amyloidosis
What is amyloidosis?
Amyloidosis is a group of diseases that result from the abnormal deposition of a particular protein, called amyloid, in various tissues of the body. Amyloid protein can be deposited in a localized area, and may not be harmful or only affect a single tissue of the body. This form of amyloidosis is called localized amyloidosis. Amyloidosis that affects tissues throughout the body is referred to as systemic amyloidosis. Systemic amyloidosis can cause serious changes in virtually any organ of the body.
Amyloidosis can occur as its own entity or "secondarily" as a result of another illness, including multiple myeloma , chronic infections (such as tuberculosis or osteomyelitis), or chronic inflammatory diseases (such as rheumatoid arthritis and ankylosing spondylitis ). Amyloidosis can also be localized to a specific body area from aging. This localized form of amyloidosis does not have systemic implications for the rest of the body. The protein that deposits in the brain of patients with Alzheimer's disease is a form of amyloid. Systemic amyloidosis has been classified into three major types that are very different from each other. These are distinguished by a two-letter code that begins with an A (for amyloid). The second letter of the code stands for the protein that accumulates in the tissues in that particular type of amyloidosis. The three types of systemic amyloidosis are primary (AL), secondary (AA), and hereditary (ATTR).
Primary Amyloidosis
Primary amyloidosis, or AL, is occurs when a specialized cell in the bone marrow (plasma cell) spontaneously overproduces a particular protein portion of an antibody called the light chain. (This is why it is coded as AL). The deposits in the tissues of persons with primary amyloidosis are AL proteins. Primary amyloidosis can occur with a bone marrow cancer of plasma cells called multiple myeloma. Primary amyloid is not associated with any other diseases, but is a disease entity of its own, usually requiring chemotherapy treatment.
Secondary Amyloidosis
When amyloidosis occurs "secondarily" as a result of another illness, such as multiple myeloma, chronic infections (e.g., tuberculosis or osteomyelitis), or chronic inflammatory diseases (e.g., rheumatoid arthritis and ankylosing spondylitis), the condition is referred to as secondary amyloidosis, or AA. The amyloid tissue deposits in secondary amyloidosis are AA proteins. The treatment of patients secondary amyloidosis is directed at treating the underlying illness in that particular patient.
Familial Amyloidosis
Familial amyloidosis, or ATTR, is a rare form of inherited amyloidosis. The amyloid deposits in familial amyloidosis are composed of the protein transthyretin, or TTR, which is made in the liver. Familial amyloidosis is inherited an autosomal dominant in genetics terminology. This means that for the offspring of a person with the condition, there is a 50% chance of inheriting it.
What are symptoms of amyloidosis?
Symptoms in patients with amyloidosis result from abnormal functioning of the particular organs involved. The heart, kidneys, liver, bowels, skin, nerves, joints, and lungs can be affected. Amyloidosis affecting the kidney leads to "nephrotic syndrome," which is characterized by severe loss of protein in the urine and swelling of the extremities.
How is amyloidosis diagnosed?
The diagnosis of amyloidosis is made by detecting the characteristic amyloid protein in a biopsy specimen of involved tissue (such as mouth, rectum, fat, kidney, heart, or liver). A needle aspiration biopsy of fat just under the skin of the belly (fat pad aspiration), developed at Boston University, offers a simple and less invasive method to diagnose systemic amyloidosis.
How is amyloidosis treated?
Treatment of amyloidosis involves correcting organ failure and treating any underlying illness (such as myeloma, infection, or inflammation). The disease itself is difficult to reverse since it is so frequently discovered after significant organ damage has already occurred. The most frequent cause of death is kidney failure . There is no specific treatment for isolated amyloidosis of unknown cause.
Sephardic Jews and Turks inherit a genetic disease Familial Mediterranean Fever, which is associated with amyloidosis and characterized by episodes of "attacks" of fever, joint, and abdominal pains. These attacks can be prevented with the medication colchicine . Armenians and Ashkenazi Jews also have a higher incidence of Familial Mediterranean Fever attacks, but do not suffer amyloid deposition disease. Other reports of amyloidosis in families are extremely rare.
Researchers are currently enrolling patients in clinical trials using a cancer chemotherapy medication, melphalan (Alkeran), in conjunction with bone marrow stem cells transplantation. The results are preliminary, but promising. Familial amyloidosis can now be cured with liver transplantation. This option requires that an accurate diagnosis of the specific protein that causes this disease. - Amyloidosis is a disorder resulting from abnormal protein (amyloid) deposits in body tissues.
- Amyloidosis can occur as an isolated disease or as a result of another illness.
- Symptoms in patients with amyloidosis result from abnormal functioning of the particular organs involved.
- Diagnosis of amyloidosis is made with a biopsy of involved tissue.
- Treatment of amyloidosis depends on the type of amyloidosis and involves correcting organ failure and treating any underlying conditions.
Medical Author: William C. Shiel Jr., MD, FACP, FACR
For more information about amyloidosis, please visit the following site:
Boston Medical Center
(http://medicine.bu.edu/amyloid/amyloid1.htm)
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