IntroductionProteins are important building blocks for all
body parts, including muscles, bones, hair, and nails. Proteins
circulate throughout the body in the blood and are normally
harmless. Occasionally, cells produce abnormal proteins that can
settle in body tissue, forming deposits and causing disease. When
these deposits of abnormal proteins were first discovered, they were
called amyloid, and the disease process amyloidosis.
In recent years, researchers have discovered that different kinds
of proteins can form amyloid deposits and have identified several
types of amyloidosis. Two of these types are closely related to
kidney disease. In primary amyloidosis, abnormal protein
production occurs as a first step and can lead to kidney disease.
Dialysis-related amyloidosis (DRA), on the other hand, is a
result of kidney disease.
Primary amyloidosis
occurs when the body produces abnormal protein fibers, which join
together to form amyloid deposits in different organs, including the
kidneys, where they cause serious damage. Injured kidneys can't
function effectively and may be unable to remove urea and other
wastes from the blood. Elevated levels of these waste products can
also damage the heart, lungs, brain, and digestive system.
One common sign of amyloidosis is the presence of abnormally high
amounts of protein in the urine, a condition known as
proteinuria. Healthy kidneys prevent protein from entering
the urine, so the presence of protein may be a sign that the kidneys
aren't working properly. A physician who finds large amounts of
protein in the urine may also perform a biopsy--take a small sample
of tissue for examination under a microscope--to confirm
amyloidosis.
No effective treatment has been found to reverse the effects of
amyloidosis. Combination drug therapy with melphalan (a cancer drug)
and prednisone (an anti-inflammatory steroid drug) may improve organ
function and survival rates by interrupting the growth of cells that
produce amyloid protein. These are the same drugs used in
chemotherapy to treat certain cancers, and they may have serious
side effects, such as nausea and vomiting, hair loss, and
fatigue.
Normal
kidneys filter excess proteins from the blood, thus preventing
levels from getting too high. When the kidneys don't work properly,
as in patients receiving dialysis, another type of protein called
beta-2-microglobulin may build up in the blood. When this
occurs, beta-2-microglobulin molecules may join together, like the
links of a chain, forming a few very large molecules from many
smaller ones. These large molecules can form deposits and eventually
damage the surrounding tissues and cause great discomfort. This
condition is called dialysis-related amyloidosis (DRA).
DRA is relatively common in patients who have been on dialysis
for more than 5 years, especially among the elderly. Dialysis
membranes don't effectively remove the large, complex
beta-2-microglobulin proteins from the bloodstream. As a result,
blood levels become elevated, and deposits form in bone, joints, and
tendons. DRA may result in pain, stiffness, and fluid in the joints.
Patients with DRA may also develop hollow cavities, or cysts, in
some of their bones; these may lead to unexpected bone fractures.
Amyloid deposits may cause tears in ligaments and tendons (the
tissue that connects the muscle to the bone). Most patients with
these problems can be helped by surgical intervention.
Half of the people with DRA also develop a condition called
carpal tunnel syndrome, which results from the unusual buildup of
protein in the wrists. Patients with this disorder may experience
numbness or tingling, sometimes associated with muscle weakness, in
their fingers and hands. This is a treatable condition.
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| Unfortunately, no cure for DRA has been found, although a
successful kidney transplant may stop the disease from progressing.
However, DRA has caught the attention of dialysis engineers who are
attempting to develop membranes that can more efficiently remove
beta-2-microglobulin from the blood.
Keeping on Top of Your Condition
Keeping in tune with your disease or condition not only makes treatment less intimidating but also increases its chance of success, and has been shown to lower a patients risk of complications. As well, as an informed patient, you are better able to discuss your condition and treatment options with your physician.
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For more information,
contact the following organizations:
Primary Amyloidosis
National Arthritis and Musculoskeletal and Skin Diseases
Information Clearinghouse
National Institutes of
Health
1 AMS Circle
Bethesda, MD 20892-3675
Phone:
1-877-22NIAMS (1-877-226-4267) or (301) 495-4484
TTY: (301)
565-2966
Fax: (301) 718-6366
Internet: www.nih.gov/niams/healthinfo
Amyloidosis
Network International, Inc.
7118 Cole Creek Drive
Houston, TX 77092-1421
Phone: 1-888-AMYLOID or (713)
466-4351
Internet: amyloidosis.org
Dialysis-Related Amyloidosis
National Kidney Foundation, Inc.
30 East 33rd
Street
New York, NY 10016
Phone: 1-800-622-9010 or (212)
889-2210
Fax: (212) 689-9261
Email: info@kidney.org
Internet: www.kidney.org
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