Amyloidosis is a systemic disorder that is classified into several types. The different types of systemic amyloidosis are classified as primary, secondary or familial (hereditary). Primary amyloidosis (also called AL, or ‘light chain’) is the most common type of systemic amyloidosis. AL results from an abnormality (dyscrasia) of plasma cells (a type of white blood cell) in the bone marrow and is closely related to multiple myeloma. Secondary (AA) amyloidosis is derived from the inflammatory protein serum amyloid A. AA occurs in association with chronic inflammatory disease such as the rheumatic diseases, familial Mediterranean fever, chronic inflammatory bowel disease, tuberculosis or empyema. Familial amyloidosis is a rare type of amyloidosis that is caused by an abnormal gene. There are several abnormal genes that can cause hereditary amyloidosis, but the most common type of hereditary amyloidosis is called ATTR and caused by mutations in the transthyretin (TTR) gene.
Senile amyloidosis, in which the amyloid is derived from wild-type (normal) transthyretin, is a slowly progressive disease that affects the hearts of elderly men. Amyloid deposits may occasionally occur in isolation without evidence of a systemic disease; isolated bladder or tracheal amyloid are the most common such presentations.
Amyloidosis is usually a multisystem disease resulting in a wide spectrum of clinical presentations. Consequently, a patient may present to, or be referred to, one of several subspecialists, most commonly a nephrologist, cardiologist or neurologist. Recent advances in therapy have rendered early and precise diagnosis critical if the patient is to fully benefit. Most patients have more than one organ involved and therefore the finding of a combination of any of the features below should heighten the suspicion of amyloidosis:
The kidney is the organ most commonly involved in AL, AA, and some rare hereditary forms but it is rarely involved in the familial forms caused by transthyretin mutations. Excessive amounts of protein in the urine (proteinuria) is the usual manifestation of renal involvement and is commonly heavy, resulting in the nephrotic syndrome. Less commonly, amyloid causes an excess of urea and other nitrogenous wastes in the blood (progressive azotemia) as the initial manifestation of renal disease. An abnormal accumulation of fluid (edema), such as swelling of the legs and abdomen, in the absence of heart failure is a feature of nephrotic syndrome, as is the presence of excess cholesterol in the blood (hypercholesterolemia) that may be profound. The kidneys often become small, pale and hard, but in amyloidosis, large kidneys are commonly seen as well. Renal tubular defects, renal vein blood clots (thrombosis) and high blood pressure (hypertension) may also be present. Amyloid may accumulate in other parts of the urogenital system, such as the bladder or urinary tubes (ureter).
Amyloidosis frequently involves the heart. Amyloid infiltration of the heart results in ventricular wall thickening and the development of heart failure. Rapidly progressive congestive heart failure with thick ventricular walls is the classical presentation of AL cardiac amyloidosis. The heart is invariably involved in senile amyloidosis, often in TTR amyloidosis and almost never in the secondary amyloidosis. Common symptoms of heart involvement include: an enlarged heart (cardiomegaly); an irregular heartbeat (arrhythmias); heart murmurs; and abnormalities of the heart seen on electrocardiograms (for example: low voltage). Congestive heart failure is the most common cardiac complication of amyloidosis. Nodular deposits of amyloid may be present on the membranous sac that surrounds the heart (pericardium) and on the lining of the heart chambers or heart valves (endocardium).
Although less common than renal or cardiac involvement, neuropathy may be a significant problem in amyloidosis. Occasionally, it is the presenting and predominant feature of AL amyloidosis. In specific mutations of familial amyloidosis (particularly Met 30, originally known as familial amyloid polyneuropathy), it is the primary feature of the disease. The neuropathy is often painless and sensorimotor in nature although neuropathic pain may be occasionally significant. These symptoms may include: sensory neuropathy with numbness and tingling sensations in the feet that progresses to the legs and eventually the upper extremities; motor neuropathy with loss of motion beginning in the feet and extending upward. Carpal tunnel syndrome is commonly seen, not due to direct nerve involvement, but rather to soft tissue infiltration causing median nerve compression. In familial amyloidosis, the peripheral neuropathy is frequently accompanied by an autonomic neuropathy characterized by diarrhea and a decrease in the amount of sweat production (hypohidrosis), a sudden drop in blood pressure when the patient stands up (postural hypotension) and, in the male, erectile dysfunction. Postural hypotension may be profound and result in recurrent fainting (syncopal) episodes. Systemic amyloidosis does not involve the central nervous system, and is unrelated to Alzheimer’s disease.
Amyloidosis may affect the liver and the spleen. Amyloid involvement in the spleen increases the risk of traumatic rupture of that organ. Some degree of hepatic involvement is common in AL amyloidosis. It is also common in AA amyloidosis but is not seen in TTR familial amyloidosis. In most cases, hepatic involvement is asymptomatic. An enlarged liver (hepatomegaly) and an enlarged spleen (splenomegaly) are the most notable signs. Generally, the amyloid-infiltrated liver feels very hard, and elevated liver enzymes (particularly alkaline phosphatase) and other liver function abnormalities may be detected early. Generally the function of the liver is not significantly affected until late in the course of the disease. Elevation of bilirubin is an ominous sign and may portend hepatic failure. Hepatic amyloidosis rarely occurs in isolation and is usually associated with organ involvement elsewhere.
Amyloidosis may also affect the gastrointestinal (digestive) system. Amyloid accumulation in the gastrointestinal tract may cause a lack of movement (motility) in the esophagus and the small and large intestines. Malabsorption, ulceration, bleeding, weak gastric activity, pseudo-obstruction of the gastrointestinal tract, protein loss, and diarrhea may also occur. Loss of taste, and a difficulty eating solid foods because of enlargement of the tongue (macroglossia) from amyloid infiltration, may contribute to weight loss, or weight loss may be a non-specific manifestation of the systemic disease. In patients with autonomic neuropathy, gastric emptying is impaired, resulting in a sensation of early satiety.
The skin is frequently involved in primary amyloidosis. Dermatologic involvement is almost exclusively limited to AL amyloid and consists of soft tissue, skin and vascular abnormalities. Periorbital purpura is a result of capillary fragility and may appear after coughing, sneezing, or straining for a bowel movement. Not infrequently, purpuric lesions may arise after such simple actions as rubbing the eyelids. Soft tissue infiltration may cause macroglossia and hoarseness, although examination of the vocal cords may appear normal. Lesions of the skin may be visible or may be so small that they may be seen only with a microscope. Waxy-looking papular lesions may appear on the face and the neck. They may also occur under the arms (axillary region), near the anus and the groin. Other areas that may be affected are the mucous areas such as the ear canal or tongue. Areas of swelling, hemorrhages under the skin (purpura), hair loss (alopecia), inflammation of the tongue (glossitis) and a dry mouth (xerostomia) may also be present.
Problems with the respiratory system that are associated with amyloidosis often parallel cardiac symptoms. In the localized form of amyloidosis, air passages and ducts may be obstructed by amyloid deposits in the nasal sinuses, voice box (larynx) and throat (trachea) and bronchial tree. Fluid collecting in the pleural space (pleural effusion) is quite common in patients with congestive heart failure due to amyloidosis, but large recurrent pleural effusions disproportionate to the degree of heart failure suggest pleural amyloidosis.
Joint abnormalities (arthropathy) occur in amyloidosis due to the accumulation of amyloid deposits in the lining of joints (synovial membranes). This occurs in AL amyloidosis and occasionally in dialysis-related amyloidosis. Articular cartilage or the synovial membrane and fluid may become involved as well. Symptoms are similar to those of rheumatoid arthritis. Amyloid deposits in muscle tissue may cause muscle weakness and muscle changes (pseudomyopathy). Symptoms of amyloidosis may also be manifested by bleeding disorders. These may result from deficiency of certain clotting factors or small amyloid deposits in blood vessels within the skin.
Amyloidosis is caused by abnormal folding of proteins leading to fibril formation in one or more body organs, systems or soft tissues. These clumps of protein are called amyloid deposits and the accumulation of amyloid deposits causes the progressive malfunction and eventual failure of the affected organ. Normally, proteins are broken down at about the same rate as they are produced, but these unusually stable amyloid deposits are deposited more rapidly than they can be broken down.
The cause of primary amyloidosis (AL) is usually a plasma cell dyscrasia, an acquired abnormality of the plasma cell in the bone marrow with production of an abnormal light chain protein (part of an antibody). Usually an excess amount of antibody protein is produced and the abnormal light chain portion or the whole antibody molecule accumulates in the body tissues in the form of amyloid deposits.
Secondary amyloidosis (AA) is caused by the inflammatory disease process that is part of the underlying disease. Approximately 50% of the people with secondary amyloidosis have rheumatoid arthritis as the underlying disease.
Familial amyloidosis is caused by an abnormality in the gene for one of several particular proteins. The most common form of hereditary amyloidosis is caused by an abnormality (mutation) in the gene for transthyretin. More than 100 different mutations in the transthyretin gene have been reported and the most common mutation has been termed V30M. Different TTR mutations are associated with amyloidosis that affects different organ systems. Rarely, mutations in genes for proteins that cause amyloidosis are fibrinogen A alpha chain, apolipoprotein A1 and A2, gelsolin, and cystatin C.
All the hereditary amyloidoses follow autosomal dominant inheritance. Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary to cause a particular disease. The abnormal gene can be inherited from either parent or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from affected parent to offspring is 50% for each pregnancy. Not everyone with the abnormal gene, however, will necessarily manifest the disease. The risk is the same for males and females.
It is estimated that there are between 3000-4000 new cases of AL amyloidosis annually in the United States, though actual incidence may be somewhat higher as a result of under-diagnosis. While the incidence is thought to be equal in males and females, about 60% of patients referred to amyloid centers are male. Primary amyloidosis has been reported in individuals as young as 20 years of age but is typically diagnosed at about age 50-65.
Individuals at risk for secondary amyloidosis (AA) include those with chronic inflammatory diseases such as rheumatic arthritis, psoriatic arthritis, chronic juvenile arthritis, ankylosing spondylitis in children, inflammatory bowel disease, and familial Mediterranean fever. People with chronic infectious diseases such as tuberculosis, leprosy, bronchiectasis, chronic osteomyelitis, and chronic pyelonephritis are also at risk. Secondary amyloidosis (AA) occurs in less than 5% of individuals with these conditions.
Familial amyloidosis caused by a transthyretin mutation occurs in approximately 1 in 100,000 Caucasians in the U.S, and more commonly in African Americans (approximately 4% in that population). This condition is prevalent in Portugal, Sweden, Japan, Ireland, Spain, France, Finland, Germany and Greece. Symptoms usually begin between 30 and 50 years of age.
Though both familial and secondary amyloidosis are probably less common than AL amyloidosis, senile amyloidosis is probably more common, but considerably underdiagnosed.
Particularly in the case of AL Amyloidosis, early diagnosis is the key to survival and post treatment quality of life. The diagnosis of amyloidosis is suspected following a detailed patient history and clinical evaluation but requires a biopsy of muscle, bone or fatty tissue to confirm the presence of amyloid. If the disease is suspected on clinical grounds, a biopsy of the involved organ will give the highest yield. The biopsy material is examined microscopically and is stained with a dye called Congo red that will produce a green color when looked at in a polarizing microscope if amyloid is present. When amyloidosis is diagnosed on a tissue biopsy it is essential that the affected individual be further evaluated to determine what organs are affected.
Once a tissue biopsy of amyloid has been established, it is mandatory to determine the type of amyloidosis. In AL amyloidosis, manifestations of a plasma cell dyscrasia will be found 98% of the time. In 2% of cases, a B-cell lymphoma is identified as the cause of AL. The specific tests that are used to make a diagnosis of the AL amyloidosis type are both immunofixation and protein electrophoresis of the blood and urine, bone marrow biopsy with immunochemical staining of plasma cells for kappa and lambda light chains and a serum free light chain assay. The dermatologic manifestations of AL amyloid may strongly suggest the diagnosis, particularly when other organ involvement suggests a systemic disease. A diagnosis of AL amyloidosis is confirmed by the presence of periorbital purpura, which is a result of capillary fragility or macroglossia.
The diagnosis of TTR hereditary amyloidosis can be confirmed by performing molecular genetic testing for mutations in the TTR gene on a blood sample. In the absence of mutations of transthyretin, very rare forms of familial amyloid may be present.
If the patient is an elderly man with clinically isolated cardiac involvement, the most likely diagnosis is senile systemic amyloid (senile cardiac amyloid), a condition in which wild-type (normal) transthyretin is deposited in the heart.
Specific immunostaining (for example, immunogold electron microscopy) of appropriately preserved tissue is available at specialized centers and offers a high specificity for determining the type of amyloid. In difficult diagnostic cases, mass spectrometry is able to determine precisely the molecular structure of the amyloid deposits- this technique is being used more and more frequently. A technique called radiolabeled serum amyloid P (SAP) scanning is available in a few centers in Europe that specialize in amyloidosis. This test is used to monitor the accumulation of amyloid deposits.
The type of treatment available is driven by the type of amyloidosis and the clinical state of the patient. In AL amyloidosis, the cause is the abnormal white blood cell (usually a plasma cell) and as such, chemotherapy aimed at eradicating those cells forms the cornerstone of treatment. Various regimens have been studied but the commonest include melphalan and dexamethasone given orally or high-dose melphalan given intravenously with autologous stem cell support. Both are equally effective but the treatments and side effects are different. High dose Melphalan with stem cell support is an involved treatment that often involves a 2-3 week hospital stay and a few months of additional recovery time. The use of oral melphalan on a monthly basis is less toxic, but is associated with a higher risk of treatment-related leukemia. Newer agents active in multiple myeloma (another disease of abnormal plasma cells), such as bortezomib or lenalidomide, are also very effective in AL and have been shown to provide a benefit in patients with relapsed disease. Often times, these drugs are incorporated into upfront treatment. The specific treatment for any individual has to be personalized to their unique situation.
The two most important determinants of long-term survival with AL are the presence and extent of cardiac involvement and hematologic response to therapy.
Supportive therapy (treatment of congestive heart failure, attention to nutrition, treatment of autonomic neuropathy etc.) is a very important concomitant measure. Given the complexity of the disease, it is recommended that treatment be performed in the center with experience of amyloidosis, or at least that the patient should have an initial evaluation at such a center, with continued communication during treatment in the local community.
Familial TTR amyloidosis is treated, if possible, by removal of the source of the abnormal TTR production. Since the dominant source is the liver, liver transplantation is currently the treatment of choice in carefully selected patients whose disease is not too far advanced. Tafamidis is a drug recently approved for familial amyloid polyneuropathy (FAP).
Genetic counseling is recommended for individuals with hereditary amyloidosis and their family members.
In senile amyloidosis, therapy is supportive, but both for this disease and for ATTR, pharmacologic therapies aimed at stabilizing the transthyretin molecule and thus preventing amyloid formation are being actively investigated.
Clinical testing of the non-stroidal agent diflunisal, a transthyretin stabilizer, is on-going.
The mainstay of secondary amyloidosis treatment is therapy of the underlying disease. Renal transplantation has been performed successfully for renal disease due to secondary amyloidosis. Eprodisate is a small molecule that inhibits the formation of amyloid fibrils, and which seems to have a modest clinical effect in patients with secondary amyloidosis.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
For information about clinical trials sponsored by private sources, contact:
For information about clinical trials conducted in Europe, contact:
Amyloidosis Treatment Centers
The following centers have amyloidosis practices where they diagnose and treat the disease, conduct research and perform clinical trials:
Boston University Medical Center, Amyloid Treatment and Research Program
Tel: (617) 638-4317
Brigham and Women’s Hospital/Harvard Vanguard Cardiac Amyloidosis Program, Boston, MA. www.brighamandwomens.org/amyloidosis
Tel: 617 421 6094
Sylvester Cancer Center, University of Miami
Dr. James Hoffman
Tel: (305)- 243- 4860
The Mayo Clinic, Rochester MN
Tel: (507) 284-2111
Tufts Medical Center, Boston, MA
Memorial Sloan Kettering, New York City
Tel: (212) 639-8808
Other US physicians with specific clinical expertise in amyloidosis:
Merrill Benson, MD. Amyloid Research Group, University of Indiana, Indianapolis, IN. Http://www.iupui.edu/~amyloid. Tel. (317) 278-3426
Cardiac Amyloidosis (also see above):
Rodney H. Falk, MD. Harvard Vanguard Medical Associates, Harvard Medical School, Brigham and Women’s Hospital, Boston MA. email@example.com. Tel. (617) 421-6094.
Mathew Maurer, MD. Columbia Presbyterian Hospital, New York, NY 212-305-9808
International Amyloid Centers (both have informative Web sites):
Italian center for the Study and Cure of Systemic Amyloidosis (Pavia, Italy) www.amiloidosi.it
National Amyloidosis Center, London, UK. www.ucl.ac.uk/medicine/amyloidosis/nac/
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