Systemic amyloidosis can be classified as follows: (1) primary systemic amyloidosis, usually with no evidence of preceding or coexisting disease, paraproteinemia, or plasma-cell dyscrasia; (2) amyloidosis associated with multiple myeloma; or (3) secondary systemic amyloidosis with evidence of coexisting previous chronic inflammatory or infectious conditions.[1]
The current nomenclature refers to amyloidoses based on a capital A (for amyloid), followed by an abbreviation for the fibril protein. Primary systemic amyloidosis is referred to as AL amyloidosis, with the A signifying amyloid and the L designating it as light-chain amyloidosis. Terms such as AL describe the protein (light chain), but do not necessarily describe the clinical phenotype. For discussion of
Primary systemic amyloidosis involves mainly mesenchymal elements, and cutaneous findings are observed in 30-40% of patients. Secondary systemic amyloidosis does not involve the skin, whereas localized amyloidosis does.
Primary systemic amyloidosis involves the deposition of insoluble monoclonal immunoglobulin (Ig) light (L) chains or L-chain fragments in various tissues, including smooth and striated muscles, connective tissues, blood vessel walls, and peripheral nerves.[2] The amyloid of primary systemic amyloidosis is made by plasma cells in the bone marrow. These L-chains are secreted into the serum. Unlike the normal L-chain and the usual form seen in patients with myeloma, these L-chains are unique in that they undergo partial lysosomal proteolysis within macrophages, and they are extracellularly deposited as insoluble amyloid filaments attached to a polysaccharide. Sometimes, instead of an intact L-chain, this amyloid has the amino-terminal fragment of an L-chain.
Other common types of amyloidosis involve amyloid A protein (AA amyloidosis) and amyloid transport protein transthyretin (ATTR amyloidosis). For discussion of those disorders, see AA (Inflammatory) Amyloidosis and Transthyretin-Related Amyloidosis.
Clinical manifestations of systemic amyloidosis reflect the organ or organs most prominently involved, which is most commonly the kidneys or heart, either individually or together.
Presenting symptoms and signs include the following:
Classically, patients present with the following:
Clinically evident mucocutaneous involvement may provide an early clue to the existence of an underlying plasma-cell dyscrasia. Petechiae and ecchymoses are the most common skin findings, because of cutaneous blood vessel involvement. The face is most commonly affected; minor trauma sometimes precipitates eyelid and periorbital purpura (pinch purpura or raccoon eyes sign).
The most characteristic skin lesion in primary systemic amyloidosis consists of waxy papules, nodules, or plaques that may be evident in the eyelids, retroauricular region, neck, or inguinal and anogenital regions. Plaques may coalesce to form large tumefactive lesions.
Cardiac infiltration may cause angina, infarction, arrhythmias, or orthostatic hypotension. Renal amyloidosis usually manifests as proteinuria, often resulting in nephrotic syndrome.
See Presentation for more detail.
The workup for systemic (AL) amyloidosis includes the following[3] :
The diagnosis is confirmed by Congo red and immunologic staining of a biopsy specimen from the abdominal fat pad or an affected organ (eg, endomyocardial biopsy for cardiac involvement, kidney biopsy for renal involvement). Staging is determined on the basis of cardiac biomarkers: N-terminal pro–B-type natriuretic peptide (NT-proBNP) or brain natriuretic peptide (BNP), troponin T or I, FLC ratio.[2]
See Workup for more detail.
Pharmacologic therapy is targeted against the abnormal plasma cell clone. Daratumumab plus hyaluronidase, in combination with cyclophosphamide, bortezomib, and dexamethasone is the current standard treatment regimen. Autologous stem cell transplantation is performed in eligible patients, especially those with an incomplete response to drug therapy.[4]
See Treatment and Medication for more detail.
Also see Amyloidosis.
In 1838, Mathias Schleiden (a German botanist) coined the term amyloid to describe the normal amylaceous constituent of plants. In 1854, Rudolf Virchow used the term amyloid. Virchow described its reaction with iodine and sulfuric acid, which, at the time, was a marker for starch; thus, the term amyloid or starchlike is used. Virchow adopted the term to describe abnormal extracellular material that is seen in the liver during autopsy.
Some 70 years after Virchow's description, Divry and associates recognized that the amyloid deposits showed apple-green birefringence when specimens stained with Congo red were viewed under polarized light. This observation remains the sine qua non of the diagnosis of amyloidosis.[5]
In 1959, with the use of electron microscopy, Cohen and Calkins first recognized that all forms of amyloidosis demonstrated a nonbranching fibrillar structure. Electron microscopy remains the most sensitive method for recognizing the disorder.[6]
Primary systemic amyloidosis is a plasma-cell dyscrasia characterized by an autonomous proliferation of plasma cells with an overproduction of a monoclonal Ig protein. The final pathway in the development of amyloidosis is the production of amyloid fibrils in the extracellular matrix. The process by which precursor proteins produce fibrils appears to be multifactorial and differs among the various types of amyloidosis.
The fibrils in primary systemic amyloidosis are composed of Ig L-chain material (protein amyloid L) consisting of intact L-chains, L-chain fragments (particularly the variable amino-terminal region), or both. Amyloid deposition occurs as a result of plasma-cell dyscrasia.
The diagnosis depends on the demonstration of amyloid deposits in tissue. The organs most commonly involved are the kidneys or heart, either individually or together.[7, 8] Autonomic and sensory neuropathies are relatively common features.
About 30-40% of patients with primary systemic amyloidosis have cutaneous findings. Mucocutaneous involvement provides early evidence of the existence of an underlying plasma-cell dyscrasia. Petechiae, purpura, and ecchymoses that occur spontaneously or after minor trauma are the most common skin signs and are found in about 15-20% of patients.[9] The most characteristic skin lesions consist of papules, nodules, and plaques that are waxy, smooth, and shiny.[10] Scalp involvement may be evident with hair loss. Mucocutaneous changes in the oral cavity include localized rubbery papules, petechiae, and ecchymoses/purpura[11] . Xerostomia may result from the infiltration of the salivary glands. Macroglossia is reported in 19% of patients with primary systemic amyloidosis.
Primary systemic amyloidosis accounts for 7% of nonhematological malignancies,[12] but few cases of gastric carcinoma in patients with primary amyloidosis have been described. Although acute pseudoobstruction is an uncommon clinical manifestation of amyloidosis, the coexistence of both gastrointestinal hemorrhage and pseudoobstruction of the small intestine should alert the clinician to a diagnosis of gastrointestinal amyloidosis.
Precisely defining the epidemiologic characteristics of amyloidosis is difficult because the disease is often undiagnosed or misdiagnosed. A systematic review of the diagnosed incidence and prevalence of AL amyloidosis in 2018 for the United States, Europe, Canada, Brazil, Japan, South Korea, Taiwan, and Russia found an estimated 74,000 cases had been diagnosed in the preceding 20 years with a prevalence of 51 cases per million. The estimated annual incidence in 2018 ranged from 6.7 cases per million in Brazil to 14.3 cases per million in Japan. The US incidence was 9.9 cases per million.[13]
In a large series of 236 cases of systemic amyloidosis, Kyle and Bayrd reported that 56% were primary cases and 26% were multiple myeloma cases.[14]
Note the following:
Theraperutic advances have markedly improved the prognosis for patients with systemic (AL) amyloidosis over the last two decades. With current treatment regimens, patients in all but the highest risk group have a median survival of >4 years and some groups have a median survival of >10 years12. However, median survival in stage 4 patients remains poor (around 6 months)
The prognosis in patients with AL amyloidosis depends on the extent of disease and the response to therapy. Cardiac involvement occurs in approximately 70% of patients with AL amyloidosis, and the severity of cardiac involvement is the primary driver of survival in these patients. Consequently, survival can be predicted through the measurement of cardiac biomarkers that are released into the circulation with cardiac involvement (ie, troponins I and T, brain natriuretic peptide [BNP], N-terminal pro-brain natriuretic peptide [NT-proBNP]). Using a staging system that includes cardiac biomarkers (see Workup/Staging), Kumar et al reported median overall survival duration and estimated 4-year survival rate by stage as follows[16] :
Reduced abnormalities in cardic biomarker levels and free light chain ratios correlates with improved survival after 3 to 6 months of treatment.[17] Lilleness et al reported that cardiac response to treatment, as indicated by BNP measured before and at 6 months after treatment, provides survival information. Cardiac response and corresponding median overall survival (OS) was as follows:
The symptoms of a patient with primary systemic amyloidosis (PSA) are rarely helpful in making the diagnosis because they are often too nonspecific. Therefore, the diagnosis is often delayed.
Presenting symptoms and signs include the following:
Classically, patients present with the following:
The organs most commonly involved are the kidneys or heart, either individually or together. The patients' symptoms reflect the organ or organs most prominently involved.
Clinically evident mucocutaneous involvement occurs in 30-40% of patients with primary systemic amyloidosis, and it provides an early clue to the existence of an underlying plasma-cell dyscrasia.
Petechiae and ecchymoses are the most common skin findings, because of cutaneous blood vessel involvement. Note the following:
The most characteristic skin lesion in primary systemic amyloidosis consists of waxy papules, nodules, or plaques that may be evident in the eyelids, retroauricular region, neck, or inguinal and anogenital regions. Plaques may coalesce to form large tumefactive lesions.
Diffuse infiltrates may resemble infiltrates of scleroderma or myxedema.
Scalp involvement may appear as diffuse or patchy alopecia.[19]
Dystrophic nail changes include brittleness, crumbling, and subungual striation.
The tongue may be infiltrated, resulting in macroglossia. Macroglossia is a classic feature of primary systemic amyloidosis. The tongue may extrude through gaps between the teeth to produce unique irregular indentations. The presence of amyloid in the oral cavity is often revealed by localized, soft, elastic papules.[20, 21]
Amyloid deposition in the smooth and striated muscles, connective tissue, blood vessel walls, and peripheral nerves may result in myocardial insufficiency, which is the most common cause of death in this fatal disease. Cardiac infiltration may cause angina, infarction, arrhythmias, or orthostatic hypotension.
Blood vessel infiltration may lead to claudication of the legs or jaw.
Renal amyloidosis usually manifests as proteinuria, often resulting in nephrotic syndrome.
Edema is frequently found and may be the result of cardiac failure or nephrotic syndrome.
Amyloid infiltration of the gastrointestinal tract may result in hemorrhage or malabsorption. Gut bleeding may also be fatal.
Hepatomegaly occurs in about 50% of patients with primary systemic amyloidosis, but splenomegaly is present in less than 10% of patients.
Autonomic and sensory neuropathies are relatively common features. Autonomic neuropathy may result in symptomatic postural hypotension, impotence, and disturbances in gastrointestinal motility.
Summers and Kendrick reported and association with CREST syndrome (ie, calcinosis, Raynaud phenomenon, esophageal dysmotility, sclerodactyly, and telangiectasia syndrome).[22] Villa et al reported on amyloid goiter.[23]
Dermatoscopic evaluation may show glomeruloid vessels within a yellowish background.[24]
The presence of diffuse skin infiltrates and the loss of scalp hair can be distressing.
Macroglossia may be associated with painful dysphagia.
Cardiac involvement may cause angina, infarction, arrhythmias, or orthostatic hypotension.[25, 26]
Congestive heart failure or arrhythmias account for death in about 40% of the cases of primary systemic amyloidosis.
Blood vessel infiltration may lead to claudication of the legs or jaw. A case of temporal arteritis also has been described.[27]
Amyloid infiltration of the gastrointestinal tract may result in hemorrhage that can cause malabsorption or even death.[28]
The workup of patients with systemic light chain (AL) amyloidosis requires adequate technology and expertise, and is best performed at specialized centers.[4] The workup includes the following[3] :
The combination of a normal SPIE and UPIE and a normal serum FLC ratio nearly rules out systemic AL amyloidosis. In patients with kidney disease, the FLC ratio is often mildly elevated, but if SPIE/UPIE are normal, a kappa:lambda ratio up to 2.5 can typically be considered normal.[3]
Assessment for organ involvement may involve the following laboratory tests[3] :
Procedures for assessment of organ involvement may include the following, if clinically indicated[29] :
Consensus criteria for organ involvement in amyloidosis, from the XII International Symposium on Amyloidosis, are as follows[30] :
The presence of an abnormality in SPEI/UPEI or FLC ratio testing is insufficient for a diagnosis of AL amyloidosis; these abnormalities are also seen in monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma. To confirm the diagnosis, it is necessary to perform a biopsy, with Congo red and immunologic staining of the tissue sample to identify amyloid and it.
The abdominal fat pad has become the most commonly selected biopsy site, replacing the older choice of rectal tissue. Abdominal fat pad biopsies for amyloidosis have sensitivity of over 80%.[3] If the specimen is negative for amyloid, tissue should be obtained from an organ or area with suspected involvement, such as the heart, kidney, liver, or sural nerve, although these have the disadvantage of being invasive procedures.[31]
Echocardiography is valuable in the evaluation of amyloid heart disease. It usually reveals a concentrically thickened left ventricle and often a thickened right ventricle, with a normal-to-small cavity. Cardiovascular magnetic resonance imaging provides high-definition structural imaging and tissue characterization that are often incremental to information obtained on echocardiography.[32, 33]
Doppler studies are useful and may show abnormal relaxation early in the course of the disease. Advanced involvement is characterized by restrictive hemodynamics.
Cardiac scintigraphy with 99mtechnetium-labeled bone-tracers has proved sensitive and specific for initial diagnosis.[34] 18F-Fluorodeoxyglucose positron-emission tomography has also been used in primary systemic amyloidosis evaluation.[35]
The best way to identify amyloid is to stain paraffin-embedded sections with alkaline Congo red and to examine them with polarized light to elicit a green fluorescence. Routine hematoxylin-eosin staining may show a homogeneous, faintly eosinophilic mass if enough amyloid is present. See the images below.
![]() View Image | Amyloidosis. Amorphous eosinophilic interstitial amyloid observed on a kidney biopsy specimen. |
![]() View Image | Amyloidosis. Congo red staining of a cardiac biopsy specimen containing amyloid, viewed under polarized light |
Analysis of a skin biopsy specimen of a papule reveals an amorphous or fissured eosinophilic mass in the papillary dermis with associated thinning or obliteration of the rete ridges. Nodules and plaques may demonstrate diffuse amyloid deposition in the reticular dermis or subcutis. Amyloid depositions are usually not associated with an inflammatory infiltrate.
The appearance of amyloid infiltration of the blood vessel walls, pilosebaceous units, arrector pili muscles, and lamina propria of sweat glands and infiltration around individual fat cells in the subcutis (known as amyloid rings) are characteristic findings. Amyloid may be deposited in the nail bed of dystrophic nails.
The finding of light chain–restricted plasma cells with amyloid may be a manifestation of myeloma or a marginal cell lymphoma. Clinical correlation is required.[36]
Prognostic models used for risk stratification in AL amyloidosis include the following[32] :
The Mayo AL amyloidosis 2012 model classifies AL amyloidosis into four stages, based on the presence of risk factors. Each of the following risk factors is assigned 1 point:
Patients are then staged as follows:
The European model divides stage III into stage IIIA and stage IIIB, based on a NT-proBNP level of 18000-8500 ng/L or > 8500 ng/L, respectively.[38]
The Boston University model replaces NT-proBNP with brain natriuretic peptide (BNP), to accommodate centers that do not have access to NT-proBNP.[39] Stages are as follows[40, 41] :
Therapy for systemic light-chain (AL) amyloidosis is directed to recovering the function of the affected organs by targeting the abnormal plasma cell clone and slowing deposition of amyloid fibrils. Patients with systemic AL amyloidosis should be considered for early treatment if they have symptomatic visceral organ involvement, significant soft tissue involvement, coagulopathy, or neuropathy.[42]
The current standard treatment regimen for AL amyloidosis is daratumumab plus hyaluronidase, in combination with, cyclophosphamide, bortezomib, and dexamethasone is the current standard regimen for first-line treatment. Autologous stem cell transplantation (ASCT) is performed in eligible patients, especially those with an incomplete response to drug therapy.[4]
Eligibility criteria for ASCT in patients with AL amyloidosis with end organ damage include the following[43] :
The goal of treatment is to achieve a complete hematologic response, with difference between involved and uninvolved free light chains (FLC) < 10 mg/L or involved FLC < 20 mg/L. Patients who achieve less than a very good partial response by cycle 3, or less than a partial response by cycle 2, should be considered for treatment modification.[42]
All patients with AL amyloidosis should be considered for enrollment in a clinical trial. Several novel treatment approaches (eg, venetoclax, ixazomib[44] ) are being studied for this disorder.[29, 42]
The treatment of primary systemic amyloidosis is directed toward the affected organ and the specific type of the disease. Chemotherapy regimens similar to those used for myeloma are employed. In addition, daratumumab, the first and only specific treatment for newly diagnosed AL amyloidosis, was granted accelerated approval in 2021 by the US Food and Drug Administration (FDA). Subcutaneous daratumumab plus hyaluronidase, in combination with bortezomib (Velcade), cyclophosphamide, and dexamethasone (D-VCd), received approval on the basis of results from the phase III ANDROMEDA trial.[45] This is currently the preferred regimen for first-line treatment.[29, 42, 4]
ANDROMEDA is an ongoing randomized, open-label study that involves 388 treatment-naive patients with measurable hematologic disease and one or more affected organs. The hematologic complete response rate in patients receiving D-VCd was 42.1%, versus 13.5% in patients receiving VCd (odds ratio=4.8; 95% CI: 2.9-8.1; P < 0.0001).[45] Because serious or fatal cardiac adverse reactions to daratumumab have occurred in patients with AL amyloidosis, it is not indicated and is not recommended for the treatment of patients with AL amyloidosis who have New York Heart Association (NYHA) class IIIB or class IV heart failure or Mayo stage IIIB AL amyloidosis, outside of controlled clinical trials.[45]
For second-line treatment, treatment selection is guided by the depth and duration of initial response, use of a class of agents not previously exposed, and limitations imposed by patients’ fitness/frailty and end-organ damage.[42] The initial regimen may be repeated, especially for patients who have been relapse-free for several years. Other second-line regimens include the following[29] :
Congestive heart failure may respond to diuretics, but larger doses are often required as the disease progresses. Calcium channel blockers and beta-blockers are contraindicated in cardiac amyloidosis, because they may cause toxicity at therapeutic levels. Digoxin has traditionally been considered contraindicated in cardiac amyloidosis because of the potential for tissue toxicity from binding of digoxin to amyloid fibrils; however, Muchtar et al suggest that digoxin can be used cautiously—at lower doses and with close monitoring of serum digoxin concentration, electrolytes and kidney function—in appropriate patients, particularly when needed for rate control of atrial fibrillation.[38]
Patients with nephrotic syndrome require supportive therapy and diuretics. Kidney failure can be successfully treated with dialysis.
Gastrointestinal involvement and neuropathy are treated symptomatically.
The following organizations have released guidelines for the management of systemic light chain amyloidosis:
The NCCN recommendation for diagnostic evaluation includes[29] :
The recommended laboratory work-up includes[29] :
The following tests are recommended based on affected organs[29] :
The diagnosis of amyloidosis is confirmed by the identification of amyloid deposits in tissue. NCCN guidelines recommend the following tests for pathological diagnosis[29] :
It is essential to confirm that patients have light chain amyloidosis (AL) rather than hereditary amyloidosis, senile amyloidosis, or secondary amyloidosis as treatments are different. Genetic testing, especially for African American patients and patients with peripheral neuropathy, must be done to avoid misdiagnosis.[29]
NCCN guidelines recommend that all newly diagnosed patients be assessed for autologous stem cell transplant (ASCT) eligibility. Patients with low tumor burden can receive ASCT immediately. Patients with high tumor burden may receive systemic therapy first, and their eligibility for transplant may be assessed based on improvements in functional status and/or organ response following treatment. The NCCN panel recommends that treatment should be in the context of a clinical trial when possible, because data are insufficient to identify optimal treatment of the underlying plasma cell disorder.[29]
EHS-ISA guidelines include the following selection criteria for ASCT eligibility[42, 43] :
Cardiac biomarkers should also be considered; elevated cardiac troponin T levels (>0.06 ng/ml) and NTproBNP > 5000 pg/mL are risk factors for poor survival.[42, 43]
Current NCCN guidelines prefer clinical trial participation but also recommend daratumumab/hyaluronidase, in combination with cyclophosphamide, bortezomib, and dexamethasone (CyBorD) as a category 1, preferred primary therapy option for patients with systemic light chain amyloidosis. Other recommended regimens include[29] :
EHS-ISA guidelines also recommend consideration of clinical trial participation, but otherwise recommend daratumumab/CyBorD for most untreated patients; if daratumumab is unavailable, bortezomib-cyclophosphamide-dexamethasone or bortezomib-melphalan-dexamethasone are alternatives.[42]
The NCCN recommends considering repeating initial therapy, especially if the patient was relapse-free for several years. Other recommended treatment regimens include[29] :
For relapsed disease, EHS-ISA guidelines offer the following firsit-choice recommendations for patients who are proteasome inhibitor naïve or have had a prolonged response to proteasome inhibitor therapy[42] :
For patients who are proteasome inhibitor–exposed, EHS-ISA first-choice recommendations vary as follows:
Chemotherapy regimens in systemic light chain (AL) amyloidosis are targeted against the abnormal plasma cell clone. The regimens are largely derived from those for multiple myeloma.[29] In addition, the monoclonal antibody daratumumab is specifically approved for AL amyloidosis, in combination with bortezomib, cyclophosphamide, and dexamethasone.
Clinical Context: Prednisone is an immunosuppressant for the treatment of autoimmune disorders; it may decrease inflammation by reversing increased capillary permeability and suppressing PMN activity. Prednisone stabilizes lysosomal membranes and suppresses lymphocytes and antibody production.
Clinical Context: Dexamethasone has many pharmacologic benefits but also significant adverse effects. It stabilizes cell and lysosomal membranes, increases surfactant synthesis, increases serum vitamin A concentration, and inhibits prostaglandin and proinflammatory cytokines (eg, TNF-alpha, IL-6, IL-2, and IFN-gamma). The inhibition of chemotactic factors and factors that increase capillary permeability inhibits recruitment of inflammatory cells into affected areas. Dexamethasone suppresses lymphocyte proliferation through direct cytolysis and inhibits mitosis. It breaks down granulocyte aggregates and improves pulmonary microcirculation. It is used in induction and reinduction therapy and given as intermittent pulses during continuation therapy.
Adverse effects are hyperglycemia, hypertension, weight loss, GI bleeding or perforation synthesis, cerebral palsy, adrenal suppression, and death. Most of the adverse effects of corticosteroids are dose or duration dependent.
Dexamethasone is readily absorbed via the GI tract and metabolized in the liver. Inactive metabolites are excreted via the kidneys. It lacks the salt-retaining property of hydrocortisone.
Patients can be switched from an intravenous to oral regimen in a 1:1 ratio.
These agents inhibit key factors in the immune system that are responsible for inflammatory responses.
Clinical Context: Melphalan inhibits mitosis by cross-linking DNA strands.
Clinical Context: Colchicine decreases leukocyte motility and phagocytosis in inflammatory responses.
These agents may inhibit the events involved in the inflammatory response associated with the disease.
Clinical Context: Lenalidomide is structurally similar to thalidomide. It elicits immunomodulatory and antiangiogenic properties. It inhibits proinflammatory cytokine secretion and increases anti-inflammatory cytokines from peripheral blood mononuclear cells.
Clinical Context: Daratumumab is a monoclonal antibody that binds with high affinity to the CD38 molecule, which is highly expressed on the surface of clonal plasma cells in light chain (AL) amyloidosis, as well as other cell types. Binding to CD38 induces rapid tumor cell death through programmed cell death and multiple immune-mediated mechanisms. Hyaluronidase human increases permeability of SC tissue by temporarily depolymerizing hyaluronan.
Indicated in combination with bortezomib, cyclophosphamide, and dexamethasone for newly diagnosed light chain (AL) amyloidosis