Approach

The diagnostic workup of amyloidosis includes a detailed history and physical exam; laboratory and pathologic evaluation (including studies to confirm the presence and type of amyloid deposits in tissue); and imaging studies.

It is important to determine amyloidosis type when making a diagnosis, as this guides treatment.

History

A detailed history should be carried out to help to determine the potential cause and type of amyloidosis.

History may reveal a prior diagnosis of monoclonal gammopathy of undetermined significance (MGUS).[57]​ Patients with MGUS have a relative risk of progression to AL amyloidosis (the most common type of amyloidosis) of eight- to ninefold.[4][57][58]​​​​​ It is important to note, however, that an incidental monoclonal gammopathy may be present in patients with other types of amyloidosis (e.g., hereditary amyloidosis, wild-type transthyretin [ATTRwt] amyloidosis), which can lead to a misdiagnosis of AL amyloidosis.[27][28][60]​​​​ Clinical awareness together with a careful family history and laboratory/pathologic evaluation (including genetic testing) are essential to avoid a misdiagnosis.[29][61]​​

Secondary (AA) amyloidosis is associated with:[16][21][22][23][24][25][26]

  • chronic inflammatory conditions (e.g., inflammatory polyarthropathy, inflammatory bowel disease [specifically Crohn disease])

  • chronic infections (e.g., bronchiectasis, tuberculosis, subcutaneous injection of illicit drugs, decubitus ulcers, chronic urinary tract infections, osteomyelitis)

  • familial periodic fever syndromes (e.g., familial Mediterranean fever, tumor necrosis factor [TNF] receptor-associated periodic fever syndromes [TRAPS], cryopyrin-associated periodic syndromes [CAPS; such as Muckle-Wells syndrome], mevalonate kinase deficiency [formerly known as hyper-IgD syndrome])

  • Castleman disease (plasma cell variant), a noncancerous lymphoproliferative disorder, but this is rare.

ATTRwt is associated with aging and affects mainly elderly men. History often includes cardiomyopathy, carpal tunnel syndrome, and spinal stenosis.[62]

Symptoms

Patients with amyloidosis frequently present with symptoms relating to a clinical syndrome of the affected organ (e.g., cardiomyopathy, nephrotic syndrome, neuropathy).[63]

Fatigue, weight loss, paresthesias, and dyspnea on exertion are the most common symptoms associated with amyloidosis and are common to all systemic forms.[41] However, these complaints are nonspecific.

Extreme weight loss (e.g., >9 kg) is common (particularly in patients with cardiac and hepatic involvement) and is suggestive of amyloidosis if associated with edema or neuropathy.[48]

Cardiac symptoms

Cardiac involvement is most commonly associated with AL amyloidosis and transthyretin (TTR)-related amyloidosis (hereditary and wild type).[41][42][48][53][54][64]​​ 

Lightheadedness can be a symptom of cardiac amyloidosis (low cardiac output with preserved ejection fraction). Patients may have jaw claudication, calf and limb claudication, and rarely angina if there is involvement of the coronary arterioles.

Fatigue and dyspnea on exertion caused by early cardiac involvement are generally not recognized as symptoms of overt heart failure and can be misdiagnosed as being stress-related or functional.

Renal involvement

Most commonly associated with AL amyloidosis, AA amyloidosis, non-TTR hereditary amyloidosis (e.g., fibrinogen A alpha-chain, apolipoprotein A), and leukocyte chemotactic factor 2 (LECT2) amyloidosis.[3][16][32][39][51][59]​​​​

Fatigue and lightheadedness are symptoms of nephrotic syndrome (hypoalbuminemia and intravascular volume contraction).

Neurologic symptoms

Nerve involvement can lead to peripheral and autonomic neuropathy, and is most commonly associated with AL amyloidosis and hereditary TTR (ATTRv) amyloidosis.[18][48][65][66][67][68]​​​ ​Mild peripheral neuropathy may occur in patients with ATTRwt amyloidosis (up to 20%).[55]

Nerve involvement is not a typical feature of AA amyloidosis, non-TTR hereditary amyloidosis, or LECT2 amyloidosis.[3]

Initial presentation of peripheral neuropathy is usually distal symmetric sensory loss (i.e., loss of temperature and pain perceptions, followed by proprioceptive loss).[50] Patients usually report dysesthesia and paresthesia of the feet and lower legs, which progress to the hands and arms over time. 

Patients with autonomic neuropathy may have erectile dysfunction, orthostatic hypotension, gastrointestinal dysfunction, or urinary dysfunction.[18][68]​​​​ Sweating abnormalities and failure of heart rate to change when body position is changed are signs of autonomic dysfunction.

Peripheral and autonomic neuropathy are important diagnostic clues for AL amyloidosis and ATTRv amyloidosis.[50]

Carpal tunnel syndrome prevalence is greatest in patients with TTR cardiac amyloidosis (20.3% vs. 4.1% in the general population), but it is also a manifestation of AL amyloidosis.[69]​​ Tinel sign (tapping over the carpal nerve at the wrist produces tingling in the thumb, index, and middle finger) and Phalen maneuver (holding the dorsal surface of both hands together in forced flexion for around 1 minute produces tingling in the thumb, index, and middle finger) should be performed to test for carpal tunnel syndrome involvement in patients reporting paresthesia in the hands.

Gastrointestinal symptoms

Steatorrhea is typical of intestinal involvement. Severe fecal incontinence alternating with 3-4 days of constipation may be present.

Pseudo-obstructive symptoms (including nausea, vomiting, postprandial abdominal cramping) and gastroparesis may be present if there is upper gastrointestinal tract involvement.

Musculoskeletal symptoms

Musculoskeletal disorders (e.g., biceps tendon rupture, hip and knee osteoarthritis, trigger finger, and spinal stenosis) are typically associated with TTR amyloidosis, and may precede cardiac or neurologic manifestations.[70][71]

Physical exam

Common physical findings include lower extremity edema and elevated jugular venous distention (due to high right-sided filling pressure).[72][73]

Many physical findings of amyloidosis are specific and diagnostic for amyloidosis, but are present in ≤15% of patients.[48]

  • Amyloid purpura: occurs in approximately 15% of patients with AL amyloidosis.[48] Typically periorbital but can occur anywhere above the nipple line. ​​

  • Eyelid petechiae: common, but evident only when the patient's eyes are closed.

  • Macroglossia: specific and diagnostic for AL amyloidosis.[48] Occurs in approximately 10% of patients but is easily overlooked because the most common presentation is dental indentations on the underside of the tongue.​

  • Enlargement of the submandibular salivary glands: specific for AL amyloidosis. It may be misinterpreted as lymphadenopathy. Salivary gland involvement results in a sicca syndrome. These patients are often misdiagnosed as having Sjögren syndrome.

  • Palpable hepatomegaly: >5 cm below the right costal margin, most commonly reported in AL amyloidosis (approximately 10% of patients).[16][48] Splenomegaly is usually of modest degree. Palpable hepatomegaly is uncommon in AA amyloidosis, but histopathologic changes in the liver may be evident. Liver involvement is rare in patients with hereditary amyloidosis.

  • Shoulder pad sign: rare, due to periarticular infiltration with amyloid; pseudohypertrophy is specific for AL amyloidosis.

  • Diffuse muscular weakness: amyloid myopathy can occur with muscle hypertrophy due to extracellular amyloid infiltration in the muscle, or can occur with muscular atrophy due to vascular occlusion leading to muscle ischemia and claudication.

  • Orthostatic hypotension with syncope: can occur if autonomic neuropathy is present (e.g., in AL amyloidosis or ATTRv amyloidosis).[Figure caption and citation for the preceding image starts]: Bilateral periorbital ecchymosis (amyloid purpura) in a patient with AL amyloidosisWilliams MU, Murphy CE, Gore RS, et al. BMJ Case Rep 2018;11:e225923. doi:10.1136/bcr-2018- 225923 [Citation ends].com.bmj.content.model.Caption@d81f22d[Figure caption and citation for the preceding image starts]: Classic periorbital purpuraMorie A. Gertz, MD; courtesy of Mayo Clinic [Citation ends].com.bmj.content.model.Caption@28547f6[Figure caption and citation for the preceding image starts]: Macroglossia in a patient with AL amyloidosisWilliams MU, Murphy CE, Gore RS, et al. BMJ Case Rep 2018;11:e225923. doi:10.1136/bcr-2018- 225923 [Citation ends].com.bmj.content.model.Caption@5a0287ae

Key diagnostic tests

The first tests to order in patients with clinically suspected amyloidosis are immunofixation electrophoresis of the serum and urine (using 24-hour urine collection), and serum immunoglobulin free light chain assay.[61][74]​​​​ 

Positive immunofixation (presence of a monoclonal protein in the serum or urine) and/or an abnormal serum immunoglobulin free light chain assay is reported in 99% of patients with AL amyloidosis.[75]

A diagnosis of AL amyloidosis should be confirmed histologically (e.g., biopsy with amyloid typing) to avoid a misdiagnosis because an incidental monoclonal gammopathy may be present in other types of amyloidosis (e.g., hereditary amyloidosis, ATTRwt amyloidosis)​.​​[27][28][60][61][76]​​

A diagnosis of AL amyloidosis is unlikely if immunofixation and serum immunoglobulin free light chain assay are normal. Patients with clinically suspected amyloidosis with equivocal or normal immunofixation and serum immunoglobulin free light chain assay should undergo a careful and prompt evaluation (including genetic testing) for other types of amyloidosis (e.g., AA amyloidosis, TTR amyloidosis, localized amyloidosis).

Biopsy studies

Histologic confirmation of amyloid deposits in tissue is essential for establishing a diagnosis of amyloidosis.

Bone marrow aspirate and biopsy, and subcutaneous fat aspirate (e.g., abdominal fat pad) are recommended in patients with suspected amyloidosis (e.g., if a monoclonal protein is present).[61] Other tissues that can be biopsied include lip (minor salivary gland) and rectum.[61]

Bone marrow aspirate and biopsy can also be used to identify clonal plasma cells and assess for coexistent multiple myeloma. See Multiple myeloma.

If bone marrow and tissue biopsy studies are negative, biopsy of an involved organ (e.g., heart, liver, kidney, nerve) should be performed as clinically indicated.[61]

Multiple tissue or organ biopsies are potentially hazardous and are not recommended.[77]​ Bone marrow biopsy combined with subcutaneous fat aspirate (e.g., abdominal fat pad) will identify amyloid deposits in most (85%) patients with amyloidosis.[78]

Apple-green birefringence on a Congo red stained aspirate or biopsy specimen is required for diagnosis.[79] Apple-green birefringence after Congo red staining confirms the presence of amyloid deposits but does not differentiate between different types of amyloid.[61]​ Amyloid typing and/or immunohistochemical studies should be carried out to confirm the type of amyloid.

Fluorescence in situ hybridization (FISH) studies should be done on bone marrow aspirate to identify molecular markers that can guide prognosis and treatment e.g., t(11;14) translocation.[80][81][Figure caption and citation for the preceding image starts]: Congo red stain blood vessel in a bone marrow biopsy demonstrating green birefringence pathognomonic of amyloidosisMorie A. Gertz, MD; courtesy of Mayo Clinic [Citation ends].com.bmj.content.model.Caption@28e57628​​​

Amyloid typing

Mass spectrometry-based proteomic analysis is currently the gold standard for amyloid typing. It is the most direct method of confirming the amyloid type (e.g., light chain, serum amyloid A [SAA; associated with AA amyloidosis], TTR).

Immuno-electron microscopy can be used on renal biopsy specimens to clarify the fibrillar nature of the amyloid, but is not part of routine clinical practice for other biopsy material.[Figure caption and citation for the preceding image starts]: Electron micrograph demonstrating classical amyloid fibrilsMorie A. Gertz, MD; courtesy of Mayo Clinic [Citation ends].com.bmj.content.model.Caption@435c0f5f

Immunohistochemical studies

Immunohistochemical staining of amyloid deposits can be attempted to distinguish the various forms of systemic amyloidosis. Commercially available antisera to immunoglobulin light chains, SAA, and TTR are typically used but may lack specificity and sensitivity.

Immunohistochemistry has lower diagnostic accuracy than mass spectrometry.[61]

Genetic testing

Genetic testing can be used to assess for hereditary amyloidosis (e.g., ATTRv, fibrinogen A alpha-chain, apolipoprotein A, lysozyme) and familial periodic fever syndromes associated with AA amyloidosis (e.g., familial Mediterranean fever, TRAPS, CAPS [Muckle-Wells syndrome], mevalonate kinase deficiency [hyper-IgD syndrome]).[82]​​[83]

Use of genetic testing is important to avoid a misdiagnosis (e.g., AL amyloidosis) in patients with hereditary amyloidosis.[29][61]​​​ 

Ancillary tests

Patients should have the following tests to guide diagnosis and prognosis, and to assess organ involvement:[61]

  • CBC with differential

  • Peripheral blood smear, serum quantitative immunoglobulins, and serum protein electrophoresis, to assess for a plasma cell disorder

  • N‐terminal pro‐B-type natriuretic peptide (NT‐proBNP; B-type natriuretic peptide [BNP] if NT‐proBNP is unavailable), serum troponin T (troponin I if troponin T is unavailable), and lipid panel, to assess for heart involvement and for prognostication

  • Urine total protein and urine protein electrophoresis (from the 24-hour urine sample)

  • Comprehensive metabolic profile (including serum blood urea nitrogen [BUN], serum creatinine, electrolytes, serum albumin, serum calcium, serum uric acid, serum lactate dehydrogenase [LDH], beta-2 microglobulin; liver function tests [LFTs]), to assess for renal and liver involvement

  • Coagulation studies (including prothrombin time [PT], partial thromboplastin time [PTT], factor X), to assess for amyloid-related coagulation abnormalities

  • Orthostatic vital sign assessment and electromyogram (if clinically significant peripheral neuropathy is present)/nerve conduction studies, to assess for nerve involvement

  • Thyroid-stimulating hormone and cortisol levels, to assess for endocrine involvement

  • Pulmonary function tests, to assess for lung involvement

Cardiac evaluation

Cardiac involvement commonly occurs in AL, ATTRv, and ATTRwt amyloidosis.[41][42][48]​​[53][54][64]​​ Late diagnosis of cardiac involvement is associated with poor outcomes.[84]

An ECG and echocardiogram (with tissue Doppler and global longitudinal strain) should be carried out in all patients (symptomatic or asymptomatic) with suspected or confirmed cardiac amyloidosis.​[54][70][85]​​​​​​ Increased left ventricular (LV) wall thickness, typical LV longitudinal strain pattern, and reduced tissue Doppler velocities are highly suggestive of cardiac amyloidosis.[54][85]​​​​ 

Cardiac MRI may be useful if an echocardiogram is suggestive or indeterminate. However, it is not diagnostic and cannot distinguish between AL and TTR cardiac amyloidosis.[70][85]​​​​ Cardiac MRI parameters should be combined with electrocardiographic, clinical, biomarker, and other imaging findings to maximize diagnostic accuracy.[85]

Cardiac scintigraphy with technetium-labeled bone tracers (99mTc-PYP or 99mTc-DPD) should be performed if TTR cardiac amyloidosis is suspected.[29] Scintigraphy is sensitive for the detection of TTR cardiac amyloidosis and enables noninvasive clinical diagnosis.[70][85][86][87]​​​​​​ However, it lacks specificity, therefore false positives may be seen. A negative monoclonal protein result alongside scintigraphy cardiac uptake (grade 2 or 3) confirms a diagnosis of TTR amyloidosis (without requiring biopsy).[61][70]​​​​ If scintigraphy cardiac uptake is 1 or 0, a biopsy is required (cardiac or non-cardiac, depending on presentation).[61]

In older men with an echocardiogram consistent with cardiac amyloidosis, a cardiac scintigraphy showing uptake of 99mTc-PYP or 99mTc-DPD in myocardial tissue increases suspicion for ATTRwt amyloidosis.

Cardiac workup for coronary artery disease is invariably normal.[88]

Imaging studies

Whole-body low-dose computed tomography (CT) or 18F-fluorodeoxyglucose positron emission tomography (FDG-PET)/CT can be used to detect osteolytic bone lesions if a monoclonal protein is detected. A skeletal survey can be used if these advanced imaging modalites are unavailable, but sensitivity is significantly lower.[61]

A chest CT can be used to evaluate lung involvement, if clinically indicated.[61]

Gastric emptying scan (if gastroparesis is present) and abdominal ultrasound or CT (as clinically indicated) can be used to evaluate liver and gastrointestinal involvement.[61] Upper and lower endoscopies can be performed if symptoms suggest gastrointestinal involvement.

123I-labeled serum amyloid P (SAP) scintigraphy can be used to assess the extent of organ involvement and dysfunction at diagnosis and during follow-up. SAP scintigraphy is standard practice in the UK and the Netherlands, but use in other countries may vary.[77][89]

Prognostication

Prognostic biomarkers for amyloidosis include: serum troponin T (troponin I if troponin T is unavailable); NT‐proBNP (BNP if NT-proBNP is unavailable); and the difference between involved and uninvolved serum free light chains (dFLC).

Serum troponin level is a sensitive marker for myocardial injury in amyloidosis; NT‐proBNP is a sensitive marker for myocardial stretch and congestive heart failure.[90][91]​​ Troponin, NT‐proBNP, and dFLC are used in the Mayo staging criteria for AL amyloidosis.[92][93][94]​ See Criteria.

Beta-2-microglobulin is predictive of survival in patients with AL amyloidosis.[95][96]

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