Introduction
Background
Paraproteinemia
Paraproteinemic neuropathy (PPN)
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Distal demyelinating symmetric neuropathy
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Chronic inflammatory demyelinating polyneuropathy (CIDP) –like
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Axonal sensorimotor peripheral neuropathy
Paraproteinemic disorders
Testing strategy
Test | Description | Comments |
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Erythrocyte sedimentation rate (ESR) | Venous blood sample. | ESR elevation is primarily due to increased levels of Ig (clonal or polyclonal) or fibrinogen |
Serum total protein and albumin | Venous blood sample. | Protein elevated in: |
Normal range: | Monoclonal gammopathy | |
Serum total protein: 6 to 8 g/dL | Dehydration | |
Serum albumin: 4 to 6 g/dL | Myeloma | |
Waldenstrom macroglobulinemia | ||
Sarcoidosis | ||
Collagen vascular disease | ||
Serum protein electrophoresis | Venous blood sample. | Indicated if serum protein and/or globulin is elevated or clinical findings raise suspicion of monoclonal gammopathy. |
M protein, if present, is a discrete spike in the γ, β or α2 region. | ||
MGUS, M peak: 0.5 to 3 g/dL, amount directly related to probability of progression to multiple myeloma or a related plasma cell malignancy. | ||
Serum M spike present in 80 % of patients with myeloma. | ||
Immunofixation | Venous blood sample. | Indicated when an M spike is found on serum electrophoresis or when clinical findings present suspicion of multiple myeloma, other plasma cell malignancy, amyloidosis, or WM. |
Monoclonal immunoglobulin: | ||
MGUS: IgG (73 %), IgA (11 %), IgM (14 %), IgD, κ or λ light chains | Defines the heavy and light chain type of the abnormal serum protein, which can discriminate between MGUS, multiple myeloma, other plasma cell malignancies, WM, and amyloidosis. | |
Multiple myeloma: IgG (50 %), IgA (20 %), IgD (few), free light chains (17 %) | ||
WM: IgM-κ | ||
Amyloidosis: IgG, IgA, IgD, IgM, κ or λ light chains; 30 % non-secretory | ||
Osteosclerotic myeloma: IgG-λ or IgA-λ | ||
Heavy-chain disease: IgG, IgA, IgM, no light chain | ||
Serum light chain quantitation | Venous blood sample. | Provides a rapid, accurate, quantitative measurement of λ and κ light-chain in serum. |
κ free light chain: 3.3 to 19.4 mg/L | Increased light chain levels are seen in most plasma cell disorders, especially the more malignant disorders such as multiple myeloma. | |
λ free light chain: 5.7 to 26.3 mg/L | Free light chain (FLC) ratio may be a risk factor for progression to malignancy [66]. | |
Unlike urine Bence-Jones protein assays, results are not affected by changes in renal function. | ||
The test is expensive and not widely available. | ||
Autoantibody panels | Normal: | Measures presence and titer of antibodies. |
Absence of antibody | Anti-MAG antibody assesses distal demyelinating sensory neuropathy. | |
Anti-GM1 antibody assesses multifocal motor neuropathy. | ||
Anti-GQ1b antibody assesses Miller-Fisher. | ||
Please note that absolute absence of autoantibodies is not required for a “normal” test for many antibodies at different labs. | ||
Cryoglobulins | Normal: | Serum blood specimen collected and separated while warm for cryoprecipitation over a period of up to 7 days. |
Less than 80 μg/ml | At very high cryoglobulin titer states, cryoprecipitates during blood collection produce structures on peripheral blood smears that may be mistaken for leukocytes or platelets by automated cell differential analyzers. | |
24-h urine protein quantification and electrophoreses | Detects excretion of monoclonal immunoglobulin. | Dipstick test for proteinuria primarily detects albumin and often misses M protein. |
Normal: | ||
Urinary protein excretion less than 150 mg/day. | Recommended for patients with serum M spike or clinically-based suspicion of monoclonal gammopathy. | |
Small amount of Bence-Jones protein not uncommon | ||
Urine immunofixation | Characterizes urinary monoclonal immunoglobulin following test of 24-h urine and should be done if serum M spike is greater than 1.5 g/dL. | Indicated if multiple myeloma, WM, primary amyloidosis, or a related disorder is suspected, even if routine urinalysis is negative for protein, 24-h urine is within normal limits, or if no M spike is seen on electrophoresis of concentrated urine sample. |
Electrodiagnostic (electro-myelogram and nerve conduction studies) | Determines whether symptoms are due to a muscle or nerve disorder by measuring conduction velocities and the presence or absence of conduction blocks. | Determines whether the polyneuropathy is axonal or demyelinating. |
Tests help to localize the anatomic site of a lesion that is causing pain, and determine the presence of active denervation. | ||
Bone marrow aspiration and biopsy | A sample is taken usually from the posterior superior iliac crest region. | Required if a high M protein level is found to investigate the possibility of multiple myeloma or lymphoma. |
Normal result is age-appropriate cellularity and lineage distribution and < 10 % plasma cells. | May reveal clinically inapparent involvement. | |
Requires local anesthesia and the assistance of an attendant. | ||
Risk of infection and bleeding. | ||
Radiographic skeletal bone survey | Two dimensional radiographs of the entire skeleton. | Survey detects lytic and sclerotic lesions as well as fractures which may be pathologic. |
There is a relatively high radiation exposure. | ||
Cerebrospinal fluid analysis | Investigate CIDP and leptomeningeal lymphomatous infiltration. | Elevated protein level is common in PPN. |
Infiltration of the CNS by Non-Hodgkin’s lymphoma will show clonal lymphocytes. | ||
Viral infection may result in increased CSF lymphocytes but will not be clonal. | ||
Autoantibodies can be tested within the CSF but the results may differ depending on the laboratory used. Absolute absence of autoantibodies is not required for a “normal” test for many antibodies at different labs. | ||
Nerve biopsy | Biopsy of the superficial peroneal nerve is ideal so that a muscle biopsy of the peroneus brevis muscle may be done simultaneously; other choices include sural or superficial radial sensory nerves. | Identifies abnormal density of small and large axons and abnormal myelin sheaths. |
Reserved for cases in which it is difficult to identify whether the process is predominantly axon degeneration or demyelination, or for cases where there is patchy, asymmetric, or focal involvement. | ||
Evaluates suspected cases of infiltrative neoplasms, paraproteinemic vasculitis, or amyloidosis. | A negative nerve biopsy does not exclude amyloid neuropathy. | |
Please note that as with serum and CSF autoantibody testing, results may differ depending on the laboratory used. | ||
Muscle biopsy | See “Nerve biopsy” for best incision site. | The procedure helps distinguish between an atypical neurogenic disorder and a primary myopathic disorder. |
Fat biopsy | A normal result is no amyloid protein. | The test is most often done when there is suspicion of amyloidosis. |
Skin biopsy | Examines the degree of myelination of small fiber neurons. | Helps ascertain the presence or absence of small fiber neuropathy. |
Epidermal nerve twig analysis via skin biopsy is sometimes done if small fiber neuropathy is suspected. | ||
Whole-body computerized tomography scan | The scan can detect lymphadenopathy, hepatosplenomegaly, and ascites. | Intravenous contrast is usually required for better visualization of lymphoid structures. |
Positron emission tomography scan | Functional images assess metabolic activity within various structures, including lymph nodes and may detect nodal, extranodal, and bone marrow involvement by lymphoma. | PET scan can be used concurrently with non-contrast CT scan to combine functional and anatomic imaging. |
Acute inflammation and infection can also result in increased uptake safety profile of the procedure, even though it is less sensitive than biopsy. |
VEGF testing for POEMS
Paraproteinemia treatment strategy
Treatment | Indication | Dose | Major contraindications |
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Intravenous immune globulin (IVIG) | FDA-approved treatment for CIDP | 2 g/kg intravenously for 3–5 days, followed by maintenance dose of 1 g/kg every 3 weeks, followed by clinical reassessment | Hypersensitivity to IVIG |
FDA-approved treatment for multifocal motor neuropathy | 0.5-2.4 g/kg per month with clinical assessment followed by clinical reassessment | IgA deficiency | |
Treatment for IgA/IgG-MGUS-CIDP | Immunoglobulin A deficiency | ||
Alternative treatment for IgM-MGUS-distal demyelinating neuropathy (or rituximab, off-label use) | |||
Treatment of CANOMAD (off label use) | |||
Corticosteroids | First line treatment for CIDP associated with M protein (off-label use) | Prednisone: | Corticosteroid hypersensitivity |
An alternative treatment for IgM/A/G-MGUS (after rituximab or plasma exchange, off label use) | 1 to 1.5 mg/kg/day orally | Fungal infection | |
Several treatment dosing regimens are available and duration is not agreed upon. | |||
Azathioprine | Alternative immunosuppressive treatment (after IVIG or corticosteroids) for CIDP associated with M protein (off-label use) | Pregnancy (category D) | |
Hypersensitivity to azathioprine | |||
Rituximab | Alternative treatment for IgM-MGUS (off-label use) | Four weekly infusions of 375 mg/m2 rituximab [51] | Hypersensitivity to rituximab |
Alternative therapy for multifocal motor neuropathy (after IVIG, off label use) | |||
Chlorambucil | Alternative therapy for IgM-MGUS (off label use) | 0.1 to 0.2 mg/kg orally daily for 3 to 6 weeks | Hypersensitivity to chlorambucil |
FDA pregnancy category D | |||
Fludarabine | Alternative therapy for IgM-MGUS (off label use) | 40 mg/m2 for 5 days every 28 days | Hypersensitivity to fludarabine |
FDA pregnancy risk category D | |||
Melphalan | Treatment for POEMS | For POEMS (high dose): 10 mg/m2 for 4 days every 28 days [58] | Hypersensitivity to melphalan |
In combination with prednisone as treatment for AL | For AL: 0.15 mg/kg once daily for 7 days every 6 weeks, increasing the dose by 2 mg in each 6 week course. Should be used in combination with prednisone. | Should not be used in patients whose disease has demonstrated prior melphalan resistance | |
Plasmapheresis (plasma exchange) | Alternative treatment of IgG/A MGUS | 3 to 5 exchanges every other day | Risks associated with frequent vascular access |
May be helpful in severe cases of cryoglobulinemia. | Risk of transmission of infective agents if fresh plasma is used as replacement fluid | ||
Anaphylaxis and allergic reactions may occur with reinfusion of plasma substitute | |||
Autologous peripheral stem cell transplant | First line treatment of POEMS syndrome | Myeloablative doses of chemotherapy and/or radiation therapy followed by infusion of peripheral blood stem cells | Patients who undergo HCT are at risk for bacterial, viral, and fungal infections |
Alternative treatment of AL, used in combination with melphalan | Early adverse effects include: nausea, vomiting, diarrhea, mouth sores | ||
Later adverse effects include: cataracts, sterility, increased risk of other neoplasias | |||
Radiation therapy | First line treatment of dominant sclerotic plasmacytoma in POEMS syndrome | Radiation therapy delivered to osteosclerotic lesions in doses of 40–50 Gy | Adverse effects depend upon the location of the area irradiated |
Increased risk of developing second malignancies in patients with Hodgkin’s Lymphoma |