Top 10 Clinical Pearls in Paraproteinemic Neuropathies

Paraproteinemic neuropathies represent an important subset of peripheral neuropathies. Once identified, further evaluation into the paraproteinemic subtype, clinical exam pattern, and electrodiagnostic phenotype helps clarify if the paraproteinemia is coincidental or causal of the neuropathy, as not all paraproteinemias cause neuropathy. Of all paraproteinemias, immunoglobulin M (IgM)-associated peripheral neuropathy, or IgM neuropathy, is of particular importance as half of IgM neuropathies also harbor anti-myelin-associated glycoprotein antibodies, which produce a characteristic demyelinating pattern on nerve conduction testing. Immunoglobulin G and immunoglobulin A paraproteinemias are less strongly associated with peripheral neuropathy, except in the setting of multiple myeloma or osteosclerotic myeloma (POEMS syndrome), which have characteristic systemic features. In multiple myeloma, chemotherapy is more likely to result in neuropathy than the myeloma itself. Finally, the presence of systemic features (e.g., cardiomyopathy, nephropathy, recurrent carpal tunnel syndrome, and autonomic insufficiency) should raise concern for hereditary or acquired light (AL) chain amyloidosis. AL amyloidosis can occur in the setting of any light or heavy chain paraproteinemia. Central to the proper evaluation of paraproteinemic neuropathy is electrodiagnostic testing, which helps delineate axonal versus demyelinating paraproteinemic neuropathy, the latter often misdiagnosed as chronic inflammatory demyelinating polyradiculoneuropathy.

Neurosurgical Intervention for Nerve and Muscle Biopsies

(1) Background: Neurologic and musculoskeletal diseases represent a considerable portion of the underlying etiologies responsible for the widely prevalent symptoms of pain, weakness, numbness, and paresthesia. Because of the subjective and often nonspecific nature of these symptoms, different diagnostic modalities have been explored and utilized. (2) Methods: Literature review. (3) Results: Nerve and muscle biopsy remains the gold standard for diagnosing many of the responsible neurological and musculoskeletal conditions. However, the need for invasive tissue sampling is diminishing as more investigations explore alternative diagnostic modalities. Because of this, it is important to explore the current role of neurosurgical intervention for nerve and muscle biopsies and its current relevance in the diagnostic landscape of neurological and musculoskeletal disorders. With consideration of the role of nerve and muscle biopsy, it is also important to explore innovations and emerging techniques for conducting these procedures. This review explores the indications and emerging techniques for neurological intervention for nerve and muscle biopsies. (4) Conclusions: The role of neurosurgical intervention for nerve and muscle biopsy remains relevant in diagnosing many neurological and musculoskeletal disorders. Biopsy is especially relevant as a supportive point of evidence for diagnosis in atypical cases. Additionally, emerging techniques have been explored to guide diagnostics and biopsy, conduct less invasive biopsies, and reduce risks of worsening neurologic function and other symptoms secondary to biopsy.

Paraproteinemia and neuropathy

Paraproteinemia is associated with different peripheral neuropathies. The major causes of neuropathy correlated with paraproteinemia are the deposition of immunoglobulin in the myelin, represented by anti-myelin-associated glycoprotein (MAG) neuropathy; deposition of immunoglobulin or its fragment in the interstitium, represented by immunoglobulin light chain amyloidosis (AL amyloidosis); and paraneoplastic mechanisms that cannot be solely attributed to the deposition of immunoglobulin or its fragment, represented by polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin change (POEMS) syndrome. Patients with anti-MAG neuropathy and POEMS syndrome present with slowing of nerve conduction parameters. This characteristic fulfills the electrodiagnostic criteria for chronic inflammatory demyelinating polyneuropathy (CIDP) defined by the European Academy of Neurology and Peripheral Nerve Society (EAN/PNS). Although direct damage caused by the deposition of amyloid can induce axonal damage in AL amyloidosis, some patients with this condition have features fulfilling the EAN/PNS electrodiagnostic criteria for CIDP. Conventional immunotherapies for CIDP, such as steroids, intravenous immunoglobulin, and plasma exchange, offer no or only minimal-to-modest benefit. Although rituximab can reduce the level of circulating autoantibodies, it may only be effective in some patients with anti-MAG neuropathy. Drugs including melphalan, thalidomide, lenalidomide, and bortezomib for POEMS syndrome and those including melphalan, thalidomide, lenalidomide, pomalidomide, bortezomib, ixazomib, and daratumumab for AL amyloidosis are considered. Since there will be more therapeutic options in the future, thereby enabling appropriate treatments for individual neuropathies, there is an increasing need for early diagnosis.

Nerve biopsy: Current indications and decision tools

After initial investigation of patients presenting with symptoms suggestive of neuropathy, a clinical decision is made for a minority of patients to undergo further assessment with nerve biopsy. Many nerve biopsies do not demonstrate a definitive pathological diagnosis and there is considerable cost and morbidity associated with the procedure. This highlights the need for appropriate selection of patients, nerves and neuropathology techniques. Additionally, concomitant muscle and skin biopsies may improve the diagnostic yield in some cases. Several advances have been made in diagnostics in recent years, particularly in genomics. The indications for nerve biopsy have consequently changed over time. This review explores the current indications for nerve biopsies and some of the issues surrounding its use. Also included are comments on alternative diagnostic modalities that may help to supplant or reduce the use of nerve biopsy as a diagnostic test. These primarily include extraneural biopsy and neuroimaging techniques such as magnetic resonance neurography and nerve ultrasound. Finally, we propose an algorithm to assist in deciding when to perform nerve biopsies.

Neuropathy associated with IgA monoclonal Gammopathy. A harbinger of AL amyloidosis

Peripheral neuropathy is seen in 15% of patients with IgA monoclonal gammopathy. Treatment and prognosis of dysproteinemic neuropathy is usually guided by the underlying plasma cell disorders, which could be either benign or malignant. The true incidence of hematologic malignancy in patients with neuropathy associated with IgA monoclonal gammopathy is not known. However, patients with IgA M-protein are generally at increased risk for malignant transformation. Since neuropathy may be the first and only organ involvement, neurologists are key contributors in identifying each patient's plasma cell dyscrasia. We report two patients who presented with severe progressive polyneuropathy, had a detectable low-level IgA lambda paraproteinemia dismissed as incidental. Both were diagnosed later with a combination of malignant plasma cell dyscrasia and AL amyloidosis resulting in multiorgan failure and death. Both patients demonstrated red flags for malignant progression including abnormal serum free light chain, rapidly progressive debilitating neuropathy refractory to immunotherapy, prominent autonomic dysfunction, and weight loss. In summary, patients with IgA monoclonal gammopathy presenting with polyneuropathy can be at risk for malignant transformation. Failure to investigate for hematologic malignancy and AL amyloidosis may cause significant delays in treatment and result in fatal outcomes.

Antibody- and macrophage-mediated segmental demyelination in chronic inflammatory demyelinating polyneuropathy: clinical, electrophysiological, immunological and pathological correlates

BACKGROUND AND PURPOSE

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a heterogeneous autoimmune disorder critically lacking diagnostic biomarkers. Autoantibodies to nodal and paranodal components have recently been described in a small subset of patients. Here, the diagnostic value of immune reactivity toward the myelin compartment was investigated.

METHODS

Ninety-four French CIDP patients were retrospectively studied. The reactivity toward the peripheral nerve was investigated. Sural nerve biopsies were examined by electron microscopy and immunofluorescence.

RESULTS

Twenty-one patients (22%) and three patients (3%) presented with a strong immunoglobulin G or immunoglobulin M reactivity respectively against the myelin compartment. The clinical, electrophysiological and morphological features were examined in nine of these patients for whom sural nerve biopsies were available. Seven patients were electrodiagnosed with definite CIDP, one with possible CIDP and one was unclassifiable but sural nerve biopsy argued for CIDP diagnosis. Electron microscopy of sural nerve biopsies demonstrated the presence of macrophage-mediated demyelination restricted to the internode in all nine patients. Immunolabelling for voltage-gated sodium channels, myelin and axonal markers confirmed the presence of segmental demyelination and of remyelination. The nodal and paranodal regions, however, were unaffected in these patients. Nerve conduction studies corroborated the multifocal and segmental profile, and seven patients showed increased duration of proximal (1.5-5.1 times) and/or distal (1.2-3.4 times) compound muscle action potential in at least two nerves.

CONCLUSION

Antibody- and macrophage-mediated demyelination appears responsible for conduction alterations in CIDP patients and nerve immunostaining assays may serve as a supportive diagnostic biomarker.

Monoclonal gammopathy of undeterminated significance and endoneurial IgG deposition: A case report

BACKGROUND

Monoclonal gammopathy of undeterminated significance is the most common form of plasma cell dyscrasia, usually considered as benign. In rare cases it may have a malignant course, sometimes limited to an organ such as peripheral nerves.

METHODS

We describe clinical, electrophysiological and pathological findings in a patient presenting a immunoglobulin G (IgG) paraproteinemic polyneuropathy clinically mimicking a chronic inflammatory demyelinating polyneuropathy.

RESULTS

Immuno-electron microscopy (immune-EM) demonstrated that the widenings of the myelin lamellae resulted from the infiltration of IgG between a significant number of myelin lamellae (with absence of inflammatory cells in the epineurium, endoneurium, and perineurium, and the lack signs of vasculitis). This patient was finally treated successfully with lenalidomide then mycophenolate mofetil.

CONCLUSIONS

In polyneuropathies associated to a monoclonal gammopathy, a nerve biopsy may clinch the diagnosis. Immuno-EM may be required to determine the role of the pathological immunoglobulin in the destruction of the peripheral nerve parenchyma. Diagnosis of such a direct involvement of peripheral nerve can endorse more aggressive treatment of real efficiency.

Treatment for IgG and IgA paraproteinaemic neuropathy

BACKGROUND

Paraproteinaemic neuropathy refers to those neuropathies associated with a monoclonal gammopathy or paraprotein. The most common of these present with a chronic, predominantly sensory, symmetrical neuropathy, similar to chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) but with relatively more sensory involvement, both clinically and neurophysiologically. The optimal treatment for neuropathies associated with IgG and IgA monoclonal gammopathy of uncertain significance is not known. This is an update of a review first published in 2007.

OBJECTIVES

To assess the effects of any treatment for IgG or IgA paraproteinaemic peripheral neuropathy.

SEARCH METHODS

On 18 January 2014 we searched the Cochrane Neuromuscular Disease Group Trials Specialized Register, CENTRAL, MEDLINE and EMBASE. We also checked bibliographies for controlled trials of treatments for IgG or IgA paraproteinaemic peripheral neuropathy. We checked clinical trials registries for ongoing studies in November 2014.

SELECTION CRITERIA

We considered for inclusion randomised controlled trials (RCTs) and quasi-RCTs using any treatment for IgG or IgA paraproteinaemic peripheral neuropathy. We excluded people with IgM paraproteins. We excluded people where the monoclonal gammopathy was considered secondary to an underlying disorder. We included participants of any age with a diagnosis of monoclonal gammopathy of uncertain significance with a paraprotein of the IgG or IgA class and a neuropathy. Included participants were not required to fulfil specific electrophysiological diagnostic criteria.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodology to select studies, extract data and analyse results. One trial author provided additional data and clarification.

MAIN RESULTS

We identified one RCT, with 18 participants, that fulfilled the predetermined inclusion criteria. The trial compared plasma exchange to sham plasma exchange in participants with IgG or IgA paraproteinaemic neuropathy over a three-week follow-up period. We identified four other studies but these were not RCTs or quasi-RCTs. The included RCT did not report our predefined primary outcome measure, change in disability six months after randomisation. The trial revealed a modest benefit of plasma exchange in the weakness component of the Neuropathy Disability Score (NDS, now the Neuropathy Impairment Score); the mean improvement with plasma exchange was 17 points (95% confidence interval (CI) 5.2 to 28.8 points) versus 1 point (95% CI -7.7 to 9.7 points) in the sham exchange group at three weeks' follow-up (mean difference (MD) 16.00; 95% CI 1.37 to 30.63, low quality evidence). There was no statistically significant difference in the overall NDS (MD 18.00; 95% CI -2.03 to 38.03, low quality evidence), vibration thresholds or neurophysiological indices. Adverse events were not reported. The trial was at low risk of bias overall, although limitations of trial size and duration reduce the quality of the evidence in support of its conclusions.

AUTHORS' CONCLUSIONS

The evidence from RCTs for the treatment of IgG or IgA paraproteinaemic neuropathy is currently inadequate. More RCTs of treatments are required. These should have adequate follow-up periods and contain larger numbers of participants, perhaps through multicentre collaboration, considering the relative infrequency of this condition. Observational or open trial data provide limited support for the use of treatments such as plasma exchange, cyclophosphamide combined with prednisolone, intravenous immunoglobulin, and corticosteroids. These interventions show potential therapeutic promise but the potential benefits must be weighed against adverse effects. Their optimal use and the long-term benefits need to be considered and validated with well-designed RCTs.

Twists and turns of determining amyloid type and amyloid-related organ damage: discordance and clinical skepticism in the era of proteomic typing

Systemic immunoglobulin light-chain primary amyloidosis (AL) is the most common type of systemic amyloidosis. Recent advances in AL amyloidosis include the use of definitive proteomic typing, confirming the type of amyloid in patients with two possible amyloid-forming proteins. Laser microdissection followed by mass spectrometry (LMD/MS) can correctly identify the amyloid type with over 95% sensitivity and specificity. We report the case of a 68-year-old man with a history of IgA lambda monoclonal gammopathy and peripheral neuropathy who was diagnosed with pelvic nodal and psoas amyloidosis. The amyloid was found to be AL kappa type by LMD/MS. While LMD/MS has been effective in distinguishing among AL, secondary amyloidosis and hereditary forms of amyloidosis, our case demonstrates that typing can also identify unusual instances of discordance between light chain isotypes associated with clonal processes.

Neuropathy and monoclonal gammopathy

The association of neuropathy with monoclonal gammopathy has been known for several years, even if the clinical and pathogenetic relevance of this association is not completely defined. This is not a marginal problem since monoclonal gammopathy is present in 1-3% of the population above 50 years in whom it is often asymptomatic, and in at least 8% of patients is associated with a symptomatic neuropathy, representing one of the leading causes of neuropathy in aged people. Monoclonal gammopathy may result from malignant lymphoproliferative diseases including multiple myeloma or solitary plasmocytoma, Waldenström's macroglobulinemia (WM), other IgM-secreting lymphoma or chronic lymphocytic leukemia, and primary systemic amyloidosis (AL). In most instances it is not associated with any of these disorders and is defined monoclonal gammopathy of undetermined significance (MGUS) for its possible, though infrequent, evolution into malignant forms. Several data support the pathogenetic role of the monoclonal gammopathy in the neuropathy particularly when of IgM isotype where IgM reactivity to several neural antigens has been reported. Increased levels of VEGF have been implicated in POEMS syndrome. However, there are as yet no defined therapies for these neuropathies, as their efficacy has not been confirmed in randomized trials.

Nerve biopsy: requirements for diagnosis and clinical value

In many instances, nerve biopsy is not necessary in the diagnostic work-up of a peripheral neuropathy. However, histological examination of a tissue sample is still mandatory to show specific lesions in various conditions involving peripheral nerves. As there are fewer laboratories that examine human nerve samples, practitioners including neurologists and general pathologists may not be completely aware of the technical issues and data that are provided by nerve biopsy. Nerve biopsy is considered an invasive diagnostic method, although, its complications are by far less disabling than most of the disorders that lead to its indications. Nevertheless, the decision to perform a nerve biopsy has to be made on a case-by-case basis, and its results must be discussed between the pathologist and the clinician who is in charge of the patient's care. In this paper, we review the minimal technical requirements for proper peripheral nerve tissue analysis. Moreover, we provide data on the usefulness of nerve biopsy in various situations including abnormal deposits, cell infiltrates, link between peripheral neuropathy and monoclonal gammopathy, and numerous hereditary disorders.

An update on nerve biopsy

Indications for nerve biopsy have decreased during the last 20 years. For the most part, this is a result of progress in the application of molecular biologic diagnostic testing for genetic peripheral neuropathies (PNs) and the increasing use of skin biopsy. The latter is primarily used to evaluate small-fiber PN, although it rarely discloses the specific etiology of a PN. Nerve biopsies are usually performed on either the sural or the superficial peroneal nerve, the latter in combination with removal of portions of the peroneus brevis muscle. The definite diagnosis of vasculitic lesions can be readily established on small paraffin-embedded nerve biopsy samples, although in some cases, the characteristic lesions are only apparent in muscle specimens. Other nerve specimens are routinely fixed in buffered glutaraldehyde and prepared for semithin sections and electron microscopy; frozen specimens are used for immunofluorescence studies. Electron microscopy is of great value in some cases of chronic inflammatory demyelinating polyneuropathies, monoclonal gammopathy, and storage diseases. Because more than 30 genes may be involved in genetic PNs, analysis of nerve lesions can direct the search for mutations in specific genes. Electron microscopy immunocytochemistry is mandatory in some cases of monoclonal dysglobulinemia. Thus, nerve biopsy is still of value in specific circumstances when it is performed by trained physicians and examined in a laboratory with expertise in nerve pathology.

Contribution of electron microscopy to the study of neuropathies associated with an IgG monoclonal paraproteinemia

A typical monoclonal IgG dysglobulinemia whether benign (monoclonal gammopathy of undetermined significance, MGUS) or malignant can give rise to peripheral neuropathy by damaging nerves. At first, neurotoxicity of the chemotherapy if the patient is treated must be ruled out in such cases. Indeed, a variety of other mechanisms have been described: endoneurial deposits of immunoglobulin, infiltration of the immunoglobulin within myelin sheaths, POEMS syndrome, deposits of amyloid, chronic inflammatory demyelinating polyradiculoneuropathy and infiltration of malignant cells. Ultrastructural examination of a nerve biopsy can be decisive in combination with routine histological and immunopathological examinations. Characterization of the mechanism of the neuropathy in a dysglobulinemic context is important as it governs therapeutic options, which in certain cases are particularly beneficial.

Diagnostic value of ultrastructural nerve examination in Charcot-Marie-Tooth disease: two CMT 1B cases with pseudo-recessive inheritance

We report two sporadic patients of CMT disease in different consanguineous families. The electrophysiological examination led to the diagnosis of a severe demyelinating neuropathy. The nerve biopsies exhibited numerous outfoldings of the myelin sheaths and onion-bulb proliferations. The consanguinity and the histological findings pointed to a diagnosis of CMT 4B. However, the detection of abnormal and regular widenings between the major dense lines of the myelin lamellae by electron microscopy led us to search for a P0 gene mutation. Two heterozygous mutations of this gene were identified: S63F and N131Y. Different aspects of uncompacted myelin lamellae have been described in some cases of P0 mutations and a few now appear to be quite specific to it. More than 30 genes are implicated in CMT and as mutation search is time- and money-consuming, we believe that in some selected patients ultrastructural examination of nerves, among other criteria, helps orientate the molecular diagnosis of CMT.

Treatment for IgG and IgA paraproteinaemic neuropathy

BACKGROUND

Paraproteinaemic neuropathy refers to those neuropathies associated with a monoclonal gammopathy or paraprotein. Typically it presents with a chronic predominantly sensory, symmetrical neuropathy, similar to chronic inflammatory demyelinating polyradiculoneuropathy but with relatively more sensory involvement, both clinically and neurophysiologically. The optimal treatment for IgG and IgA monoclonal gammopathy of uncertain significance neuropathies is not known.

OBJECTIVES

The objective of this review is to examine the efficacy of any treatment for IgG or IgA paraproteinaemic peripheral neuropathy.

SEARCH STRATEGY

We performed searches of the Cochrane Neuromuscular Disease Group Trials register (May 2005), MEDLINE (from January 1966 to May 2005), EMBASE (from January 1980 to May 2005). We also checked bibliographies for controlled trials of treatments for IgG or IgA paraproteinaemic peripheral neuropathy.

SELECTION CRITERIA

We included randomised and quasi-randomised controlled trials using any treatment for IgG or IgA paraproteinaemic peripheral neuropathy. People with IgM paraproteins were excluded. We excluded participants where the monoclonal gammopathy was considered secondary to an underlying disorder. We included participants of any age with a diagnosis of monoclonal gammopathy of uncertain significance with a paraprotein of the IgG or IgA class and a neuropathy. Included participants were not required to fulfil specific electrophysiological diagnostic criteria.

DATA COLLECTION AND ANALYSIS

The full texts of potentially relevant studies were obtained and assessed and independent data extraction was performed by three authors. Additional data and clarification were received from one author.

MAIN RESULTS

We identified only one randomised controlled trial with 18 participants which fulfilled the predetermined inclusion criteria. Four other trials were identified but these were not randomised controlled trials. The included trial revealed a modest short-term benefit of plasma exchange in IgG or IgA paraproteinaemic neuropathy, over a short follow-up period, when compared to sham plasma exchange.

AUTHORS' CONCLUSIONS

The evidence from randomised controlled trials for the treatment of IgG or IgA paraproteinaemic neuropathy is currently inadequate. More randomised controlled trials of treatments are required. These should have adequate follow-up periods and contain larger numbers of participants, perhaps through multicentre collaboration, considering the relative infrequency of this condition. Observational or open trial data provide limited support for the use of treatments such as plasma exchange, cyclophosphamide combined with prednisolone, intravenous immunoglobulin and corticosteroids. These show potential therapeutic promise but the potential benefits must be weighed against adverse effects. Their optimal use and the long-term benefits need to be considered and validated with well-designed randomised controlled trials.

Sensitivity and specificity of electrodiagnostic criteria for CIDP using ROC curves: comparison to patients with diabetic and MGUS associated neuropathies

INTRODUCTION

Electrodiagnostic testing plays a key role in the characterization of neuropathies. To this end, sets of electrodiagnostic criteria have been proposed to define chronic inflammatory demyelinating polyneuropathy (CIDP). These criteria sets differ because of the number of data points within the sets, the number of required abnormal measures within a criterion, and the cutoff value of each measure.

OBJECTIVE

To evaluate the sensitivity and specificity of the published criteria for defining CIDP in comparison to diabetic polyneuropathy (DMPN) and monoclonal gammopathy of undetermined significance associated neuropathies (MGUS-PN).

DESIGN/METHODS

Electrodiagnostic studies of 21 patients with biopsy proven CIDP, 35 patients with MGUS-PN, and 82 patients with DMPN were analyzed. Data were compared against 4 different published criteria sets. Receiver operator characteristic (ROC) curves were used to determine the ideal threshold values for individual electrodiagnostic parameters.

RESULTS/CONCLUSION

None of the currently published criteria sets could adequately separate CIDP from DMPN and MGUS-PN. Analysis of our data using ROC curves shows that the best discrimination was achieved using the following criteria: (1) FWL>145%ULN in one nerve or 110%ULN in two nerves in separate nerve roots. (2) Motor CV<90%LLN in four nerves with at least one nerve <70%LLN. Furthermore, proximal-to-distal amplitude ratio alone is not adequate to define conduction block. Although electrodiagnostic studies are important for evaluating CIDP, these studies by themselves cannot be used to define this neuropathy.

IgG Neuropathy: An Immunoelectron Microscopic Study

There are many potential mechanisms of peripheral nerve impairment by a monoclonal IgG dysglobulinemia. In this study, using electron microscopy, we observed widening of the myelin lamellae comparable to that commonly described in IgM neuropathies with antimyelin-associated glycoprotein activity. Such features have yet to be described in IgG neuropathies. In addition, we observed deposits of a granular material in the interstitial tissue of the nerve. By immunoelectron microscopy, we demonstrated the presence of the IgG in the lesions of myelin and the endoneurial space. A direct link between monoclonal dysglobulinemia (regardless of type) and polyneuropathy should be confirmed by nerve biopsy, because the result may influence treatment.

Treatment of dysimmune neuropathies

Several therapies are currently used in dys-immune neuropathies including steroids,plasma exchange (PE), high-dose intravenous immunoglobulins(IVIg), and immuno-suppressive agents (IS). Even if there is substantial evidence that these treatments may improve the course of the neuropathy, their effectiveness is far from being complete and is sometime hampered by the occurrence of associated side effects. In Guillain-Barré syndrome (GBS),IVIg and PE are similarly effective in accelerating the recovery but there is still little evidence that they can reduce mortality or long-term disability. Recent reports on the association of intravenous methylprednisolone or interferon-beta (IFN-beta) to IVIg did not result in significant further improvement. In chronic inflammatory demyelinating polyradiculoneuropathy(CIDP) steroids, PE, and IVIG are initially similarly effective. The short-term effect of PE and IVIgand the side effects associated with the long-term use of steroids have prompted the use of several IS, interferon and,more recently, the anti-CD20 monoclonal-antibody Rituximab, but their efficacy has still to be proved in controlled studies. The recent identification of multifocal motor neuropathy(MMN) was shortly followed by the finding of an effective therapy. Almost 80% of patients respond toIVIg whose effect needs to be maintained with periodic infusions for long periods of time, and tends to decrease after several years. Also in this condition a number of immune modulating agents have been used to reduce the frequency or improve the effectiveness of IVIg,but their efficacy has not been sofar confirmed in randomized trials. Similar conclusions can be drawn for neuropathies associated with monoclonal gammopathies where only PE and IVIg have proved to be effective in controlled studies,while the promising initial results obtained with Rituximab in neuropathy associated IgM monoclonal gammopathy awaits confirmation from controlled trials.

IgA monoclonal gammopathy of undetermined significance with peripheral neuropathy

Monoclonal gammopathy of undetermined significance (MGUS) and peripheral neuropathy may be causally linked. In most cases, the M-protein is of IgG or IgM type. Peripheral neuropathy associated with IgA MGUS is uncommon, and there are limited reports. Here, we report a case of a 55-year-old male who was diagnosed to have symmetrical sensorimotor peripheral neuropathy associated with IgA MGUS with deposits of IgA-monoclonal protein in the myelin sheath.

Different clinical, electrophysiological and immunological features of CIDP associated with paraproteinaemia

Chronic inflammatory demyelinating polyneuropathy (CIDP) is frequently associated with monoclonal gammopathies of undetermined significance (MGUS), Waldenström disease and osteosclerotic myeloma. There are still controversies about the role of these paraproteinaemias in determining the clinical features and the response to treatment of CIDP. We review the clinical, electrophysiological and immunological features and the response to treatment of patients with CIDP associated with paraproteinaemias. The available literature suggest some conclusions: presence of antimyelin-associated glycoprotein (MAG) antibody (Ab) identifies patients with mainly sensory CIDP and low response to treatment; CIDP associated with IgM-paraproteinaemia without anti-MAG Ab probably are similar to CIDP not associated with paraproteinaemia as well as CIDP with IgG- or IgA-MGUS; however, some patients with IgA-MGUS can show features similar to CIDP with IgM paraproteinaemia and anti-MAG Ab. Low response to immunomodulating treatment in patients with mainly motor CIDP should prompt a careful research of an underlying osteosclerotic myeloma.

Dominantly inherited peripheral neuropathies

Since 1886, the year that Charcot and Marie and Tooth described a genetic "peroneal muscular atrophy syndrome," electrophysiological and histological studies of the peripheral nervous system have greatly aided the characterization of this syndrome, which falls among the hereditary sensory-motor neuropathies. Two principal forms of Charcot-Marie-Tooth (CMT) disease have been distinguished: CMT 1, corresponding to a demyelinating type, and CMT 2, corresponding to an axonal type. The modes of transmission of these types are variable, recessive or dominant, autosomal, or X-linked. Our discussion here is confined to the dominant forms. In recent years, advances in molecular biology have greatly modified the approach to CMT disease and related neuropathies (such as hereditary neuropathy with liability to pressure palsies). With increased knowledge of responsible gene mutations and several other loci identified by linkage studies, our understanding of the pathophysiology of these neuropathies is increasing; however, with greater understanding, the classification of these disorders is becoming more complex. In this review we present and discuss the currently characterized subtypes, with emphasis on their known histological aspects. While nerve biopsy has lost its diagnostic importance in certain forms of the disease, such as CMT 1A, CMT 1B, and X-linked CMT (CMT X), it remains important for better characterizing the lesions of CMT 2 and forms of genetic peroneal atrophy in which DNA study is unrevealing.

Paraproteinemic neuropathies

The occurrence of a peripheral neuropathy (PN) in association with a monoclonal gammopathy is quite common and suggests that monoclonal proteins may play a pathogenetic role in peripheral nervous system damage. In fact, paraproteinemic PN constitute an heterogeneous group of disorders related to various pathogenetic factors, and the histopathologic features in peripheral nerve biopsies differ from one condition to another. In several well defined disorders, the responsibility of the monoclonal component in the development of the PN has been evidenced. This is the case for most of the PN associated with an IgM monoclonal gammopathy, either a monoclonal gammopathy of undetermined significance (MGUS) or Waldenstrom's macroglobulinemia. The responsibility of the monoclonal protein in the occurrence of amyloid neuropathy related to multiple myeloma is also recognized. However, most IgG or IgA MGUS, as well as the monoclonal component in POEMS syndrome, have an uncertain causal relationship with the neuropathy. PN associated with monoclonal cryoglobulin (type 1) are occasional and differ from those associated with mixed cryoglobulins (types 2 or 3).

Neuropathy and monoclonal gammopathy

The association of neuropathy with monoclonal gammopathy has been known for several years, even if the nosological position of these neuropathies is still debated. Similarly unsettled is the pathogenetic role and diagnostic relevance in clinical practice of the antineural antibodies frequently associated with monoclonal gammopathies of undetermined significance of IgM isotype, as well as the most effective therapy (if any) to be used in these patients. Over the past 12 months these issues have been addressed in several papers whose results will be critically reviewed here.