Paraproteinemic neuropathies

Paraproteinemic Neuropathies

OBJECTIVE

Coexistence of polyneuropathy and gammopathy is a common but potentially challenging situation in clinical practice. This article reviews the clinical, electrophysiologic, and hematologic phenotypes of the paraproteinemic neuropathies and the diagnostic and treatment strategies for each.

LATEST DEVELOPMENTS

Advances in our understanding of the underlying pathophysiology of various paraproteinemic neuropathies and their corresponding phenotypes have identified potential new therapeutic targets. Therapeutic strategies to diminish anti-myelin-associated glycoprotein (MAG) IgM antibodies have shown partial and inconsistent efficacy; however, antigen-specific immune therapy is being investigated as a novel treatment to remove the presumably pathogenic anti-MAG antibody. Advances in genetic and cell signaling studies have resulted in the approval of Bruton tyrosine kinase inhibitors for Waldenström macroglobulinemia. Monoclonal antibodies are being investigated for the treatment of light chain amyloidosis.

ESSENTIAL POINTS

Early recognition and treatment of underlying plasma cell disorders improves clinical outcomes in patients with paraproteinemic neuropathy. Despite significant progress, our knowledge regarding underlying mechanisms for paraproteinemic neuropathy is still limited. Clinicians' awareness of clinical phenotypes, electrophysiologic hallmarks, and hematologic findings of the different paraproteinemic neuropathies is crucial to promptly identify and treat patients and to avert misdiagnosis. Multidisciplinary collaboration among specialists, including neurologists and hematologists, is paramount for the optimal treatment of these patients with overlapping conditions.

Neurological Adverse Events Induced by Immune Checkpoint Inhibitors in Non-Small Cell Lung Cancer: Current Perspectives and New Development

Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of multiple malignancies, especially in non-small cell lung cancer (NSCLC). With the extensive application of ICIs in clinical practice, clinicians have to manage their toxicities, which are often termed immune-related adverse events (irAEs). Several ICIs, such as nivolumab, pembrolizumab, atezolizumab, and durvalumab, have been approved by the US Food and Drug Administration (FDA) to treat advanced NSCLC, accompanied by a broad spectrum of toxicity reactions. However, ICIs-associated neurological toxicities, regarding polyneuropathy, Bell palsy, encephalopathy, and myasthenia gravis, as uncommon emerging toxicities have not been well recognized, present a challenge for clinicians to improve awareness of supervision, recognition, and management before death from them. Herein, we have summarized the incidence, diagnosis, clinical manifestations, potential mechanisms, treatments, and outcomes of ICIs-related neurotoxicity and optimized the management approach for NSCLC patients. Prompt recognition and proper management are indispensable to reduce the morbidity of these patients with immune-related neurological toxicities.

Approach to Neuropathic Pain

Neuropathic pain is a common chief complaint encountered by neurologists and primary care providers. It is caused by disorders involving the somatosensory nervous system. The clinical evaluation of neuropathic pain is challenging and requires a multifaceted systematic approach with an emphasis on a thorough history and physical examination to identify characteristic signs and symptoms. Ancillary laboratory investigations, targeted imaging, and electrodiagnostic studies further help identify underlying etiologies to guide specific treatments. Management of neuropathic pain encompasses treating the underlying pathology as well as symptomatic control with nonpharmacological, pharmacological, and interventional therapies. Here, we present an approach to help evaluate patients with neuropathic pain.

Severe Paraproteinemic Demyelinating Neuropathy With Impaired Excitability of the Distal Segments of the Peripheral Nerves

ABSTRACT

We report clinical and detailed nerve conduction findings in case of polyneuropathy associated with kappa light chains monoclonal gammopathy of undetermined significance with progression to lymphoproliferative disorder. A 55-year-old man had a predominantly distal, chronic (5 years duration), slowly progressive, symmetric, predominantly sensory impairment with sensory ataxia, and mild weakness. M protein was identified by serum protein electrophoresis. The kappa/lambda ratio of free light chains was significantly elevated to 11.96. The cerebrospinal fluid protein level was elevated at 3.5 g/L. This case study has revealed 2 unusual electrophysiological phenomena-a very unusual prolongation of distal motor latencies of compound muscle action potentials (CMAP) up to 86.5 ms and impaired excitability of the distal segments of the peripheral nerves. The distal CMAP areas were considerably lower compared with the proximal CMAP areas. Radiography of the skull revealed osteolytic lesions.

Paraproteinemias and Peripheral Nerve Disease

This article provides an overview of the clinical features, diagnosis, and treatment of the major paraprotein-related peripheral neuropathies, including monoclonal gammopathy of undetermined significance, Waldenström macroglobulinemia, POEMS syndrome, multiple myeloma, transthyretin amyloidosis, and light chain amyloidosis. For each paraprotein neuropathy, the epidemiology, demographics, systemic findings, and electrophysiologic features are presented. Pharmacologic treatment of transthyretin amyloid polyneuropathy also is reviewed.

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.

Monoclonal Gammopathies of 'Neurological Significance': Paraproteinemic Neuropathies

OBJECTIVES

To study the clinical profile and outcomes of patients with paraproteinemic neuropathy (PPN) and to explore the utility of nerve conduction studies (NCSs) to differentiate between the demyelinating subtypes.

METHODS

We did a retrospective analysis of patients diagnosed with PPN between January 2010 and December 2019 in an inpatient setting. The study population consisted of patients above 16 years of age presenting with clinical features suggestive of chronic peripheral neuropathy and on evaluation was found to have PPN.

RESULTS

A total of 74 patients were identified. The patients were predominantly in the 6th decade, and the majority were males. The subtypes of PPN were monoclonal gammopathy of undetermined significance (MGUS) (45.9%), POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, monoclonal plasma cell disorder, and skin changes) (24.3%), solitary plasmacytoma (17.6%), multiple myeloma (8.1%), and AL amyloidosis (4.1%). There are specific features on NCS which can help in identifying POEMS syndrome and IgM MGUS. The majority of patients with PPN tend to stabilize or improve with treatment; however, many have a severe residual disability. New terminology and classification of these entities as 'monoclonal gammopathies of neurological significance' can aid in early diagnosis and the development of effective treatment, to prevent residual disability.

CONCLUSION

PPN has a heterogeneous spectrum of clinical, biochemical, and electrophysiological features. NCS can help distinguish POEMS syndrome and IgM MGUS from other demyelinating subtypes.

Temporal dispersion in demyelination of POEMS syndrome and Castleman disease

Objective

We detailed the electrophysiological patterns of peripheral nerve temporal dispersion across spectrum of POEMS syndrome and Castleman disease (CD).

Methods

Compound muscle action potentials (CMAP) duration of 3 patients with POEMS syndrome and 2 with hyaline vascular type CD without clonal plasma cell dyscrasia were retrospectively analysed.

Results

Median and ulnar nerves distal CMAP duration were prolonged in all patients irrespective of plasma cell dyscrasia or M protein. All lower limbs distal CMAP responses were absent. Greatest distal CMAP duration prolongation was observed in median nerves for POEMS syndrome (17.0 ms, 158% upper limit normal) and in ulnar nerves for CD (9.8 ms, 47% upper limit normal). Distal/proximal CMAP duration ratio of <0.7 were seen in 33% of median and ulnar nerves studied among POEMS syndrome. Among nerves with ratio >0.7, all had distal CMAP duration prolongation (Range 7%-158% of upper limit normal).

Conclusions

Abnormal distal CMAP dispersion is not uncommon in POEMS syndrome and CD without clonal plasma cell dyscrasia or M protein. POEMS syndrome has greater distal CMAP duration in median and ulnar nerves, particularly in median nerve that can reach up to 150% of upper limit normal, compared to <50% in CD.

Significance

Detailed electrophysiological analysis of distal CMAP duration may help in distinguishing POEMS syndrome and CD.

Polyneuropathie im Alter

Das periphere Nervensystem ist im Laufe des Alternsprozesses Veränderungen unterworfen. So kommt es unter anderem zu einer Abschwächung von Muskeleigenreflexen und Propriozeption. Davon abzugrenzen sind Polyneuropathien als krankhafte Veränderungen des peripheren Nervensystems. Die jährliche Inzidenz von Polyneuropathien wird auf 118/100.000 geschätzt, die Prävalenz liegt bei etwa 1 %, für ältere Populationen werden 7 % angegeben. Die Ursachen sind vielfältig und ähnlich den Ursachen von Neuropathien des jüngeren Alters: Neben metabolischen, immunvermittelten, hereditären, toxischen und infektiösen Ätiologien können Polyneuropathien Ausdruck von Systemerkrankungen sein. Entsprechend der Altersverteilung der verschiedenen Ursachen sind Neuropathien im Zusammenhang mit Diabetes, monoklonalen Gammopathien und Malignomen im Alter häufiger. Allerdings nimmt der Anteil der kryptogenen Neuropathien, also ohne eindeutige Ursache, mit dem Alter zu. Bei alten Menschen führen Polyneuropathien zu einer zusätzlichen Beeinträchtigung der Mobilität und einem erhöhten Sturzrisiko, was auch die Abklärung funktioneller Fähigkeiten erforderlich macht.

Distinctive patterns of peripheral neuropathy across the spectrum of plasma cell disorders

Many patients with plasma cell disorders suffer from peripheral neuropathy, but differential diagnosis with chronic inflammatory demyelinating polyneuropathy (CIDP) is difficult. We aimed to (1) identify factors useful for differential diagnosis between peripheral neuropathy associated with plasma cell disorders versus CIDP and (2) determine whether neuropathy presentations and severity varied across the spectrum of different plasma cell disorders. A retrospective chart review of 18 monoclonal gammopathy of unknown significance (MGUS) patients, 15 POEMS syndrome patients and 34 CIDP patients between January 2005 and December 2016 was conducted. The peripheral neuropathy associated with plasma cell disorders seemed to be more sensory oriented compared to CIDP. MGUS patients were significantly older than CIDP patients (median age 70 vs. 59, respectively, p = 0.027). POEMS syndrome patients showed significantly higher platelet count at the time of neuropathy presentation compared to CIDP (p = 0.028). Lambda type MGUS patients were associated with less severe symptoms compared to POEMS syndrome patients despite harboring lambda monoclonal gammopathy as a common denominator. Kappa type MGUS patients showed predominantly axonal type neuropathy compared to its counterpart and POEMS syndrome. Careful inspection of clinical profiles and symptoms of patients presenting with neuropathy can help to discriminate those with underlying plasma cell disorders. The phenotype of neuropathy, platelet count and age at presentation seem to be the most useful indicators.

Peripheral Neuropathy

Peripheral neuropathy is a commonly encountered disorder in clinical practice. In light of an aging population and the diabetes and obesity pandemic, the prevalence of peripheral neuropathy is increasing, posing a significant public health concern. This article provides a diagnostic framework for neuropathies and summarizes treatment options.

Immune-mediated neuropathies

Since the discovery of an acute monophasic paralysis, later coined Guillain-Barré syndrome, almost 100 years ago, and the discovery of chronic, steroid-responsive polyneuropathy 50 years ago, the spectrum of immune-mediated polyneuropathies has broadened, with various subtypes continuing to be identified, including chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and multifocal motor neuropathy (MMN). In general, these disorders are speculated to be caused by autoimmunity to proteins located at the node of Ranvier or components of myelin of peripheral nerves, although disease-associated autoantibodies have not been identified for all disorders. Owing to the numerous subtypes of the immune-mediated neuropathies, making the right diagnosis in daily clinical practice is complicated. Moreover, treating these disorders, particularly their chronic variants, such as CIDP and MMN, poses a challenge. In general, management of these disorders includes immunotherapies, such as corticosteroids, intravenous immunoglobulin or plasma exchange. Improvements in clinical criteria and the emergence of more disease-specific immunotherapies should broaden the therapeutic options for these disabling diseases.

Immune Axonal Polyneuropathy

PURPOSE OF REVIEW

Immune axonal polyneuropathy is caused by a diverse group of disorders that share similar presentations and treatment regimens. This article focuses on the clinical findings, evaluation, and management of immune-mediated causes of axonal polyneuropathy, focusing primarily on large fiber sensorimotor polyneuropathy.

RECENT FINDINGS

Specific characteristics of an immune-mediated polyneuropathy have been incorporated in a new diagnostic screening tool that is highly sensitive and can easily be used in the outpatient clinic setting. New insights into autoantibodies may help identify the presence of an underlying autoimmune or paraneoplastic disease as the cause of a polyneuropathy.

SUMMARY

This article provides readers with further understanding into the autoimmune causes of axonal polyneuropathy and will help the clinician recognize key clinical features that may lead to timely diagnosis and treatment.

Acute Autonomic Symptoms with Anti-myelin-associated Glycoprotein Neuropathy as a Presentation of Small B Cell Lymphoma: A Case Report and Literature Review

The association of symmetrical distal sensorimotor polyneuropathy with anti-myelin-associated glycoprotein antibodies (MAG) has been well established. Although autonomic symptoms are uncommon with anti-MAG antibody neuropathy (MAN). We are presenting an unusual case, who developed acute onset urinary retention, orthostatic hypotension, bradycardia and was found to have MAN. She was a 68-year-old lady, presented with progressive ascending numbness, weakness of her extremities and balance problems. On neurological examination, she had generalized muscle weakness, reduced perception to all modalities of sensation with marked impairment of vibration and position sense in the lower limbs. Reflexes were diminished throughout and Romberg sign was positive. Initial lab work including thyroid-stimulating hormone (TSH), vitamin B12, Hb1c, and routine lab reports was normal. The patient then developed acute urinary retention, severe orthostatic hypotension, and symptomatic bradycardia. Workup during this time revealed M spike on serum electrophoresis with IgM kappa on immunofixation. IgM titers were higher than normal. Initially, she was thought to have monoclonal gammopathy of undetermined significance (MGUS) related neuropathy but further workup showed very high levels of anti-MAG antibody titer. Further workup including a bone marrow biopsy revealed a small B cell lymphoma. Only a few cases have reported a small B cell lymphoma presenting with MAN-associated autonomic symptoms. She is currently being treated with rituximab with significant improvement in her neuropathic symptoms. Further case studies are needed to show whether autonomic symptoms are the feature of MAN or this atypical presentation is the paraneoplastic manifestation of the lymphoma.

Electrophysiologic features of POEMS syndrome compared with MGUS-related neuropathy

INTRODUCTION

Polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes (POEMS) syndrome and monoclonal gammopathy of undetermined significance (MGUS) are paraproteinemic disorders that can cause demyelinating polyneuropathy. Herein we assessed the findings of nerve conduction studies (NCS) in patients with POEMS syndrome and MGUS-related neuropathy to determine whether the NCS characteristics can help differentiate between these conditions.

METHODS

We enrolled 24 POEMS and 37 MGUS-related neuropathy patients. NCS parameters, including compound muscle action potential (CMAP), motor conduction velocity (MCV), and terminal latency index (TLI), were evaluated.

RESULTS

Compared with MGUS-related neuropathy patients, POEMS syndrome patients demonstrated a greater reduction in both the upper and lower limb CMAPs and a greater reduction in the median and ulnar MCVs. The TLIs were significantly higher in POEMS patients.

DISCUSSION

NCS can help distinguish POEMS syndrome from MGUS-related neuropathy. Reduced CMAPs, slow MCVs, and high TLIs are indicative of POEMS syndrome rather than MGUS-related neuropathy. Muscle Nerve 56: E73-E77, 2017.

Peripheral neuropathies

Peripheral neuropathies are diseases of the peripheral nervous system that can be divided into mononeuropathies, multifocal neuropathies, and polyneuropathies. Symptoms usually include numbness and paresthesia. These symptoms are often accompanied by weakness and can be painful. Polyneuropathies can be divided into axonal and demyelinating forms, which is important for diagnostic reasons. Most peripheral neuropathies develop over months or years, but some are rapidly progressive. Some patients only suffer from mild, unilateral, slowly progressive tingling in the fingers due to median nerve compression in the wrist (carpal tunnel syndrome), while other patients can be tetraplegic, with respiratory insufficiency within 1-2 days due to Guillain-Barré syndrome. Carpal tunnel syndrome, with a prevalence of 5% and incidence of 1-2 per 1000 person-years, is the most common mononeuropathy. Population-based data for chronic polyneuropathy are relatively scarce. Prevalence is estimated at 1% and increases to 7% in persons over 65 years of age. Incidence is approximately 1 per 1000 person-years. Immune-mediated polyneuropathies like Guillain-Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy are rare diseases, with an annual incidence of approximately 1-2 and 0.2-0.5 per 100 000 persons respectively. Most peripheral neuropathies are more prevalent in older adults and in men, except for carpal tunnel syndrome, which is more common in women. Diabetes is a common cause of peripheral neuropathy and is associated with both mono- and polyneuropathies. Among the group of chronic polyneuropathies, in about 20-25% no direct cause can be found. These are slowly progressive axonal polyneuropathies.

Monoclonal gammopathy: The good, the bad and the ugly

Monoclonal gammopathy of undetermined significance (MGUS) is a condition characterized by the presence of a monoclonal gammopathy (MG) in which the clonal mass has not reached a predefined state in which the condition is considered malignant. It is a precursor to conditions such as multiple myeloma or lymphoma at a rate of ~1%/year. Thus, from a hematologic standpoint, MGUS is a fairly benign condition. However, it is now recognized that organ damage resulting from just the MG without the need MM or lymphoma can occur. One of the most recognized is nephropathy secondary to monoclonal gammopathy of renal significance (MGRS). Other well-recognized conditions include neuropathies, oculopathies and dermopathies. Some conditions such as autoimmune diseases and coagulopathies are less common and recognized. Finally, systemic involvement of multiple organs is well described in several entities. In all of these conditions, the role of the MG is no longer insignificant. Thus, the term MGUS should be avoided when describing these entities.

Drugs for the treatment of peripheral neuropathies

Peripheral neuropathies are frequent in association with systemic diseases as well as isolated disorders. Recent advances in the therapy of specific neuropathies led to the approval of new drugs/treatments. This review selected those peripheral neuropathies where the most recent approvals were provided and revised the potential future developments in diabetic and toxic-induced neuropathies, although they do not have a currently available causal therapy in view of their epidemiological and social relevance. Data have been extracted from the most important published trials and from clinical experience. In addition, data from the Food and Drug Administration and European Medicine Agency indications on the treatment of the selected peripheral neuropathies and from recently updated international guidelines have also been included. The website of the U.S. National Institutes of Health www.clinicaltrials.gov registry has been used as the reference database for phase III clinical trials not yet published or ongoing. This review gives a general overview of the most recent advances in the treatment of amyloid, inflammatory, and paraproteinemic peripheral neuropathies. Moreover, it briefly describes the unmet medical need in disabling and frequent conditions, such as diabetic and chemotherapy-induced neuropathy, highlighting the most promising therapeutic approaches to their treatment.

A sporadic case of late-onset familial amyloid polyneuropathy with a monoclonal gammopathy

A 77-year-old Portuguese woman reported gradual worsening of burning and numbness in the feet and hands, fatigue, anorexia, weight loss, diarrhoea and decreased visual acuity. She had a medical history of atrial fibrillation and recent episodes of dizziness and blood pressure fluctuations. There was no relevant family history. The diagnostic workup documented a severe axonal sensorimotor peripheral neuropathy, a monoclonal IgG kappa protein on serum, a severe left ventricular hypertrophy on the echocardiogram and probable vitreous deposits of amyloid on ophthalmologic examination. Pain and dysautonomia with an axonal neuropathy and multisystemic involvement raised the possibility of amyloidosis. The presence of a detectable monoclonal protein, older age at disease onset and absence of family history of disease usually suggest immunoglobulin light-chain amyloidosis. However, in this case, both the genetic testing and the biopsy of the salivary glands confirmed transthyretin amyloidosis. In those patients with a monoclonal protein, particularly in sporadic and late-onset cases, the diagnosis of transthyretin amyloidosis can be challenging, mimicking immunoglobulin light-chain amyloidosis.