Neurofascin IgG4 antibodies in CIDP associate with disabling tremor and poor response to IVIg

An immuno-DOT diagnostic assay for autoimmune nodopathy

OBJECTIVES

Autoimmune nodopathy (AN) is a life-threatening peripheral neuropathy mediated by four autoantibodies targeting axoglial cell adhesion molecules at the nodes of Ranvier: Neurofascin-155 (Nfasc155), PanNeurofascin (PanNfasc), Contactin-1 (CNTN1), and Contactin-associated protein 1 (CASPR1). Antibody detection is a strong biomarker for AN diagnosis and treatment monitoring. The aim of this study was to develop an immuno-dot assay (immuno-DOT) compatible with routine implementation in medical laboratories.

METHODS

This new approach was compared to standard techniques: indirect immunofluorescence assay, cell-based assay, and ELISA. Sensitivities (Se) and specificities (Sp) were calculated on a cohort composed of 58 patients diagnosed with AN, 50 seronegative patients with chronic inflammatory demyelinating polyradiculoneuropathy, 20 healthy controls, 30 patients with Guillain-Barré syndrome, 20 with monoclonal gammopathy and 20 with Charcot-Marie-Tooth disease. The patients were diagnosed with AN based on compatible electro-clinical arguments and at least two positive standard techniques.

RESULTS

Immuno-DOT sensitivities and specificities were Se=91 %, Sp=97 % for anti-Nfasc155; Se=80 %, Sp=94 % for anti-PanNfasc; Se=93 %, Sp=98 % for anti-CNTN1; and Se=87 %, Sp=94 % for anti-CASPR1. Immuno-DOT allowed the diagnosis within 3 h and the accurate follow-up of the immune reactivity and isotype, and dot intensity correlated with antibody titers following treatments. A longitudinal study indicated that immuno-DOT yielded reliable results even after six months of storage at -20 °C.

CONCLUSIONS

The diagnostic performance of immuno-DOT was satisfactory and compatible with routine implementation in medical laboratories.

[Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP)]

Chronic inflammatory demyelinating polyneuropathy (CIDP) is the most common chronic autoimmune disease of the peripheral nervous system. It is often difficult to diagnose, but severaly therapeutic options are nowadays available to reduce neurological deficits and to improve the disease course. This article exemplifies the management of CIDP by a typical case study.

Conduction slowing, conduction block and temporal dispersion in demyelinating, dysmyelinating and axonal neuropathies: Electrophysiology meets pathology

Nerve conduction studies are usually the first diagnostic step in peripheral nerve disorders and their results are the basis for planning further investigations. However, there are some commonplaces in the interpretation of electrodiagnostic findings in peripheral neuropathies that, although useful in the everyday practice, may be misleading: (1) conduction block and abnormal temporal dispersion are distinctive features of acquired demyelinating disorders; (2) hereditary neuropathies are characterized by uniform slowing of conduction velocity; (3) axonal neuropathies are simply diagnosed by reduced amplitude of motor and sensory nerve action potentials with normal or slightly slow conduction velocity. In this review, we reappraise the occurrence of uniform and non-uniform conduction velocity slowing, conduction block and temporal dispersion in demyelinating, dysmyelinating and axonal neuropathies attempting, with a translational approach, a correlation between electrophysiological and pathological features as derived from sensory nerve biopsy in patients and animal models. Additionally, we provide some hints to navigate in this complex field.

Recurrent CNTN1 antibody-positive nodopathy: a case report and literature review

Background

Contactin-1 (CNTN1) antibody-positive nodopathy is rare and exhibits distinct clinical symptoms such as tremors and ataxia. However, the mechanisms of these symptoms and the characteristics of the cerebral spinal fluid (CSF) remain unknown.

Case presentation

Here, we report a case of recurrent CNTN1 antibody-positive nodopathy. Initially, a 45-year-old woman experiencing numbness in the upper limbs and weakness in the lower limbs was diagnosed with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Eleven years later, her symptoms worsened, and she began to experience tremors and ataxia. Tests for serum CNTN1, GT1a, and GQ1b antibodies returned positive. Subsequently, she was diagnosed with CNTN1 antibody-positive nodopathy and underwent plasmapheresis therapy, although the treatment's efficacy was limited. To gain a deeper understanding of the disease, we conducted a comprehensive literature review, identifying 52 cases of CNTN1 antibody-positive nodopathy to date, with a tremor prevalence of 26.9%. Additionally, we found that the average CSF protein level in CNTN1 antibody-positive nodopathy was 2.57 g/L, with 87% of patients exhibiting a CSF protein level above 1.5 g/L.

Conclusion

We present a rare case of recurrent CNTN1 antibody-positive nodopathy. Our findings indicate a high prevalence of tremor (26.9%) and elevated CSF protein levels among patients with CNTN1 antibody-positive nodopathy.

Anti-neurofascin-155 antibody mediated a distinct phenotype of chronic inflammatory demyelinating polyradiculoneuropathy

BACKGROUND

To investigate Ranvier's autoantibodies prevalence and isotypes in various peripheral neuropathy variants, compare clinical features between seronegative and seropositive patients, and elucidate immune mechanisms underlying antibody generation.

METHODS

Antibodies against anti-neurofascin-155 (NF155), NF186, contactin-1 (CNTN1), CNTN2, contactin-associated protein 1 (CASPR1), and CASPR2 were identified through cell-based assays. Plasma cytokines were analyzed in anti-NF155 antibody-positive chronic inflammatory demyelinating polyneuropathy (NF155+ CIDP) and Ranvier's antibodies-negative CIDP (Ab- CIDP) patients using a multiplexed fluorescent immunoassay, validated in vitro in a cell culture model.

RESULTS

In 368 plasma samples, 50 Ranvier's autoantibodies were found in 45 individuals, primarily in CIDP cases (25 out of 69 patients) and in 10 out of 122 Guillain-Barré syndrome patients. Anti-NF155 and CNTN1-IgG were exclusive to CIDP. Fourteen samples were NF155-IgG, primarily IgG4 subclass, linked to CIDP features including early onset, tremor, sensory disturbance, elevated CSF protein, prolonged motor latency, conduction block, and poor treatment response. NF155-IgG had low sensitivity (20.28%) but high specificity (100%) for CIDP, rising to 88.88% with tremor and prolonged motor latency. Cytokine profiling in NF155+ CIDP revealed distinct immune responses involving helper T cells, toll-like receptor pathways. Some NF155+ CIDP patients had circulating NF155-specific B cells producing NF155-IgG without antigen presence, suggesting therapeutic potential.

CONCLUSION

The study emphasizes the high specificity and sensitivity of NF155-IgG for diagnosing CIDP characterized by distinctive features. Further investigation into circulating NF155-specific B cell phenotypes may pave the way for B cell directed therapy.

Prospective open-label trial with rituximab in patients with chronic inflammatory demyelinating polyradiculoneuropathy not responding to conventional immune therapies

BACKGROUND

To evaluate the efficacy of rituximab in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) patients not responding to conventional immune therapies.

METHODS

An open-label, prospective exploratory study was conducted with intravenous rituximab on 17 CIDP patients who had not responded to at least two first-line therapies. The primary endpoint was to determine the proportion of patients who showed improvement 6 months after rituximab therapy. The percentage of responders to rituximab, along with a 95% CI, was reported and compared with the 30% response rate after other immunosuppressive drugs previously documented in the literature.

RESULTS

13 of the 17 treated patients (76.5%) showed improvement at 6 months (95% CI 50.1 to 93.2). Among the 14 patients who completed the 12-month follow-up (2 were lost to follow-up after showing improvement at months 8 and 10, and 1 deteriorated at 6 months), 13 (92.9%) demonstrated improvement at 12 months (95% CI 66.1 to 99.8). Nerve conduction parameters improved by at least 20% in two nerves in 6 out of 15 (40%) patients at 6 months and in 7 out of 13 (53.9%) at 12 months. None of the treated patients withdrew from the study due to side effects. There was a significant reduction of circulating CD19+ cells 15 days, 2, 6 and 12 months after treatment.

CONCLUSION

Rituximab seems to be a safe therapy in most patients with CIDP not responding to conventional immune therapies. The high percentage of patients who improved in this study suggests a possible positive effect of rituximab which is worth investigating in future randomised controlled clinical trials.

TRIAL REGISTRATION NUMBER

NCT05877040.

Clinical characteristics of patients with autoimmune nodopathy with anti-neurofascin155 antibodies

Background

According to the latest guidelines on chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), patients with CIDP with anti-neurofascin 155 (NF155) antibodies are referred to as autoimmune nodopathy (AN), an autoimmune disorder distinct from CIDP. We aimed to compare the clinical data of patients with AN with anti-NF155 antibodies with those of anti-NF155 antibodies-negative patients with CIDP, and to summarize the clinical characteristics of patients with AN with anti-NF155 antibodies.

Methods

Nine patients with AN with anti-NF155 antibodies and 28 serologically negative patients with CIDP were included in this study. Diagnosis was made according to the diagnostic criteria in the European Academy of Neurology (EAN)/Peripheral Nerve Society (PNS) guidelines on CIDP published in 2021. Demographics, clinical manifestations, electrophysiological examination, cerebrospinal fluid (CSF) tests, and response to treatment were retrospectively analyzed.

Results

Compared with serologically negative patients with CIDP, those patients with AN with anti-NF155 antibodies were younger (p=0.007), had a younger onset age (p=0.009), more frequent ataxia (p=0.019), higher CSF protein levels (p=0.001), and more frequent axon damage in electrophysiology (p=0.025). The main characteristics of patients with AN with anti-NF155 antibodies include younger age and onset age, limb weakness, sensory disturbance, ataxia, multiple motor-sensory peripheral neuropathies with demyelination and axonal damage on electrophysiological examination, markedly elevated CSF protein levels, and varying degrees of response to immunotherapy.

Conclusions

Patients with AN with anti-NF155 antibodies differed from serologically negative patients with CIDP in terms of clinical characteristics. When AN is suspected, testing for antibodies associated with the nodes of Ranvier is essential for early diagnosis and to guide treatment.

Clinical Features of Autoimmune Nodopathy With Anti-Neurofascin-155 Antibodies in South Koreans

BACKGROUND AND PURPOSE

Anti-neurofascin-155 (NF155) antibody is one of the autoantibodies associated with autoimmune nodopathy. We aimed to determine the clinical features of South Korean patients with anti-NF155-antibody-positive autoimmune nodopathy.

METHODS

The sera of 68 patients who fulfilled the diagnostic criteria for chronic inflammatory demyelinating polyneuropathy (CIDP) were tested for anti-NF155 antibodies using a cell-based assay (CBA) and enzyme-linked immunosorbent assay (ELISA). The anti-NF155-positive sera were also assayed for NF155 immunoglobulin G (IgG) subclasses, and for anti-NF186 and NF140 antibodies. The clinical features of the patients were reviewed retrospectively.

RESULTS

Among the 68 patients, 6 (8.8%) were positive for anti-NF155 antibodies in both the CBA and ELISA. One of those six patients was also positive for anti-NF186 and anti-NF140 antibodies. IgG4 was the predominant subclass in four patients. The mean age at onset was 32.2 years. All six positive patients presented with progressive sensory ataxia. Five patients treated using corticosteroids presented a partial or no response. All six patients were treated using intravenous immunoglobulin (IVIg). Among them, five exhibited a partial or poor response and the other exhibited a good response. All three patients treated using rituximab showed a good response.

CONCLUSIONS

The clinical characteristics of the patients were consistent with those in previous studies. Anti-NF155 antibody assay is necessary for diagnosing autoimmune nodopathy and its appropriate treatment, especially in young patients with CIDP who present with sensory ataxia and poor therapeutic responses to corticosteroids and IVIg.

Chronic Inflammatory Demyelinating Polyradiculoneuropathy: Current Therapeutic Approaches and Future Outlooks

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a treatable autoimmune disorder, for which different treatment options are available. Current first-line evidence-based therapies for CIDP include intravenous and subcutaneous immunoglobulins, corticosteroids and plasma exchanges. Despite lack of evidence, cyclophosphamide, rituximab and mycophenolate mofetil are commonly used in circumstances of refractoriness and, more debatably, of perceived overdependence on first-line therapies. Rituximab is currently the object of a randomized controlled trial for CIDP. Based on case series, and although rarely considered, haematopoietic autologous stem cell transplants may be effective in refractory disease, with low mortality and high remission rates. A new therapeutic option has appeared with efgartigimod, a neonatal Fc receptor blocker, recently shown to significantly lower relapse rate versus placebo, after withdrawal from previous immunotherapy. Other neonatal Fc receptor blockers, nipocalimab and batoclimab, are under study. The C1 complement-inhibitor SAR445088, acting in the proximal portion of the classical complement system, is currently the subject of a new study in treatment-responsive, refractory and treatment-naïve subjects. Finally, Bruton Tyrosine Kinase inhibitors, which exert anti-B cell effects, may represent another future research avenue. The widening of the therapeutic armamentarium enhances the need for improved evaluation of treatment effects and reliable biomarkers in CIDP.

Paraneoplastic neuropathies and peripheral nerve hyperexcitability disorders

Peripheral neuropathy is a common referral for patients to the neurologic clinics. Paraneoplastic neuropathies account for a small but high morbidity and mortality subgroup. Symptoms include weakness, sensory loss, sweating irregularity, blood pressure instability, severe constipation, and neuropathic pain. Neuropathy is the first presenting symptom of malignancy among many patients. The molecular and cellular oncogenic immune targets reside within cell bodies, axons, cytoplasms, or surface membranes of neural tissues. A more favorable immune treatment outcome occurs in those where the targets reside on the cell surface. Patients with antibodies binding cell surface antigens commonly have neural hyperexcitability with pain, cramps, fasciculations, and hyperhidrotic attacks (CASPR2, LGI1, and others). The antigenic targets are also commonly expressed in the central nervous system, with presenting symptoms being myelopathy, encephalopathy, and seizures with neuropathy, often masked. Pain and autonomic components typically relate to small nerve fiber involvement (nociceptive, adrenergic, enteric, and sudomotor), sometimes without nerve fiber loss but rather hyperexcitability. The specific antibodies discovered help direct cancer investigations. Among the primary axonal paraneoplastic neuropathies, pathognomonic clinical features do not exist, and testing for multiple antibodies simultaneously provides the best sensitivity in testing (AGNA1-SOX1; amphiphysin; ANNA-1-HU; ANNA-3-DACH1; CASPR2; CRMP5; LGI1; PCA2-MAP1B, and others). Performing confirmatory antibody testing using adjunct methods improves specificity. Antibody-mediated demyelinating paraneoplastic neuropathies are limited to MAG-IgM (IgM-MGUS, Waldenström's, and myeloma), with the others associated with cytokine elevations (VEGF, IL6) caused by osteosclerotic myeloma, plasmacytoma (POEMS), and rarely angiofollicular lymphoma (Castleman's). Paraneoplastic disorders have clinical overlap with other idiopathic antibody disorders, including IgG4 demyelinating nodopathies (NF155 and Contactin-1). This review summarizes the paraneoplastic neuropathies, including those with peripheral nerve hyperexcitability.

[Modern aspects of diagnosis and treatment of chronic inflammatory demyelinating polyneuropathy in children]

OBJECTIVE

Analysis of demographic, clinical, laboratory, electrophysiological and neuroimaging data and pathogenetic therapy of pediatric patients with chronic inflammatory demyelinating polyneuropathy (CIDP).

MATERIAL AND METHODS

Patients (n=30) were observed in a separate structural unit of the Russian Children's Clinical Hospital of the Russian National Research Medical University named after. N.I. Pirogova Ministry of Health of the Russian Federation in the period from 2006 to 2023. The examination was carried out in accordance with the recommendations of the Joint Task Force of the European Federation of Neurological Societies and the Peripheral Nerve Society on the Management of CIDP (2021). All patients received immunotherapy, including intravenous immunoglobulin (IVIG) (n=1), IVIG and glucocorticosteroids (GCS) (n=17, 56.7%), IVIG+GCS+plasmapheresis (n=12, 40.0%). Alternative therapy included cyclophosphamide (n=1), cyclophosphamide followed by mycophenolate mofetil (n=1), rituximab (n=2, 6.6%), azathioprine (n=3), mycophenolate mofetil (n=2, 6.6%).

RESULTS

In all patients, there was a significant difference between scores on the MRCss and INCAT functional scales before and after treatment. At the moment, 11/30 (36.6%) patients are in clinical remission and are not receiving pathogenetic therapy. The median duration of remission is 48 months (30-84). The longest remission (84 months) was observed in a patient with the onset of CIDP at the age of 1 year 7 months.

CONCLUSION

Early diagnosis of CIDP is important, since the disease is potentially curable; early administration of pathogenetic therapy provides a long-term favorable prognosis.

Anti-contactin 1 Antibody-associated Membranous Nephropathy in Chronic Inflammatory Demyelinating Polyneuropathy with Several Autoantibodies

A 50-year-old man diagnosed with anti-contactin 1 (CNTN1) antibody-associated chronic inflammatory demyelinating polyneuropathy (CIDP) was referred to our department for the evaluation of proteinuria. A kidney biopsy revealed membranous nephropathy (MN). Immunohistochemistry for CNTN1 revealed positive granular staining along the glomerular basement membrane, confirming anti-CNTN1 antibody-associated MN. Immunofluorescence showed a full-house pattern, and several autoantibodies, such as anti-nuclear antibody, anti-double-strand DNA antibody, and anti-cardiolipin antibody, were detected in the patient's serum. Although limited autoantibodies have been investigated in some of the reported cases, a variety of autoantibodies might be produced in anti-CNTN1 antibody-associated CIDP, accompanied by MN.

Nodal-paranodal antibodies in HIV-immune mediated radiculo-neuropathies: Clinical phenotypes and relevance

BACKGROUND

The frequency of nodal-paranodal antibodies in HIV-infected patients with chronic immune-mediated radiculo-neuropathies (IMRN) has not been previously described.

METHODS

HIV-infected patients who met the inclusion criteria for chronic IMRN were screened for immunoglobulin G (IgG) antibodies directed against nodal (neurofascin (NF)186) and paranodal (NF155, contactin-1 (CNTN1) and contactin-associated protein(Caspr1)) cell adhesion molecules, using a live, cell-based assay. To explore potential pathogenicity, binding of human IgG to myelinated co-cultures was assessed by incubation with patients' sera positive for nodal or paranodal antibodies. Normal human serum was added as a source of complement to assess for complement activation as a mechanism for myelin injury.

RESULTS

Twenty-four HIV-infected patients with IMRN were included in the study, 15 with chronic inflammatory demyelinating polyneuropathy (CIDP), 4 with ventral root radiculopathies (VRR), and 5 with dorsal root ganglionopathies (DRG). Five patients with CIDP had combined central and peripheral demyelination (CCPD). Three patients (12.7%) tested positive for neurofascin IgG1 antibodies in the following categories: 1 patient with VRR was NF186 positive, and 2 patients were NF155 positive with DRG and mixed sensory-motor demyelinating neuropathy with optic neuritis, respectively.

CONCLUSION

The frequency of nodal-paranodal antibodies is similar among IMRN regardless of HIV status. Interpretation of the results in the context of HIV is challenging as there is uncertainty regarding pathogenicity of the antibodies, especially at low titres. Larger prospective immune studies are required to delineate pathogenicity in the context of HIV, and to establish a panel of antibodies to predict for a particular clinical phenotype.

[The significance of autoantibodies against nodal and paranodal proteins in autoimmune nodopathies]

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is recognized as a syndrome caused by multiple pathologies. Since the 2010s, it has been clarified that autoantibodies against membranous proteins localized in the nodes of Ranvier and paranodes are positive in subsets of CIDP patients, leading to proposing a new disease concept called autoimmune nodopathies, which is independent of CIDP, in the revised international CIDP guidelines. This article reviews the significance of these autoantibodies, especially anti-neurofascin 155 and anti-contactin 1 antibodies, which have been the most prevalent and achieved a higher degree of consensus.

Nerve transcriptomes in autoimmune and genetic demyelinating neuropathies: Pathogenic pathway assessment of nerve demyelination

The pathogenesis of autoimmune demyelinating neuropathies is poorly understood compared to inherited demyelinating forms. We performed whole transcriptome (RNA-Seq) using nerve biopsy tissues of patients with different autoimmune and inherited demyelinating neuropathies (CIDP n = 10, POEMS n = 18, DADS n = 3, CMT1 n = 3) versus healthy controls (n = 6). A limited number of differentially expressed genes compared to healthy controls were identified (POEMS = 125, DADS = 15, CMT = 14, CIDP = 5). Divergent pathogenic pathways including inflammatory, demyelinating and neurite regeneration such as with the triggering receptor expressed on myeloid cells (TREM1) part of the immunoglobulin superfamily and RhoGD1 are found. Shared and discordant pathogenic injury are discovered between autoimmune and inherited forms.

The unique properties of IgG4 and its roles in health and disease

IgG4 is the least abundant subclass of IgG in human serum and has unique functional features. IgG4 is largely unable to activate antibody-dependent immune effector responses and, furthermore, undergoes Fab (fragment antigen binding)-arm exchange, rendering it bispecific for antigen binding and functionally monovalent. These properties of IgG4 have a blocking effect, either on the immune response or on the target protein of IgG4. In this Review, we discuss the unique structural characteristics of IgG4 and how these contribute to its roles in health and disease. We highlight how, depending on the setting, IgG4 responses can be beneficial (for example, in responses to allergens or parasites) or detrimental (for example, in autoimmune diseases, in antitumour responses and in anti-biologic responses). The development of novel models for studying IgG4 (patho)physiology and understanding how IgG4 responses are regulated could offer insights into novel treatment strategies for these IgG4-associated disease settings.

Case Report: Telitacicept in treating a patient with NF155+ autoimmune nodopathy: a successful attempt to manage recurrent elevated sero-anti-NF155 antibodies

This report presents a case of a neurofascin-155 (NF155)+ autoimmune nodopathy (AN) patient who exhibited resistance to conventional treatments but responded positively to telitacicept therapy. Telitacicept, a dual inhibitor of B lymphocyte stimulator (BLyS) and A proliferation-inducing ligand (APRIL), suppressed the development and survival of plasma cells and mature B cells. The patient's unique clinical features were consistent with NF155+ AN, showing limited response to standard treatments like rituximab and a recurrent significant increase in anti-NF155 antibody titers. Administering telitacicept (160mg, ih) led to an improvement in clinical symptoms, inflammatory neuropathy cause and treatment (INCAT) scale and inflammatory Rasch-built overall disability scale (I-RODS), and stabilized anti-NF155 antibody levels without a rebound. This case demonstrates telitacicept as a potential novel therapy for NF155+ AN, particularly when conventional treatments fail. Further investigation into its safety, efficacy, dosage, and treatment cycle in NF155+ AN is warranted.

Clinical and pathophysiological implications of autoantibodies in autoimmune neuropathies

Autoimmune neuropathies are a heterogeneous group of rare and disabling diseases in which the immune system targets peripheral nervous system antigens and that respond to immune therapies. This review focuses on Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy, polyneuropathy associated with IgM monoclonal gammopathy, and autoimmune nodopathies. Autoantibodies targeting gangliosides, proteins in the node of Ranvier, and myelin-associated glycoprotein have been described in these disorders, defining subgroups of patients with similar clinical features and response to therapy. This topical review describes the role of these autoantibodies in the pathogenesis of autoimmune neuropathies and their clinical and therapeutic importance.

Antineurofascin IgG2-associated paediatric autoimmune nodopathy

In this case series of four paediatric patients, we present the first described cases of immunotherapy-responsive autoimmune nodopathy with IgG2 antineurofascin antibodies. In three cases, the antineurofascin antibodies were predominantly of the IgG2 subclass, a novel finding in comparison to previously described adult cases where IgG4 and/or IgG1/3 have typically been described. One patient had low signal for IgG2 with predominant IgG1 and IgG4 antibodies, a pattern commonly seen in adult patients. Two patients had antibodies targeting all three neurofascin isoforms (155, 186, and 140), whereas antibodies in the sera from the third targeted only the nodal isoforms 186 and 140, and the fourth patient only neurofascin 155. The three patients with IgG2 predominant antibodies appear to be responsive to intravenous immunoglobulin (IVIG) to varying degrees thus far, whereas the patient with IgG1/4 antibodies had poor response to IVIG but good response to steroids. Although the full clinical significance of IgG2 predominant antineurofascin antibodies in the context of childhood polyneuropathy remains unclear, emerging evidence of serological-phenotypic correlation may inform prognostication and therapeutic decision-making, warranting further study into this area. WHAT THIS PAPER ADDS: Paediatric immunotherapy-responsive nodopathies were associated with antineurofascin antibodies predominantly of the IgG2 subclass in 3 out of 4 patients. Identification of antibodies and understanding their phenotypic relevance could predict response to treatment and guide therapeutic decision-making in children.

Different binding and pathogenic effect of neurofascin and contactin-1 autoantibodies in autoimmune nodopathies

Introduction

IgG4 autoantibodies against paranodal proteins are known to induce acute-onset and often severe sensorimotor autoimmune neuropathies. How autoantibodies reach their antigens at the paranode in spite of the myelin barrier is still unclear.

Methods

We performed in vitro incubation experiments with patient sera on unfixed and unpermeabilized nerve fibers and in vivo intraneural and intrathecal passive transfer of patient IgG to rats, to explore the access of IgG autoantibodies directed against neurofascin-155 and contactin-1 to the paranodes and their pathogenic effect.

Results

We found that in vitro incubation resulted in weak paranodal binding of anti-contactin-1 autoantibodies whereas anti-neurofascin-155 autoantibodies bound to the nodes more than to the paranodes. After short-term intraneural injection, no nodal or paranodal binding was detectable when using anti-neurofascin-155 antibodies. After repeated intrathecal injections, nodal more than paranodal binding could be detected in animals treated with anti-neurofascin-155, accompanied by sensorimotor neuropathy. In contrast, no paranodal binding was visible in rats intrathecally injected with anti-contactin-1 antibodies, and animals remained unaffected.

Conclusion

These data support the notion of different pathogenic mechanisms of anti-neurofascin-155 and anti-contactin-1 autoantibodies and different accessibility of paranodal and nodal structures.

Clinical profile of autoimmune nodopathy with anti-neurofascin 186 antibody

OBJECTIVE

Nodal/paranodal autoantibodies identified a group of peripheral neuropathies independent from chronic inflammatory demyelinating polyneuropathy (CIDP). However, nodopathy with antibody against neurofascin 186 (NF186) was rarely reported. We presented a cohort of patients with anti-NF186 antibody and described the clinical profile of them.

METHODS

In this retrospective study, 195 patients diagnosed with CIDP and immune mediated idiopathic neuropathies were enrolled. Cell-based assay was used to screen anti-NF186 and anti-NF155 antibodies in serum samples. Teased-fiber immunofluorescence were used as a confirmatory assay. Clinical data of seropositive patients were collected and analyzed.

RESULTS

Among the patients with anti-NF186 antibody, seven patients (58.3%) presented acute or subacute disorder onset. Four patients (33.3%) were found to have asymmetric weakness or numbness. Distal weakness and/or numbness was the core feature. Sensory ataxia, tremor and central nervous system demyelination were rarely observed. Nerve conduction studies revealed predominant demyelinating with/without axonal loss. Brachial plexus MRI was normal in the majority of patients (6/7, 85.7%). Five patients (5/9, 55.6%) showed response to intravenous immunoglobulin. Eight patients (8/10, 80.0%) improved after corticosteroids. All patients (3/3,100%) responded to rituximab.

INTERPRETATION

In the study, we depicted the clinical profile of nodopathy with anti-NF186 antibody. The diversity of clinical features, electrophysiology results and pathological findings was specific in nodopathy with anti-NF186 antibody. Screening of autoantibody against NF186 in acute-onset neuropathy is recommended.

Peripherally-induced Movement Disorders: An Update

Background

Peripherally-induced movement disorders (PIMD) should be considered when involuntary or abnormal movements emerge shortly after an injury to a body part. A close topographic and temporal association between peripheral injury and onset of the movement disorders is crucial to diagnosing PIMD. PIMD is under-recognized and often misdiagnosed as functional movement disorder, although both may co-exist. Given the considerable diagnostic, therapeutic, and psychosocial-legal challenges associated with PIMD, it is crucial to update the clinical and scientific information about this important movement disorder.

Methods

A comprehensive PubMed search through a broad range of keywords and combinations was performed in February 2023 to identify relevant articles for this narrative review.

Results

The spectrum of the phenomenology of PIMD is broad and it encompasses both hyperkinetic and hypokinetic movements. Hemifacial spasm is probably the most common PIMD. Others include dystonia, tremor, parkinsonism, myoclonus, painful leg moving toe syndrome, tics, polyminimyoclonus, and amputation stump dyskinesia. We also highlight conditions such as neuropathic tremor, pseudoathetosis, and MYBPC1-associated myogenic tremor as examples of PIMD.

Discussion

There is considerable heterogeneity among PIMD in terms of severity and nature of injury, natural course, association with pain, and response to treatment. As some patients may have co-existing functional movement disorder, neurologists should be able to differentiate the two disorders. While the exact pathophysiology remains elusive, aberrant central sensitization after peripheral stimuli and maladaptive plasticity in the sensorimotor cortex, on a background of genetic (two-hit hypothesis) or other predisposition, seem to play a role in the pathogenesis of PIMD.

Case report: Anti-CNTN1 antibody-associated nodopathies disease with asymmetric onset

Anti-contactin-1 (CNTN1) IgG4 antibody-associated nodopathies is an autoimmune antibody-mediated peripheral neuropathy with a unique clinical presentation, pathophysiology, electrophysiology, and therapeutic response. The critical histopathological features are a dense lymphoplasmacytic infiltrate, a storiform pattern of fibrosis, and obliterative phlebitis. Here, a 62-year-old male patient presented with subacute unilateral limb onset, progressive exacerbation, marked weakness of the extremities, cranial, and autonomic nerve involvement. Neurophysiology showed slowed motor nerve conduction velocity (MCV), prolonged distal motor delay (DML), slowed sensory nerve conduction velocity (SCV), decreased sensory nerve activity potential (SNAP) amplitude, decreased amplitude of bilateral neuromotor conduction, abnormal cutaneous sympathetic response (SSR) in both lower extremities, axonal damage, prolonged F-wave latency, and discrete waves. In the initial phase, there was a response to intravenous immunoglobulin (IVIG), and corticosteroids and rituximab were also effective. After 1 year follow-up, the patient improved significantly. This article reports on a patient with nodular disease with anti-contactin-1 (CNTN1) IgG4 antibodies and reviews the literature to improve clinicians' understanding of the disease.

Vision Loss as a Presenting Feature of Chronic Inflammatory Demyelinating Polyneuropathy: A Case Series

BACKGROUND

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired, immune-mediated, and clinically heterogeneous demyelinating disease affecting the nerve roots and peripheral nerves. We report a series of 4 patients who presented with early and progressive vision loss in the context of new-onset CIDP: 3 due to papilledema and 1 due to optic neuropathy without papilledema.

METHODS

This was a retrospective case series of 4 patients with vision loss as a presenting feature of CIDP evaluated at the Hospital of the University of Pennsylvania from January 2016 to August 2021. Demographic, clinical, diagnostic, and treatment data were collected via retrospective medical record review.

RESULTS

Case 1 was a 51-year-old man with 2 months of progressive bilateral papilledema associated with reduced visual acuity (count fingers at 1 foot in each eye) and severely constricted visual fields. Case 2 was a 36-year-old man with 4 months of worsening headaches, reduced visual acuity (count fingers at 1 foot in each eye), severely constricted visual fields, and papilledema. Case 3 was a 39-year-old man with papilledema causing progressive vision loss (20/80 in both eyes), headaches, and relapsing limb sensorimotor deficits. Case 4 was a 19-year-old man with 3 months of progressive bilateral visual decline (20/400 in the right eye, 20/600 in the left eye), central scotoma, and optic disc pallor consistent with optic neuropathy without papilledema. All 4 patients met clinical and electrodiagnostic criteria of CIDP. Cases 3 and 4 each tested positive for serum neurofascin-155 IgG4 antibodies. All patients were managed with immunomodulatory therapy. Cases 1 and 2 also each required surgical intervention with bilateral optic nerve sheath fenestration and cerebrospinal fluid (CSF) shunting procedures.

CONCLUSION

Vision loss from optic neuropathy with or without papilledema has rarely been reported in CIDP, and typically has been described in the context of longstanding disease. Our cases highlight how CIDP can present with early vision loss that may be profound and challenging to manage if diagnosis is delayed. CIDP should be considered in any patient with new progressive vision loss when associated with peripheral sensorimotor symptoms and elevated CSF protein. The small subgroup of CIDP patients with neurofascin-155 antibodies may be at particular risk of optic nerve involvement.

The effect of tremor on disability assessment in chronic inflammatory demyelinating polyradiculoneuropathy

Tremor in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is common, often unresponsive to treatment, and may contribute to disability. We aim to investigate whether tremor is associated with disability as measured in daily practice and clinical trials, independent of other impairments. We included 76 CIDP patients in this cross-sectional study. We assessed tremor with the Tremor Research Group essential tremor rating assessment scale (TETRAS) and the Fahn-Tolosa-Marin clinical rating scale (FTM). Disability was measured with the inflammatory Rasch-built overall disability scale (I-RODS) and the adjusted Inflammatory Neuropathy Cause and Treatment disability scale (INCAT-DS, categorized separately in arm score, or total score). Impairments including strength, sensory impairment, and fatigue were measured using specific impairment scales. We tested whether "the presence of a clinically relevant tremor" (based on TETRAS and FTM) or "tremor severity" (FTM part B sum score) was associated with disability scores (I-RODS, INCAT-DS total score, and INCAT-DS arm score), independent of the impairment scores, using multivariate regression. Both "the presence of a clinically relevant tremor" and "tremor severity" were significantly associated with disability measured by the INCAT-DS (arm score and total score), but not the I-RODS, independent of strength, sensory impairment, and fatigue. The explained variances were low. Clinically relevant tremor can (partly) explain disability in CIDP, as measured with the INCAT-DS, independent of muscle strength, sensory deficits, and fatigue. To assess disease activity in CIDP patients with tremor, both impairment and disability outcomes should be assessed, as disability is caused partly by tremor while the effect of immunotherapy on tremor seems limited.

[Diagnostic value of F wave changes in patients with Charcot-Marie-Tooth1A and chronic inflammatory demyelinating polyneuropathy]

OBJECTIVE

To analyze and compare the characteristics and causes of F wave changes in patients with Charcot-Marie-Tooth1A (CMT1A) and chronic inflammatory demyelinating polyneuropathy (CIDP).

METHODS

Thirty patients with CMT1A and 30 patients with CIDP were enrolled in Peking University Third Hospital from January 2012 to December 2018. Their clinical data, electrophysiological data(nerve conduction velocity, F wave and H reflex) and neurological function scores were recorded. Some patients underwent magnetic resonance imaging of brachial plexus and lumbar plexus, and the results were analyzed and compared.

RESULTS

The average motor conduction velocity (MCV) of median nerve was (21.10±10.60) m/s in CMT1A and (31.52±12.46) m/s in CIDP. There was a significant difference between the two groups (t=-6.75, P < 0.001). About 43.3% (13/30) of the patients with CMT1A did not elicit F wave in ulnar nerve, which was significantly higher than that of the patients with CIDP (4/30, 13.3%), χ²=6.65, P=0.010. Among the patients who could elicit F wave, the latency of F wave in CMT1A group was (52.40±17.56) ms and that in CIDP group was (42.20±12.73) ms. There was a significant difference between the two groups (t=2.96, P=0.006). The occurrence rate of F wave in CMT1A group was 34.6%±39%, and that in CIDP group was 70.7%±15.2%. There was a significant difference between the two groups (t=-5.13, P < 0.001). The MCV of median nerve in a patient with anti neurofascin 155 (NF155) was 23.22 m/s, the latency of F wave was 62.9-70.7 ms, and the occurrence rate was 85%-95%. The proportion of brachial plexus and lumbar plexus thickening in CMT1A was 83.3% (5/6) and 85.7% (6/7), respectively. The proportion of brachial plexus and lumbar plexus thickening in the CIDP patients was only 25.0% (1/4, 2/8). The nerve roots of brachial plexus and lumbar plexus were significantly thickened in a patient with anti NF155 antibody.

CONCLUSION

The prolonged latency of F wave in patients with CMT1A reflects the homogenous changes in both proximal and distal peripheral nerves, which can be used as a method to differentiate the CIDP patients characterized by focal demyelinating pathology. Moreover, attention should be paid to differentiate it from the peripheral neuropathy caused by anti NF155 CIDP. Although F wave is often used as an indicator of proximal nerve injury, motor neuron excitability, anterior horn cells, and motor nerve myelin sheath lesions can affect its latency and occurrence rate. F wave abnormalities need to be comprehensively analyzed in combination with the etiology, other electrophysiological results, and MRI imaging.

Anti-LGI4 Antibody Is a Novel Juxtaparanodal Autoantibody for Chronic Inflammatory Demyelinating Polyneuropathy

BACKGROUND AND OBJECTIVES

The objective of this study was to discover novel nodal autoantibodies in chronic inflammatory demyelinating polyneuropathy (CIDP).

METHODS

We screened for autoantibodies that bind to mouse sciatic nerves and dorsal root ganglia (DRG) using indirect immunofluorescence (IFA) assays with sera from 113 patients with CIDP seronegative for anti-neurofascin 155 and anticontactin-1 antibodies and 127 controls. Western blotting, IFA assays using HEK293T cells transfected with relevant antigen expression plasmids, and cell-based RNA interference assays were used to identify target antigens. Krox20 and Periaxin expression, both of which independently control peripheral nerve myelination, was assessed by quantitative real-time PCR after application of patient and control sera to Schwann cells.

RESULTS

Sera from 4 patients with CIDP, but not control sera, selectively bound to the nodal regions of sciatic nerves and DRG satellite glia (p = 0.048). The main immunoglobulin G (IgG) subtype was IgG4. IgG from these 4 patients stained a 60-kDa band on Western blots of mouse DRG and sciatic nerve lysates. These features indicated leucine-rich repeat LGI family member 4 (LGI4) as a candidate antigen. A commercial anti-LGI4 antibody and IgG from all 4 seropositive patients with CIDP showed the same immunostaining patterns of DRG and cultured rat Schwann cells and bound to the 60-kDa protein in Western blots of LGI4 overexpression lysates. IgG from 3 seropositive patients, but none from controls, bound to cells cotransfected with plasmids containing LGI4 and a disintegrin and metalloprotease domain-containing protein 22 (ADAM22), an LGI4 receptor. In cultured rat Schwann and human melanoma cells constitutively expressing LGI4, LGI4 siRNA effectively downregulated LGI4 and reduced patients' IgG binding compared with scrambled siRNA. Application of serum from a positive patient to Schwann cells expressing ADAM22 significantly reduced the expression of Krox20, but not Periaxin. Anti-LGI4 antibody-positive patients had a relatively old age at onset (mean age 58 years), motor weakness, deep and superficial sensory impairment with Romberg sign, and extremely high levels of CSF protein. Three patients showed subacute CIDP onset resembling Guillain-Barré syndrome.

DISCUSSION

IgG4 anti-LGI4 antibodies are found in some elderly patients with CIDP who present subacute sensory impairment and motor weakness and are worth measuring, particularly in patients with symptoms resembling Guillain-Barré syndrome.

CIDP-like autoimmune nodopathy complicated with focal segmental glomerulosclerosis: a case study and literature review

BACKGROUND

This study aimed to investigate the role of neurofascin186 (NF186) in the pathogenesis of the concurrent focal segmental glomerulosclerosis (FSGS) in CIDP-like autoimmune nodopathy patients.

METHODS

We presented a case of CIDP-like autoimmune nodopathy complicated with FSGS. We measured NF186 antibodies by cell-binding assay (CBA) method. We performed immunofluorescence analysis in the renal cryosection samples from a patient with minimal nephropathy with rabbit anti-NF186 antibody or NF186 antibody positive human serum. Then we performed western blotting of recombinant NF186 protein and component of NF186 including Ig and FNIII domains incubating with human serum and corresponding rabbit polyclonal antibody. Cases of CIDP complicated with FSGS were searched form PubMed and reviewed.

RESULTS

We reported a 66-year-old Chinese woman with CIDP-like autoimmune nodopathy and concurrent FSGS. Her NF186 antibody was positive. The fluorescent signal for NF186 was detected in the renal tissue sections of the patient with minimal nephropathy. The staining for NF186 matched the podocyte spatially. In western blotting analysis, patients had antibodies in their serum recognizing the NF186 protein and their antibodies recognized the Ig domain of NF186. 3 cases of CIDP-like autoimmune nodopathy with positive NF186 antibody and FSGS have been reported. All these patients were responsive to corticosteroids rather than the intravenous immunoglobulin, in terms of both the neuropathy and renal disease.

CONCLUSIONS

NF186 was probably a targeted antigen in the pathogenesis of concurrent FSGS in CIDP-like autoimmune nodopathy with positive NF186 antibody. CIDP-like autoimmune nodopathy with positive NF186 antibody and FSGS is a rare entity, which may be responsive to corticosteroids combined with immunosuppressant.

Comparison of IVIg and TPE efficacy in the treatment of neurological disorders: a systematic literature review

Background:

Intravenous immunoglobulin (IVIg) and therapeutic plasma exchange (TPE) are among the main immunotherapies for neurological disorders. Their benefit is greatest in immune-mediated conditions, but their distinct efficacy cannot be simply explained.

Objectives:

This review aimed to systematically identify studies comparing the efficacy of TPE and IVIg treatments for selected autoimmune neurological disorders and identify optimal therapies for each condition.

Data Sources and Methods:

PubMed, MEDLINE and Embase databases were searched for original publications from 1990 to 2021. Additional publications were identified via expert recommendations. Conference abstracts older than 2017, review articles and articles without information on TPE and IVIg comparison in title and abstract were excluded. Risks of bias were descriptively addressed, without a meta-analysis.

Results:

Forty-four studies were included on Guillain–Barré syndrome (20 studies – 12 adult, 5 paediatric, 3 all ages), myasthenia gravis (11 studies –8 adult, 3 paediatric), chronic immune–mediated polyradiculoneuropathy (3 studies –1 adult, 2 paediatric), encephalitis (1 study in adults), neuromyelitis optica spectrum disorders (5 studies –2 adult, 3 all ages) and other conditions (4 studies – all ages). TPE and IVIg were mostly similarly efficacious, measured by clinical outcomes and disease severity scores. Some studies recommended IVIg as easy to administer. TPE procedures, however, have been simplified and the safety has been improved. TPE is currently recommended for management of neuromyelitis optica spectrum disorder relapses and some myasthenia gravis subtypes, in which rapid removal of autoantibodies is crucial.

Conclusion:

Despite some limitations (e.g. the low evidence levels), this review provides an extensive 30-year-long overview of treatments for various conditions. Both IVIg and TPE are usually comparably efficacious options for autoimmune neurological disorders, with few exceptions. Treatment choices should be patient-tailored and based on available clinical resources. Better designed studies are needed to provide higher-level quality of evidence regarding clinical efficacy of TPE and IVIg treatments.

Value of Antibody Determinations in Chronic Dysimmune Neuropathies

Chronic dysimmune neuropathies encompass a group of neuropathies that share immune-mediated pathomechanism. Chronic dysimmune antibody-related neuropathies include anti-MAG neuropathy, multifocal motor neuropathy, and neuropathies related to immune attack against paranodal antigens. Such neuropathies exhibit distinguishing pathomechanism, clinical and response to therapy features with respect to chronic inflammatory demyelinating polyradiculoneuropathy and its variants, which represent the most frequent form of chronic dysimmune neuropathy. This narrative review provides an overview of pathomechanism; clinical, electrophysiological, and biochemical features; and treatment response of the antibody-mediated neuropathies, aiming to establish when and why to look for antibodies in chronic dysimmune neuropathies.

Axonal loss at time of diagnosis as biomarker for long-term disability in chronic inflammatory demyelinating polyneuropathy

INTRODUCTION/AIMS

We hypothesized that early, pretreatment axonal loss would predict long-term disability, supported by a pilot study of selected patients with chronic inflammatory demyelinating polyneuropathy (CIDP). To further test this hypothesis, we examined a larger consecutive group of CIDP patients.

METHODS

Needle electromyography and motor and sensory nerve conduction studies were carried out in 30 CIDP patients at pretreatment and follow-up 5 to 28 years later. Changes in amplitudes were expressed as axonal Z scores and changes in conduction as demyelination Z scores and correlated with findings of the Inflammatory Rasch-built Overall Disability Scale (I-RODS), the Neuropathy Impairment Score (NIS), and isokinetic dynamometry (IKS).

RESULTS

At follow-up, the median I-RODS score was 73, the NIS was 23, and the IKS was 56%. The median axonal Z score was unchanged at follow-up. Conversely, the corresponding demyelination Z scores improved. The initial axonal loss was correlated with the clinical outcome and was an independent predictor of outcome by multivariate regression analysis. Axonal loss at follow-up was also correlated with the clinical outcome. Only the follow-up demyelination Z score was correlated with the clinical outcomes. Furthermore, the latency until treatment initiation was predictive of all three clinical outcome scores at follow-up, and of axonal loss and demyelination at follow-up.

DISCUSSION

The present study findings indicate that pretreatment axonal loss at diagnosis in CIDP is predictive of long-term disability, neurological impairment, and strength. A delay in treatment is associated with more pronounced axonal loss and a worse clinical outcome.

Complement inhibition prevents glial nodal membrane injury in a GM1 antibody-mediated mouse model

The involvement of the complement pathway in Guillain-Barré syndrome pathogenesis has been demonstrated in both patient biosamples and animal models. One proposed mechanism is that anti-ganglioside antibodies mediate neural membrane injury through the activation of complement and the formation of membrane attack complex pores, thereby allowing the uncontrolled influx of ions, including calcium, intracellularly. Calcium influx activates the calcium-dependent protease calpain, leading to the cleavage of neural cytoskeletal and transmembrane proteins and contributing to subsequent functional failure. Complement inhibition has been demonstrated to provide effective protection from injury in anti-ganglioside antibody-mediated mouse models of axonal variants of Guillain-Barré syndrome; however, the role of complement in the pathogenesis of demyelinating variants has yet to be established. Thus, it is currently unknown whether complement inhibition would be an effective therapeutic for Guillain-Barré syndrome patients with injuries to the Schwann cell membrane. To address this, we recently developed a mouse model whereby the Schwann cell membrane was selectively targeted with an anti-GM1 antibody resulting in significant disruption to the axo-glial junction and cytoplasmic paranodal loops, presenting as conduction block. Herein, we utilize this Schwann cell nodal membrane injury model to determine the relevance of inhibiting complement activation. We addressed the early complement component C2 as the therapeutic target within the complement cascade by using the anti-C2 humanized monoclonal antibody, ARGX-117. This anti-C2 antibody blocks the formation of C3 convertase, specifically inhibiting the classical and lectin complement pathways and preventing the production of downstream harmful anaphylatoxins (C3a and C5a) and membrane attack complexes. Here, we demonstrate that C2 inhibition significantly attenuates injury to paranodal proteins at the node of Ranvier and improves respiratory function in ex vivo and in vivo Schwann cell nodal membrane injury models. In parallel studies, C2 inhibition also protects axonal integrity in our well-established model of acute motor axonal neuropathy mediated by both mouse and human anti-GM1 antibodies. These data demonstrate that complement inhibition prevents injury in a Schwann cell nodal membrane injury model, which is representative of neuropathies associated with anti-GM1 antibodies, including Guillain-Barré syndrome and multifocal motor neuropathy. This outcome suggests that both the motor axonal and demyelinating variants of Guillain-Barré syndrome should be included in future complement inhibition clinical trials.

Nodo-paranodopathies: Concepts, Clinical Implications, and Management

Peripheral neuropathies are traditionally categorized into demyelinating or axonal. It has been proposed that dysfunction at nodal/paranodal region may be a key for better understanding of pathophysiology in patients with immune mediated neuropathies. In last few years, antibodies targeting node and paranode of myelinated nerves have been increasingly detected in patients with immune mediated neuropathies. These patients have clinical phenotype similar common inflammatory neuropathies like Guillain Barre syndrome and chronic inflammatory demyelinating polyradiculoneuropathy with some additional atypical neurological and systemic features, and they respond poorly to conventional first line immunotherapies like IVIG. This review summarizes the structure of the node, concept and pathophysiology of nodopathies. We provide an overview of clinical phenotypes in patients with specific nodal/paranodal antibodies, along with electrophysiological and other diagnostic features and suggest therapeutic line of management based on current evidence.

Autoimmune nodopathies, an emerging diagnostic category

PURPOSE OF REVIEW

In the last decade, antibodies targeting cell adhesion molecules of the node of Ranvier were described in patients with autoimmune neuropathies. These nodal/paranodal antibodies associate with specific clinicopathological features that are different from classical chronic inflammatory demyelinating polyneuropathy (CIDP). In this review, we will summarize recent findings establishing autoimmune nodopathies (AN) as a new category of autoimmune neuropathies.

RECENT FINDINGS

AN include anti-contactin 1, anti-contactin-associated protein 1, anti-neurofascin 155 and anti-pan-neurofascin antibody-mediated neuropathies. Their clinical spectrum includes acute, subacute or chronic onset sensory-motor neuropathies mimicking Guillain-Barré syndrome (GBS) and CIDP, although they differ in their response to standard therapy with intravenous immunoglobulin (IVIG). Neurophysiologically they overlap with acquired demyelinating neuropathies, but ultrastructural studies and animal models demonstrated antibody-mediated pathology restricted to the node of Ranvier. Anti-contactin1 and anti-pan-neurofascin also associate with nephrotic syndrome. Nodal/paranodal antibodies are predominantly of the immunoglobulin (IgG)4 subclass during the chronic phase of the disease, but complement-fixing IgG3 antibodies are detected during the early phase and associate with aggressive onset and IVIG response. Nodal/paranodal antibodies testing is key in the diagnosis of AN.

SUMMARY

AN have emerged as a new diagnostic category pathologically different from acquired demyelinating neuropathies. Clinically they overlap with GBS and CIDP although they associate with specific clinical features that should lead to clinical suspicion. Nodal/paranodal antibodies are key effector mechanisms of disease and good diagnostic and disease-monitoring biomarkers in AN.

Case report: Autoimmune nodopathy with concurrent serum and CSF IgG4 anti-neurofascin 155 antibodies

Objective

To report a case of autoimmune nodopathy (AN) with concurrent serum and CSF immunoglobulin (Ig)G4 anti-neurofascin 155 (NF155) and anti-GD1b antibodies.

Methods

A 20-year-old male presented distal weakness of the 4 limbs, hypoesthesia, absent tendon reflexes and sensory ataxia. Nerve conduction studies (NCS), MRI, and autoantibody tests were performed.

Results

NCS revealed a diffuse demyelinating neuropathy in the peripheral nerve with motor and sensory involvement. MRI of the cervical and lumbar plexus showed diffuse enlargement. IgG4 anti-NF155 antibodies in both serum and CSF and IgG anti-GD1b antibodies in serum were positive. After treatment with IVIg, rituximab, and plasma exchange, the titer of the patient’s anti-NF155 antibodies decreased, but symptoms did not significantly improve.

Discussion

This patient presented a typical clinical feature of AN with serum and CSF anti-NF155 antibodies and serum anti-GD1b antibodies coexistent but poor response to IVIg, rituximab and plasma exchange. Early detection of antibodies may be helpful in both diagnosis and therapy of the disease. And prospective studies are necessary to demonstrate the potential role of anti-NF155 antibodies in CSF and help further understand this complex and heterogeneous disease.

IgG4 Valency Modulates the Pathogenicity of Anti–Neurofascin-155 IgG4 in Autoimmune Nodopathy

Background and Objectives

IgG4 autoantibodies to neurofascin-155 (Nfasc155) are associated with a subgroup of patients with chronic inflammatory demyelinating polyneuropathy (CIDP), currently named autoimmune nodopathy. We previously demonstrated that those antibodies alter conduction along myelinated axons by inducing Nfasc155 depletion and paranode destruction. In blood, IgG4 have the potency to exchange their moiety with other unrelated IgG4 through a process called Fab-arm exchange (FAE). This process results in functionally monovalent antibodies and may affect the pathogenicity of autoantibodies. Here, we examined this issue and whether FAE is beneficial or detrimental for Nfasc155 autoimmune nodopathy.

Methods

The bivalency and monospecificity of anti-Nfasc155 were examined by sandwich ELISA in 10 reactive patients, 10 unreactive CIDP patients, and 10 healthy controls. FAE was induced in vitro using reduced glutathione and unreactive IgG4, and the ratio of the κ:λ light chain was monitored. To determine the pathogenic potential of bivalent anti-Nfasc155 IgG4, autoantibodies derived from patients were enzymatically cleaved into monovalent Fab and bivalent F(ab’)₂ or swapped with unreactive IgG4 and then were injected in neonatal animals.

Results

Monospecific bivalent IgG4 against Nfasc155 were detected in the serum of all reactive patients, indicating that a fraction of IgG4 have not undergone FAE in situ. These IgG4 were, nonetheless, capable of engaging into FAE with unreactive IgG4 in vitro, and this decreased the levels of monospecific antibodies and modulated the ratio of the κ:λ light chain. When injected in animals, monovalent anti-Nfasc155 Fab did not alter the formation of paranodes; by contrast, both native anti-Nfasc155 IgG4 and F(ab’)₂ fragments strongly impaired paranode formation. The promotion of FAE with unreactive IgG4 also strongly diminished the pathogenic potential of anti-Nfasc155 IgG4 in animals and decreased IgG4 clustering on Schwann cells.

Discussion

Our findings demonstrate that monospecific and bivalent anti-Nfasc155 IgG4 are detected in patients and that those autoantibodies are the pathogenic ones. The transformation of anti-Nfasc155 IgG4 into monovalent Fab or functionally monovalent IgG4 through FAE strongly decreases paranodal alterations. Bivalency thus appears crucial for Nfasc155 clustering and paranode destruction.

Anti-Neurofascin Antibodies Associated with White Matter Diseases of the Central Nervous System: A Red Flag or a Red Herring?

Autoantibodies against nodal and paranodal proteins, specifically anti-neurofascin antibodies (ANFAs), have been recently described in central and peripheral nervous system demyelinating disorders. We retrospectively reviewed the charts of six individuals evaluated at our Multiple Sclerosis Program who tested positive for serum ANFAs on Western blot. We describe these patients’ clinical and diagnostic findings and attempt to identify features that might guide clinicians in checking for ANFAs. In our series, the women-to-men ratio was 2:1. At presentation, the median age was 60 years (range 30–70). The clinical presentation was pleiotropic and included incomplete transverse myelitis (n = 3), progressive myelopathy (n = 1), recurrent symmetric polyneuropathy (n = 1), and nonspecific neurological symptoms (n = 1). Atypical features prompting further workup included coexisting upper and lower motor neuron features, older age at presentation with active disease, atypical spinal cord MRI features, and unusual cerebrospinal fluid findings. The serum ANFAs panel was positive for the NF-155 isoform in five patients (IgM n = 2; IgG n = 2; both n = 1) and the NF-140 isoform in two (IgG n = 2). Larger studies are needed to assess the relevance of ANFAs in demyelinating nervous system diseases, their impact on long-term clinical outcomes, and associated therapeutic implications.

Guillain-Barré-like syndrome: an uncommon feature of CASPR2 and LGI1 autoimmunity

Contactin-associated protein-like 2 (CASPR2) and leucine-rich glioma-inactivated 1 (LGI1) are essential components of the voltage-gated Kv1 potassium channel complex and are extensively expressed in both central and peripheral nervous system. Autoimmune CASPR2 and LGI1 disorders commonly present with Morvan syndrome (Mos) and/or limbic encephalitis, but whether Guillain-Barré syndrome (GBS) is a specific clinical phenotype is unknown. Here, we first reported an adult patient with dual CASPR2 and LGI1 antibodies in both serum and cerebrospinal fluid, who initially presented with a GBS-like syndrome and developed a typical MoS and respiratory paralysis, with a rapid resolution of his neurological symptoms and disappearance of autoantibodies after treatment with plasma exchange. Additionally, we also provided an overview of the previously reported GBS cases associated with CASPR2 or LGI1 antibodies. These cases expand the phenotypic spectrum of CASPR2 and LGI1 autoimmune syndromes, implying that these two antigens, especially CASPR2, are likely to participate in the etiology of GBS as a potential new target antigen, which deserves further exploration.

Myoclonus and tremor in chronic inflammatory demyelinating polyneuropathy: a multichannel electromyography analysis

BACKGROUND

Information regarding involuntary movements in chronic inflammatory polyneuropathy (CIDP) is gradually increasing. Our goal is to identify the types of involuntary movements in CIDP.

METHODS

All patients who were followed with the diagnosis of CIDP were invited for clinical and electrophysiological evaluations. Demographic and clinical findings (age, gender, duration of illness, diagnosis, treatments) were noted. Clinical examination and multichannel surface electromyography were done. We also performed routine upper and lower extremity peripheral nerve conduction studies, F-waves, long latency reflexes, blink reflex, mixed nerve silent period and cutaneous silent period in all patients.

RESULTS

Twenty-two patients accepted the invitation. Eleven patients with CIDP had involuntary movements. Ten (45.5%) patients with CIDP had tremor and seven (31.8%) had short-duration and high-amplitude myoclonus. Regarding demographic, clinical and electrophysiological features, there was no significant difference between patients with and without tremor. The latencies of R1, R2 and R2c components of BR were longer among CIDP patients without tremor compared to CIDP patients with tremor. Presence of myoclonus (p = 0.007) and delayed F-waves (p = 0.008) were associated with the presence of tremor.

CONCLUSION

Tremor and myoclonus were frequent in CIDP. The fact that myoclonus was detected in the majority of patients only by multichannel surface EMG who were clinically evaluated as pure tremor suggests that a more detailed electrophysiological evaluation is required. There was no difference in the medications used or other clinical features between patients with and without tremor.

Frequency and clinical correlates of anti-nerve antibodies in a large population of CIDP patients included in the Italian database

OBJECTIVE

To investigate the frequency and clinical correlates of anti-nerve autoantibodies in an unselected series of Italian patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) METHODS: Sera from 276 CIDP patients fulfilling the EFNS/PNS criteria and included in the Italian CIDP database were examined for the presence of anti-nerve autoantibodies. Results were correlated with the clinical data collected in the database.

RESULTS

Anti-neurofascin155 (NF155) antibodies were found in 9/258 (3.5%) patients, anti-contactin1 (CNTN1) antibodies in 4/258 (1.6%) patients, and anti-contactin-associated protein1 (Caspr1) in 1/197 (0.5%) patients, while none had reactivity to gliomedin or neurofascin 186. Predominance of IgG4 isotype was present in 7of the 9 examined patients. Anti-NF155 patients more frequently had ataxia, tremor, and higher CSF protein levels than antibody-negative patients. Anti-CNTN1 patients more frequently had a GBS-like onset, pain, and ataxia and had more severe motor impairment at enrollment than antibody-negative patients. They more frequently received plasmapheresis, possibly reflecting a less satisfactory response to IVIg or steroids. IgM antibodies against one or more gangliosides were found in 6.5% of the patients (17/260) and were more frequently directed against GM1 (3.9%). They were frequently associated with a progressive course, with a multifocal sensorimotor phenotype and less frequent cranial nerve involvement and ataxia.

CONCLUSIONS

Anti-paranodal and anti-ganglioside antibodies are infrequent in patients with CIDP but are associated with some typical clinical association supporting the hypothesis that CIDP might be a pathogenically heterogeneous syndrome possibly explaining the different clinical presentations.

Autoimmune Neurological Disorders with IgG4 Antibodies: a Distinct Disease Spectrum with Unique IgG4 Functions Responding to Anti-B Cell Therapies

The main IgG4 antibody-mediated neurological disorders (IgG4-ND) include MuSK myasthenia; CIDP with nodal/paranodal antibodies to Neurofascin-155, contactin-1/caspr-1, or pan-neurofascins; anti-LGI1 and CASPR2-associated limbic encephalitis, Morvan syndrome, or neuromyotonia; and several cases of the anti-IgLON5 and anti-DPPX-spectrum CNS diseases. The paper is centered on the clinical spectrum of IgG4-ND and their immunopathogenesis highlighting the unique functional effects of the IgG4 subclass compared to IgG1-3 antibody subclasses. The IgG4 antibodies exert pathogenic effects on their targeted antigens by blocking enzymatic activity or disrupting protein-protein interactions affecting signal transduction pathways, but not by activating complement, binding to inhibitory FcγRIIb receptor or engaging in cross-linking of the targeted antigen with immune complex formation as the IgG1-IgG3 antibody subclasses do. IgG4 can even inhibit the classical complement pathway by affecting the affinity of IgG1-2 subclasses to C1q binding. Because the IgG4 antibodies do not trigger inflammatory processes or complement-mediated immune responses, the conventional anti-inflammatory therapies, especially with IVIg, immunosuppressants, and plasmapheresis, are ineffective or not sufficiently effective in inducing long-term remissions. In contrast, aiming at the activated plasmablasts connected with IgG4 antibody production is a meaningful therapeutic target in IgG4-ND. Indeed, data from large series of patients with MuSK myasthenia, CIDP with nodal/paranodal antibodies, and anti-LGI1 and CASPR2-associated syndromes indicate that B cell depletion therapy with rituximab exerts long-lasting clinical remissions by targeting memory B cells and IgG4-producing CD20-positive short-lived plasma cells. Because IgG4 antibody titers seem reduced in remissions and increased in exacerbation, they may serve as potential biomarkers of treatment response supporting further the pathogenic role of self-reacting B cells. Controlled trials are needed in IgG4-ND not only with rituximab but also with the other anti-B cell agents that target CD19/20, especially those like obexelimab and obinutuzumab, that concurrently activate the inhibitory FcγRIIb receptors which have low binding affinity to IgG4, exerting a more prolonged anti-B cell action affecting also antigen presentation and cytotoxic T cells. Antibody therapies targeting FcRn, testing those anti-FcRn inhibitors that effectively catabolize the IgG4 antibody subclass, may be especially promising.

The Role of the Complement System in Chronic Inflammatory Demyelinating Polyneuropathy: Implications for Complement-Targeted Therapies

Chronic inflammatory demyelinating polyneuropathy (CIDP) is the most common, heterogeneous, immune-mediated neuropathy, characterized by predominant demyelination of motor and sensory nerves. CIDP follows a relapsing-remitting or a progressive course and causes substantial disability. The pathogenesis of CIDP involves a complex interplay of multiple aberrant immune responses, creating a pro-inflammatory environment, subsequently inflicting damage on the myelin sheath. Though the exact triggers are unclear, diverse immune mechanisms encompassing cellular and humoral pathways are implicated. The complement system appears to play a role in promoting macrophage-mediated demyelination. Complement deposition in sural nerve biopsies, as well as signs of increased complement activation in serum and CSF of patients with CIDP, suggest complement involvement in CIDP pathogenesis. Here, we present a comprehensive overview of the preclinical and clinical evidence supporting the potential role of the complement system in CIDP. This understanding furnishes a strong rationale for targeting the complement system to develop new therapies that could serve the unmet needs of patients affected by CIDP, particularly in those refractory to standard therapies.

Clinical and diagnostic features of anti-neurofascin-155 antibody-positive neuropathy in Han Chinese

Objective

To investigate the clinical features of Han Chinese patients with anti‐neurofascin‐155 (NF155) antibody‐positive neuropathy.

Methods

We screened 194 patients with peripheral neuropathy for NF155 antibodies using a cell‐based assay (CBA) and teased‐fiber immunofluorescence assay. We summarized the clinical findings of seropositive patients.

Results

The sera from 17 patients reacted to human embryonic kidney 293 cells transfected with NF155. Eleven of these patients had the immunoglobulin G (IgG) 4 isotype, a younger onset age, tremor, higher levels of cerebrospinal fluid protein, a larger diameter of the lumbosacral nerve root on magnetic resonance imaging, and the distal demyelinating symmetric phenotype. Most patients responded to steroids and rituximab. For the remaining six seropositive patients in CBA, the predominant antibody isotype was IgG3, IgG1, or undetectable, and only one patient with IgG3 showed a positive result in the teased‐fiber immunofluorescence assay. These patients did not share the typical features displayed by patients with the IgG4 isotype.

Interpretation

In the Han Chinese population, a significant proportion of patients who fulfilled the criteria for chronic inflammatory demyelinating polyradiculoneuropathy diagnosis had anti‐NF155 IgG4 antibody‐positive neuropathy and displayed specific phenotypes. Ambiguous staining patterns may appear, and the potential for false positivity should be considered. For patients who presented with specific phenotypes, identifying antibodies and subtypes involved a significant laboratory workup.

Consensus recommendation on the use of therapeutic plasma exchange for adult neurological diseases in Southeast Asia from the Southeast Asia therapeutic plasma exchange consortium

Therapeutic plasma exchange (TPE) is an effective and affordable treatment option in most parts of Southeast Asia (SEA). In 2018, the SEA TPE Consortium (SEATPEC) was established, consisting of regional neurologists working to improve outcome of various autoimmune neurological diseases. We proposed an immunotherapeutic guideline prioritizing TPE for this region. We reviewed disease burden, evidence-based treatment options, and major guidelines for common autoimmune neurological disorders seen in SEA. A modified treatment algorithm based on consensus agreement by key-opinion leaders was proposed. Autoimmune antibody diagnostic testing through collaboration with accredited laboratories was established. Choice of first-line immunotherapies (IVIg/corticosteroid/TPE) is based on available evidence, clinicians’ experience, contraindications, local availability, and affordability. TPE could be chosen as first-line therapy for GBS, CIDP, MG (acute/short term), IgG, A paraproteinemic neuropathy, and NMDAR encephalitis. Treatment is stopped for acute monophasic conditions such as GBS and ADEM following satisfactory outcome. For chronic immune disorders, a therapy taper or long-term maintenance therapy is recommended depending on the defined clinical state. TPE as second-line treatment is indicated for IVIg or corticosteroids refractory cases of ADEM, NMOSD (acute), MG, and NMDAR/LGI1/CASPR2/Hashimoto’s encephalitis. With better diagnosis, treatment initiation with TPE is a sustainable and effective immunotherapy for autoimmune neurological diseases in SEA.