BACKGROUND AND AIMS:Autoimmune nodopathy (AN) is a subtype of antibody-mediated inflammatory neuropathy targeting the node of Ranvier (NoR). Diagnosis requires detection of anti-(para)nodal autoantibodies like contactin-1 and neurofascin-155 via ELISA or cell-based assays, but protocols are inconsistent. Causes of node autoimmunity are unknown, and respiratory infections, including SARS-CoV-2 infection or COVID-19 vaccination as triggers, have not been thoroughly investigated. We aim to establish and validate a next-generation automated ELISA for anti-(para)nodal antibodies and investigate whether low-titer antibodies occur in recently COVID-19-vaccinated healthy individuals. METHODS:We used the Ella platform to customize an automated ELISA for anti-contactin-1, -neurofascin-155, and -Caspr-1 serum IgG. Patients with known AN (23 anti-neurofascin, 13 anti-contactin-1, and 8 anti-Caspr-1), 64 patients with seronegative (sub) acute inflammatory neuropathies, and 30 healthy controls served for validation, including quality analysis versus standard ELISA. Thirty-seven diagnostic samples of patients with suspected AN and 280 sera of healthcare workers included in the CoVacSer study, collected 3 weeks after COVID-19 vaccination or infection, were tested for anti-contactin-1 and anti-neurofascin-155. RESULTS:The automated ELISA showed high sensitivity (87.5%-100%) and specificity (98.4%-100%) for identifying AN, with reduced hands-on time, high automation, and similar quality and titer characteristics as standard ELISA. Low-titer anti-neurofascin-155, but no anti-contactin-1 autoantibodies, were detected in 1/280 post-SARS-CoV-2-vaccination or infection sera (0.36%). Longitudinal testing and clinical assessment did not indicate SARS-CoV-2-related neurological symptoms. INTERPRETATION:We provide a highly automated, rapid, universally applicable test platform for anti-(para)nodal antibodies. The low frequency of anti-(para)nodal antibodies and absence of clinical AN manifestations in COVID-19-vaccinated individuals support vaccination safety regarding AN development.

Severe neuropathies with predominant involvement of motor fibres can resemble lower motor neuron disease (LMND) phenotypes. Given the fatal prognosis of LMND, identifying underlying autoimmune syndromes is crucial to provide treatment options to patients. We investigated a novel autoantibody binding pattern observed on murine teased sciatic nerve fibres. Target antigens were identified using immunoprecipitation combined with mass spectrometry. Target specificity of these autoantibodies was validated in cell-based assays, neutralization assays and knock-out models. A retrospective study cohort consisting of different neuropathies (chronic inflammatory demyelinating polyradiculopathy n = 86, Guillain-Barré syndrome n = 37, multifocal motor neuropathy n = 18, diabetic neuropathy n = 30, other inflammatory neuropathies n = 10), amyotrophic lateral sclerosis (n = 50), multiple sclerosis (n = 50) and healthy controls (n = 50) was negative for septin multimer autoantibodies. Histopathological analysis of skin and the sural nerve including electron microscopy was performed in one seropositive patient, and autoantibody binding was characterized in vitro. Extensive immunotherapy was initiated in one patient, with clinical and serological follow-up over 4 years. Among 3543 total samples tested, three patients (two male, one female)-diagnosed with the LMND variant of amyotrophic lateral sclerosis (aged 65, 72 and 79 years, respectively)-showed a novel and distinct autoantibody binding pattern of indirect immunofluorescence staining on peripheral nerves, targeting Schmidt-Lanterman incisures (SLIs), paranodes and the abaxonal myelin. Target identification and validation revealed septin multimers as autoantibody epitopes. Despite the primarily intracellular location of septins, autoantibody binding was evident in living myelinated dorsal root ganglia, primarily at SLIs ('incisuropathy'). Septin multimer autoantibodies further initiated complement deposition on fixed and permeabilized cell-based assays. Sural nerve and skin biopsies showed inflammation, myelin and axonal pathology. Extensive immunotherapy in one patient was followed by disease stabilization over 3 years. The other two patients died of rapid disease progression: one of them received no immunotherapy while the other had ineffective treatments with single administrations of intravenous immunoglobulin and rituximab. Our data suggest that septin multimer autoimmunity occurs in severe motor-predominant neuropathies which can clinically resemble a neurodegenerative LMND. Screening for septin multimer autoantibodies should be considered in patients presenting with this phenotype. Follow-up studies need to determine the direct pathogenicity of septin multimer autoantibodies, their potential as a biomarker of an autoimmune syndrome and responses to immunotherapy in larger cohorts.

Super-resolution microscopy offers the ability to visualize molecular structures in biological samples with unprecedented detail. However, the full potential of these techniques is often hindered by a lack of automated, user-independent workflows. Here, we present an open-source toolkit that automates dSTORM super-resolution microscopy using deep learning for segmentation and object detection. This standalone program enables reliable segmentation of diverse biomedical images, even in low-contrast samples, surpassing existing solutions. Integrated into the imaging pipeline, it rapidly processes high-content data in minutes, reducing manual labor. Demonstrated by biological examples, such as microtubules in cell culture and the βII-spectrin in nerve fibers, our approach makes super-resolution imaging faster, more robust, and easy to use, even by nonexperts. This broadens its potential applications in biomedicine, including high-throughput experimentation.

IntroductionIn autoimmune nodopathies, autoantibodies target the nodes of Ranvier, impairing saltatory nerve conduction. Understanding the impact of autoantibody binding on protein assembly is crucial for gaining insights into the pathogenicity of different autoantibodies. We investigated nodal, paranodal, and cytoskeletal axonal proteins in teased fibers from a sural nerve biopsy of a patient with anti-pan-neurofascin autoantibodies. Conventional diagnostic tools, including fluorescence microscopy, often miss subtle alterations at the ultrastructural level.MethodsWe utilized direct stochastic optical reconstruction microscopy (dSTORM), a super-resolution fluorescence imaging technique, to assess the nanoscale architecture of nodal, paranodal, and cytoskeletal axonal proteins.ResultWhile conventional fluorescence microscopy revealed severe paranodal and nodal damage in 14% of the nodes, with 86% appearing normal at first glance, the super-resolved images revealed a decreased neurofascin-155 and Caspr-1 density, but preserved colocalization of these adhesion proteins in paranodes that initially seemed normal. At the nodes, sodium channel density and distribution remained intact, but neurofascin-186 density was reduced. Axonal beta-IV spectrin was altered only in severely damaged nodes. This indicates that axonal integrity is largely preserved, with a potentially reversible decrease in paranodal and nodal adhesion proteins in patients with nodopathy revealing subtle alterations in nodal integrity that are not apparent with conventional imaging.DiscussionThese likely reversible changes may explain the rapid recovery seen in patients with anti-pan-neurofascin autoantibodies following autoantibody depletion. Conversely, the small percentage of severely and axonally damaged nodes may account for the residual symptoms experienced by most patients.

The objective of this study was to assess the frequency of IgG autoantibodies in patients with fibromyalgia syndrome (FMS), to characterize their binding to dorsal root ganglion (DRG) neurons and glial cells, and to assess whether specific DRG binding patterns correlate with clinical symptoms. Sera of a cohort of 184 patients with FMS and 55 control sera were used to test binding of patient IgG on rat DRG sections. ELISA, Western blot, and preadsorption tests were used to search for potential target antigens. We found binding to DRGs in 68 of 184 FMS sera and in none of the control sera. We could identify 9 binding clusters including binding to neurons and to cells labelled with the satellite glial cell marker fatty acid binding protein 7 (FABP7). Current pain intensity correlated positively with IgG binding to FABP7 immunoreactive structures, and burning pain was associated with binding to transient receptor potential vanilloid 1 immunoreactive neurons. Specific antibody detection revealed 13 of 68 sera positive for anti-citrullinated peptide antibodies, 9 of 68 positive for SOX1 antibodies, 7 of 68 positive for antibodies against the serotonin receptor 5HT1AR, and 3 of 68 positive for fibroblast growth factor 3 antibodies. Our findings support the notion of an immune activation in a subgroup of patients with FMS.

IntroductionAutoantibodies against fibroblast growth factor receptor 3 (FGFR3) have been suggested as a diagnostic marker in both sensory large and small fiber neuropathy. Yet, their clinical relevance remains unclear and no standardized protocols for antibody testing exist. Here, we evaluate an anti-FGFR3 ELISA protocol in an inter-laboratory comparison.MethodsWe performed anti-FGFR3 ELISA on 42 serum samples of patients with sensory neuronopathy (n = 18), small fiber neuropathy (n = 18), and healthy controls (n = 6) in two independent centers in France (center 1) and Germany (center 2) using identical protocols, with double immunofluorescence staining on rat dorsal root ganglion (DRG) sections as a confirmational test.ResultsOverall ELISA concordance was 34/42 (81.0%, Cohen’s kappa = 0.61, substantial agreement). Discordance occurred for sera with optical densities (OD) near the cut-off. ODs correlated (r = 0.68, p < 0.0001), but were lower at center 2 (median = 0.076 vs 0.293, p < 0.0001), indicating that cut-off values are laboratory-specific. 11/16 (68.8%) ELISA-double-positive sera stained small DRG neurons, colocalizing with commercial anti-FGFR3 antibody, while positive binding was only found in 1/20 (5%) of ELISA-negative sera (p < 0.0001). DRG-positive samples showed higher ODs than negative ones (p < 0.0001).DiscussionWe provide and evaluate a detailed ELISA protocol for anti-FGFR3 diagnostic assessment. Positive results near the threshold should be interpreted cautiously. Anti-FGFR3 DRG staining may be a useful confirmatory method and could increase diagnostic specificity. This study facilitates future studies on the diagnostic relevance of anti-FGFR3 autoantibodies in sensory neuropathies.

ABSTRACT Background and Aims Reliable detection of antibodies against nodal targets is vital for the diagnosis of autoimmune nodopathies. The performance characteristics of recently developed in‐house assays are unknown. We compared testing at four centres. Methods Each submitted 29–40 serum samples to a coordinating centre from one of three groups: (1) autoimmune nodopathy patients, with positive nodal/paranodal antibodies; (2) seronegative patients with other inflammatory neuropathies, and (3) healthy individuals or those with other neurological diseases. The coordinating centre recoded all samples and returned 160 identical aliquots to each testing centre for blinded testing. Once data from all centres had been received by the coordinating centre, unblinded results were returned for analysis. Sensitivity was defined by the proportion of group 1 samples returned as positive. Accuracy was defined as 0.075(sensitivity) + 0.925(specificity). Results Centres performed various combinations of ELISA, cell‐based (CBAs) and teased‐nerve fibre assays. All labs produced highly accurate results (96%–100%) and concordance for the overall result across at least 3 or all 4 test centres was observed for 98% and 89% of the samples respectively. However, 10/30 individual assays (6/14 CBAs and 4/16 ELISAs) were less than 90% sensitive. Only 3 assays had more than 1 false positive result (2 ELISAs and 1 CBA). Combining different assay modalities to produce an overall result did not improve accuracy. Inter‐laboratory consistency in the determination of antibody subclasses was poor. Interpretation Although most samples were correctly categorised in all 4 centres, the use of a specific test modality or multiple tests did not guarantee accuracy. Early and repeated interlaboratory testing with sharing of samples is important to understand test performance and reproducibility, identify areas for improvement and maintain consistency. To aid this, we provide detailed methods for the best performing tests. Further standardisation of antibody subclass determination is required.

Autoimmune nodopathies are characterized by autoantibodies targeting proteins of the nodes of Ranvier of peripheral nerves. Anti-Contactin-1 (CNTN1) autoantibodies are associated with sensorimotor neuropathy and severe sensory ataxia. While damage to the nodal architecture due to axoglial disjunction is considered the primary pathogenic mechanism of autoimmune nodopathies, the reason for the severe sensory ataxia, accompanied by proprioceptive impairment, remains unclear. We therefore aimed to investigate the expression of CNTN1 in muscle spindles and the binding of IgG from patients with anti-CNTN1 and other paranodal/nodal autoantibodies to these structures. Using immunofluorescence staining of murine muscle tissue, we demonstrate that CNTN1 is expressed in annulospiral fibers of muscle spindles. IgG from patients with anti-CNTN1 autoantibodies showed specific binding to these structures, whereas IgG of patients with other paranodal autoantibodies did not. Additionally, IgG from a subset of patients with autoimmune neuropathy and severe sensory ataxia that were negatively tested for paranodal autoantibodies showed distinct binding to annulospiral fibers. Our findings suggest that CNTN1 might play a role in proprioceptive signal transmission at annulospiral fibers and autoantibody-mediated dysfunction at annulospiral fibers may contribute to severe sensory ataxia. These results highlight annulospiral fibers as potential targets for future research on autoantibody-mediated neuropathies.

BACKGROUND AND OBJECTIVES:Autoimmune nodopathy with anti-contactin1 (CNTN1) autoantibodies is a rare sensory-motor neuropathy characterized by subacute-onset sensory ataxia and variable disease courses. Comorbidities such as glomerulonephritis and diabetes mellitus are observed in some patients. The diversity in clinical presentation may reflect differences in the targeted CNTN1 epitopes. METHODS:To investigate the relationship between clinical features and the underlying epitopes, we analyzed serum samples from 16 anti-CNTN1-positive patients. Binding epitopes were assessed using cell-based assays with recombinant CNTN1 variants and peptide microarrays. RESULTS:Epitope mapping in 16 patients revealed that 13 harbored antibodies targeting CNTN1 immunoglobulin (Ig) domains while 3 recognized fibronectin (Fn) domains. Glomerulonephritis was exclusively observed in patients with autoantibodies binding to the Ig domain, whereas diabetes mellitus and a chronic course of disease were more prevalent in patients with binding to the fibronectin domain. DISCUSSION:Our findings highlight the heterogeneity of anti-contactin1 nodopathies, suggesting that distinct epitope-binding patterns may underlie different clinical manifestations and may be associated with different pathogenic mechanisms and comorbidities.

IntroductionAutoimmune nodopathy (AN) is a new entity in the field of peripheral neuropathies and is defined by the presence of auto-antibodies against structures of the node of Ranvier combined with specific clinico-pathophysiological features and therapy response in affected patients. The target-specific antibodies do not only serve as diagnostic biomarkers but also for treatment evaluation during follow-up.Case reportWe report a 66-year-old female patient with various autoimmune diseases, including a history of membranous glomerulonephritis which presented with acute-onset, sensorimotor tetraparesis, cranial nerve involvement, and mild respiratory insufficiency. Under the suspicion of Guillain–Barré syndrome, she received intravenous immunoglobulins (IVIg) and achieved remission. At 8 months later, she relapsed with now a poor response to IVIg and developed additional features such as severe sensory ataxia, tremor, and neuropathic pain. Anti-contactin-1 IgG2 antibodies were detected, and the diagnosis was reverted to AN. Plasma exchange and rituximab treatment led to a serological remission and corresponding significant clinical improvement, and the therapy was paused. At 2 years after symptom onset, her condition worsened again with sensorimotor symptoms and severe neuropathic pain despite seronegativity for contactin-1. However, serum binding assays to teased nerve fiber staining showed recurring antibody reactivity against paranodal structures. Caspr-1 was identified as a new target antigen via cell-based assay, and high-titer antibodies of the IgG4 subclass were confirmed via ELISA. Hence, a new cycle of plasma exchange and regular rituximab treatment was initiated, with subsequent clinical improvement and serological remission. The serum neurofilament light chain (sNFL) levels were assessed retrospectively and rose and fell together with the antibody titer.DiscussionThis case demonstrates that autoimmunity to (para)nodal structures can reoccur especially in patients prone to autoimmune disorders and can switch its target antigen and subclass in the course of disease. The presence of auto-antibodies against different targets at the node of Ranvier has direct implications for therapeutic management. We suggest a close follow-up of patients with AN after successful therapy. In case of deterioration despite seronegativity, non-specific tests such as teased fiber assays and repeated screening for different target antigens should be considered.

BACKGROUND AND OBJECTIVES:Autoimmune nodopathies with antibodies against the paranodal proteins show a distinct phenotype of a severe sensorimotor neuropathy. In some patients, complete remission can be achieved after treatment with rituximab whereas others show a chronic course. For optimal planning of treatment, predicting the course of disease and therapeutic response is crucial. METHODS:We stimulated peripheral blood mononuclear cells in vitro to find out whether secretion of specific autoantibodies may be a predictor of the course of disease and response to rituximab. RESULTS:Three patterns could be identified: In most patients with anti-Neurofascin-155-, anti-Contactin-1-, and anti-Caspr1-IgG4 autoantibodies, in vitro production of autoantibodies was detected, indicating autoantigen-specific memory B cells and short-lived plasma cells/plasmablasts as the major source of autoantibodies. These patients generally showed a good response to rituximab. In a subgroup of patients with anti-Neurofascin-155-IgG4 autoantibodies and insufficient response to rituximab, no in vitro autoantibody production was found despite high serum titers, indicating autoantibody secretion by long-lived plasma cells outside the peripheral blood. In the patients with anti-pan-Neurofascin autoantibodies-all with a monophasic course of disease-no in vitro autoantibody production could be measured, suggesting a lack of autoantigen-specific memory B cells. In some of them, autoantibody production by unstimulated cells was detectable, presumably corresponding to high amounts of autoantigen-specific plasmablasts-well in line with a severe but monophasic course of disease. DISCUSSION:Our data suggest that different B-cell responses may occur in autoimmune nodopathies and may serve as markers of courses of disease and response to rituximab.

Autoimmune nodopathy is a new entity of immune-mediated neuropathies associated with antibodies against nodal-paranodal epitopes. We present a detailed clinical and serological work-up of a patient with autoimmune nodopathy with anti-neurofascin-155 (anti-NF-155) IgG4 antibodies who was treated with low-dose (500 mg) rituximab, which led to a decrease of anti-NF-155 antibody titer, depletion of B cells, normalization of the levels of neurofilament light chain in serum, and significant clinical improvement. This case suggests that a low-dose rituximab could be as effective as previously reported much higher doses, and presumably with a lower risk of adverse effects and infections.

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.

Autoimmune neuropathy associated with antibodies against pan-neurofascin is a new subtype of nodo-paranodopathy. It is relevant because it is associated with high morbidity and mortality. Affected patients often require intensive care unit treatment for several months, and data on the reversibility and long-term prognosis are limited. The pathogenicity including IgG subclass-associated mechanisms has not been unravelled, nor directly compared to anti-neurofascin-155 IgG4-related pathology. Understanding the underlying pathology might have a direct impact on treatment of these severely affected patients. By a multicentre combined prospective and retrospective approach, we provide clinical data of a large cohort of patients with anti-neurofascin-associated neuropathy (n = 18) including longitudinal titre and neurofilament light chain assessment via Ella® and relate clinical data to in vitro pathogenicity studies of anti-neurofascin antibodies. We assessed antibody binding characteristics and the pathogenic effects of anti-pan-neurofascin versus neurofascin-155 antibodies on living myelinating dorsal root ganglia co-cultures. Additionally, we analysed the IgG subclass profile and the complement binding capacity and effector functions considering the effects of intravenous immunoglobulin preparations via enzyme-linked immunosorbent and cell-based assays. In contrast to chronic neurofascin-155 IgG4-associated neuropathy, anti-pan-neurofascin-associated disease presented with a high morbidity and mortality, but as a monophasic and potentially reversible disorder. During follow-up, antibodies were no longer detectable in 8 of 11 patients. Anti-pan-neurofascin had direct access to the nodes of Ranvier in myelinating cultures titre-dependently, most probably inducing this severe phenotype. Antibody preincubation led to impaired paranode formation, destruction of paranodal architecture and alterations on paranodal myelin and sensory neurons in the cultures, with more severe effects than neurofascin-155 antibodies. Besides IgG4, subclass IgG3 was detected and associated with complement binding and cytotoxic effects in vitro. As a possible correlate of axonal damage in vivo, we detected highly increased serum neurofilament light chain levels (sNF-L), correlating to serum C3a. Still, sNF-L was not identified as a marker for poor prognosis, but rather as an intra- and interindividual marker for acuteness, severity and course, with a strong decrease during recovery. Our data provide evidence that anti-pan-neurofascin antibodies directly attack the node and induce severe and acute, but potentially reversible, nodo-paranodal pathology, possibly involving complement-mediated mechanisms. Screening for autoantibodies thus is crucial to identify this subset of patients who benefit from early antibody-depleting therapy. Titre and sNF-L might serve as valuable follow-up parameters. The prospect of a favourable outcome has high relevance for physicians, patients and relatives during months of critical care.

Purpose of review Autoimmune nodopathies are immune-mediated neuropathies associated with antibodies targeting the peripheral node of Ranvier. Recently, antibodies against all neurofascin-isoforms (pan-neurofascin) have been linked to a clinical phenotype distinct from previously described autoimmune nodopathies. Here, we aim at highlighting the molecular background and the red flags for diagnostic assessment and provide treatment and surveillance approaches for this new disease. Recent findings Neurofascin-isoforms are located at different compartments of the node of Ranvier: Neurofascin-186 at the axonal nodal gap, and Neurofascin-155 at the terminal Schwann cell loops at the paranode. Pan-neurofascin antibodies recognize a common epitope on both isoforms and can access the node of Ranvier directly. Depending on their subclass profile, antibodies can induce direct structural disorganization and complement activation. Affected patients present with acute and immobilizing sensorimotor neuropathy, with cranial nerve involvement and long-term respiratory insufficiency. Early antibody-depleting therapy is crucial to avoid axonal damage, and remission is possible despite extended disease and high mortality. The antibody titer and serum neurofilament light chain levels can serve as biomarkers for diagnosis and therapy monitoring. Summary Pan-neurofascin-associated autoimmune nodopathies has unique molecular and clinical features. Testing should be considered in severe and prolonged Guillain-Barré-like phenotype.

The node of Ranvier is the key element in saltatory conduction along myelinated axons, but its specific protein organization remains elusive in the human species. To shed light on nanoscale anatomy of the human node of Ranvier in health and disease, we assessed human nerve biopsies of patients with polyneuropathy by super-resolution fluorescence microscopy. We applied direct stochastic optical reconstruction microscopy (dSTORM) and supported our data by high-content confocal imaging combined with deep learning-based analysis. As a result, we revealed a ∼ 190 nm periodic protein arrangement of cytoskeletal proteins and axoglial cell adhesion molecules in human peripheral nerves. In patients with polyneuropathy, periodic distances increased at the paranodal region of the node of Ranvier, both at the axonal cytoskeleton and at the axoglial junction. In-depth image analysis revealed a partial loss of proteins of the axoglial complex (Caspr-1, neurofascin-155) in combination with detachment from the cytoskeletal anchor protein ß2-spectrin. High content analysis showed that such paranodal disorganization occurred especially in acute and severe axonal neuropathy with ongoing Wallerian degeneration and related cytoskeletal damage. We provide nanoscale and protein-specific evidence for the prominent, but vulnerable role of the node of Ranvier for axonal integrity. Furthermore, we show that super-resolution imaging can identify, quantify and map elongated periodic protein distances and protein interaction in histopathological tissue samples. We thus introduce a promising tool for further translational applications of super resolution microscopy.

Background and Objectives Nodo-paranodopathies are peripheral neuropathies with dysfunction of the node of Ranvier. Affected patients who are seropositive for antibodies against adhesion molecules like contactin-1 and neurofascin show distinct clinical features and a disruption of the paranodal complex. An axoglial dysjunction is also a characteristic finding of diabetic neuropathy. Here, we aim to investigate a possible association of antibody-mediated nodo-paranodopathy and diabetes mellitus (DM). Methods We retrospectively analyzed clinical data of 227 patients with chronic inflammatory demyelinating polyradiculoneuropathy and Guillain-Barre syndrome from multiple centers in Germany who had undergone diagnostic testing for antiparanodal antibodies targeting neurofascin-155, pan-neurofascin, contactin-1-associated protein 1, and contactin-1. To study possible direct pathogenic effects of antiparanodal antibodies, we performed immunofluorescence binding assays on human pancreatic tissue sections. Results The frequency of DM was 33.3% in seropositive patients and thus higher compared with seronegative patients (14.1%, OR = 3.04, 95% CI = 1.31-6.80). The relative risk of DM in seropositive patients was 3.4-fold higher compared with the general German population. Seropositive patients with DM most frequently harbored anti-contactin-1 antibodies and had higher antibody titers than seropositive patients without DM. The diagnosis of DM preceded the onset of neuropathy in seropositive patients. No immunoreactivity of antiparanodal antibodies against pancreatic tissue was detected. Discussion We report an association of nodo-paranodopathy and DM. Our results suggest that DM may be a potential risk factor for predisposing to developing nodo-paranodopathy and argue against DM being induced by the autoantibodies. Our findings set the basis for further research investigating underlying immunopathogenetic connections.