Antibody-Mediated Nodo- and Paranodopathies.

The recent discovery of pathogenic antibodies targeting cell adhesion molecules of the node of Ranvier has prompted efforts to develop a new classification for a subset of antibody-mediated peripheral neuropathies. These autoimmune nodo- and paranodopathies encompass epitopes such as neurofascin 155, neurofascin 186, contactin-1, and contactin-associated protein 1, with a high likelihood of involving additional yet unidentified proteins. So far, the investigation of this subset of patients was primarily focused on adults, with only rare reports of pediatric cases. Low awareness among pediatricians and insufficient availability of appropriate diagnostic methods in many laboratories may mask a higher pediatric incidence than currently observed. Diagnosis is made by transfected cell-based assays and ELISA to characterize the specific target antigen and antibody subclass that provides insight into the pathophysiology. Clinical features often resemble those of CIDP or GBS in adults, whilst in pediatric patients, although rare, an atypical CIDP phenotype has predominantly been reported. Yet, in contrast to classical immune-mediated neuropathies, the clinical course is usually rapidly progressive, and response to classical first-line therapy often poor. Although electrophysiological signs of demyelination are observed, segmental demyelination and inflammation are not present on pathological examination. Rather, few neuropathological reports demonstrate features of axonal neuropathy without signs of true de- or remyelination. This review aims to summarize recent findings on such nodo- and paranodoneuropathies, shining light on features of these disorders in pediatric patients, a still little-explored field with only a few reports currently present.

Proteinuria is a key to suspect autoimmune nodopathies.

BACKGROUND AND PURPOSE: Reports of patients who have autoimmune nodopathies concurrent with nephrotic syndrome are increasing. We investigated whether proteinuria could be a biomarker of autoimmune nodopathies. METHODS: Qualitative urinalysis results were retrospectively obtained from 69 patients who were diagnosed with chronic inflammatory demyelinating polyneuropathy (CIDP) at a hospital in Japan. Proteinuria was graded as mild to severe (i.e., mild, 30-99; moderate, 100-299; severe, 300 mg/dL or more) according to the results of the urine dipstick test. Autoantibodies against the paranodal proteins contactin 1 (CNTN1), neurofascin 155 (NF155), and contactin-associated protein 1 (Caspr1) and the nodal protein neurofascin 186 (NF186) were measured, and the predominant IgG subclass was determined by enzyme-linked immunosorbent assay in sera from the 69 patients. RESULTS: Four patients (6%), five patients (7%), and one (1%) patient were positive for anti-CNTN1, anti-NF155, and anti-Caspr1 IgG4 antibodies, respectively. No patients had IgG4 antibodies against NF186. Proteinuria of mild or greater levels was found in three patients with anti-CNTN1 IgG4 and two patients with anti-NF155 IgG4 antibodies. The autoantibody-positive patients more frequently had proteinuria of mild or greater levels than the seronegative patients (p = 0.01). CONCLUSIONS: Proteinuria is a possible biomarker of autoimmune nodopathies associated with autoantibodies targeting CNTN1 or NF155. Urinalysis results should be carefully checked for quick differentiation of autoimmune nodopathies from CIDP. Patients who present with nephrotic syndrome should be tested for anti-CNTN1 IgG4 antibodies, and patients who exhibit mild proteinuria should be tested for anti-NF155 IgG4 antibodies.

Therapy-resistant autoimmune nodopathy with anti-neurofascin 155 antibodies: a case report.

This study reports the case of a previously healthy man in his late 20s who began experiencing symptoms 3 months before admission to our hospital, including arm and leg weakness and distal hypesthesia. Initially, the patient responded to corticosteroid therapy. However, as his symptoms progressed, he underwent plasmapheresis and received intravenous immunoglobulin therapy, neither of which led to any discernible improvement. With rapid symptom progression during subsequent hospital visits, further investigation led to the detection of neurofascin 155 antibodies. Based on existing evidence of its efficacy, rituximab treatment was initiated. To date, the patient has received three doses of rituximab, which has been partially ineffective. Thus, treatment is ongoing and includes a combination of rituximab and subcutaneous immunoglobulin.

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.

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.

Low-dose rituximab treatment in a patient with anti-neurofascin-155 IgG4 autoimmune nodopathy.

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.

Combined Central and Peripheral Demyelination: Two Case Reports.

Combined central and peripheral demyelination (CCPD) is a rare disease characterized by demyelinating lesions in both the central nervous system (CNS) and peripheral nervous system (PNS). CCPD can present with acute, subacute, or chronic onset. The initial symptom may be of CNS origin, PNS origin, or both. The clinical manifestations of CCPD are quite heterogeneous, and there are no well-defined diagnostic criteria. In MRI imaging of CCPD cases, demyelinating lesions can be seen in areas such as the brain, cerebellum, brainstem, optic nerve, and spinal cord. Common electromyography (EMG) findings in patients with CCPD include decreased motor nerve conduction velocities, decreased or absent sensory nerve action potentials, prolonged F-wave latency, and decreased amplitude of compound muscle action potentials. Neurofascin (NF) is a transmembrane protein and anti-neurofascin (anti-NF) antibodies directed against NF can be positive in cases of CCPD. Four main NF polypeptides are produced by alternative splicing: NF 186, NF 180, NF 166, and NF 155. The investigation of anti-NF in CCPD cases is therefore important for etiological considerations. Here, we discussed three cases diagnosed with CCPD based on clinical, neuroimaging, EMG, and anti-NF antibody results in light of the literature.

Anti-pan-neurofascin nodopathy: cause of fulminant neuropathy.

Autoimmune nodopathies are inflammatory diseases of the peripheral nervous system with clinical and neurophysiological peculiar characteristics. In this nosological category, we find patients with autoantibodies against Neurofascin 140/186 and 155, Contactin1, and Caspr1 directed precisely towards nodal and paranodal structures. These antibodies are extremely rare and cause severe clinical symptoms. We describe the clinical case of a patient with autoimmune nodopathy caused by the coexistence of anti-neurofascin (NF) 186/140 and 155, characterized by progressive weakness in all limbs leading to tetraplegia, involving cranial nerves, and respiratory insufficiency. Response to first-line treatments was good followed by rapid dramatic clinical relapse. There are few reported cases of anti-pan NF neuropathy in the literature, and they present a clinical phenotype similar to our patient. In these cases, early recognition of clinical red flags of nodopathies and serial neurophysiological studies can facilitate the diagnosis. However, the severe clinical relapse suggests a possible early use of immunosuppressive therapies for this rare category of patients.

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.

Anti-neurofascin 155 Antibody-positive Neuropathy in a Human Immunodeficiency Virus-infected Patient.

Human immunodeficiency virus (HIV)-associated neuropathy is a common complication of HIV infection and has several clinical subtypes. HIV-associated chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a demyelinating neuropathy whose clinical features are known to differ from those of CIDP in the HIV-uninfected population. We herein report a case of CIDP in an HIV-infected patient who was finally diagnosed with anti-neurofascin 155 (NF155) antibody-positive neuropathy. The clinical features, including clinical findings and therapeutic responses, were typical of paranodal antibody-mediated neuropathy. To our knowledge, this is the first case of anti-NF155 antibody-associated neuropathy in an HIV-infected patient.

Pathology explains various mechanisms of auto-immune inflammatory peripheral neuropathies.

Autoimmune neuropathies are a heterogeneous group of rare and disabling diseases in which the immune system is thought to target antigens in the peripheral nervous system: they usually respond to immune therapies. Guillain-Barré syndrome is divided into several subtypes including "acute inflammatory demyelinating polyradiculoneuropathy," "acute motor axonal neuropathy," "acute motor sensory neuropathy," and other variants. Chronic forms such as chronic inflammatory demyelinating polyneuropathy (CIDP) and other subtypes and polyneuropathy associated with IgM monoclonal gammopathy; autoimmune nodopathies also belong to this group of auto-immune neuropathies. It has been shown that immunoglobulin G from the serum of about 30% of CIDP patients immunolabels nodes of Ranvier or paranodes of myelinated axons. Whatever the cause of myelin damage of the peripheral nervous system, the initial attack on myelin by a dysimmune process may begin either at the internodal area or in the paranodal and nodal regions. The term "nodoparanodopathy" was first applied to some "axonal Guillain-Barré syndrome" subtypes, then extended to cases classified as CIDP bearing IgG4 antibodies against paranodal axoglial proteins. In these cases, paranodal dissection develops in the absence of macrophage-induced demyelination. In contrast, the mechanisms of demyelination of other dysimmune neuropathies induced by macrophages are unexplained, as no antibodies have been identified in such cases. The main objective of this presentation is to show that the pathology illustrates, confirms, and may explain such mechanisms.

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.

[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.

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.

Direct fluorescent labeling of NF186 and NaV1.6 in living primary neurons using bioorthogonal click chemistry.

The axon initial segment (AIS) is a highly specialized neuronal compartment that regulates the generation of action potentials and maintenance of neuronal polarity. Live imaging of the AIS is challenging due to the limited number of suitable labeling methods. To overcome this limitation, we established a novel approach for live labeling of the AIS using unnatural amino acids (UAAs) and click chemistry. The small size of UAAs and the possibility of introducing them virtually anywhere into target proteins make this method particularly suitable for labeling of complex and spatially restricted proteins. Using this approach, we labeled two large AIS components, the 186 kDa isoform of neurofascin (NF186; encoded by Nfasc) and the 260 kDa voltage-gated Na+ channel (NaV1.6, encoded by Scn8a) in primary neurons and performed conventional and super-resolution microscopy. We also studied the localization of epilepsy-causing NaV1.6 variants with a loss-of-function effect. Finally, to improve the efficiency of UAA incorporation, we developed adeno-associated viral (AAV) vectors for click labeling in neurons, an achievement that could be transferred to more complex systems such as organotypic slice cultures, organoids, and animal models.

Pediatric-Onset Chronic Inflammatory Demyelinating Polyneuropathy: A Multicenter Study.

BACKGROUND: To evaluate the clinical features, demographic features, and treatment modalities of pediatric-onset chronic inflammatory demyelinating polyneuropathy (CIDP) in Turkey. METHODS: The clinical data of patients between January 2010 and December 2021 were reviewed retrospectively. The patients were evaluated according to the Joint Task Force of the European Federation of Neurological Societies and the Peripheral Nerve Society Guideline on the management of CIDP (2021). In addition, patients with typical CIDP were divided into two groups according to the first-line treatment modalities (group 1: IVIg only, group 2: IVIg + steroid). The patients were further divided into two separate groups based on their magnetic resonance imaging (MRI) characteristics. RESULTS: A total of 43 patients, 22 (51.2%) males and 21 (48.8%) females, were included in the study. There was a significant difference between pretreatment and post-treatment modified Rankin scale (mRS) scores (P < 0.05) of all patients. First-line treatments include intravenous immunoglobulin (IVIg) (n = 19, 44.2%), IVIg + steroids (n = 20, 46.5%), steroids (n = 1, 2.3%), IVIg + steroids + plasmapheresis (n = 1, 2.3%), and IVIg + plasmapheresis (n = 1, 2.3%). Alternative agent therapy consisted of azathioprine (n = 5), rituximab (n = 1), and azathioprine + mycophenolate mofetil + methotrexate (n = 1). There was no difference between the pretreatment and post-treatment mRS scores of groups 1 and 2 (P > 0.05); however, a significant decrease was found in the mRS scores of both groups with treatment (P < 0.05). The patients with abnormal MRI had significantly higher pretreatment mRS scores compared with the group with normal MRI (P < 0.05). CONCLUSIONS: This multicenter study demonstrated that first-line immunotherapy modalities (IVIg vs IVIg + steroids) had equal efficacy for the treatment of patients with CIDP. We also determined that MRI features might be associated with profound clinical features, but did not affect treatment response.

Extracellular Tau Oligomers Damage the Axon Initial Segment.

BACKGROUND: In Alzheimer's disease (AD) brain, neuronal polarity and synaptic connectivity are compromised. A key structure for regulating polarity and functions of neurons is the axon initial segment (AIS), which segregates somatodendritic from axonal proteins and initiates action potentials. Toxic tau species, including extracellular oligomers (xcTauOs), spread tau pathology from neuron to neuron by a prion-like process, but few other cell biological effects of xcTauOs have been described. OBJECTIVE: Test the hypothesis that AIS structure is sensitive to xcTauOs. METHODS: Cultured wild type (WT) and tau knockout (KO) mouse cortical neurons were exposed to xcTauOs, and quantitative western blotting and immunofluorescence microscopy with anti-TRIM46 monitored effects on the AIS. The same methods were used to compare TRIM46 and two other resident AIS proteins in human hippocampal tissue obtained from AD and age-matched non-AD donors. RESULTS: Without affecting total TRIM46 levels, xcTauOs reduce the concentration of TRIM46 within the AIS and cause AIS shortening in cultured WT, but not TKO neurons. Lentiviral-driven tau expression in tau KO neurons rescues AIS length sensitivity to xcTauOs. In human AD hippocampus, the overall protein levels of multiple resident AIS proteins are unchanged compared to non-AD brain, but TRIM46 concentration within the AIS and AIS length are reduced in neurons containing neurofibrillary tangles. CONCLUSION: xcTauOs cause partial AIS damage in cultured neurons by a mechanism dependent on intracellular tau, thereby raising the possibility that the observed AIS reduction in AD neurons in vivo is caused by xcTauOs working in concert with endogenous neuronal tau.

Super-resolution imaging pinpoints the periodic ultrastructure at the human node of Ranvier and its disruption in patients with polyneuropathy.

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 âˆ¼ 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.

Anti-rituximab antibodies in patients with refractory autoimmune nodopathy with anti-neurofascin-155 antibody.

Background: Recent studies have reported that similar to other IgG4 autoimmune diseases, such as muscle-specific kinase antibody-associated myasthenia gravis, most anti-neurofascin-155 (anti-NF155) nodopathies respond well to rituximab treatment, regardless of the dosage. However, there are still a few patients for which rituximab is ineffective for unknown reasons. Currently, there are no studies on the mechanism of ineffective treatment with rituximab. Methods: A 33-year-old Chinese man presenting with numbness, tremor, and muscle weakness for 4 years was recruited for this study. Anti-NF155 antibodies were identified by cell-based assay and confirmed by immunofluorescence assay on teased fibers. The anti-NF155 immunoglobulin (IgG) subclasses were also detected by immunofluorescence assay. Anti-rituximab antibodies (ARAs) were quantitatively analyzed using enzyme-linked immunosorbent assay (ELISA), and peripheral B cell counts were determined by flow cytometry. Results: The patient exhibited anti-NF155 IgG4-antibody positivity. After the first round of rituximab infusion, the patient showed stratified outcomes with improvements in numbness, muscle weakness and ambulation. However, after three rounds of rituximab infusion, the patient's symptoms deteriorated, and the numbness, tremor and muscle weakness returned. No obvious improvement was found after plasma exchange and another round of rituximab treatment. 14 days after the last treatment with rituximab, ARAs were detected. And the titers gradually decreased on day 28 and 60 but remained higher than normal. Peripheral CD19+ B cell counts were less than 1% within the 2-month period following the final rituximab administration. Conclusions: In this study, ARAs presented in a patient with anti-NF155 nodopathy undergoing rituximab treatment and showed an unfavorable impact on rituximab efficacy. This is the first case to report the occurrence of ARAs in patients with anti-NF155 antibodies. We suggest that ARAs should be tested early during the initial intervention, especially in patients who respond poorly to rituximab treatment. In addition, we believe it is necessary to investigate the association between ARAs and B cell counts, their effect on clinical efficacy, and their potential adverse reactions in a larger cohort of patients with anti-NF155 nodopathy.

Growing Spectrum of Autoimmune Nodopathies.

PURPOSE OF REVIEW: Recognition of node of Ranvier as the site of injury in inflammatory neuropathies contributed to discovery of antibodies against the nodal/paranodal structures. These antibodies mediate a unique type of inflammatory neuropathies that are different from typical chronic inflammatory demyelinating polyneuropathy. This review discusses the advancements made in the field of autoimmune neuropathies secondary to antibodies to nodal and paranodal proteins. RECENT FINDINGS: Neuropathies caused by antibodies to nodal-paranodal antigens including neurofascin 186, neurofascin 155, contactin1, and contactin-associated protein1 were termed as autoimmune nodopathies (AN) in 2021. Since the initial description almost a decade ago, newer cohorts have expanded the clinical spectrum of AN. In addition to IgG4, other subclasses of IgG such as IgG1/IgG3 have been identified, particularly in relation to acute presentations and anti-pan neurofascin antibody disease. In vitro and in vivo studies have also supported antibody-mediated pathogenicity of many of these biomarkers. Antibodies to nodal-paranodal antigens have emerged as a biomarker for a novel type of immune-mediated neuropathies. These antibodies have distinct pathogenic mechanisms and produce a unique set of clinicopathologic features. Their clinical profile and treatment may also vary depending on the antibody isotype. B cell depleting therapies are effective in managing some of these patients.