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

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.

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.

Exploring the depths of IgG4: insights into autoimmunity and novel treatments

IgG4 subclass antibodies represent the rarest subclass of IgG antibodies, comprising only 3-5% of antibodies circulating in the bloodstream. These antibodies possess unique structural features, notably their ability to undergo a process known as fragment-antigen binding (Fab)-arm exchange, wherein they exchange half-molecules with other IgG4 antibodies. Functionally, IgG4 antibodies primarily block and exert immunomodulatory effects, particularly in the context of IgE isotype-mediated hypersensitivity reactions. In the context of disease, IgG4 antibodies are prominently observed in various autoimmune diseases combined under the term IgG4 autoimmune diseases (IgG4-AID). These diseases include myasthenia gravis (MG) with autoantibodies against muscle-specific tyrosine kinase (MuSK), nodo-paranodopathies with autoantibodies against paranodal and nodal proteins, pemphigus vulgaris and foliaceus with antibodies against desmoglein and encephalitis with antibodies against LGI1/CASPR2. Additionally, IgG4 antibodies are a prominent feature in the rare entity of IgG4 related disease (IgG4-RD). Intriguingly, both IgG4-AID and IgG4-RD demonstrate a remarkable responsiveness to anti-CD20-mediated B cell depletion therapy (BCDT), suggesting shared underlying immunopathologies. This review aims to provide a comprehensive exploration of B cells, antibody subclasses, and their general properties before examining the distinctive characteristics of IgG4 subclass antibodies in the context of health, IgG4-AID and IgG4-RD. Furthermore, we will examine potential therapeutic strategies for these conditions, with a special focus on leveraging insights gained from anti-CD20-mediated BCDT. Through this analysis, we aim to enhance our understanding of the pathogenesis of IgG4-mediated diseases and identify promising possibilities for targeted therapeutic intervention.

Semiquantitative assessment of preganglionic nerves for chronic immune-mediated neuropathies using brachial plexus magnetic resonance imaging

Background

Brachial plexus magnetic resonance imaging (MRI) is an important noninvasive supplementary diagnostic method of chronic immune peripheral neuropathies, but few MRI studies on the preganglionic nerves have been conducted. This retrospective cross-sectional study aimed to establish a reliable assessment for brachial plexus preganglionic nerve thickness and to use this method to assess and compare nerve characteristics in various types of peripheral neuropathies.

Methods

Hospitalized patients diagnosed as positive for anti-neurofascin-155 (NF155)-positive autoimmune nodopathy (AN) (NF155+), chronic inflammatory demyelinating polyneuropathy (CIDP), or multifocal motor neuropathy (MMN) at Huashan Hospital of Fudan University in Shanghai, China, who underwent brachial plexus MRI between October 2011 and August 2023 were consecutively recruited for this study. We also recruited participants who underwent brachial plexus MRI during this period with no history of trauma, inflammation, tumors, compression, or degenerative conditions as healthy controls. According to our self-developed semiquantitative assessment of preganglionic nerves, we assessed the bilateral preganglionic C5-C8 nerves individually and scored the enlargement degree from 0 to 4 points. Furthermore, a sum score ≥20 was defined as definite enlargement.

Results

A total of 122 participants were enrolled, including 28 with NF155+, 40 with CIDP, 15 with MMN, and 39 healthy controls. In the comparison of the single-nerve scores, we found that there was a significant difference distribution among the four groups (χ2 test; P<0.001), with the patients with NF155+ exhibiting the highest scores in each of the bilateral C5-C8 nerves. In the comparison of the sum scores, a descending tendency was observed in patients NF155+, CIDP, and MMN, with median scores of 11, 4, and 0 points, respectively (Kruskal-Wallis test; P=0.003, P<0.001, and P=0.005, respectively for NF155+ vs. CIDP, NF155+ vs. MMN, and CIDP vs. MMN). The proportion of definite enlargement in those with NF155+ was greater than that in healthy controls (21% vs. 0%; χ2 test; P=0.004), and the sum score at 0 points was lower in the NF155+ group than in CIDP, MMN, and healthy control groups (7% vs. 37%, 87%, and 41%, respectively; χ2 test; P<0.001).

Conclusions

This semiquantitative assessment can be a valuable tool for measuring preganglionic nerve enlargement, which was found to be decreased, respectively, in those with NF155+, CIDP, and MMN. Presence of definite enlargement could be a strong indicator of NF155+ in clinic.

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.

[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.

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.

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.

Effect of low-dose rituximab treatment on autoimmune nodopathy with anti-contactin 1 antibody

Background

Autoimmune nodopathy with anti-contactin-1 (CNTN1) responds well to rituximab instead of traditional therapies. Although a low-dose rituximab regimen was administered to patients with other autoimmune diseases, such as myasthenia gravis and neuromyelitis optica spectrum disorders, and satisfactory outcomes were obtained, this low-dose rituximab regimen has not been trialed in anti-CNTN1-positive patients.

Methods

Anti–CNTN1 nodopathy patients were enrolled in this prospective, open-label, self-controlled pilot study. A cell-based assay was used to detect anti-CNTN1 antibodies and their subclasses in both serum and cerebrospinal fluid. Clinical features were evaluated at baseline, 2 days, 14 days, and 6 months after single low-dose rituximab treatment (600 mg). The titers of the subclasses of anti-CNTN1 antibody and peripheral B cells were also evaluated at baseline, 2 days, and 6 months after the rituximab regimen.

Results

Two patients with anti–CNTN1 antibodies were enrolled. Both patients had neurological symptoms including muscle weakness, tremor, sensory ataxia, numbness and mild nephrotic symptoms. In the field of neurological symptoms, sensory ataxia markedly improved, and the titer of anti-CNTN1 antibody as well as CD19+ B cells decreased only two days following low-dose rituximab treatment. Other neurological symptoms improved within two weeks of rituximab treatment. At the 6-month follow-up, all neurological symptoms steadily improved with steroid reduction, and both the anti-CNTN1 antibody titer and CD19+ B cells steadily decreased. No adverse events were observed after this single low-dose rituximab treatment.

Conclusions

We confirmed the clinical efficacy of low-dose rituximab by B cell depletion in autoimmune nodopathy with anti-CNTN1 antibody. This rapid and long-lasting response suggests that low-dose rituximab is a promising option for anti-CNTN1 nodopathy.