Report of a fulminant anti-pan-neurofascin-associated neuropathy responsive to rituximab and bortezomib

Different Patterns of Autoantibody Secretion by Peripheral Blood Mononuclear Cells in Autoimmune Nodopathies

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.

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.

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.

Pan-Neurofascin autoimmune nodopathy - a life-threatening, but reversible neuropathy

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.

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.

Anti-NF155/NF186 IgG4 Antibody Positive Autoimmune Nodopathy

Patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) seropositive for autoantibodies against nodal and paranodal proteins display distinct clinical presentations. In the latest study, CIDP with autoantibodies against paranodal proteins was defined as autoimmune nodopathy (AN). We herein present a case of 39-year-old male with anti- neurofascin (NF) 155 and NF186 IgG4 antibody with gait disturbance and tremor, who was followed up for 4 months and demonstrated clinical improvements after apparently effective rituximab therapy. In addition, a literature review was conducted to investigate the clinical characteristics of anti-NF155/NF186-positive AN.

Therapeutic Monoclonal Antibody Therapies in Chronic Autoimmune Demyelinating Neuropathies

Autoimmune diseases of the peripheral nervous system have so far been treated mainly with exogenous high-dose intravenous immunoglobulins (IVIg), that act through several mechanisms, including neutralization of pathogenic autoantibodies, modulation of lymphocyte activity, interference with antigen presentation, and interaction with Fc receptors, cytokines, and the complement system. Other therapeutic strategies have recently been developed, in part to address the increasing shortage of IVIg, prime among which is the use of B cell depleting monoclonal antibodies, or small molecule inhibitors targeting the B-cell specific kinases. Rituximab, a chimeric monoclonal antibody against CD20 + B lymphocytes, is currently the most used, especially in anti-MAG antibody neuropathy and autoimmune neuropathies with antibodies to nodal/paranodal antigens that are unresponsive to IVIg. After several reports of its efficacy in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), rituximab is currently under investigation in three Phase 2 trials in CIDP. In addition, the possible role of complement activation in the pathogenesis of chronic autoimmune neuropathies has brought into consideration drugs that can block the complement cascade, such as eculizumab, a monoclonal antibody already assessed in acute polyradiculoneuropathies, and approved for myasthenia gravis. Preliminary data on eculizumab in multifocal motor neuropathy have been published, but randomized controlled studies are pending. Moreover, the neonatal Fc receptor, that recycles IgGs by preventing their lysosome degradation, is an important and attractive pharmacological target. Antibodies against FcRn, which reduce circulating IgG (both pathogenic and non-pathogenic) have been developed. The FcRn blocker efgartigimod, a humanized IgG1-derived Fc fragment, which competitively inhibits the FcRn, has recently been approved for the treatment of myasthenia gravis and is currently under investigation in CIDP. In addition, the anti-human FcRn monoclonal antibody rozanolixizumab is currently being assessed in phase 2 trials in CIDP. However, none of the abovementioned monoclonal antibodies is currently approved for treatment of any immune-mediated neuropathies. While more specific and individualized therapies are being developed, the possibility of combined treatments targeting different pathogenic mechanisms deserves consideration as well.

IgG4 Autoantibodies in Organ-Specific Autoimmunopathies: Reviewing Class Switching, Antibody-Producing Cells, and Specific Immunotherapies

Organ-specific autoimmunity is often characterized by autoantibodies targeting proteins expressed in the affected tissue. A subgroup of autoimmunopathies has recently emerged that is characterized by predominant autoantibodies of the IgG4 subclass (IgG4-autoimmune diseases; IgG4-AID). This group includes pemphigus vulgaris, thrombotic thrombocytopenic purpura, subtypes of autoimmune encephalitis, inflammatory neuropathies, myasthenia gravis and membranous nephropathy. Although the associated autoantibodies target specific antigens in different organs and thus cause diverse syndromes and diseases, they share surprising similarities in genetic predisposition, disease mechanisms, clinical course and response to therapies. IgG4-AID appear to be distinct from another group of rare immune diseases associated with IgG4, which are the IgG4-related diseases (IgG4-RLD), such as IgG4-related which have distinct clinical and serological properties and are not characterized by antigen-specific IgG4. Importantly, IgG4-AID differ significantly from diseases associated with IgG1 autoantibodies targeting the same organ. This may be due to the unique functional characteristics of IgG4 autoantibodies (e.g. anti-inflammatory and functionally monovalent) that affect how the antibodies cause disease, and the differential response to immunotherapies of the IgG4 producing B cells/plasmablasts. These clinical and pathophysiological clues give important insight in the immunopathogenesis of IgG4-AID. Understanding IgG4 immunobiology is a key step towards the development of novel, IgG4 specific treatments. In this review we therefore summarize current knowledge on IgG4 regulation, the relevance of class switching in the context of health and disease, describe the cellular mechanisms involved in IgG4 production and provide an overview of treatment responses in IgG4-AID.

Case report: Amnestic mild cognitive impairment in multiple domains associated with neurofascin 186 autoantibodies: Case series with follow-up and review

BACKGROUND

Neurofascin 186 autoantibodies are known to occur with a diseased peripheral nervous system. Recently, also additional central nervous system (CNS) involvement has been reported in conjunction with neurofascin 186 autoantibodies. Our case enlarges the spectrum of neurofascin 186 antibody-related disease to include mild cognitive impairment (MCI).

METHODS

We report here a case after having examined the patient files retrospectively, including diagnostics such as blood and cerebrospinal fluid (CSF) analysis involving the determination of neural autoantibodies, brain magnetic resonance imaging (MRI), brain fluorodesoxyglucose positron emission tomography (FDG-PET), and extensive neuropsychological testing.

RESULTS

We report on two patients with MCI. Brain MRI showed cerebral microangiopathy in both patients, but brain FDG-PET demonstrated pathology in the right prefrontal cortex, in the right inferior parietal cortex, and in both lateral occipital cortices in one patient. Neurofascin 186 antibodies were detected in serum in both patients, and neurofascin 186 autoantibodies were also detected in the CSF of one of these patients. At follow-up six month later, neurofascin 186 autoantibodies disappeared in one patient while persisting in the other.

CONCLUSION

We report on two individuals presenting MCI associated with neurofascin 186 antibodies, thus expanding the potential spectrum of neurofascin 186-associated disease. This report supports the recommendation to consider also neurofascin 186 autoantibodies in not just peripheral nerve disease, but also in disorders involving CNS autoimmunity. More studies are needed to clarify the lack of association between neurofascin 186 autoantibodies and cognitive decline.