Autoimmune Neuropathy Research Articles

Immune-Mediated Neuropathies: Top 10 Clinical Pearls.

Immune-mediated neuropathies encompass a range of neurological disorders, including chronic inflammatory demyelinating polyradiculoneuropathy, Guillain-Barré syndrome, multifocal motor neuropathy, autoimmune autonomic neuropathies, and paranodal nodopathies. Recognizing clinical patterns is key to narrowing the broad range of differential diagnoses in immune-mediated neuropathies. Electrodiagnostic testing is a useful tool to support the diagnosis of immune-mediated neuropathies. Our understanding of autoimmune demyelinating neuropathies is rapidly advancing, particularly with the discovery of nodal and paranodal antibodies. Recent advances in neuropathy treatment include the utilization of neonatal Fc receptors to reduce antibody recycling, and the development of complement inhibitors to reduce inflammatory damage, offering promising new therapeutic avenues. Timely identification of immune-mediated neuropathies is imperative as delay in diagnosis and treatment may lead to irreversible disability.

Autoimmune Optic Neuropathy

Autoimmune optic neuropathy represents a chronic, heterogeneous disease that is usually accompanied by bilateral vision loss and is caused by injury occurring through autoimmune mechanisms. Autoimmune optic neuropathy can occur as a component of autoimmune or collagen vascular diseases, as well as it can be seen in an isolated way. Plasmapheresis and monoclonal antibodies are used together with steroids in the treatment of autoimmune optic neuropathy, the pathophysiology of which is not yet fully understood despite advances in existing laboratory and imaging devices. This rare clinical picture usually results in vision loss when it is not properly diagnosed, treated quickly and effectively.

Antibodies in Autoimmune Neuropathies: What to Test, How to Test, Why to Test.

Autoimmune neuropathies are a heterogeneous group of immune-mediated disorders of the peripheral nerves. Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) are the archetypal acute and chronic forms. Over the past few decades, pathogenic antibodies targeting antigens of the peripheral nervous system and driving peripheral nerve damage in selected patients have been described. Moreover, the detection of these antibodies has diagnostic and therapeutic implications that have prompted a modification of the GBS and CIDP diagnostic algorithms. GBS diagnosis is based in clinical criteria, and systematic testing of anti-ganglioside antibodies is not required. Nonetheless, a positive anti-ganglioside antibody test may support the clinical suspicion when diagnosis of GBS (GM1 IgG), Miller Fisher (GQ1b IgG), or acute sensory-ataxic (GD1b IgG) syndromes is uncertain. Anti-myelin-associated glycoprotein (MAG) IgM and anti-disialosyl IgM antibodies are key in the diagnosis of anti-MAG neuropathy and chronic ataxic neuropathy, ophthalmoplegia, M-protein, cold agglutinins, and disialosyl antibodies spectrum neuropathies, respectively, and help differentiating these conditions from CIDP. Recently, the field has been boosted by the discovery of pathogenic antibodies targeting proteins of the node of Ranvier contactin-1, contactin-associated protein 1, and nodal and paranodal isoforms of neurofascin (NF140, NF186, or NF155). These antibodies define subgroups of patients with specific clinical (most importantly poor or partial response to conventional therapies and excellent response to anti-CD20 therapy) and pathologic (node of Ranvier disruption in the absence of inflammation) features that led to the definition of the "autoimmune nodopathy" diagnostic category and to the incorporation of nodal/paranodal antibodies to clinical routine testing. The purpose of this review was to provide a practical vision for the general neurologist of the use of antibodies in the clinical assessment of autoimmune neuropathies.

Memory inflation: Beyond the acute phase of viral infection.

Memory inflation is confirmed as the most commonly dysregulation of host immunity with antigen-independent manner in mammals after viral infection. By generating large numbers of effector/memory and terminal differentiated effector memory CD8+ T cells with diminished naïve subsets, memory inflation is believed to play critical roles in connecting the viral infection and the onset of multiple diseases. Here, we reviewed the current understanding of memory inflated CD8+ T cells in their distinct phenotypic features that different from exhausted subsets; the intrinsic and extrinsic roles in regulating the formation of memory inflation; and the key proteins in maintaining the expansion and proliferation of inflationary populations. More importantly, based on the evidences from both clinic and animal models, we summarized the potential mechanisms of memory inflation to trigger autoimmune neuropathies, such as Guillain-Barré syndrome and multiple sclerosis; the correlations of memory inflation between tumorigenesis and resistance of tumour immunotherapies; as well as the effects of memory inflation to facilitate vascular disease progression. To sum up, better understanding of memory inflation could provide us an opportunity to beyond the acute phase of viral infection, and shed a light on the long-term influences of CD8+ T cell heterogeneity in dampen host immune homeostasis.

The multiple roles of nerve biopsy in the diagnosis and prognosis of suspected immune neuropathies

IntroductionThe value of a sural nerve biopsy for the diagnosis of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is controversial. Evidence-based recommendations for its implementation are lacking. We investigated factors leading to biopsy and analyzed biopsy outcomes and consequences, assessed the predictability of biopsy outcomes through clinical parameters to avoid unnecessary biopsies, and compared results with electrophysiological and clinical severity to determine their prognostic value.Methods190 sural nerve biopsies were analyzed in two cohorts. One consisted of 163 biopsies and the second of 72 biopsies from the prospective Immune-mediated Neuropathies Biomaterial and Data registry (INHIBIT). Both have an intersection of 45 patients. 75 data sets from patients without biopsy were used. Analysis of nerve conduction studies, treatment, overall disability sum score (ODSS), biopsy outcomes, and diagnosis was performed.Results51% of biopsied patients received the diagnosis CIDP (77% fulfilled EFNS/PNS criteria), 21% were not CIDP typical, and 27% were unspecific. Biopsied patients responded less frequently to immunotherapies at time of biopsy than non-biopsied patients (p = 0.003). Immunotherapy was initiated more frequently after biopsy (p < 0.001) and more often with intravenous immunoglobulins (p < 0.0001). 76% of all biopsied patients met the electrophysiological criteria for CIDP. Sensory nerve action potential amplitudes of 0 µV still provide 73% of histological diagnostic value. Histologic signs of degeneration predicted ODSS worsening after 1 year (p = 0.028) but disease severity did not correlate with histological damage severity.DiscussionThe main indication for nerve biopsy was the treatment of refractory cases of autoimmune neuropathies with the therapeutic consequence of treatment initiation or escalation. Sural biopsy also provided prognostic information. Even with extinguished sural SNAP, the biopsy can still have diagnostic value.

The Presence of Ganglionic Acetylcholine Receptor Antibodies in Sera from Patients with Functional Gastrointestinal Disorders: A Preliminary Study.

Functional gastrointestinal disorders (FGIDs), including functional dyspepsia (FD) and irritable bowel syndrome (IBS), are characterized by chronic and recurrent gastrointestinal symptoms. Clinically, FD and IBS often resemble gastrointestinal dysmotility caused by autoimmune autonomic neuropathy. We examined the seropositive frequency of autoantibodies against ganglionic nicotinic acetylcholine receptors (gnAChRs) in patients presenting with FGIDs. To elucidate the seropositivity of gnAChR antibodies and the clinical features of seropositive FD and IBS. We measured autoantibodies against the gnAChR α3 and β4subunits using luciferase immunoprecipitation systems. Serum samples from patients with any autonomic symptoms were obtained from hospitals in Japan between January 2012 and August 2018 (1787 serum samples of 1381 patients). We selected FD and IBS patients and compared the clinical characteristics and prevalence of autonomic symptoms between those with seropositive and seronegative IBS and FD. Nine IBS and two FD cases (one comorbid case with IBS) were found. We found four patients (36.4%) in whom gnAChR antibodies were positive in these eleven patients. Sicca symptoms were observed in three of four cases (75%) of seropositive FGID compared with zero of seven cases (0%) of seronegative FGID. We found patients with gnAChR antibodies in FD and IBS patients. These data will be valuable for elucidating the pathophysiology of these FGIDs and developing new treatment strategies.

P026 Neurofascin antibodies complicating a case of severe systemic lupus erythematosus

Abstract Background/Aims Juvenile-onset systemic lupus erythematosus (jSLE) is an autoimmune disease that results in increased disease activity and damage compared to adult-onset SLE. There is increased medication burden, severe organ manifestations and higher incidence of renal, cardiovascular and neuropsychiatric (NP) involvement. Anti-nervous system (NS) antibodies are seen across immune mediated diseases including SLE. Myelin oligodendrocyte glycoprotein (MOG) and neurofascin (NF) 186 antibodies are particularly associated with higher frequencies of NP-SLE. These patients can present with the distinct clinical phenotype associated with that antibody (i.e., demyelination with MOG, neuropathy with NF186). Methods We present an SLE patient with progressive neurological features and anti-NF antibodies who responds well to ocrelizumab after modest response to initial immunotherapy. Results An 18 year old female has active jSLE including malar rash, alopecia, arthralgia, aphthous ulcers, headaches. She presents with lower limb and ascending abdominal paraesthesia and left 6th cranial nerve palsy alongside a recent respiratory tract infection. ANA 1:5120 homogenous pattern, high dsDNA, low C3 and C4, thrombocytopenia and antibodies to Sm, Ro, RNP, anti-Rib-P and strongly positive lupus anticoagulant antibodies and low titre anti-cardiolipin (aCL) IgG and IgM. Lumbar puncture is unremarkable. Nerve conduction studies (NCS) demonstrate progressive predominant motor inflammatory neuropathy without demyelination. CT, MRI brain and MRI spine are normal. She is treated as atypical Guillain-Barre Syndrome (GBS)/ Miller-Fischer with 5 days IV immunoglobulin 2g/kg and also for active SLE with 3 days 500mg IV methylprednisolone. She is intubated following worsening dysphagia, dysarthria, muscle weakness and reduced consciousness. Plasma exchange and pulsed cyclophosphamide are subsequently given. Eye and facial movements worsen with NCS showing worsening patchy axonal sensorimotor polyneuropathy. Serial MRI brain is suggestive of posterior reversible encephalopathy syndrome (PRES). Autonomic instability is seen with labile blood pressure and tachycardia. Given the unusual presentation, anti-NF antibodies are tested and identified at 1:3200 positive, NF155 and 186, both IgG1 and IgG2. Given previous adverse reaction to rituximab, she received ocrelizumab which lead to a marked improvement in her sensorimotor symptoms and functionality. C3 and C4 levels show considerable improvement which is sustained and dsDNA levels normalise. B cell depletion therapy was chosen following a small case series of patients with neurofascin antibodies who developed severe autoimmune neuropathies. Half of these patients responded well to rituximab. One proposed mechanism being the targeting of immature CD20+ B cells inhibits plasmablast generation, which may be responsible for neurofascin antibody production early on in the disease. Conclusion Anti-NS antibodies are seen in SLE patients and their presence can suggest increased frequency of NP-SLE suggesting a potential future role as a biomarker. One should consider anti-NF antibody testing in patients with a GBS-like illness with progressive neuropathy, respiratory involvement and autonomic dysfunction despite standard immunotherapy. Disclosure P. Yee: None. M. Mouyis: None.

Inter-laboratory comparison of routine autoantibody detection methods for autoimmune neuropathies and myasthenia gravis.

Serological tests are important to detect autoantibodies (autoAbs) in patients with autoimmune neuropathies (AN) and myasthenia gravis (MG) as they are biomarkers for diagnosis, stratification, treatment selection, and monitoring. However, tests to detect autoAbs frequently lack proper standardization and results differ across diagnostic laboratories. We compared results for tests routinely performed in Spanish diagnostic laboratories to detect AN and MG autoAbs. In the Spanish Society of Immunology Autoimmunity Group national workshop, serum samples from 13 patients with AN or MG were tested for anti-ganglioside, anti-myelin-associated glycoprotein (MAG), anti-nicotinic acetylcholine receptor (AChR), and anti-muscle-specific kinase (MuSK) autoAbs using reference methods and were distributed for analysis to 27 participating laboratories using their routine methods. Overserved were inter-laboratory variability and worryingly low sensitivity, especially for anti-ganglioside immunoglobulin G and anti-MAG autoAb detection. This pilot study reflects autoAbs detection state of the art in AN and MG testing in leading diagnostic laboratories in Spain, highlighting the need for standardization prior to clinical use.

AUTOIMMUNE OPTIC NEUROPATHY (AON) PROFILE AT OPHTHALMOLOGY OUTPATIENT CLINIC OF A TERTIARY HOSPITAL IN SURABAYA, INDONESIA

Highlights Autoimmune optic neuropathy (AON) is one of the diseases that involve the central nervous system (CNS) and can result in disability if not treated quickly and appropriately. The autoimmune optic neuropathy (AON) patient’s profile, including disease etiology and therapy, is essential to minimize the incidence of AON. Abstract Background: Autoimmune optic neuropathy (AON) is a kind of optic neuritis that causes progressive and severe vision loss. The presence of an autoimmune disease usually characterizes the diagnosis of this disease. Several autoimmune processes that can cause AON are Multiple Sclerosis (MS), Neuromyelitis Optica Spectrum Disorder (NMOSD), Myelin Oligodendrocyte Glycoprotein Immunoglobulin (MOG-IgG), and other disorders, specifically systemic autoimmune disease, such as Systemic Lupus Erythematous (SLE), Sjogren’s Syndrome, and Sarcoidosis. Risk factors for AON involve young adults and women. Most of the patients received therapy according to the ONTT protocol and underwent outpatient treatment with oral methylprednisolone or prednisone. Objective: The study aimed to obtain the autoimmune optic neuropathy (AON) profile in patients at the Ophthalmology Outpatient Installation of Dr. Soetomo General Academic Hospital Surabaya, Indonesia, in the 2017-2022 Period. Material and Method: This retrospective descriptive study used medical records; 70 subjects were included. Result: Most subjects suffered from SLE (55.7%) as the cause of AON and received therapy according to the ONTT protocol, namely oral methylprednisolone or prednisone (67.1%) with outpatient therapy. Some patients were given other therapies (25.7%), such as mecobalamin and other B complex vitamins. Conclusion: AON is an uncommon condition. However, if not treated promptly and effectively, it can result in handicaps. This study may serve as a reference for future relevant research and as an attempt to prevent the disease.

Chapter 16 - Focal inflammatory neuropathies

This chapter focuses on neuropathies that present with focal involvement of nerve roots, plexus, and/or peripheral nerves associated with autoimmune and inflammatory mechanisms that present with focal involvement of nerve roots, plexus and/or peripheral nerves. The clinical presentation, diagnosis, and treatment of focal autoimmune demyelinating neuropathies, focal nonsystemic vasculitic disorders (diabetic and nondiabetic radiculoplexus neuropathies, postsurgical inflammatory neuropathy, and neuralgic amyotrophy), and focal neuropathies associated with sarcoidosis and bacterial and viral infections are reviewed.

Management of chronic inflammatory demyelinating polyradiculoneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is the most common chronic autoimmune neuropathy. Its management has considerably evolved over the last decade. In 2021, the diagnostic guidelines for CIDP were updated and the diagnostic criteria simplified. They enable better characterization of the electro-clinical phenotype of the disease, and emphasize supportive criteria, in particular neuro-muscular imaging. In terms of pathophysiology, the discovery of antibodies directed against antigens in the nodal and paranodal regions has given rise to the concept of autoimmune nodopathy. Finally, the preliminary results of the ADHERE study on efgartigimod have rekindled hopes of a new, effective therapy for CIDP.

The molecular mimicry and COVID-19

A significant part of the complications of COVID-19 and manifestations of post-COVID syndrome is associated with autoimmune reactions caused by SARS-CoV-2. The key mechanism for enabling autoimmunity in COVID-19 results from molecular mimicry, which is involved in developing cytokine storm, systemic multiorgan hyperinflammation, endothelial dysfunction, also being a trigger for arising post-COVID-19 autoimmune diseases (autoimmune thrombocytopenia, autoimmune vasculitis, Guillain–Barrésyndrome, Miller–Fisher syndrome, autoimmune neuropathy, autoimmune thyroiditis, rheumatoid arthritis, etc.). Overall, there have been identified 59 common immune determinants in 80 epitopes of the SARS-CoV-2 spike protein and 53 anti-inflammatory proteins, receptors regulating cell proliferation, differentiation and apoptosis as well as immune response. It was found that among the 37 viral proteins, only 8 of them bear no immunogenic regions identical to human proteins. Cross-reactivity results in emergence of more than 15 distinct types of autoantibodies including antiphospholipid antibodies against cardiolipin and beta-2-glycoprotein I, antibodies specific to transmembrane adenosine receptor A2b, adiponectin, phosphatidylserine-prothrombin, antinuclear antigens, mitochondrial M2, type I interferons, and other cytokines, chemokines, complement components and cell membrane proteins. Autoantibodies formed during COVID-19 react to antigens of cells located in the thyroid gland, cardiac and skeletal muscles, lung, joints, liver, kidneys, brain and bone marrow, peripheral nervous system, skin and adipose tissue, gastrointestinal tract, testicles, eyes as well as mitochondrial antigens, mediating development of severe disease-related complications and post-COVID syndrome. The presence of 24 homologous pentapeptides with those found inB. pertussis, C. diphtheriae,C. tetani,H. influenzaeandN. meningitidisposes a risk of developing ineffective vaccination immune response paralleled with higher risk of autoimmune complications. It is imperative to take into account the phenomenon of molecular mimicry while proposing new approaches for rehabilitation and treatment of COVID-19 as well as in development and testing of vaccines against SARS-CoV-2.

Editorial: Biomarkers in the diagnosis, prognosis, and prediction of autoimmune and hereditary optic neuropathies

Editorial: Biomarkers in the diagnosis, prognosis, and prediction of autoimmune and hereditary optic neuropathies

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

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

Autoimmune Axonal Neuropathies.

This article reviews autoimmune axonal neuropathies, their characteristic clinical features, disease and antibody associations, appropriate ancillary testing, treatment, and prognosis. In 2021, the American College of Rheumatology and the Vasculitis Foundation released new summary guidelines for the treatment of antineutrophil cytoplasmic autoantibody-associated vasculitides. In addition, novel autoantibodies have been recently identified; they are often paraneoplastic and associated with axonal neuropathies. Recognition of autoimmune axonal neuropathies is important because of the potential for effective treatment to either reverse deficits or slow the progression of disease. It is necessary to properly assess for associations with other systemic disorders (eg, systemic vasculitis, connective tissue disease, neoplasm) so that adequate treatment for both neurologic and non-neurologic aspects of the disease can be initiated.

2,4-Dinitrophenol does not exert neuro-regenerative potential in experimental autoimmune neuritis

ObjectiveWe evaluated the potential neuro-regenerative effects of the mitochondrial uncoupler 2,4-Dinitrophenol in experimental autoimmune neuritis, an animal model for an acute autoimmune neuropathy. MethodsExperimental autoimmune neuritis was induced in Lewis rats. Different concentrations of 2,4-Dinitrophenol (1 mg/kg, 0.1 mg/kg and 0.01 mg/kg) were applied during the recovery phase of the neuritis (at days 18, 22 and 26) and compared to the vehicle. Any effects were assessed through functional, electrophysiological, and morphological analysis via electron microscopy of all groups at day 30. Additional immune-histochemical analysis of inflammation markers and remyelination of the sciatic nerves were performed for the dosage of 1 mg/kg and control. ResultsNo enhancement of functional or electrophysiological recovery was observed in all 2,4-Dinitrophenol-treated groups. Cellular inflammation markers of T cells (CD3+) were comparable to control, and an increase of macrophages (IbA1+) invasion in the sciatic nerves was observed. Treatment with 2,4-Dinitrophenol reduced axonal swelling in myelinated and unmyelinated fibers with an increased production of brain-derived neurotrophic factor. ConclusionOur findings do not support the hypothesis that repurposing of the mitochondrial uncoupler 2,4-Dinitrophenol exerts functionally relevant neuro-regenerative effects in autoimmune neuritis.

Disease activity in chronic inflammatory demyelinating polyneuropathy: association between circulating B-cell subsets, cytokine levels, and clinical outcomes.

Chronic inflammatory demyelinating polyneuropathy (CIDP), a common and treatable autoimmune neuropathy, is frequently misdiagnosed. The aim of this study is to evaluate the relationship between immunological markers and clinical outcome measures in a mixed cohort of patients with typical CIDP and CIDP variants at different disease stages. Twenty-three typical, 16 multifocal and five distal CIDP patients were included. Twenty-five sex and age-matched healthy controls and 12 patients with Charcot-Marie-Tooth type 1A (CMT1A) disease served as controls. Peripheral B-cell populations were analyzed by flow cytometry. IL6, IL10, TNFA mRNA and mir-21, mir-146a, and mir-155-5p expression levels were evaluated by real-time polymerase chain reaction in peripheral blood mononuclear cells (PBMC) and/or skin biopsy specimens. Results were then assessed for a possible association with clinical disability scores and intraepidermal nerve fiber densities (IENFD) in the distal leg. We detected a significant reduction in naive B cells (P ≤ 0.001), plasma cells (P ≤ 0.001) and regulatory B cells (P < 0.05), and an elevation in switched memory B cells (P ≤ 0.001) in CIDP compared to healthy controls. CMT1A and CIDP patients had comparable B-cell subset distribution. CIDP cases had significantly higher TNFA and IL10 gene expression levels in PBMC compared to healthy controls (P < 0.05 and P ≤ 0.01, respectively). IENFDs in the distal leg showed a moderate negative correlation with switched memory B-cell ratios (r = -0.51, P < 0.05) and a moderate positive correlation with plasma cell ratios (r = 0.46, P < 0.05). INCAT sum scores showed a moderate positive correlation with IL6 gene expression levels in PBMC (r = 0.54, P < 0.05). Altered B-cell homeostasis and IL10 and TNFA gene expression levels imply chronic antigen exposure and overactivity in the humoral immune system, and seem to be a common pathological pathway in both typical CIDP and CIDP variants.

Anti-myelin-associated glycoprotein neuropathy: Where do we stand?

Myelin-associated glycoprotein (MAG) is a transmembrane glycoprotein concentrated in periaxonal Schwann cell and oligodendroglial membranes of myelin sheaths that serves as an antigen for immunoglobulin M (IgM) monoclonal antibodies. Individuals who harbor anti-MAG antibodies classically develop a progressive autoimmune peripheral neuropathy characterized clinically by ataxia, distal sensory loss, and gait instability, and electrophysiologically by distally accentuated conduction velocity slowing. Although off-label immunotherapy is common, there are currently no proven effective disease-modifying therapeutics, and most patients experience slow accumulation of disability over years and decades. The typically slowly progressive nature of this neuropathy presents unique challenges when trying to find effective anti-MAG therapeutic agents. Drug development has also been hampered by the lack of validated outcome measures that can detect clinically meaningful changes in a reasonable amount of time as well as by the lack of disease activity biomarkers. In this invited review, we provide an update on the state of clinicometric outcome measures and disease activity biomarkers in anti-MAG neuropathy. We highlight the insensitivity of widely used existing clinicometric outcome measures such as the Inflammatory Neuropathy Cause and Treatment (INCAT) disability score as well as the INCAT sensory subscore in anti-MAG neuropathy, referencing the two previous negative randomized controlled clinical trials evaluating rituximab. We then discuss newly emerging candidate therapeutic agents, including tyrosine kinase inhibitors and enhanced B-cell-depleting agents, among others. We conclude with a practical approach to the evaluation and management of anti-MAG neuropathy patients.

Clinical course features of atypical demyelinating optic neuritis: case series

Optic neuritis (ON) can often occur at the onset of a demyelinating autoimmune CNS disease or as one of its clinical manifestations. The introduction of novel laboratory techniques, technical advances in magnetic resonance imaging (MRI), electrophysiologic studies, and ocular imaging have significantly expanded the spectrum of autoimmune optic neuropathies. Identification of different forms of ON based on clinical and instrumental data can lead to early diagnosis of the underlying neurologic disorder. According to current guidelines, one can distinguish between typical ON, which are mainly associated with multiple sclerosis (MS), and atypical ON, which are the main clinical manifestation of neuromyelitis optica spectrum disorders (NMOSD) and diseases associated with myelin oligodendrocyte glycoprotein antibodies (MOGAD). In this paper, we present four clinical cases of atypical ON at the onset of NMOSD and MOGAD and illustrate the high diagnostic value of a multidisciplinary approach.

An update on optic neuritis.

Optic neuritis (ON) is the most common cause of subacute optic neuropathy in young adults. Although most cases of optic neuritis (ON) are classified as typical, meaning idiopathic or associated with multiple sclerosis, there is a growing understanding of atypical forms of optic neuritis such as antibody mediated aquaporin-4 (AQP4)-IgG neuromyelitis optica spectrum disorder (NMOSD) and the recently described entity, myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD). Differentiating typical ON from atypical ON is important because they have different prognoses and treatments. Findings of atypical ON, including severe vision loss with poor recovery with steroids or steroid dependence, prominent optic disc edema, bilateral vision loss, and childhood or late adult onset, should prompt serologic testing for AQP4-IgG and MOG-IgG. Although the traditional division of typical and atypical ON can be helpful, it should be noted that there can be severe presentations of otherwise typical ON and mild presentations of atypical ON that blur these traditional lines. Rare causes of autoimmune optic neuropathies, such as glial fibrillary acidic protein (GFAP) and collapsin response-mediator protein 5 (CRMP5) autoimmunity also should be considered in patients with bilateral painless optic neuropathy associated with optic disc edema, especially if there are other accompanying suggestive neurologic symptoms/signs. Typical ON usually recovers well without treatment, though recovery may be expedited by steroids. Atypical ON is usually treated with intravenous steroids, and some forms, such as NMOSD, often require plasma exchange for acute attacks and long-term immunosuppressive therapy to prevent relapses. Since treatment is tailored to the cause of the ON, elucidating the etiology of the ON is of the utmost importance.