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Background and Aims: Chronic inflammatory demyelinating polyneuropathy (CIDP) is a rare immune-mediated disease of the peripheral nerves, with significant unmet treatment needs. Clinical trials in CIDP are challenging; thus, new trial designs are needed. We present design of an open-label phase 2 study (NCT04658472) evaluating efficacy and safety of SAR445088, a monoclonal antibody targeting complement C1s, in CIDP. Methods: This phase 2, proof-of-concept, multicenter, open-label trial will evaluate the efficacy, and safety of SAR445088 in 90 patients with CIDP across three groups: (1) currently treated with standard-of-care (SOC) therapies, including immunoglobulin or corticosteroids (SOC-Treated); (2) refractory to SOC (SOC-Refractory); and (3) naïve to SOC (SOC-Naïve). Enrolled participants undergo a 24-week treatment period (part A), followed by an optional treatment extension for up to an additional 52 weeks (part B). In part A, the primary endpoint for the SOC-Treated group is the percentage of participants with a relapse after switching from SOC to SAR445088. The primary endpoint for the SOC-Refractory and SOC-Naïve groups is the percentage of participants with a response, compared to baseline. Secondary endpoints include safety, tolerability, immunogenicity, and efficacy of SAR445088 during 12-week overlapping period (SOC-Treated). Part B evaluates long-term safety and durability of efficacy. Data analysis will be performed using Bayesian statistics (predefined efficacy thresholds) and historical data-based placebo assumptions to support program decision-making. Interpretation: This innovative trial design based on patient groups and Bayesian statistics provides an efficient paradigm to evaluate new treatment candidates across the CIDP spectrum and can help accelerate development of new therapies.

Lleixa and Caballero-avila et al. report that antibodies targeting the flotillin-1/2 complex are present in a subgroup of patients with multiple sclerosis. Further studies are needed to understand the clinical and pathological relevance of anti-flotillin-1/2 autoantibodies in multiple sclerosis. Multiple sclerosis is a tissue-specific autoimmune disease of the central nervous system in which the antigen(s) remains elusive. Antibodies targeting the flotillin-1/2 complex have been described in 1-2% of the patients in a recent study. Other candidate antigens as anoctamin-2 or neurofascin-155 have been previously described in multiple sclerosis patients, although their clinical relevance remains uncertain. Our study aims to analyse the frequency and clinical relevance of antibodies against neurofascin-155, anoctamin-2 and flotillin-1/2 complex in multiple sclerosis. Serum (n = 252) and CSF (n = 50) samples from 282 multiple sclerosis patients were included in the study. The control group was composed of 260 serum samples (71 healthy donors and 189 with other neuroinflammatory disorders). Anti-flotillin-1/2, anti-anoctamin-2 and anti-neurofascin-155 antibodies were tested by cell-based assays using transfected cells. We identified six multiple sclerosis patients with antibodies against the flotillin-1/2 complex (2.1%) and one multiple sclerosis patient with antibodies against anoctamin-2 (0.35%). All multiple sclerosis patients were negative for anti-neurofascin-155 antibodies. Three of the anti-flotillin-1/2 positive patients showed anti-flotillin-1/2 positivity in other serum samples extracted at different moments of their disease. Immunoglobulin G subclasses of anti-flotillin-1/2 antibodies were predominantly one and three. We confirm that antibodies targeting the flotillin-1/2 complex are present in a subgroup of patients with multiple sclerosis. Further studies are needed to understand the clinical and pathological relevance of anti-flotillin-1/2 autoantibodies in multiple sclerosis.

Background and ObjectivesRecent outbreaks of Zika virus (ZIKV) in South and Central America have highlighted significant neurologic side effects. Concurrence with the inflammatory neuropathy Guillain-Barré syndrome (GBS) is observed in 1:4,000 ZIKV cases. Whether the neurologic symptoms of ZIKV infection are immune mediated is unclear. We used rodent and human live cellular models to screen for anti-peripheral nerve reactive IgG and IgM autoantibodies in the sera of patients with ZIKV with and without GBS.MethodsIn this study, 52 patients with ZIKV-GBS were compared with 134 ZIKV-infected patients without GBS and 91 non-ZIKV controls. Positive sera were taken forward for target identification by immunoprecipitation and mass spectrometry, and candidate antigens were validated by ELISA and cell-based assays. Autoantibody reactions against glycolipid antigens were also screened on an array.ResultsOverall, IgG antibody reactivities to rat Schwann cells (SCs) (6.5%) and myelinated cocultures (9.6%) were significantly higher, albeit infrequent, in the ZIKV-GBS group compared with all controls. IgM antibody immunoreactivity to dorsal root ganglia neurones (32.3%) and SCs (19.4%) was more frequently observed in the ZIKV-GBS group compared with other controls, whereas IgM reactivity to cocultures was as common in ZIKV and non-ZIKV sera. Strong axonal-binding ZIKV-GBS serum IgG antibodies from 1 patient were confirmed to react with neurofascin 155 and 186. Serum from a ZIKV-infected patient without GBS displayed strong myelin-binding and putative antilipid antigen reaction characteristics. There was, however, no significant association of ZIKV-GBS with any known antiglycolipid antibodies.DiscussionAutoantibody responses in ZIKV-GBS target heterogeneous peripheral nerve antigens suggesting heterogeneity of the humoral immune response despite a common prodromal infection.

Inflammatory neuropathies are a heterogeneous group of rare diseases of the peripheral nervous system that include acute and chronic diseases, such as Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). The etiology and pathophysiological mechanisms of inflammatory neuropathies are only partly known, but are considered autoimmune disorders in which an aberrant immune response, including cellular and humoral components, is directed towards components of the peripheral nerve causing demyelination and axonal damage. Therapy of these disorders includes broad-spectrum immunomodulatory and immunosuppressive treatments, such as intravenous immunoglobulin, corticosteroids, or plasma exchange. However, a significant proportion of patients do not respond to any of these therapies, and treatment selection is not optimized according to disease pathophysiology. Therefore, research on disease pathophysiology aiming to reveal clinically and functionally relevant disease mechanisms and the development of new treatment approaches are needed to optimize disease outcomes in CIDP and GBS. This topical review describes immunological progress that may help guide therapeutic strategies in the future in these two disorders. Supplementary Information The online version contains supplementary material available at 10.1007/s13311-021-01117-3.

Introduction: Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an immune-mediated syndrome characterized clinically by weakness and/or numbness that evolves over 2 months or more. The heterogeneity of clinical features necessitates an individualized approach to disease monitoring that takes lessons learned from clinical trials and applies them to clinical practice. Areas covered: This review discusses the importance of clinimetrics and biomarkers in CIDP diagnosis and disease monitoring. Highlighted are the challenges of defining responses to immunotherapy, the usefulness, and limitations of utilizing evidence-based clinical outcome measures during routine clinical care, and the evolving understanding of how diagnostic and disease activity biomarkers may reshape our treatment and disease monitoring paradigms. Expert opinion: Although disability and impairment outcome measures are commonly used in CIDP to indicate disease status, the nonspecific nature of these metrics limits the ability to attribute a change in any given metric to a change in CIDP. This interpretive challenge may be magnified by inconsistencies in the direction of change as well as a strong placebo effect. There is a need to improve our understanding of minimally important changes in existing outcome measures as a means to personalize treatment and to better assess disease activity status with biomarker discovery.

We describe the distinctive features (with images and video) of a case of chronic inflammatory demyelinating polyneuropathy (CIDP) with giant nerves. The main clinical findings were insidious onset, gait ataxia and sensory symptoms. Electrodiagnostic studies showed very slow nerve conduction velocities, multiple conduction blocks, distal CMAP duration increase and absence of F-waves. The protein level in the cerebrospinal fluid was very high. Nerve ultrasound showed swelling of all peripheral nerves outside entrapment sites, with significant variability within different segments of the same nerve; nerves were massively enlarged (up to 10-fold normal values). Brain MRI showed hypertrophic cranial nerves, with gadolinium-enhancement. Spinal MRI showed hypertrophy of spinal roots and cauda equine, with gadolinium enhancement. Genetic test (PMP22 duplication/deletion, Whole Exome Sequencing panel for neuropathies) resulted negative. The patient had a relapsing-remitting course and responded to immunoglobulin treatment. In CIDP with hypertrophic nerves, there is discrepancy between severe nerve hypertrophy and mild clinical symptoms. Nerve enlargement seems inversely related to nerve conduction velocity and directly correlated with disease duration, but not associated with disease severity.

Previous studies have described the clinical, serological and pathological features of patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and antibodies directed against the paranodal proteins neurofascin-155, contactin-1 (CNTN1), contactin-associated protein-1 (Caspr1), or nodal forms of neurofascin. Such antibodies are useful for diagnosis and potentially treatment selection. However, antibodies targeting Caspr1 only or the Caspr1/CNTN1 complex have been reported in few patients with CIDP. Moreover, it is unclear if these patients belong to the same pathophysiological subgroup. Using cell-based assays in routine clinical testing, we identified sera from patients with CIDP showing strong membrane reactivity when both CNTN1 and Caspr1 were co-transfected (but not when CNTN1 was transfected alone). Fifteen patients (10 male; aged between 40 and 75) with antibodies targeting Caspr1/CNTN1 co-transfected cells were enrolled for characterization. The prevalence of anti-Caspr1/CNTN1 antibodies was 1.9% (1/52) in the Sant Pau CIDP cohort, and 4.3% (1/23) in a German cohort of acute-onset CIDP. All patients fulfilled European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) definite diagnostic criteria for CIDP. Seven (47%) were initially diagnosed with Guillain-Barré syndrome due to an acute-subacute onset. Six (40%) patients had cranial nerve involvement, eight (53%) reported neuropathic pain and 12 (80%) ataxia. Axonal involvement and acute denervation were frequent in electrophysiological studies. Complete response to intravenous immunoglobulin was not observed, while most (90%) responded well to rituximab. Enzyme-linked immunosorbent assay (ELISA) and teased nerve fibre immunohistochemistry confirmed reactivity against the paranodal Caspr1/CNTN1 complex. Weaker reactivity against Caspr1 transfected alone was also detected in 10/15 (67%). Sera from 13 of these patients were available for testing by ELISA. All 13 samples reacted against Caspr1 by ELISA and this reactivity was enhanced when CNTN1 was added to the Caspr1 ELISA. IgG subclasses were also investigated by ELISA. IgG4 was the predominant subclass in 10 patients, while IgG3 was predominant in other three patients. In conclusion, patients with antibodies to the Caspr1/CNTN1 complex display similar serological and clinical features and constitute a single subgroup within the CIDP syndrome. These antibodies likely target Caspr1 primarily and are detected with Caspr1-only ELISA, but reactivity is optimal when CNTN1 is added to Caspr1 in cell-based assays and ELISA.

This special commentary refers to ‘Epidemiological and cohort study finds no association between COVID-19 and Guillain-Barré syndrome’ by Keddie et al. (doi:10.1093/brain/awaa433).

Background: The frequency of cognitive impairment (CI) reported in neuromyelitis optica spectrum disorder (NMOSD) is highly variable, and its relationship with demographic and clinical characteristics is poorly understood. We aimed to describe the cognitive profile of NMOSD patients, and to analyse the cognitive differences according to their serostatus; furthermore, we aimed to assess the relationship between cognition, demographic and clinical characteristics, and other aspects linked to health-related quality of life (HRQoL). Methods: This cross-sectional study included 41 patients (median age, 44 years; 85% women) from 13 Spanish centres. Demographic and clinical characteristics were collected along with a cognitive z-score (Rao’s Battery) and HRQoL patient-centred measures, and their relationship was explored using linear regression. We used the Akaike information criterion to model which characteristics were associated with cognition. Results: Fourteen patients (34%) had CI, and the most affected cognitive domain was visual memory. Cognition was similar in AQP4-IgG-positive and -negative patients. Gender, mood, fatigue, satisfaction with life, and perception of stigma were associated with cognitive performance (adjusted R2 = 0.396, p < 0.001). Conclusions: The results highlight the presence of CI and its impact on HRQoL in NMOSD patients. Cognitive and psychological assessments may be crucial to achieve a holistic approach in patient care.

Background and ObjectivesIgG4 autoantibodies to neurofascin-155 (Nfasc155) are associated with a subgroup of patients with chronic inflammatory demyelinating polyneuropathy (CIDP), currently named autoimmune nodopathy. We previously demonstrated that those antibodies alter conduction along myelinated axons by inducing Nfasc155 depletion and paranode destruction. In blood, IgG4 have the potency to exchange their moiety with other unrelated IgG4 through a process called Fab-arm exchange (FAE). This process results in functionally monovalent antibodies and may affect the pathogenicity of autoantibodies. Here, we examined this issue and whether FAE is beneficial or detrimental for Nfasc155 autoimmune nodopathy.MethodsThe bivalency and monospecificity of anti-Nfasc155 were examined by sandwich ELISA in 10 reactive patients, 10 unreactive CIDP patients, and 10 healthy controls. FAE was induced in vitro using reduced glutathione and unreactive IgG4, and the ratio of the κ:λ light chain was monitored. To determine the pathogenic potential of bivalent anti-Nfasc155 IgG4, autoantibodies derived from patients were enzymatically cleaved into monovalent Fab and bivalent F(ab’)2 or swapped with unreactive IgG4 and then were injected in neonatal animals.ResultsMonospecific bivalent IgG4 against Nfasc155 were detected in the serum of all reactive patients, indicating that a fraction of IgG4 have not undergone FAE in situ. These IgG4 were, nonetheless, capable of engaging into FAE with unreactive IgG4 in vitro, and this decreased the levels of monospecific antibodies and modulated the ratio of the κ:λ light chain. When injected in animals, monovalent anti-Nfasc155 Fab did not alter the formation of paranodes; by contrast, both native anti-Nfasc155 IgG4 and F(ab’)2 fragments strongly impaired paranode formation. The promotion of FAE with unreactive IgG4 also strongly diminished the pathogenic potential of anti-Nfasc155 IgG4 in animals and decreased IgG4 clustering on Schwann cells.DiscussionOur findings demonstrate that monospecific and bivalent anti-Nfasc155 IgG4 are detected in patients and that those autoantibodies are the pathogenic ones. The transformation of anti-Nfasc155 IgG4 into monovalent Fab or functionally monovalent IgG4 through FAE strongly decreases paranodal alterations. Bivalency thus appears crucial for Nfasc155 clustering and paranode destruction.

Objective: To investigate the frequency and clinical correlates of anti-nerve autoantibodies in an unselected series of Italian patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) Methods: Sera from 276 CIDP patients fulfilling the EFNS/PNS criteria and included in the Italian CIDP database were examined for the presence of anti-nerve autoantibodies. Results were correlated with the clinical data collected in the database. Results: Anti-neurofascin155 (NF155) antibodies were found in 9/258 (3.5%) patients, anti-contactin1 (CNTN1) antibodies in 4/258 (1.6%) patients, and anti-contactin-associated protein1 (Caspr1) in 1/197 (0.5%) patients, while none had reactivity to gliomedin or neurofascin 186. Predominance of IgG4 isotype was present in 7of the 9 examined patients. Anti-NF155 patients more frequently had ataxia, tremor, and higher CSF protein levels than antibody-negative patients. Anti-CNTN1 patients more frequently had a GBS-like onset, pain, and ataxia and had more severe motor impairment at enrollment than antibody-negative patients. They more frequently received plasmapheresis, possibly reflecting a less satisfactory response to IVIg or steroids. IgM antibodies against one or more gangliosides were found in 6.5% of the patients (17/260) and were more frequently directed against GM1 (3.9%). They were frequently associated with a progressive course, with a multifocal sensorimotor phenotype and less frequent cranial nerve involvement and ataxia. Conclusions: Anti-paranodal and anti-ganglioside antibodies are infrequent in patients with CIDP but are associated with some typical clinical association supporting the hypothesis that CIDP might be a pathogenically heterogeneous syndrome possibly explaining the different clinical presentations.

Background and ObjectivesEvidence regarding the safety and efficacy of messenger RNA (mRNA) vaccines in patients with myasthenia gravis (MG) after immunosuppressive therapies is scarce. Our aim is to determine whether the mRNA-1273 vaccine is safe and able to induce humoral and cellular responses in patients with MG.MethodsWe performed an observational, longitudinal, prospective study including 100 patients with MG of a referral center for MG in our country, conducted from April 2021 to November 2021 during the vaccination campaign. The mRNA-1273 vaccine was scheduled for all participants. Blood samples were collected before vaccination and 3 months after a second dose. Clinical changes in MG were measured using the MG activities of daily life score at baseline and 1 week after the first and second doses. A surveillance of all symptoms of coronavirus disease 2019 (COVID-19) was conducted throughout the study. Humoral and cellular immune responses after vaccination were assessed using a spike-antibody ELISA and interferon gamma release assay in plasma. The primary outcomes were clinically significant changes in MG symptoms after vaccination, adverse events (AEs), and seroconversion and T-cell immune response rates.ResultsNinety-nine patients completed the full vaccination schedule, and 98 had 2 blood samples taken. A statistically significant worsening of symptoms was identified after the first and second doses of the mRNA-1273 vaccine, but this was not clinically relevant. Mild AEs occurred in 14 patients after the first dose and in 21 patients after the second dose. Eighty-seven patients developed a humoral response and 72 patients showed a T-cell response after vaccination. A combined therapy with prednisone and other immunosuppressive drugs correlated with a lower seroconversion ratio (OR = 5.97, 95% CI 1.46–24.09, p = 0.015) and a lower T-cell response ratio (OR = 2.83, 95% CI 1.13–7.13, p = 0.024).DiscussionOur findings indicate that the mRNA vaccination against COVID-19 is safe in patients with MG and show no negative impact on the disease course. Patients achieved high humoral and cellular immune response levels.Classification of EvidenceThis study provides Class IV evidence that patients with MG receiving the mRNA-1273 vaccine did not show clinical worsening after vaccination and that most of the patients achieved high cellular or immune response levels.

Background and ObjectivesTo study the clinical and laboratory features of antineurofascin-155 (NF155)–positive autoimmune nodopathy (AN).MethodsPatients with anti-NF155 antibodies detected on routine immunologic testing were included. Clinical characteristics, treatment response, and functional scales (modified Rankin Scale [mRS] and Inflammatory Rasch-built Overall Disability Scale [I-RODS]) were retrospectively collected at baseline and at the follow-up. Autoantibody and neurofilament light (NfL) chain levels were analyzed at baseline and at the follow-up.ResultsForty NF155+ patients with AN were included. Mean age at onset was 42.4 years. Patients presented with a progressive (75%), sensory motor (87.5%), and symmetric distal-predominant weakness in upper (97.2%) and lower extremities (94.5%), with tremor and ataxia (75%). Patients received a median of 3 (2–4) different treatments in 46 months of median follow-up. Response to IV immunoglobulin (86.8%) or steroids (72.2%) was poor in most patients, whereas 77.3% responded to rituximab. HLA-DRB1*15 was detected in 91.3% of patients. IgG4 anti-NF155 antibodies were predominant in all patients; anti-NF155 titers correlated with mRS within the same patient (r = 0.41, p = 0.004). Serum NfL (sNfL) levels were higher in anti-NF155+ AN than in healthy controls (36.47 vs 7.56 pg/mL, p < 0.001) and correlated with anti-NF155 titers (r = 0.43, p = 0.001), with I-RODS at baseline (r = −0.88, p < 0.001) and with maximum I-RODS achieved (r = −0.58, p = 0.01). Anti-NF155 titers and sNfL levels decreased in all rituximab-treated patients.DiscussionAnti-NF155 AN presents a distinct clinical profile and good response to rituximab. Autoantibody titers and sNfL are useful to monitor disease status in these patients. The use of untagged-NF155 plasmids minimizes the detection of false anti-NF155+ cases.Classification of EvidenceThis study provides Class IV evidence that anti-NF155 antibodies associate with a specific phenotype and response to rituximab.

Background and ObjectivesAn important challenge in diagnosing anti–NMDA receptor (NMDAR) encephalitis (NMDARe) is differentiating it from a first episode of psychosis (FEP) caused by a psychiatric disease (pFEP). CSF antibody testing distinguishes these diseases, but spinal taps are difficult to obtain in psychiatric facilities. A separate problem is the lack of biomarkers of NMDARe severity and outcome. Here we assessed the performance of neurofilament light chain (NfL) testing in these settings.MethodsIn this observational study, NfL levels were determined with single-molecule array in patients with NMDARe, pFEP, herpes simplex encephalitis (HSE), and healthy participants (HC), with the last 2 groups used as controls. Receiver operating characteristic (ROC) analyses were performed to assess the prediction accuracy of serum NfL (sNfL) levels for NMDARe and pFEP and to obtain clinically useful cutoffs.ResultsOne hundred eighteen patients with NMDARe (33 with isolated psychosis at presentation), 45 with pFEP, 36 with HSE, and 36 HC were studied. Patients with NMDARe with seizures/status epilepticus, intensive care unit admission, and CSF pleocytosis (>20 white blood cells/µL) and without early immunotherapy were more likely to have higher NfL (mainly in CSF) than individuals with NMDARe without these features. NfL levels at diagnosis of NMDARe did not correlate with outcome at 1-year follow-up assessed with the modified Rankin Scale. Patients with NMDARe had significantly higher sNfL than individuals with pFEP and HC and lower sNfL than patients with HSE. ROC analysis of sNfL between NMDARe with isolated psychosis and pFEP provided an area under the curve of 0.93 (95% CI 0.87–0.99) and an sNfL cutoff ≥15 pg/mL to distinguish these disorders (sensitivity 85%, specificity 96%, positive likelihood ratio 19.3). Forty-three of 45 (96%) patients with pFEP had sNfLp < 0.001). None of the patients with HSE and 35 of 36 (97%) HC had sNfLDiscussionNfL measured at diagnosis of NMDARe associated with features of disease severity but not with long-term outcome. Young patients with FEP and sNfL ≥15 pg/mL had a 120 times higher chance of having NMDARe than those with pFEP. This cutoff correctly classified 96% of patients with pFEP and 85% of patients with NMDARe with isolated psychosis. Patients with FEP of unclear etiology and sNfL ≥15 pg/mL should undergo CSF NMDAR antibody testing.

International audience; Background: Ofatumumab, a subcutaneous anti-CD20 monoclonal antibody, selectively depletes B cells. Teriflunomide, an oral inhibitor of pyrimidine synthesis, reduces T-cell and B-cell activation. The relative effects of these two drugs in patients with multiple sclerosis are not known.Methods: In two double-blind, double-dummy, phase 3 trials, we randomly assigned patients with relapsing multiple sclerosis to receive subcutaneous ofatumumab (20 mg every 4 weeks after 20-mg loading doses at days 1, 7, and 14) or oral teriflunomide (14 mg daily) for up to 30 months. The primary end point was the annualized relapse rate. Secondary end points included disability worsening confirmed at 3 months or 6 months, disability improvement confirmed at 6 months, the number of gadolinium-enhancing lesions per T1-weighted magnetic resonance imaging (MRI) scan, the annualized rate of new or enlarging lesions on T2-weighted MRI, serum neurofilament light chain levels at month 3, and change in brain volume.Results: Overall, 946 patients were assigned to receive ofatumumab and 936 to receive teriflunomide; the median follow-up was 1.6 years. The annualized relapse rates in the ofatumumab and teriflunomide groups were 0.11 and 0.22, respectively, in trial 1 (difference, -0.11; 95% confidence interval [CI], -0.16 to -0.06; P

IntroductionRecent outbreaks of Zika virus (ZIKV) in South and Central America have highlighted significant neurological side effects. Concurrence with the inflammatory neuropathy Guillain-Barré syndrome (GBS) is observed in 1:4000 ZIKV cases. Whether the neurological symptoms of ZIKV infection are a consequence of autoimmunity or direct neurotoxicity is unclear.MethodsWe employed rat dorsal root ganglion (DRG) neurons, Schwann cells (SCs), and human stem cell-derived sensory neurons myelinated with rat SCs as cellular models to screen for IgG and IgM autoantibodies reactive to peripheral nerve in sera of ZIKV patients with and without GBS. In this study, 52 ZIKV-GBS patients were compared with 134 ZIKV-infected patients, and 91 non-ZIKV controls. Positive sera were taken forward for target identification by immunoprecipitation and mass spectrometry, and candidate antigens validated by ELISA and cell-based assays. Autoantibody reactions against glycolipid antigens were also screened on an array.ResultsOverall, IgG antibody reactivity to rat SCs (6.5%) and myelinated co-cultures (9.6%) were significantly higher, albeit infrequently, in the ZIKV-GBS group compared to all controls. IgM antibody immunoreactivity to DRGs (32.3%) and SCs (19.4%) was more frequently observed in the ZIKV-GBS group compared to other controls, while IgM reactivity to co-cultures was as common in ZIKV and non-ZIKV sera. Strong axonal-binding ZIKV-GBS serum IgG antibodies from one patient were confirmed to react with neurofascin-155 and 186. Serum from a ZIKV non-GBS patient displayed strong myelin-binding and anti-lipid antigen reaction characteristics. There was no significant association of ZIKV-GBS with any anti-glycolipid antibodies.ConclusionAutoantibodies in ZIKV associated GBS patients’ sera target heterogeneous peripheral nerve antigens suggesting heterogeneity of the humoral immune response despite a common prodromal infection.

ObjectiveTo investigate whether serum levels of contactin-1, a paranodal protein, correlate with paranodal injury as seen in patients with CIDP with antibodies targeting the paranodal region.MethodsSerum contactin-1 levels were measured in 187 patients with CIDP and 222 healthy controls. Paranodal antibodies were investigated in all patients.ResultsSerum contactin-1 levels were lower in patients (N = 41) with paranodal antibodies compared with patients (N = 146) without paranodal antibodies (p < 0.01) and showed good discrimination between these groups (area under the curve 0.84; 95% CI: 0.76–0.93).ConclusionsThese findings suggest that serum contactin-1 levels have the potential to serve as a possible diagnostic biomarker of paranodal injury in CIDP.Classification of EvidenceThis study provides class II evidence that serum contactin-1 levels can discriminate between patients with CIDP with or without paranodal antibodies with a sensitivity of 71% (95% CI: 56%–85%) and a specificity of 97% (95% CI: 83%–100%).

Background The assessment of self-reported outcomes in neuromyelitis optica spectrum disorder (NMOSD) is limited by the lack of validated disease-specific measures. The SymptoMScreen (SyMS) is a patient-reported questionnaire for measuring symptom severity in different domains affected by multiple sclerosis (MS), but has not been thoroughly evaluated in NMOSD. The aim of this study was to assess the psychometric properties of the SyMS in a sample of patients with NMOSD. Methods A non-interventional, cross-sectional study in adult subjects with NMOSD (Wingerchuk 2015 criteria) was conducted at 13 neuroimmunology clinics applying the SyMS. A non-parametric item response theory procedure, Mokken analysis, was performed to assess the underlying dimensional structure and scalability of items and overall questionnaire. All analyses were performed with R (v4.0.3) using the mokken library. Results A total of 70 patients were studied (mean age: 47.5 ± 15 years, 80% female, mean Expanded Disability Status Scale score: 3.0 [interquartile range 1.5, 4.5]). Symptom severity was low (median SyMS score: 19.0 [interquartile range 10.0, 32.0]). The SyMS showed a robust internal reliability (Cronbach’s alpha: 0.90 [95% confidence interval 0.86, 0.93]) and behaved as a unidimensional scale with all items showing scalability coefficients > 0.30. The overall SyMS scalability was 0.45 conforming to a medium scale according to Mokken’s criteria. Fatigue and body pain were the domains with the highest scalability coefficients. The SyMS was associated with disability (rho: 0.586), and physical and psychological quality of life (rho: 0.856 and 0.696, respectively). Conclusions The SyMS shows appropriate psychometric characteristics and may constitute a valuable and easy-to-implement option to measure symptom severity in patients with NMOSD.

Background and Aims Recently a number of antigens have been identified as pathogenic antibody targets in cases of primary membranous glomerulonephritis(MGN), including phospholipase A2 receptor (PLA2R), thrombospondin type 1 domain containing 7A(THSD7A), and NELL-1, while exostosin is found in secondary (lupus associated) MGN. However, other as yet undiscovered antigens are thought to exist. Although rare, there is a recognised association between chronic inflammatory demyelinating polyneuriopathy (CIDP) and nephrotic syndrome. Method We investigated the link between CICP and MGN and the associations with Contactin-1(CNTN1), a node of Ranvier neuronal protein, as a potential common autoantigen, by immunohistochemistry, RT-PCR and proteomic analysis of isolated glomeruli. We tested sera from 468 patients with suspected immune-mediated neuropathies, 295 with idiopathic MGN, and 210 disease controls, for CNTN1 antibodies. Results We describe a series of 16 patients, all presenting with CIDP, nephrotic syndrome due to MGN, and with circulating and deposited anti-contactin-1 (CNTN1) antibodies (IgG4 predominant in those tested) in the kidney. The onset and resolution of both disorders had a close temporal relationship, and the majority of cases were resistant to first-line therapies typically employed for inflammatory neuropathies, but achieved a good outcome with non-standard treatment. Importantly, four (1.4%) further patients with isolated MGN identified from a serum bank of 295 idiopathic MGN patients with no CIDP were also positive for anti-CNTN1 antibodies. CNTN1 protein was detected by mass spectroscopy within glomeruli from patients with CNTN1 antibodies, but not in healthy kidney or anti-PLA2R associated MGN. CNTN1 mRNA was found in renal cortical tissue. Conclusion These data provide evidence that CNTN1 antibodies precipitate both autoimmune neuropathy and MGN. The temporal correlation of these disorders, as well as the presence of CNTN1 protein and antibodies in both peripheral nerve and diseased glomeruli, supports a common antibody-mediated pathological process, and defines a new antigenic target in MGN. CNTN1 antibodies have diagnostic and therapeutic relevance, and may additionally serve as a means of monitoring disease activity in both conditions. Other factors may explain presentation with isolated neurological disease or MGN.

Jose E Meca-Lallana,1 Daniel Prefasi,2 Francisco Pérez-Miralles,3 Lucía Forero,4 María Sepúlveda,5 Carmen Calles,6 María L Martínez-Ginés,7 Inés González-Suárez,8 Sabas Boyero,9 Lucía Romero-Pinel,10 Ángel P Sempere,11 Virginia Meca-Lallana,12 Luis Querol,13 Lucienne Costa-Frossard,14 Hugo de Castro-Trapiello,2 Neus Canal,15 Jorge Maurino2 1Clinical Neuroimmunology Unit and Multiple Sclerosis CSUR. Department of Neurology. Hospital Universitario “Virgen de la Arrixaca”, IMIB-Arrixaca, Murcia, Spain; 2Medical Department, Roche Farma, Madrid, Spain; 3Unit of Neuroimmunology, Department of Neurology, Hospital Universitari i Politècnic La Fe, Valencia, Spain; 4Department of Neurology, Hospital Universitario Puerta del Mar, Cádiz, Spain; 5Department of Neurology, Hospital Clínic i Provincial de Barcelona, Barcelona, Spain; 6Department of Neurology, Hospital Universitari Son Espases, Palma de Mallorca, Spain; 7Department of Neurology, Hospital Universitario Gregorio Marañón, Madrid, Spain; 8Department of Neurology, Hospital Universitario Álvaro Cunqueiro, Vigo, Spain; 9Department of Neurology, Hospital Universitario Cruces, Bilbao, Spain; 10Department of Neurology, Hospital Universitari de Bellvitge, Barcelona, Spain; 11Department of Neurology, Hospital General Universitario de Alicante, Alicante, Spain; 12Department of Neurology, Hospital Universitario La Princesa, Madrid, Spain; 13Department of Neurology, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain; 14Department of Neurology, Hospital Universitario Ramón y Cajal, Madrid, Spain; 15Department of Statistics, IQVIA, Barcelona, SpainCorrespondence: Jorge MaurinoRoche Farma, Ribera Del Loira, 50, Madrid, 28042, SpainTel +34 913 24 81 00Email jorge.maurino@roche.comBackground: Perception of stigma was associated with low self-esteem, psychological problems, and decreased health-seeking behavior among patients with different neurological disorders. The purpose of this study was to assess stigmatization and its impact in patients with neuromyelitis optica spectrum disorder (NMOSD).Methods: A non-interventional study was conducted at thirteen neuroimmunology clinics in Spain. Patients with a diagnosis of NMOSD (2015 Wingerchuk criteria) were included. The 8-item Stigma Scale for Chronic Illness (SSCI-8), the Expanded Disability Status Scale (EDSS), the 29-item Multiple Sclerosis Impact Scale (MSIS-29), the Beck Depression Inventory-Fast Screen (BDI-FS), the MOS Pain Effects Scale (MOS-PES) and the Fatigue Impact Scale for Daily Use (D-FIS) were used to assess the perception of stigma, disability, quality of life, mood, pain, and fatigue, respectively. Associations between outcome measures were analyzed using Spearman’s rank correlation.Results: Seventy-one patients were studied (mean age: 47.4 years ± 14.9, 81.7% female, mean time since disease onset: 9.9 years ± 8.1). The median EDSS score was 3.0 (interquartile range 1.5, 4.5). Stigma prevalence was 61.4% (n=43). Thirty-one patients (43.6%) had depression. The SSCI-8 score showed a significant correlation with both physical (rho=0.576, p< 0.0001) and psychological (rho=0.608, p< 0.0001) MSIS-29 scales scores, EDSS score (rho=0.349, p=0.0033), BDI-FS score (rho= 0.613, p< 0.0001), MOS-PES score (rho= 0.457, p< 0.0001), and D-FIS score (rho=0.556, p< 0.0001).Conclusion: Stigma is a common phenomenon affecting over 6 out of 10 patients with NMOSD. Understanding stigma may be useful to develop educational strategies improving NMOSD knowledge.Keywords: neuromyelitis optica spectrum disorder, stigma, quality of life, depression, patient-reported outcomes

[Background and purpose] Prognosis of myasthenia gravis (MG) in patients with thymoma is not well established. Moreover, it is not clear whether thymoma recurrence or unresectable lesions entail a worse prognosis of MG., [Methods] This multicenter study was based on data from a Spanish neurologist-driven MG registry. All patients were aged >18 years at onset and had anti-acetylcholine receptor antibodies. We compared the clinical data of thymomatous and nonthymomatous patients. Prognosis of patients with recurrent or nonresectable thymomas was assessed., [Results] We included 964 patients from 15 hospitals; 148 (15.4%) had thymoma-associated MG. Median follow-up time was 4.6 years. At onset, thymoma-associated MG patients were younger (52.0 vs. 60.4 years, p < 0.001), had more generalized symptoms (odds ratio [OR]: 3.02, 95% confidence interval [CI]: 1.95–4.68, p < 0.001) and more severe clinical forms according to the Myasthenia Gravis Foundation of America (MGFA) scale (OR: 1.6, 95% CI: 1.15–2.21, p = 0.005). Disease severity based on MGFA postintervention status (MGFA-PIS) was higher in thymomatous patients at 1 year, 5 years, and the end of follow-up. Treatment refractoriness and mortality were also higher (OR: 2.28, 95% CI: 1.43–3.63, p = 0.001; hazard ratio: 2.46, 95% CI: 1.47–4.14, p = 0.001). Myasthenic symptoms worsened in 13 of 27 patients with recurrences, but differences in long-term severity were not significant. Fifteen thymomatous patients had nonresectable thymomas with worse MGFA-PIS and higher mortality at the end of follow-up., [Conclusions] Thymoma-associated MG patients had more severe myasthenic symptoms and worse prognosis. Thymoma recurrence was frequently associated with transient worsening of MG, but long-term prognosis did not differ from nonrecurrent thymoma. Patients with nonresectable thymoma tended to present severe forms of MG., This work is supported by Fondo de Investigaciones Sanitarias (FIS) grant FIS19/01774, Instituto de Salud Carlos III and cofunded by the European Union (ERDF/ESF, A Way to Make Europe/Investing in Your Future). Rodrigo Álvarez-Velasco was supported by a PhD for Medical Doctors grant from the Pla Estratègic de Recerca i Innovació en Salut (PERIS), Generalitat de Catalunya (SLT008/18/00207). Elena Cortés-Vicente was supported by a Juan Rodés grant (JR19/00037) from the Fondo de Investigación en Salud, Instituto de Salud Carlos III, Ministry of Health (Spain).

Objective: To revise the 2010 consensus guideline on chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Methods: Seventeen disease experts, a patient representative, and two Cochrane methodologists constructed 12 Population/Intervention/Comparison/Outcome (PICO) questions regarding diagnosis and treatment to guide the literature search. Data were extracted and summarized in GRADE summary of findings (for treatment PICOs) or evidence tables (for diagnostic PICOs). Results: Statements were prepared according to the GRADE Evidence-to-Decision frameworks. Typical CIDP and CIDP variants were distinguished. The previous term “atypical CIDP” was replaced by “CIDP variants” because these are well characterized entities (multifocal, focal, distal, motor, or sensory CIDP). The levels of diagnostic certainty were reduced from three (definite, probable, possible CIDP) to only two (CIDP and possible CIDP), because the diagnostic accuracy of criteria for probable and definite CIDP did not significantly differ. Good Practice Points were formulated for supportive criteria and investigations to be considered to diagnose CIDP. The principal treatment recommendations were: (a) intravenous immunoglobulin (IVIg) or corticosteroids are strongly recommended as initial treatment in typical CIDP and CIDP variants; (b) plasma exchange is strongly recommended if IVIg and corticosteroids are ineffective; (c) IVIg should be considered as first-line treatment in motor CIDP (Good Practice Point); (d) for maintenance treatment, IVIg, subcutaneous immunoglobulin or corticosteroids are recommended; (e) if the maintenance dose of any of these is high, consider either combination treatments or adding an immunosuppressant or immunomodulatory drug (Good Practice Point); and (f) if pain is present, consider drugs against neuropathic pain and multidisciplinary management (Good Practice Point).

Altres ajuts: Fondo Europeo de Desarrollo Regional (FEDER); Generalitat Valenciana (PROMETEO/2018/135, PROMETEO/2019/075). IIB Background and purpose: MORC2 mutations have been described as a rare cause of axonal Charcot-Marie-Tooth disease (CMT2Z). The aim of this work was to determine the frequency and distribution of these mutations throughout Spain, to provide a comprehensive phenotypical description and, if possible, to establish a genotype-phenotype correlation. Methods: Retrospectively, data on patients diagnosed with CMT2Z in Spain were collected and clinical, electrophysiological and muscle imaging information were analysed. Results: Fifteen patients with CMT2Z were identified throughout Spain, seven of them belonging to a single kindred, whilst the rest were sporadic. The most common mutation was p.R252W, and four new mutations were identified. Eleven patients were categorized as having a scapuloperoneal phenotype, with asymmetric muscle weakness, early proximal upper limb involvement and frequent spontaneous muscular activity with distal sensory impairment and pes cavus, whilst two presented with a more classic length dependent sensory motor phenotype. This distinction was corroborated by the distribution of muscle fatty infiltration in muscle imaging. Two other patients were classified as having a neurodevelopmental phenotype consisting in congenital or early onset, delay in motor milestones, and global developmental delay in one of them. Nerve conduction studies revealed an unequivocally axonal neuropathy with frequent spontaneous activity, and serum creatine kinase levels were increased in 50% of the patients. Conclusions: MORC2 mutations are a rare cause of CMT in Spain, but in-depth phenotyping reveals a recognizable phenotypic spectrum that will be clinically relevant for future identification of this disease.

Background Guillain-Barre syndrome (GBS) is an acute inflammatory neuropathy with a heterogeneous presentation. Although some evidences support the role of autoantibodies in its pathogenesis, the target antigens remain unknown in a substantial proportion of GBS patients. The objective of this study is to screen for autoantibodies targeting peripheral nerve components in Guillain-Barre syndrome. Methods Autoantibody screening was performed in serum samples from all GBS patients included in the International GBS Outcome study by 11 different Spanish centres. The screening included testing for anti-ganglioside antibodies, anti-nodo/paranodal antibodies, immunocytochemistry on neuroblastoma-derived human motor neurons and murine dorsal root ganglia (DRG) neurons, and immunohistochemistry on monkey peripheral nerve sections. We analysed the staining patterns of patients and controls. The prognostic value of anti-ganglioside antibodies was also analysed. Results None of the GBS patients (n = 100) reacted against the nodo/paranodal proteins tested, and 61 (61%) were positive for, at least, one anti-ganglioside antibody. GBS sera reacted strongly against DRG neurons more frequently than controls both with IgG (6% vs 0%; p = 0.03) and IgM (11% vs 2.2%; p = 0.02) immunodetection. No differences were observed in the proportion of patients reacting against neuroblastoma-derived human motor neurons. Reactivity against monkey nerve tissue was frequently detected both in patients and controls, but specific patterns were only detected in GBS patients: IgG from 13 (13%) patients reacted strongly against Schwann cells. Finally, we confirmed that IgG anti-GM1 antibodies are associated with poorer outcomes independently of other known prognostic factors. Conclusion Our study confirms that (1) GBS patients display a heterogeneous repertoire of autoantibodies targeting nerve cells and structures; (2) gangliosides are the most frequent antigens in GBS patients and have a prognostic value; (3) further antigen-discovery experiments may elucidate other potential antigens in GBS.

ObjectiveTo study baseline serum neurofilament light chain (sNfL) levels as a prognostic biomarker in Guillain-Barré syndrome (GBS).MethodsWe measured NfL in serum (98 samples) and cerebrospinal fluid (CSF) (24 samples) of patients with GBS prospectively included in the International GBS Outcome Study (IGOS) in Spain using single-molecule array (SiMoA) and compared them with 53 healthy controls (HCs). We performed multivariable regression to analyse the association between sNfL levels and functional outcome at 1 year.ResultsPatients with GBS had higher NfL levels than HC in serum (55.49 pg/mL vs 9.83 pg/mL, p319 pg/mL), inability to run (>248 pg/mL) and ability to run (ConclusionBaseline sNfL levels are increased in patients with GBS, are associated with disease severity and axonal variants and have an independent prognostic value in patients with GBS.

Background Chronic inflammatory demyelinating polyneuropathy (CIDP) is a rare neurological disorder characterised by muscle weakness and impaired sensory function. The present study provides a comprehensive literature review of the burden of illness of CIDP. Methods Systematic literature search of PubMed, Embase, and key conferences in May 2019. Search terms identified studies on the epidemiology, humanistic burden, current treatment, and economic burden of CIDP published since 2009 in English. Results Forty-five full texts and nineteen conference proceedings were identified on the epidemiology (n = 9), humanistic burden (n = 7), current treatment (n = 40), and economic burden (n = 8) of CIDP. Epidemiological studies showed incidence and prevalence of 0.2–1.6 and 0.8–8.9 per 100,000, respectively, depending on geography and diagnostic criteria. Humanistic burden studies revealed that patients experienced physical and psychosocial burden, including impaired physical function, pain and depression. Publications on current treatments reported on six main types of therapy: intravenous immunoglobulins, subcutaneous immunoglobulins, corticosteroids, plasma exchange, immunosuppressants, and immunomodulators. Treatments may be burdensome, due to adverse events and reduced independence caused by treatment administration setting. In Germany, UK, France, and the US, CIDP economic burden was driven by direct costs of treatment and hospitalisation. CIDP was associated with indirect costs driven by impaired productivity. Conclusions This first systematic review of CIDP burden of illness demonstrates the high physical and psychosocial burden of this rare disease. Future research is required to fully characterise the burden of CIDP, and to understand how appropriate treatment can mitigate burden for patients and healthcare systems.

• International CIDP registries were compared to assess infrastructure and collected clinical data, diagnostic data and biomaterials to enhance future research and improve standards of care in CIDP.

Objectives We aimed to define the clinical and serological characteristics of pan-neurofascin antibody-positive patients. Methods We tested serum from patients with suspected immune-mediated neuropathies for antibodies directed against nodal/paranodal protein antigens using a live cell-based assay and solid-phase platform. The clinical and serological characteristics of antibody-positive and seronegative patients were then compared. Sera positive for pan-neurofascin were also tested against live myelinated human stem cell-derived sensory neurons for antibody binding. Results Eight patients with IgG1-subclass antibodies directed against both isoforms of the nodal/paranodal cell adhesion molecule neurofascin were identified. All developed rapidly progressive tetraplegia. Cranial nerve deficits (100% vs 26%), autonomic dysfunction (75% vs 13%) and respiratory involvement (88% vs 14%) were more common than in seronegative patients. Four patients died despite treatment with one or more modalities of standard immunotherapy (intravenous immunoglobulin, steroids and/or plasmapheresis), whereas the four patients who later went on to receive the B cell-depleting therapy rituximab then began to show progressive functional improvements within weeks, became seronegative and ultimately became functionally independent. Conclusions IgG1 pan-neurofascin antibodies define a very severe autoimmune neuropathy. We urgently recommend trials of targeted immunotherapy for this serologically classified patient group.

The chronic inflammatory neuropathies (CINs) are rare, very disabling autoimmune disorders that generally respond well to immune therapies such as intravenous immunoglobulin (IVIg). The most common forms of CIN are chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), multifocal motor neuropathy, and polyneuropathy associated with monoclonal gammopathy of unknown significance. The field of CIN has undergone a major advance with the identification of IgG4 autoantibodies directed against paranodal proteins in patients with CIDP. Although these autoantibodies are only found in a small subset of patients with CIDP, they can be used to guide therapeutic decision-making, as these patients have a poor response to IVIg. These observations provide proof of concept that identifying the target antigens in tissue-specific antibody-mediated autoimmune diseases is important, not only to understand their underlying pathogenic mechanisms, but also to correctly diagnose and treat affected patients. This state-of-the-art Review focuses on the role of autoantibodies against nodes of Ranvier in CIDP, a clinically relevant emerging field of research. The role of autoantibodies in other immune-mediated neuropathies, including other forms of CIN, primary autoimmune neuropathies, neoplasms, and systemic diseases that resemble CIN, are also discussed.

ObjectiveTo describe the clinical, serologic and histologic features of a cohort of patients with brachio-cervical inflammatory myopathy (BCIM) associated with systemic sclerosis (SSc) and unravel disease-specific pathophysiologic mechanisms occurring in these patients.MethodsWe reviewed clinical, immunologic, muscle MRI, nailfold videocapillaroscopy, muscle biopsy, and response to treatment data from 8 patients with BCIM-SSc. We compared cytokine profiles between patients with BCIM-SSc and SSc without muscle involvement and controls. We analyzed the effect of the deregulated cytokines in vitro (fibroblasts, endothelial cells, and muscle cells) and in vivo.ResultsAll patients with BCIM-SSc presented with muscle weakness involving cervical and proximal muscles of the upper limbs plus Raynaud syndrome, telangiectasia and/or sclerodactilia, hypotonia of the esophagus, and interstitial lung disease. Immunosuppressive treatment stopped the progression of the disease. Muscle biopsy showed pathologic changes including the presence of necrotic fibers, fibrosis, and reduced capillary number and size. Cytokines involved in inflammation, angiogenesis, and fibrosis were deregulated. Thrombospondin-1 (TSP-1), which participates in all these 3 processes, was upregulated in patients with BCIM-SSc. In vitro, TSP-1 and serum of patients with BCIM-SSc promoted proliferation and upregulation of collagen, fibronectin, and transforming growth factor beta in fibroblasts. TSP-1 disrupted vascular network, decreased muscle differentiation, and promoted hypotrophic myotubes. In vivo, TSP-1 increased fibrotic tissue and profibrotic macrophage infiltration in the muscle.ConclusionsPatients with SSc may present with a clinically and pathologically distinct myopathy. A prompt and correct diagnosis has important implications for treatment. Finally, TSP-1 may participate in the pathologic changes observed in muscle.

[Objective] To describe the characteristics of patients with very-late-onset myasthenia gravis (MG)., [Methods] This observational cross-sectional multicenter study was based on information in the neurologist-driven Spanish Registry of Neuromuscular Diseases (NMD-ES). All patients were >18 years of age at onset of MG and onset occurred between 2000 and 2016 in all cases. Patients were classified into 3 age subgroups: early-onset MG (age at onset, [Results] A total of 939 patients from 15 hospitals were included: 288 (30.7%) had early-onset MG, 227 (24.2%) late-onset MG, and 424 (45.2%) very-late-onset MG. The mean follow-up was 9.1 years (SD 4.3). Patients with late onset and very late onset were more frequently men (p < 0.0001). Compared to the early-onset and late-onset groups, in the very-late-onset group, the presence of anti–acetylcholine receptor (anti-AChR) antibodies (p < 0.0001) was higher and fewer patients had thymoma (p < 0.0001). Late-onset MG and very-late-onset MG groups more frequently had ocular MG, both at onset (, [Conclusions] Patients with MG are primarily ≥65 years of age with anti-AChR antibodies and no thymoma. Although patients with very-late-onset MG may present life-threatening events at onset, they achieve a good outcome with fewer immunosuppressants when diagnosed and treated properly.

BACKGROUND: Investigations of myelin oligodendrocyte glycoprotein (MOG) antibodies are usually focused on demyelinating syndromes, but the entire spectrum of MOG antibody-associated syndromes in children is unknown. In this study, we aimed to determine the frequency and distribution of paediatric demyelinating and encephalitic syndromes with MOG antibodies, their response to treatment, and the phenotypes associated with poor prognosis. METHODS: In this prospective observational study, children with demyelinating syndromes and with encephalitis other than acute disseminated encephalomyelitis (ADEM) recruited from 40 secondary and tertiary centres in Spain were investigated for MOG antibodies. All MOG antibody-positive cases were included in our study, which assessed syndromes, treatment and response to treatment (ie, number of relapses), outcomes (measured with the modified Rankin scale [mRS]), and phenotypes associated with poor prognosis. We used Fisher's exact and Wilcoxon rank sum tests to analyse clinical features, and survival Cox regression to analyse time to antibody negativity. FINDINGS: Between June 1, 2013, and Dec 31, 2018, 239 children with demyelinating syndromes (cohort A) and 296 with encephalitis other than ADEM (cohort B) were recruited. 116 patients had MOG antibodies, including 94 (39%) from cohort A and 22 (7%) from cohort B; 57 (49%) were female, with a median age of 6·2 years (IQR 3·7-10·0). Presenting syndromes in these 116 patients included ADEM (46 [68%]), encephalitis other than ADEM (22 [19%]), optic neuritis (20 [17%]), myelitis (13 [11%]), neuromyelitis optica spectrum disorders (six [5%]), and other disorders (nine [8%]). Among the patients with autoimmune encephalitis in cohort B (n=64), MOG antibodies were more common than all neuronal antibodies combined (22 [34%] vs 21 [33%]). After a median follow-up of 42 months (IQR 22-67), 33 (28%) of the 116 patients had relapses, including 17 (17%) of 100 diagnosed at first episode. Steroids, intravenous immunoglobulin, or plasma exchange were used in 100 (86%) patients at diagnosis, and 32 (97%) of 33 at relapses. Rituximab was mainly used at relapses (11 [33%]). 99 (85%) of 116 patients had substantial recovery (mRS 2; one died). Phenotypes of poor prognosis included ADEM-like relapses progressing to leukodystrophy-like features, and extensive cortical encephalitis evolving to atrophy. Time to antibody negativity was longer in patients with relapses (HR 0·18, 95% CI 0·05-0·59). INTERPRETATION: The spectrum of paediatric MOG antibody-associated syndromes is wider than previously reported and includes demyelinating syndromes and encephalitis. Recognition of these disorders has important clinical and prognostic implications. FUNDING: Mutua Madrileña Foundation; ISCIII-Subdirección General de Evaluación y Fomento de la Investigación Sanitaria; Fondo Europeo de Desarrollo Regional; Pediatrics Spanish Society; Departament de Salut, Generalitat de Catalunya; Marato TV3 Foundation; Red Española de Esclerosis Múltiple; La Caixa Foundation; and Fundació CELLEX.