Excellent response to anti-CD38 therapy with daratumumab in a patient with severe refractory CANOMAD.

BACKGROUND: Intravenous immunoglobulin (IVIG) and rituximab are considered the first-line and second-line treatments for Chronic Ataxic Neuropathy and Ophthalmoplegia with IgM-paraprotein, cold Agglutinins, and anti-Disialosyl antibodies (CANOMAD), with an overall clinical response around 50%. New anti-CD38 daratumumab, targeting long-lived plasma cells, has been reported as a promising therapy for treatment-refractory antibody-mediated disorders. We report the first case of a severe refractory CANOMAD, successfully treated with daratumumab. METHODS: A patient in their 70s with severe relapsing CANOMAD, refractory to IVIG, steroids, rituximab and ibrutinib developed severe tetraparesis and respiratory failure. Plasma exchange (PE) improved motor and ventilatory function; however, after 6 weeks, patient remained PE dependent. Intravenous daratumumab was initiated at 16 mg/kg weekly for 3 weeks, every 2 weeks for the second and third month, and monthly afterwards. RESULTS: After 3 weeks of starting daratumumab, PE was discontinued and, since then, the patient evolved to complete recovery. Antidisialosyl antibody titres decreased after PE and remained stable during daratumumab. Serum neurofilament light-chain levels were elevated in the exacerbation phase and normalised after daratumumab. The patient remains in clinical remission under monthly daratumumab, 12 months after initiation. CONCLUSIONS: The first patient with aggressive treatment-refractory CANOMAD treated with daratumumab provides proof-of-principle evidence that daratumumab may be an effective treatment in IgM-related neuropathies.

Clinical relevance of distinguishing autoimmune nodopathies from CIDP: longitudinal assessment in a large cohort.

BACKGROUND: The aim of this study was to determine treatment response and whether it is associated with antibody titre change in patients with autoimmune nodopathy (AN) previously diagnosed as chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), and to compare clinical features and treatment response between AN and CIDP. METHODS: Serum IgG antibodies to neurofascin-155 (NF155), contactin-1 (CNTN1) and contactin-associated protein 1 (CASPR1) were detected with cell-based assays in patients diagnosed with CIDP. Clinical improvement was determined using the modified Rankin scale, need for alternative and/or additional treatments and assessment of the treating neurologist. RESULTS: We studied 401 patients diagnosed with CIDP and identified 21 patients with AN (10 anti-NF155, 6 anti-CNTN1, 4 anti-CASPR1 and 1 anti-NF155/anti-CASPR1 double positive). In patients with AN ataxia (68% vs 28%, p=0.001), cranial nerve involvement (34% vs 11%, p=0.012) and autonomic symptoms (47% vs 22%, p=0.025) were more frequently reported; patients with AN improved less often after intravenous immunoglobulin treatment (39% vs 80%, p=0.002) and required additional/alternative treatments more frequently (84% vs 34%, p<0.001), compared with patients with CIDP. Antibody titres decreased or became negative in patients improving on treatment. Treatment withdrawal was associated with a titre increase and clinical deterioration in four patients. CONCLUSIONS: Distinguishing CIDP from AN is important, as patients with AN need a different treatment approach. Improvement and relapses were associated with changes in antibody titres, supporting the pathogenicity of these antibodies.

Autoimmune nodopathies, an emerging diagnostic category.

PURPOSE OF REVIEW: In the last decade, antibodies targeting cell adhesion molecules of the node of Ranvier were described in patients with autoimmune neuropathies. These nodal/paranodal antibodies associate with specific clinicopathological features that are different from classical chronic inflammatory demyelinating polyneuropathy (CIDP). In this review, we will summarize recent findings establishing autoimmune nodopathies (AN) as a new category of autoimmune neuropathies. RECENT FINDINGS: AN include anti-contactin 1, anti-contactin-associated protein 1, anti-neurofascin 155 and anti-pan-neurofascin antibody-mediated neuropathies. Their clinical spectrum includes acute, subacute or chronic onset sensory-motor neuropathies mimicking Guillain-Barré syndrome (GBS) and CIDP, although they differ in their response to standard therapy with intravenous immunoglobulin (IVIG). Neurophysiologically they overlap with acquired demyelinating neuropathies, but ultrastructural studies and animal models demonstrated antibody-mediated pathology restricted to the node of Ranvier. Anti-contactin1 and anti-pan-neurofascin also associate with nephrotic syndrome. Nodal/paranodal antibodies are predominantly of the immunoglobulin (IgG)4 subclass during the chronic phase of the disease, but complement-fixing IgG3 antibodies are detected during the early phase and associate with aggressive onset and IVIG response. Nodal/paranodal antibodies testing is key in the diagnosis of AN. SUMMARY: AN have emerged as a new diagnostic category pathologically different from acquired demyelinating neuropathies. Clinically they overlap with GBS and CIDP although they associate with specific clinical features that should lead to clinical suspicion. Nodal/paranodal antibodies are key effector mechanisms of disease and good diagnostic and disease-monitoring biomarkers in AN.

High prevalence of paraspinal muscle involvement in adults with McArdle disease.

INTRODUCTION/AIMS: Very few studies analyzing the pattern of muscle involvement in magnetic resonance imaging (MRI) of patients with McArdle disease have been reported to date. We aimed to examine the pattern of muscle fat replacement in patients with McArdle disease. METHODS: We performed a retrospective study including all patients with genetically confirmed McArdle disease followed in our center from January 2010 to March 2021. Clinical data were collected from the medical record. Whole-body MRI was performed as part of the diagnostic evaluation. The distribution of muscle fat replacement and its severity were analyzed. RESULTS: Nine patients were included. Median age at onset was 7 y (range, 5-58) and median age at the time when MRI was performed was 57.3 y (range, 37.2-72.8). At physical examination, four patients had permanent weakness: in three the weakness was limited to paraspinal muscles, whereas in one the weakness involved the paraspinal and proximal upper limb muscles. Muscle MRI showed abnormalities in six of the seven studied patients. In all of them, fat replacement of paravertebral muscles was found. Other muscles frequently affected were the tongue in three, subscapularis in three, and long head of biceps femoris and semimembranosus in two. DISCUSSION: Our findings suggest that paraspinal muscle involvement is common in McArdle disease and support the need to include this disease in the differential diagnosis of the causes of paraspinal muscle weakness. Involvement of the tongue and subscapularis are also frequent in McArdle disease.

Antibodies to the Caspr1/contactin-1 complex in chronic inflammatory demyelinating polyradiculoneuropathy.

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.

Autoantibody screening in Guillain-Barré syndrome.

BACKGROUND: Guillain-Barré 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-Barré 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.

Serum neurofilament light chain predicts long-term prognosis in Guillain-Barré syndrome patients.

OBJECTIVE: To study baseline serum neurofilament light chain (sNfL) levels as a prognostic biomarker in Guillain-Barré syndrome (GBS). METHODS: We 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. RESULTS: Patients with GBS had higher NfL levels than HC in serum (55.49 pg/mL vs 9.83 pg/mL, p<0.0001) and CSF (1308.5 pg/mL vs 440.24 pg/mL, p=0.034). Patients with preceding diarrhoea had higher sNfL than patients with respiratory symptoms or no preceding infection (134.90 pg/mL vs 47.86 pg/mL vs 38.02 pg/mL, p=0.016). sNfL levels correlated with Guillain-Barré Syndrome Disability Score and Inflammatory Rasch-built Overall Disability Scale (I-RODS) at every timepoint. Patients with pure motor variant and Miller Fisher syndrome showed higher sNfL levels than patients with sensorimotor GBS (162.18 pg/mL vs 95.50 pg/mL vs 38.02 pg/mL, p=0.025). Patients with acute motor axonal neuropathy cute motor axonal neuropathy had higher sNfL levels than other variants (190.55 pg/mL vs 46.79 pg/mL, p=0.013). sNfL returned to normal levels at 1 year. High baseline sNfL levels were associated with inability to run (OR=1.65, 95% CI 1.14 to 2.40, p=0.009) and lower I-RODS (ß -2.60, 95% CI -4.66 to -0.54, p=0.014) at 1 year. Cut-off points predicting clinically relevant outcomes at 1 year with high specificity were calculated: inability to walk independently (>319 pg/mL), inability to run (>248 pg/mL) and ability to run (<34 pg/mL). CONCLUSION: Baseline 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.

Autoantibodies in chronic inflammatory demyelinating polyradiculoneuropathy.

PURPOSE OF REVIEW: Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a heterogeneous disorder that includes diverse clinical presentations and immunopathological mechanisms. Antibodies targeting proteins of the node of Ranvier are present in a subset of CIDP patients. These autoantibodies are pathogenic and associate with specific clinical phenotypes and therapeutic peculiarities. This review summarizes the novel insights that the discovery of novel autoantibodies has brought to the understanding of CIDP. RECENT FINDINGS: Several reports have confirmed the association of the antineurofascin 155 (NF155) antibodies with tremor, ataxia and poor response to IVIG, and with novel pathological features in CIDP patients. The association of nephrotic syndrome with anticontactin 1 (CNTN1) and antinodal neurofascin antibodies has also been described. Also, complement-fixing IgG3 antibodies targeting paranodal proteins have been associated with acute-onset CIDP. Importantly, detection of these autoantibodies has helped selecting CIDP patients for rituximab treatment. Finally, anti-CNTN1 and anti-NF155 antibodies have proven to be the first pathogenic autoantibodies described in CIDP. SUMMARY: The discovery of autoantibodies against nodal and paranodal proteins has proven useful in clinical practice, has uncovered novel pathophysiological mechanisms, clinical phenotypes, therapeutic response and prognosis within the CIDP disease spectrum and has boosted the search for other clinically relevant autoantibodies.

Membrane Proteome-Wide Screening of Autoantibodies in CIDP Using Human Cell Microarray Technology.

BACKGROUND AND OBJECTIVES: Autoantibody discovery in complex autoimmune diseases is challenging. Diverse successful antigen identification strategies are available, but, so far, have often been unsuccessful, especially in the discovery of protein antigens in which conformational and post-translational modification are critical. Our study assesses the utility of a human membrane and secreted protein microarray technology to detect autoantibodies in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). METHODS: A cell microarray consisting of human embryonic kidney-293 cells expressing >5,000 human proteins was used. First, a validation step was performed with 4 serum samples from patients with autoimmune nodopathy (AN) to assess the ability of this technology to detect circulating known autoantibodies. The ability of the cell microarray technology to discover novel IgG autoantibodies was assessed incubating the array with 8 CIDP serum samples. Identified autoantibodies were subsequently validated using cell-based assays (CBAs), ELISA, and/or tissue immunohistochemistry and analyzed in a cohort of CIDP and AN (n = 96) and control (n = 100) samples. RESULTS: Serum anti-contactin-1 and anti-neurofascin-155 were detected by the human cell microarray technology. Nine potentially relevant antigens were found in patients with CIDP without other detectable antibodies; confirmation was possible in six of them: ephrin type-A receptor 7 (EPHA7); potassium-transporting ATPase alpha chain 1 and subunit beta (ATP4A/4B); leukemia-inhibitory factor (LIF); and interferon lambda 1, 2, and 3 (IFNL1, IFNL2, IFNL3). Anti-ATP4A/4B and anti-EPHA7 antibodies were detected in patients and controls and considered unrelated to CIDP. Both anti-LIF and anti-IFNL antibodies were found in the same 2 patients and were not detected in any control. Both patients showed the same staining pattern against myelinating fibers of peripheral nerve tissue and of myelinating neuron-Schwann cell cocultures. Clinically relevant correlations could not be established for anti-LIF and anti-IFNL3 antibodies. DISCUSSION: Our work demonstrates the utility of human cell microarray technology to detect known and discover unknown autoantibodies in human serum samples. Despite potential CIDP-associated autoantibodies (anti-LIF and anti-IFNL3) being identified, their clinical and pathogenic relevance needs to be elucidated in bigger cohorts.

Antibodies against the flotillin-1/2 complex in patients with 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.

mRNA COVID-19 Vaccination Does Not Exacerbate Symptoms or Trigger Neural Antibody Responses in Multiple Sclerosis.

BACKGROUND AND OBJECTIVE: In people with multiple sclerosis (pwMS), concern for potential disease exacerbation or triggering of other autoimmune disorders contributes to vaccine hesitancy. We assessed the humoral and T-cell responses to SARS-CoV-2 after mRNA vaccination, changes in disease activity, and development of antibodies against central or peripheral nervous system antigens. METHODS: This was a prospective 1-year longitudinal observational study of pwMS and a control group of patients with other inflammatory neurologic disorders (OIND) who received an mRNA vaccine. Blood samples were obtained before the first dose (T1), 1 month after the first dose (T2), 1 month after the second dose (T3), and 6 (T4), 9 (T5), and 12 (T6) months after the first dose. Patients were assessed for the immune-specific response, annualized relapse rate (ARR), and antibodies to onconeuronal, neural surface, glial, ganglioside, and nodo-paranodal antigens. RESULTS: Among 454 patients studied, 390 had MS (22 adolescents) and 64 OIND; the mean (SD) age was 44 (14) years; 315 (69%) were female; and 392 (87%) were on disease-modifying therapies. Antibodies to the receptor-binding domain were detected in 367 (86%) patients at T3 and 276 (83%) at T4. After a third dose, only 13 (22%) of 60 seronegative patients seroconverted, and 255 (92%) remained seropositive at T6. Cellular responses were present in 381 (93%) patients at T3 and in 235 (91%) patients at T6 including all those receiving anti-CD20 therapies and in 79% of patients receiving fingolimod. At T3 (429 patients) or T6 (395 patients), none of the patients had developed CNS autoantibodies. Seven patients had neural antibodies that were already present before immunization (3 adult patients with MS had MOG-IgG, 2 with MG and 1 with MS had neuronal cell surface antibodies [unknown antigen], and 1 with MS had myelin antibody reactivity [unknown antigen]. Similarly, no antibodies against PNS antigens were identified at T3 (427 patients). ARR was lower in MS and not significantly different in patients with OIND. Although 182 (40%) patients developed SARS-CoV-2 infection, no cases of severe COVID-19 or serious adverse events occurred. DISCUSSION: In this study, mRNA COVID-19 vaccination was safe and did not exacerbate the autoimmune disease nor triggered neural autoantibodies or immune-mediated neurologic disorders. The outcome of patients who developed SARS-CoV-2 infection was favorable.

CSF Findings in Relation to Clinical Characteristics, Subtype, and Disease Course in Patients With Guillain-Barré Syndrome.

BACKGROUND AND OBJECTIVES: To investigate CSF findings in relation to clinical and electrodiagnostic subtypes, severity, and outcome of Guillain-Barré syndrome (GBS) based on 1,500 patients in the International GBS Outcome Study. METHODS: Albuminocytologic dissociation (ACD) was defined as an increased protein level (>0.45 g/L) in the absence of elevated white cell count (<50 cells/µL). We excluded 124 (8%) patients because of other diagnoses, protocol violation, or insufficient data. The CSF was examined in 1,231 patients (89%). RESULTS: In 846 (70%) patients, CSF examination showed ACD, which increased with time from weakness onset: ≤4 days 57%, >4 days 84%. High CSF protein levels were associated with a demyelinating subtype, proximal or global muscle weakness, and a reduced likelihood of being able to run at week 2 (odds ratio [OR] 0.42, 95% CI 0.25-0.70; p = 0.001) and week 4 (OR 0.44, 95% CI 0.27-0.72; p = 0.001). Patients with the Miller Fisher syndrome, distal predominant weakness, and normal or equivocal nerve conduction studies were more likely to have lower CSF protein levels. CSF cell count was <5 cells/µL in 1,005 patients (83%), 5-49 cells/µL in 200 patients (16%), and ≥50 cells/µL in 13 patients (1%). DISCUSSION: ACD is a common finding in GBS, but normal protein levels do not exclude this diagnosis. High CSF protein level is associated with an early severe disease course and a demyelinating subtype. Elevated CSF cell count, rarely ≥50 cells/µL, is compatible with GBS after a thorough exclusion of alternative diagnoses. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that CSF ACD (defined by the Brighton Collaboration) is common in patients with GBS.

Neurofilament Light Chain Levels in Anti-NMDAR Encephalitis and Primary Psychiatric Psychosis.

BACKGROUND AND OBJECTIVES: An 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. METHODS: In 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. RESULTS: One 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 sNfL<15 pg/mL, whereas only 5 of 33 (15%) with NMDARe with isolated psychosis were below this cutoff (risk estimation NMDARe vs pFEP: odds ratio 120.4 [95% CI 21.8-664], p < 0.001). None of the patients with HSE and 35 of 36 (97%) HC had sNfL<15 pg/mL. DISCUSSION: NfL 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.

Clinical and Laboratory Features in Anti-NF155 Autoimmune Nodopathy.

BACKGROUND AND OBJECTIVES: To study the clinical and laboratory features of antineurofascin-155 (NF155)-positive autoimmune nodopathy (AN). METHODS: Patients 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. RESULTS: Forty 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. DISCUSSION: Anti-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 EVIDENCE: This study provides Class IV evidence that anti-NF155 antibodies associate with a specific phenotype and response to rituximab.

An International Perspective on Preceding Infections in Guillain-Barré Syndrome: The IGOS-1000 Cohort.

BACKGROUND AND OBJECTIVES: Infections play a key role in the development of Guillain-Barré syndrome (GBS) and have been associated with specific clinical features and disease severity. The clinical variation of GBS across geographical regions has been suggested to be related to differences in the distribution of preceding infections, but this has not been studied on a large scale. METHODS: We analyzed the first 1,000 patients included in the International GBS Outcome Study with available biosamples (n = 768) for the presence of a recent infection with Campylobacter jejuni, hepatitis E virus, Mycoplasma pneumoniae, cytomegalovirus, and Epstein-Barr virus. RESULTS: Serologic evidence of a recent infection with C. jejuni was found in 228 (30%), M. pneumoniae in 77 (10%), hepatitis E virus in 23 (3%), cytomegalovirus in 30 (4%), and Epstein-Barr virus in 7 (1%) patients. Evidence of more than 1 recent infection was found in 49 (6%) of these patients. Symptoms of antecedent infections were reported in 556 patients (72%), and this proportion did not significantly differ between those testing positive or negative for a recent infection. The proportions of infections were similar across continents. The sensorimotor variant and the demyelinating electrophysiologic subtype were most frequent across all infection groups, although proportions were significantly higher in patients with a cytomegalovirus and significantly lower in those with a C. jejuni infection. C. jejuni-positive patients were more severely affected, indicated by a lower Medical Research Council sum score at nadir (p = 0.004) and a longer time to regain the ability to walk independently (p = 0.005). The pure motor variant and axonal electrophysiologic subtype were more frequent in Asian compared with American or European C. jejuni-positive patients (p < 0.001, resp. p = 0.001). Time to nadir was longer in the cytomegalovirus-positive patients (p = 0.004). DISCUSSION: Across geographical regions, the distribution of infections was similar, but the association between infection and clinical phenotype differed. A mismatch between symptom reporting and serologic results and the high frequency of coinfections demonstrate the importance of broad serologic testing in identifying the most likely infectious trigger. The association between infections and outcome indicates their value for future prognostic models.

Serum Contactin-1 in CIDP: A Cross-Sectional Study.

OBJECTIVE: To 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. METHODS: Serum contactin-1 levels were measured in 187 patients with CIDP and 222 healthy controls. Paranodal antibodies were investigated in all patients. RESULTS: Serum 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). CONCLUSIONS: These findings suggest that serum contactin-1 levels have the potential to serve as a possible diagnostic biomarker of paranodal injury in CIDP. CLASSIFICATION OF EVIDENCE: This 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%).

Antibodies against nodo-paranodal proteins are not present in genetic neuropathies.

OBJECTIVE: To study the presence of nodal and paranodal immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies in patients with genetic neuropathies. METHODS: A total of 108 patients with genetic neuropathies from 3 different centers were included. The presence of IgG and IgM antibodies against neurofascin-155 (NF155), nodal neurofascin (NF186 and NF140), and contactin-1 (CNTN1) were investigated with a cell-based assay (CBA) using immunocytochemistry in transfected HEK293 cells. Sera with positive or uncertain results were further tested by ELISA and immunohistochemistry in pig teased-nerve fibers. RESULTS: Six patients with Charcot-Marie-Tooth disease (CMT) had an uncertain staining pattern for IgM against nodal neurofascin that was not confirmed by ELISA. Two patients with CMT had an uncertain staining pattern for IgG against nodal neurofascin that was not confirmed by ELISA or immunohistochemistry. One patient with CMT with a confirmed GJB1 mutation tested positive for IgG against NF155 by CBA and ELISA (1/900), but was not confirmed by immunohistochemistry and was ultimately classified as negative. CONCLUSIONS: Antibodies against nodal or paranodal antigens were not detected in our cohort of patients with CMT, as previously reported. Some patients may falsely test positive for any of the techniques; confirmatory techniques should be incorporated into the routine testing.

Autoantibodies in immune-mediated inflammatory neuropathies. / Autoanticuerpos en neuropatías inflamatorias inmunomediadas.

Inflammatory neuropathies are a rare and heterogeneous group of diseases of the nervous system characterized by the dysfunction and damage of different structures of the peripheral nerves. This group includes Guillain-Barré syndrome, chronic demyelinating inflammatory polyradiculoneuropathy, multifocal motor neuropathy or neuropathies associated with monoclonal gammopathy. The aetiology of these diseases is unknown, but B cells and autoantibodies play a key role in their pathogenesis. Autoantibodies against peripheral nerve molecules such as gangliosides, proteins of the Ranvier node or myelin-associated glycoprotein have been described, allowing the identification of subgroups of patients with specific clinical phenotypes. For all these reasons, these antibodies are useful in clinical practice. This review focuses on the diagnostic and therapeutic relevance of autoantibodies in inflammatory neuropathies.

Clinical and laboratory features of anti-MAG neuropathy without monoclonal gammopathy.

Antibodies against myelin-associated glycoprotein (MAG) almost invariably appear in the context of an IgM monoclonal gammopathy associated neuropathy. Very few cases of anti-MAG neuropathy lacking IgM-monoclonal gammopathy have been reported. We investigated the presence of anti-MAG antibodies in 69 patients fulfilling diagnostic criteria for CIDP. Anti-MAG antibodies were tested by ELISA and confirmed by immunohistochemistry. We identified four (5.8%) anti-MAG positive patients without detectable IgM-monoclonal gammopathy. In two of them, IgM-monoclonal gammopathy was detected at 3 and 4-year follow-up coinciding with an increase in anti-MAG antibodies titers. In conclusion, anti-MAG antibody testing should be considered in chronic demyelinating neuropathies, even if IgM-monoclonal gammopathy is not detectable.

Absence of pathogenic mutations in CD59 in chronic inflammatory demyelinating polyradiculoneuropathy.

OBJECTIVE: Mutations in CD59 cause CIDP-like polyneuropathy in children with inherited chronic hemolysis. We hypothesized that mutations in CD59 might be found in a subset of sporadic CIDP patients. METHODS: 35 patients from two centers, fulfilling the EFNS/PNS diagnostic criteria for CIDP were included. CD59 coding region was amplified by PCR and Sanger sequenced. RESULTS: One rare variant was detected in a patient which resulted in a synonymous change and predicted to be neutral. Pathogenic variants were absent in our cohort. INTERPRETATION: Our pilot study suggests that mutations in CD59 are absent in adult-onset sporadic CIDP.