Pediatric Opsoclonus-myoclonus Syndrome Research Articles

Brain Volumes in Opsoclonus-Myoclonus Ataxia Syndrome: A Longitudinal Study.

Little is known about the longitudinal trajectory of brain growth in children with opsoclonus-myoclonus ataxia syndrome. We performed a longitudinal evaluation of brain volumes in pediatric opsoclonus-myoclonus ataxia syndrome patients compared with age- and sex-matched healthy children. This longitudinal case-control study included brain magnetic resonance imaging (MRI) scans from consecutive pediatric opsoclonus-myoclonus ataxia syndrome patients (2009-2020) and age- and sex-matched healthy control children. FreeSurfer analysis provided automatic volumetry of the brain. Paired t tests were performed on the curvature of growth trajectories, with Bonferroni correction. A total of 14 opsoclonus-myoclonus ataxia syndrome patients (12 female) and 474 healthy control children (406 female) were included. Curvature of the growth trajectories of the cerebral white and gray matter, cerebellar white and gray matter, and brainstem differed significantly between opsoclonus-myoclonus ataxia syndrome patients and healthy control children (cerebral white matter, P = .01; cerebral gray matter, P = .01; cerebellar white matter, P < .001; cerebellar gray matter, P = .049; brainstem, P < .01). We found abnormal brain maturation in the supratentorial brain, brainstem, and cerebellum in children with opsoclonus-myoclonus ataxia syndrome.

Clinical Analysis of Pediatric Opsoclonus-Myoclonus Syndrome in One of the National Children's Medical Center in China.

Objective: To study the clinical characteristics and treatment of pediatric opsoclonus-myoclonus syndrome (OMS).Methods: We analyzed the clinical data of nine children OMS between June 2017 and Nov 2020.Results: Nine children (M/F = 3:6, median onset age was 18 months) diagnosed with OMS were included in the study. Before onset, human rhinovirus and respiratory syncytial virus were seen in one patient, respectively. And one patient received Japanese encephalitis vaccination. Three patients had neuroblastoma, and one patient had ganglioneuroblastoma. All patients' symptoms were improved after receiving surgery (for four patients with tumor), intravenous human immunoglobulin and pulsed methylprednisolone. However, four patients without mass relapsed and became relapse free after rituximab treatment. The relapse rate was 44.4% (4/9). The OMS severity score at the last follow-up was significantly lower than the OMS severity score at onset (3.0 ± 1.0 vs. 11.0 ± 2.2, paired-samples t-test, P < 0.001). All patients had at least one item of neurological symptoms or neuropsychological disturbances.Conclusion: For pediatric OMS, human rhinovirus infection and respiratory syncytial virus infection can be seen before onset. Rituximab is effective in reducing relapse. Improving recognition and long-term prognosis in OMS is urgent.

NK Cell-mediated Neuroblastoma Cell Lysis is Enhanced by IgG From Patients With Pediatric Opsoclonus-Myoclonus Syndrome.

Pediatric opsoclonus-myoclonussyndrome (OMS) is a rare autoimmune disorder of which 50% are associated with neuroblastoma (NB). We investigated whether surface-binding autoantibodies in OMS can enhance natural killer (NK) cell-mediated cytotoxicity in these patients. OMS immunoglobulin G (IgG) bound to NB cell lines and NK cell-mediated cytotoxicity to NB cells was enhanced after preincubation with OMS-IgG, but not IgG from NB without OMS or healthy controls. Activation of NK cells by surface-binding autoantibodies may be an additional mechanism of antitumor immunity in children with NB and OMS.

IQ predictors in pediatric opsoclonus myoclonus syndrome: a large international cohort study

To determine predictors of full-scale IQ (FSIQ) in an international pediatric opsoclonus myoclonus syndrome (OMS) cohort. In this retrospective and prospective cohort study at three academic medical centers (2006-2013), the primary outcome measure, FSIQ, was categorized based on z-score: above average (≥+1), average (+1 to -1), mildly impaired (-1 to -2), and impaired (<-2). Univariate analysis and multivariable linear regression modeling using stepwise selection with Akaike's information criterion was performed to understand the relationship between exposures and FSIQ. Of 81 participants, 37 with sufficient data had mean FSIQ 84.38 (SD 20.55) and median 90 (40-114) at latest available evaluation (mean age 8y 5mo). Twenty (54%), nine (24.3%), and eight (21.6%) had normal, mildly impaired, and impaired FSIQ respectively. The final multivariable linear regression model included 34 participants with evaluable data: number of relapses occurring before neuropsychological testing (p<0.001) and OMS severity score at last follow-up (p<0.001) predicted FSIQ (adjusted R2 =0.64). There was a mean decrease of 2.4 FSIQ points per OMS relapse. Number of relapses negatively correlates with FSIQ in pediatric OMS. Demographic and clinical measures available at OMS onset did not predict FSIQ. Strategies to reduce OMS relapses may improve intellectual outcomes.

Multifactorial analysis of opsoclonus-myoclonus syndrome etiology ("Tumor" vs. "No tumor") in a cohort of 356 US children.

Pediatric opsoclonus-myoclonus syndrome (OMS) presents a paradox of etiopathogenesis: A neuroblastic tumor (NB) is found in only one half of the cases, the others are ascribed to infections or designated as idiopathic. From an IRB-approved observational study of 356 US children with OMS, secondary analysis of "etiology" and related factors was performed on a well-characterized cohort. The "Tumor" (n=173) and "No Tumor" groups (n=183), as defined radiologically, were compared according to multiple factors considered potentially differentiating. Data were analyzed retrospectively using parametric and nonparametric tests as indicated. Patients with NB were not distinguishable by prodromal symptoms, OMS onset age, gender, race/ethnicity, OMS severity, rank order of neurological sign appearance, or geographic distribution. Various CSF immunologic biomarker abnormalities of OMS did not vary in the presence or absence of a detectable tumor: frequency of six lymphocyte subsets, or concentrations of 18 cytokines/chemokines, cytokine antagonists, chemokine receptors, cell adhesion molecules, or neuronal/glial markers. Prior responsiveness to conventional immunotherapy was not contingent on tumor/no tumor designation. Multiple convergent factors provide compelling empirical evidence and rationalize the concept that OMS is one neurological disorder, regardless of apparent etiology. Limitations to the current clinical etiologic classifications as paraneoplastic, parainfectious/post-infectious, and idiopathic etiology require antigen-based biological solutions to tease out the molecular pathophysiology of viral/tumoral mechanisms. Systematic studies, regardless of presumed etiology, will be necessary to find the highest-yield combination of imaging approaches, screening for infectious agents, and new biomarkers. Two testable hypotheses for future research are presented.

Use of Induction Immunotherapy Plus Rituximab for the Treatment of Pediatric Opsoclonus-Myoclonus Syndrome (P2.311)

Use of Induction Immunotherapy Plus Rituximab for the Treatment of Pediatric Opsoclonus-Myoclonus Syndrome (P2.311)

Dexamethasone, Intravenous Immunoglobulin, and Rituximab Combination Immunotherapy for Pediatric Opsoclonus-Myoclonus Syndrome

BackgroundAlthough pulse-dose dexamethasone is increasingly favored for treating pediatric opsoclonus-myoclonus syndrome (OMS), and multimodal immunotherapy is associated with improved clinical response, there have been no neuroimmunologic studies of dexamethasone-based multimodal disease-modifying therapy. MethodsIn this observational retrospective study, 19 children with OMS (with or without associated neuroblastoma) underwent multibiomarker evaluation for neuroinflammation. Nine children of varying OMS severity, duration, and treatment status were treated empirically with pulse dexamethasone, intravenous immunoglobulin (IVIg), and rituximab combination immunotherapy (DEXIR-CI). Another 10 children on dexamethasone alone or with IVIg at initial evaluation only provided a comparison group. Motor severity (total score) was scored rater-blinded via videotapes using the validated OMS Evaluation Scale. ResultsDEXIR-CI was associated with a 69% reduction in group total score (P = 0.004) and was clinically well tolerated. Patients given the dexamethasone combination exhibited significantly lowered B cell frequencies in cerebrospinal fluid (−94%) and blood (−76%), normalizing the cerebrospinal fluid B cell percentage. The number of patients with positive inflammatory markers dropped 87% (P = 0.002) as did the number of markers. Cerebrospinal fluid oligoclonal bands were positive in four of nine pretreatment patients but zero of six post-treatment patients. In the comparison group, partial response to dexamethasone alone or with IVIg was associated with multiple positive markers for neuroinflammation despite an average of seven months of treatment. ConclusionsMultimechanistic dexamethasone-based combination immunotherapy increases the therapeutic armamentarium for OMS, providing a viable option for less severely affected individuals. Partial response to dexamethasone with or without IVIg is indicative of ongoing neuroinflammation and should be treated promptly and accordingly.

Pediatric opsoclonus-myoclonus syndrome: the role of functional brain connectivity studies.

This commentary is on the original article by Chekroud et al. on pages 98–104 of this issue.

CSF neurofilament light chain is elevated in OMS (decreasing with immunotherapy) and other pediatric neuroinflammatory disorders

Using a panel of seven brain cell-specific biomarkers in cerebrospinal fluid (CSF), pediatric opsoclonus–myoclonus syndrome (OMS) (n=234) was compared to pediatric non-inflammatory neurological controls (n=84) and other inflammatory neurological disorders (OIND) (n=44). Only CSF NFL was elevated in untreated OMS versus controls (+83%). It was 87% higher in OIND than in OMS. On combination treatment with front-loaded ACTH, IVIg, rituximab, median CSF NFL decreased by 60% to control levels. These biochemical data suggest neuronal/axonal injury in some children with OMS without indicators of astrogliosis, and reduction on sufficient immunotherapy.

200: Pharmacodynamics of immunotherapy for opsoclonus–myoclonus syndrome: Impact on cytokines/chemokines

Pediatric opsoclonus–myoclonus syndrome (OMS) is a neuroblastoma-associated neuroinflammatory disorder. The purpose of this study was to evaluate the capacity of immunotherapies used in treating OMS to normalize several putative biomarkers of disease activity. Soluble BAFF and APRIL and a variety of chemokine ligands for CXCR3, CXCR5, CCR4, CCR7 were measured in cerebrospinal fluid (CSF) and serum by ELISA in 433 children (296 OMS, 109 controls, 28 other inflammatory neurological disorders/OIND). A blinded scorer rated motor severity on the validated OMS evaluation scale. In untreated OMS, significant elevations of CSF BAFF (+57%), CXCL10 (+2.7-fold), CXCL13 (+16.5-fold) and serum CCL22 (+55%) and CCL17 (+121%) concentrations were found ( P P = 0.0003). In conclusion, striking distinctions in immunotherapy effects on BAFF/APRIL, CXCL13/CXCR5, CCL22/CCR4, and CCL21/CCR7 signaling were found. The contrasting pharmacodynamic patterns may offer utility as treatment biomarkers.

CCR7 signaling in pediatric opsoclonus–myoclonus: Upregulated serum CCL21 expression is steroid-responsive

Identifying and blocking chemokine inflammatory mediators in pediatric opsoclonus–myoclonus syndrome (OMS) is critical to the treatment of this autoimmune, paraneoplastic, neurological disorder. In a prospective, case-control, clinico-scientific study of children with OMS compared to non-inflammatory neurological controls and other inflammatory neurological disorders, CCL19 (n=369) and CCL21 (n=312) were quantified in CSF and serum, respectively, by ELISA. Both cross-sectional and longitudinal effects of OMS and various immunotherapies were evaluated. Significant upregulation of CCL21 concentration (mean±SD) (+32%) was found in serum of untreated OMS (630±133pg/mL), compared to controls (478±168pg/mL), (p<0.0001). Both corticosteroids and ACTH (corticotropin) significantly lowered CCL21 to control levels, as they did in combination with IVIg, rituximab, cyclophosphamide or other treatments, without additional reduction attributable to the other agents. In a pilot longitudinal study of ACTH-based triple therapy, the mean serum CCL21 concentration fell 59% from elevated to less than 1 SD below controls 1week after high-dose ACTH, gradually returning to the control mean with ACTH tapering by 3weeks and out to 12weeks (p<0.0001). In contrast, CCL19, detectable in CSF, was not significantly altered by OMS or various immunotherapies. In the “high” CCL21 subgroup, higher serum concentrations of CCL22 (+57%) and CXCL13 (+40%), as well as the CSF concentration of BAFF (+64%), also were found. Elevated serum CCL21, not CSF CCL19, correlates with OMS severity and duration in pediatric OMS. Corticosteroids and ACTH were the only immunotherapies evaluated that down-regulated CCL21 production. Validation studies are needed to assess treatment biomarker status.

Cytokines, cytokine antagonists, and soluble adhesion molecules in pediatric OMS and other neuroinflammatory disorders

ObjectiveTo test for hypothesized disease- and treatment-induced changes in cytokines and adhesion molecules in children with opsoclonus-myoclonus syndrome (OMS). MethodsMultiplex bead assay technology was used for simultaneous measurement of 34 soluble cytokines in cerebrospinal fluid (CSF) and serum. Soluble intercellular adhesion molecule-1 (sICAM-1) and vascular cell adhesion molecule-1 (sVCAM-1) were measured by ELISA. In total, there were 388 children (239 OMS, 114 controls, and 35 other inflammatory neurological disorders (OIND)). ResultsIn untreated OMS, mean CSF IL-6 was elevated 2.3-fold, but 67-fold in OIND, without significant differences in other CSF cytokines. Mean serum concentrations of sIL-2Ra (+50%) and CXCL1 (+70%) (p<0.0001) were also raised. CSF CCL5 was more often detected in untreated OMS than controls (p=0.005), as was serum CCL11 and IL-13 in treated OMS. Mean CSF CCL4 and IL-1Ra were selectively higher in IVIg-treated OMS (p≤0.0001). CSF sICAM-1 was elevated only in OIND (3.3-fold); serum sICAM-1 was higher in untreated OMS (+21%); and sVCAM-1 was not affected. No correlations with OMS severity or duration were identified. ConclusionsNovel cytokine, cytokine antagonist, and soluble adhesion molecule abnormalities due to OMS or treatment were found. However, the normality of much of the data strengthens previous findings implicating B cell mechanisms.

CCR4 Agonists CCL22 and CCL17 are Elevated in Pediatric OMS Sera: Rapid and Selective Down-Regulation of CCL22 by ACTH or Corticosteroids

To study the role of Th2-attracting chemokines in opsoclonus-myoclonus syndrome (OMS), a serious neurological paraneoplastic disorder in need of better immunological understanding and therapy. The CCR4 agonists CCL22 and CCL17 were measured in serum by ELISA in children with OMS (238 and 260, respectively), pediatric controls (115 and 143), and other inflammatory neurological disorders (33 and 24). Both CCL22 (+55 %) and CCL17 (+121 %) were significantly elevated in untreated OMS compared to controls and inter-correlated (p < 0.0001). Their concentrations in untreated OMS also were higher than in OIND (21 %, 41 %). The concentration of CCL22 in ACTH and steroids groups (not IVIg) was 51 % lower than in controls, but only a smaller effect of ACTH on CCL17 was found. Prospective longitudinal studies revealed a precipitous 81 % drop in CCL22 even by the first week of high-dose ACTH therapy, staying below control mean for at least 12 weeks, and a 34 % reduction after 8 months of combined treatment. Response to ACTH was dose-related (r = -0.50, p < 0.0001). Luminex detection confirmed the ELISA results for CCL22, which were about 200 % higher. These data reveal an elevated serum concentration of Th2-attracting chemokines CCL22 and CCL17 in OMS. Marked and rapid reduction in CCL22, not CCL17, with either ACTH or steroid therapy suggests differential regulation and cellular sources of CCR4 ligands, and CCL22 as a potential candidate biomarker for ACTH or corticosteroid effect.

BAFF/APRIL system in pediatric OMS: relation to severity, neuroinflammation, and immunotherapy

BackgroundB-cell dysregulation has been implicated but not fully characterized in pediatric opsoclonus-myoclonus syndrome (OMS), a neuroblastoma-associated neuroinflammatory disorder.ObjectiveTo assess the role of B-cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL), two critical B cell-modulating cytokines, as potential biomarkers of disease activity and treatment biomarkers in OMS.MethodsSoluble BAFF and APRIL were measured in cerebrospinal fluid (CSF) and serum by ELISA in 433 children (296 OMS, 109 controls, 28 other inflammatory neurological disorders (OIND)). BAFF-R receptors on circulating CD19+ B cells were measured by flow cytometry. A blinded scorer rated motor severity on the OMS Evaluation Scale. Immunotherapies were evaluated cross-sectionally and longitudinally.ResultsThe mean CSF BAFF concentration, which was elevated in untreated OMS and OIND, correlated with OMS severity category (P = 0.006), and reduction by adrenocorticotropic hormone or corticotropin (ACTH) (−61%) or corticosteroids (−38%) was seen at each level of severity. In contrast, CSF APRIL was normal in OMS and OIND and unaffected by immunotherapy. When the entire OMS dataset was dichotomized into ‘high’ versus ‘normal’ CSF BAFF concentration, the phenotype of the high group included greater motor severity and number of CSF oligoclonal bands, and a higher concentration of inflammatory chemokines CXCL13 and CXCL10 in CSF and CXCL9 and CCL21 in serum. Serum APRIL was 6.7-fold higher in the intravenous immunoglobulins (IVIg) group, whereas serum BAFF was 2.6-fold higher in the rituximab group. The frequency of B cell BAFF-R expression was similar in untreated and treated OMS. Longitudinal studies of CSF BAFF revealed a significant decline in ACTH-treated patients (with or without rituximab) (P < 0.0001). Longitudinal studies of serum APRIL showed a 2.9-fold increase after 1 to 2 g/kg IVIg monotherapy (P = 0.0003).ConclusionsStriking distinctions in BAFF/APRIL signaling were found. OMS displayed heterogeneity in CSF BAFF expression, which met many but not all criteria as a potential biomarker of disease activity. We speculate that CSF BAFF may have more utility in a biomarker panel than as a stand-alone biomarker, and that the selective upregulation of both serum APRIL by IVIg and BAFF by rituximab, as well as downregulation of CSF BAFF by ACTH/steroids, may have utility as treatment biomarkers.

Active Comparator-Controlled, Rater-Blinded Study of Corticotropin-Based Immunotherapies for Opsoclonus-Myoclonus Syndrome

To test the efficacy and safety of corticotropin-based immunotherapies in pediatric opsoclonus-myoclonus syndrome, 74 children received corticotropin alone or with intravenous immunoglobulin (groups 1 and 2, active controls); or both with rituximab (group 3) or cyclophosphamide (group 4); or with rituximab plus chemotherapy (group 5) or steroid sparers (group 6). There was 65% improvement in motor severity score across groups (P < .0001), but treatment combinations were more effective than corticotropin alone (P = .0009). Groups 3, 4, and 5 responded better than group 1; groups 3 and 5 responded better than group 2. The response frequency to corticotropin was higher than to prior corticosteroids (P < .0001). Fifty-five percent had adverse events (corticosteroid excess), more so with multiagents (P = .03); and 10% had serious adverse events. This study demonstrates greater efficacy of corticotropin-based multimodal therapy compared with conventional therapy, greater response to corticotropin than corticosteroid-based therapy, and overall tolerability.

Key role of CXCL13/CXCR5 axis for cerebrospinal fluid B cell recruitment in pediatric OMS

To study aberrant B cell trafficking into the CSF in opsoclonus–myoclonus syndrome (OMS), chemoattractants CXCL13 and CXCL12, and B cell frequency and CXCR5 expression, were evaluated. CSF CXCL13 concentration and the CSF/serum ratio were higher in untreated OMS than controls, related directly to OMS severity and inversely to OMS duration, and correlated with CSF B cell frequency and oligoclonal bands. CXCL12 showed the opposite pattern. Selective accumulation of CXCR5+ memory B cells in CSF was found. In ACTH-treated OMS, CXCL13, but not CXCL12, was lower. These data implicate the chemokine/chemoreceptor pair CXCL13/CXR5 in B cell recruitment to the CNS in OMS. CXCL13 and CXCL12 may serve as reciprocal biomarkers of disease activity, but CXCL13 also had utility as a treatment biomarker.

Elevated B-cell activating factor BAFF, but not APRIL, correlates with CSF cerebellar autoantibodies in pediatric opsoclonus-myoclonus syndrome

Childhood opsoclonus-myoclonus syndrome (OMS) occurs idiopathic or, in association with a neuroblastoma, as a paraneoplastic syndrome. Since autoantibodies were identified in some patients, an autoimmune pathogenesis has been suspected. While the newly discovered B-cell activating factors BAFF and APRIL are involved in systemic autoimmune diseases, their association with neuroimmunological diseases is hardly understood. We here investigated the BAFF and APRIL levels in serum and cerebrospinal fluid (CSF) of OMS patients and their correlation with surface-binding autoantibodies. BAFF and APRIL were both determined by ELISA, and autoantibodies to cerebellar granular neurons (CGN) have been investigated by flow cytometry in 17 OMS patients, 16 neuroblastoma (NB) patients, 13 controls and 11 children with inflammatory neurological diseases (IND). BAFF, but no APRIL, was elevated in the CSF of OMS children and IND children. However, in contrast to IND patients, OMS patients did not have a blood–brain-barrier disturbance, indicating that BAFF was produced intrathecally in OMS patients, but not in IND patients. CSF BAFF levels showed a correlation with CSF CGN autoantibodies ( r 2 = 0.58, p < 0.05). These data indicate that an activated B-cell system in the cerebrospinal fluid is involved in the pathogenesis of OMS, and BAFF may be a candidate parameter for the activation of B-cell immune system.

Therapeutic down-regulation of central and peripheral B-cell-activating factor (BAFF) production in pediatric opsoclonus–myoclonus syndrome

Opsoclonus–myoclonus syndrome (OMS) is an autoimmune, paraneoplastic, central nervous system disorder, characterized by cerebrospinal fluid (CSF) B-cell expansion and various putative autoantibodies. To investigate the role of B-cell activating factor (BAFF) in OMS and the effect of disease-modifying immunotherapies used to treat it, BAFF was measured by enzyme-linked immunoadsorbent assay in the CSF and serum of 161 children with OMS and 116 pediatric controls. The mean concentration of CSF BAFF and the CSF/serum BAFF ratio were significantly higher in untreated OMS compared to neurological controls. CSF and serum BAFF levels were significantly lower in children treated with ACTH or corticosteroids, as was the CSF/serum BAFF ratio. There was a strong, negative correlation between CSF or serum BAFF levels and ACTH dose. Monthly IVIg infusions had no net impact on BAFF levels, and the combination of IVIg with ACTH or steroids did not reduce or enhance their anti-BAFF effects. These data indicate that BAFF production is increased centrally, not peripherally, in OMS, implying astrocytic over production. The novel dose-related central and peripheral anti-BAFF properties of ACTH, especially, have implications for other BAFF-related autoimmune disorders, infectious diseases, and cancers.

Analysis of antibodies to neuronal surface antigens in adult opsoclonus–myoclonus

Antibodies against neuronal surface antigens (NSA-ab) have been described in pediatric opsoclonus–myoclonus syndrome (OMS). We analyzed the presence of NSA-ab by flow cytometry and immunocytochemistry of live cerebellar granular neurons (CGN) in the serum of 25 adult patients with idiopathic (14) and paraneoplastic (11) OMS. Paraneoplastic, but not idiopathic, OMS sera showed a CGN surface binding by flow cytometry higher than that of controls (mean MFI (median fluorescence intensity): 29 ± 6.9 vs. 20 ± 5.8; p = 0.001) but only one serum had a binding greater than three standard deviations of controls. OMS sera did not label live CGN by immunocytochemistry. Unlike pediatric OMS, NSA-ab were not detected in adult cases suggesting that the immunity to NSA in OMS is heterogeneous.

Identification of autoantigens in pediatric opsoclonus-myoclonus syndrome

Pediatric opsoclonus–myoclonus syndrome (OMS) is a rare disease, including eye movement disturbances, muscle jerks, ataxia and developmental disturbances as the main symptoms. In 50% of patients, OMS is associated with a neuroblastoma as a paraneoplastic neurological syndrome. Since autoantibodies have been detected in some patients and OMS patients respond to immunosuppression, an autoimmune etiology has been suspected in OMS. A variety of autoantibodies have been reported in association with OMS. In paraneoplastic OMS, some patients have anti-Hu antibodies, directed against a group of RNA-binding proteins expressed in neurons and tumor cells. Autoantibodies against α-enolase and KH-type splicing regulatory protein could also be demonstrated. However, these autoantibodies are not specific for OMS. By contrast, autoantibodies against surface epitopes of cerebellar granular cells and neuroblastoma cells have been demonstrated exclusively in OMS patients, and these autoantibodies have pathogenic effects on neuroblastoma cells. Taken together, OMS is associated with surface-binding autoantibodies with pathogenic effects, indicating a humoral immune-mediated process as the underlying cause for OMS.