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Objective: This study was undertaken to investigate factors associated with aquaporin-4 (AQP4)-IgG serostatus change using a large serological database., Methods: This retrospective study utilizes Mayo Clinic Neuroimmunology Laboratory data from 2007 to 2021. We included all patients with ≥2 AQP4-IgG tests (by cell-based assay). The frequency and clinical factors associated with serostatus change were evaluated. Multivariable logistic regression analysis examined whether age, sex, or initial titer was associated with serostatus change., Results: There were 933 patients who had ≥2 AQP4-IgG tests with an initial positive result. Of those, 830 (89%) remained seropositive and 103 (11%) seroreverted to negative. Median interval to seroreversion was 1.2 years (interquartile range [IQR] = 0.4-3.5). Of those with sustained seropositivity, titers were stable in 92%. Seroreversion was associated with age ≤ 20 years (odds ratio [OR] = 2.25; 95% confidence interval [CI] = 1.09-4.63; p = 0.028) and low initial titer of ≤1:100 (OR = 11.44, 95% CI = 3.17-41.26, p < 0.001), and 5 had clinical attacks despite seroreversion. Among 62 retested after seroreversion, 50% returned to seropositive (median = 224 days, IQR = 160-371). An initial negative AQP4-IgG test occurred in 9,308 patients. Of those, 99% remained seronegative and 53 (0.3%) seroconverted at a median interval of 0.76 years (IQR = 0.37-1.68)., Interpretation: AQP4-IgG seropositivity usually persists over time with little change in titer. Seroreversion to negative is uncommon (11%) and associated with lower titers and younger age. Seroreversion was often transient, and attacks occasionally occurred despite prior seroreversion, suggesting it may not reliably reflect disease activity. Seroconversion to positive is rare (<1%), limiting the utility of repeat testing in seronegative patients unless clinical suspicion is high. ANN NEUROL 2023;94:727-735., (© 2023 The Authors. Annals of Neurology published by Wiley Periodicals LLC on behalf of American Neurological Association.)

Objective: To describe phenotypes, treatment response, and outcomes of autoimmunity targeting a synaptic vesicle coat protein, the neuronal (B2) form of adaptor protein-3 (AP3)., Methods: Archived serum and CSF specimens (from 616,025 screened) harboring unclassified synaptic antibodies mimicking amphiphysin-immunoglobulin G (IgG) on tissue-based indirect immunofluorescence assay (IFA) were re-evaluated for novel IgG staining patterns. Autoantigens were identified by western blot and mass spectrometry. Recombinant western blot and cell-binding assay (CBA) were used to confirm antigen specificity. Clinical data were obtained retrospectively., Results: Serum (10) and CSF (6) specimens of 10 patients produced identical IFA staining patterns throughout mouse nervous system tissues, most prominently in cerebellum (Purkinje neuronal perikarya, granular layer synapses, and dentate regions), spinal cord gray matter, dorsal root ganglia, and sympathetic ganglia. The antigen revealed by mass spectrometry analysis and confirmed by recombinant assays (western blot and CBA) was AP3B2 in all. Of 10 seropositive patients, 6 were women; median symptom onset age was 42 years (range 24-58). Clinical information was available for 9 patients, all with subacute onset and rapidly progressive gait ataxia. Neurologic manifestations were myeloneuropathy (3), peripheral sensory neuropathy (2), cerebellar ataxia (2), and spinocerebellar ataxia (2). Five patients received immunotherapy; none improved, but they did not worsen over the follow-up period (median 36 months; range 3-94). Two patients (both with cancer) died. One of 50 control sera was positive by western blot only (but not by IFA or CBA)., Conclusion: AP3B2 (previously named β-neuronal adaptin-like protein) autoimmunity appears rare, is accompanied by ataxia (sensory or cerebellar), and is potentially treatable., (Copyright © 2019 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.)

Objective: To describe an expanded phenotypic spectrum and longitudinal outcome in 256 LGI1-IgG-seropositive and/or CASPR2-IgG-seropositive patients., Methods: Patients were identified through service neural autoantibody evaluation. Ninety-five had longitudinal follow-up (7-456 months; median = 35)., Results: Among 3,910 patients tested, 196 were LGI1-IgG positive, 51 were CASPR2-IgG positive, and 9 were dual positive. Cerebrospinal fluid testing was less sensitive than serum testing, detecting only 24 of 38 (63%) LGI1-IgG-positive and 5 of 6 (83%) CASPR2-IgG-positive patients. LGI1-IgG-positive specimens had higher voltage-gated potassium channel-IgG immunoprecipitation values (0.33nmol/l, range = 0.02-5.14) than CASPR2-IgG-positive specimens (0.10nmol/l, range = 0.00-0.45, p < 0.001). Of patients presenting with pain or peripheral nervous system (PNS) manifestations, 39% were LGI1-IgG seropositive (7% had solely neuropathy or pain). Multivariate analysis identified age as the only significant predictor of central nervous system (CNS) versus PNS involvement (>50 years; odds ratio = 15, p < 0.001). Paroxysmal dizziness spells (PDS), a unique LGI1-IgG accompaniment (14% of patients), frequently delayed the diagnosis. T2-mesiotemporal hyperintensity was more common in LGI1-IgG-positive (41%) than in CASPR2-IgG-positive patients (p = 0.033). T1-bright basal ganglia were confined to LGI1-IgG-positive patients with faciobrachial-dystonic seizures (9 of 39, 31%). Cancer was found in 44% of LGI1-IgG/CASPR2-IgG dual seropositive patients (one-third thymoma). Response to initial immunotherapy was favorable in 97%; mean modified Rankin score was 3 (range = 1-5) at onset and 1.74 (range = 0-6) at last follow-up, with 9% having severe refractory disability, 20% being asymptomatic, 28% receiving immunotherapy, and 58% receiving antiepileptic medication., Interpretation: Older age is a strong predictor of CNS involvement in patients seropositive for CASPR2-IgG or LGI1-IgG. Pain, peripheral manifestations, and stereotypic paroxysmal dizziness spells are common with LGI1-IgG. Response to initial immunotherapy is often favorable, but some patients remain severely disabled, requiring long-term immunotherapy and/or antiepileptic medications. Ann Neurol 2017;82:79-92., (© 2017 American Neurological Association.)

Introduction: Paraneoplastic autoantibody screening of 150,000 patient sera by tissue-based immunofluorescence incidentally revealed 170 with unsuspected signal recognition particle (SRP) immunoglobulin G (IgG), which is a recognized biomarker of autoimmune myopathy. Of the 77 patients with available information, 54 had myopathy. We describe the clinical/laboratory associations., Methods: Distinctive cytoplasm-binding IgG (mouse tissue substrate) prompted western blot, enzyme-linked immunoassay, and immunoprecipitation analyses. Available histories were reviewed., Results: The immunostaining pattern resembled rough endoplasmic reticulum, and mimicked Purkinje-cell cytoplasmic antibody type 1 IgG/anti-Yo. Immunoblotting revealed ribonucleoprotein reactivity. Recombinant antigens confirmed the following: SRP54 IgG specificity alone (17); SRP72 IgG specificity alone (3); both (32); or neither (2). Coexisting neural autoantibodies were identified in 28% (low titer). Electromyography revealed myopathy with fibrillation potentials; 78% of biopsies had active necrotizing myopathy with minimal inflammation, and 17% had inflammatory myopathy. Immunotherapy responsiveness was typically slow and incomplete, and relapses were frequent on withdrawal. Histologically confirmed cancers (17%) were primarily breast and hematologic, with some others., Conclusions: Autoimmune necrotizing SRP myopathy, both idiopathic and paraneoplastic, is underdiagnosed in neurological practice. Serological screening aids early diagnosis. Cancer surveillance and appropriate immunosuppressant therapy may improve outcome. Muscle Nerve 53: 925-932, 2016., (© 2015 The Authors. Muscle & Nerve Published by Wiley Periodicals, Inc.)

Objective: To assess, in a surgical biopsy cohort of active demyelinating lesions, the diagnostic utility of aquaporin-4 (AQP4) immunohistochemistry in identifying neuromyelitis optica (NMO) or NMO spectrum disorder (NMOSD) and describe pathologic features that should prompt AQP4 immunohistochemical analysis and AQP4-immunoglobulin G (IgG) serologic testing., Methods: This was a neuropathologic cohort study of 20 surgical biopsies (19 patients; 11 cord/9 brain), performed because of diagnostic uncertainty, interpreted as active demyelinating disease and containing 2 or more of the following additional features: tissue vacuolation, granulocytic infiltrates, or astrocyte injury., Results: AQP4 immunoreactivity was lost in 18 biopsies and increased in 2. Immunopathologic features of the AQP4 loss cohort were myelin vacuolation (18), dystrophic astrocytes and granulocytes (17), vascular hyalinization (16), macrophages containing glial fibrillary acid protein (GFAP)-positive debris (14), and Creutzfeldt-Peters cells (0). All 14 cases with available serum tested positive for AQP4-IgG after biopsy. Diagnosis at last follow-up was NMO/NMOSD (15) and longitudinally extensive transverse myelitis (1 each relapsing and single). Immunopathologic features of the AQP4 increased cohort were macrophages containing GFAP-positive debris and granulocytes (2), myelin vacuolation (1), dystrophic astrocytes (1), Creutzfeldt-Peters cells (1), and vascular hyalinization (1). Diagnosis at last follow-up was multiple sclerosis (MS) and both tested AQP4-IgG seronegative after biopsy., Conclusions: AQP4 immunohistochemistry with subsequent AQP4-IgG testing has diagnostic utility in identifying cases of NMO/NMOSD. This study highlights the importance of considering NMOSD in the differential diagnosis of tumefactive brain or spinal cord lesions. AQP4-IgG testing may avert biopsy and avoid ineffective therapies if these patients are erroneously treated for MS., (© 2014 American Academy of Neurology.)

Importance: Short transverse myelitis (STM; <3 vertebral segments) is considered noncharacteristic of neuromyelitis optica (NMO) spectrum disorders (NMOSDs). Nonappreciation of the potential for STM to occur in NMOSD may lead to increased disability from delay in diagnosis and appropriate treatment., Objectives: To determine the frequency of short lesions at the initial myelitis manifestation of NMOSD and to compare the demographic, clinical, and radiological characteristics of aquaporin-4-IgG (AQP4-IgG) seropositive and seronegative STM., Design, Setting, and Participants: We reviewed the records and images of patients at the Mayo Clinic who were identified as AQP4-IgG positive from 1996 to 2014. Inclusion criteria were first STM episode, magnetic resonance imaging performed 90 days or less from symptom onset, spinal cord T2-hyperintense lesion less than 3 vertebral segments, AQP4-IgG seropositivity, and a final diagnosis of NMO or NMOSD. Patients with an initial longitudinally extensive transverse myelitis were excluded (n = 151). Patients with STM who were seronegative for AQP4-IgG among an Olmsted County population-based cohort of inflammatory demyelinating disorders of the central nervous system were used as a control group., Main Outcomes and Measures: Delay to diagnosis in months, clinical and radiological characteristics, and disability measured by ambulatory status., Results: Twenty-five patients who were AQP4-IgG seropositive with an initial STM represented 14% of initial myelitis episodes among patients with NMOSD. The STM episode was defined as the first manifestation of NMOSD in 10 patients (40%) preceded by optic neuritis in 13 patients (52%) and preceded by a nausea and vomiting episode in 2 patients (8%). In comparison with the excluded patients with NMOSD who had an initial longitudinally extensive transverse myelitis, delay to diagnosis/treatment was greater when initial lesions were short (P = .02). In AQP4-IgG-positive STM cases, subsequent myelitis episodes were longitudinally extensive in 92%. Attributes more common in patients with AQP4-IgG-positive STM than in 27 population-based patients with AQP4-IgG-negative STM included the following: nonwhite race/ethnicity; tonic spasms; coexisting autoimmunity; magnetic resonance imaging (central cord lesions, T1 hypointensity, and a brain inconsistent with multiple sclerosis); and cerebrospinal fluid (oligoclonal bands lacking)., Conclusions and Relevance: Short transverse myelitis is not uncommon in NMOSD and, when it is present, delays diagnosis and treatment. Clinical and radiological characteristics identified in this study may help select patients with STM who are at the highest risk for an NMOSD. Short transverse myelitis does not exclude consideration of AQP4-IgG testing or NMOSD diagnosis.

Objective: To describe the detection frequency and clinical associations of immunoglobulin G (IgG) targeting dipeptidyl-peptidase-like protein-6 (DPPX), a regulatory subunit of neuronal Kv4.2 potassium channels., Methods: Specimens from 20 patients evaluated on a service basis by tissue-based immunofluorescence yielded a synaptic immunostaining pattern consistent with DPPX-IgG (serum, 20; CSF, all 7 available). Transfected HEK293 cell-based assay confirmed DPPX specificity in all specimens. Sixty-nine patients with stiff-person syndrome and related disorders were also evaluated by DPPX-IgG cell-based assay., Results: Of 20 seropositive patients, 12 were men; median symptom onset age was 53 years (range, 13-75). Symptom onset was insidious in 15 and subacute in 5. Twelve patients reported prodromal weight loss. Neurologic disorders were multifocal. All had one or more brain or brainstem manifestations: amnesia (16), delirium (8), psychosis (4), depression (4), seizures (2), and brainstem disorders (15; eye movement disturbances [8], ataxia [7], dysphagia [6], dysarthria [4], respiratory failure [3]). Nine patients reported sleep disturbance. Manifestations of central hyperexcitability included myoclonus (8), exaggerated startle (6), diffuse rigidity (6), and hyperreflexia (6). Dysautonomia involved the gastrointestinal tract (9; diarrhea [6], gastroparesis, and constipation [3]), bladder (7), cardiac conduction system (3), and thermoregulation (1). Two patients had B-cell neoplasms: gastrointestinal lymphoma (1), and chronic lymphocytic leukemia (1). Substantial neurologic improvements followed immunotherapy in 7 of 11 patients with available treatment data. DPPX-IgG was not detected in any of the stiff-person syndrome patients., Conclusions: DPPX-IgG is a biomarker for an immunotherapy-responsive multifocal neurologic disorder of the central and autonomic nervous systems., (© 2014 American Academy of Neurology.)

Importance: Using an aquaporin-4 (AQP4) M1-isoform-specific enzyme-linked immunosorbent assay (ELISA) and a fixed transfected cell-based assay (CBA), we tested AQP4-IgG in a northern California population representative cohort of 3293 potential cases with multiple sclerosis (MS). Seropositive cases were tested additionally by fluorescence-activated cell sorting, a live transfected cell-based assay., Observations: Sera samples were available in 1040 cases; 7 yielded positive results, 4 by ELISA alone and 3 by both ELISA and CBA. Clinical data (episodes of optic neuritis and longitudinally extensive transverse myelitis [reported on at least 1 magnetic resonance imaging spine]) supported the alternative diagnosis of neuromyelitis optica for 2 patients as seropositive by both ELISA and CBA. These 2 patients alone tested positive by a fluorescence-activated cell-sorting assay. The diagnosis of MS was considered correct in the other 5 patients. Thus, 5 ELISA results and 1 fixed CBA result were false positive., Conclusions and Relevance: Sensitive serological evaluation for AQP4-IgG in this large population-representative cohort of predominantly white non-Hispanic patients with MS reveals that neuromyelitis optica spectrum disorder is rarely misdiagnosed as MS in contemporary US neurological practice (0.2%). The frequency of a false-positive result for ELISA and CBA in this MS cohort were 0.5% and 0.1%, respectively. This finding reflects the superior specificity of CBA and justifies caution in interpreting AQP4-IgG results obtained by ELISA.

Importance: Studies focused on recurrent longitudinally extensive transverse myelitis (rLETM) are lacking., Objectives: To determine the aquaporin 4 (AQP4) IgG detection rate using recombinant human APQ4-based assays in sequential serum specimens collected from patients with rLETM categorized as negative by first-generation tissue-based indirect immunofluorescence (IIF) assay and to define the clinical characteristics and motor disability outcomes in AQP4-IgG-positive rLETM., Design, Setting, and Participants: A search of the Mayo Clinic computerized central diagnostic index (October 1, 2005, through November 30, 2011), cross-linked with the Neuroimmunology Laboratory database, identified 48 patients with rLETM, of whom 36 (75%) were positive and 12 (25%) negative for neuromyelitis optica (NMO) IgG (per IIF of serial serum specimens). Stored serum specimens from "seronegative" patients were retested with recombinant human AQP4-based assays, including enzyme-linked immunosorbent, transfected cell-based, and fluorescence-activated cell-sorting assays. Control patients included 140 AQP4-IgG-positive patients with NMO, of whom a subgroup of 20 initially presented with 2 attacks of transverse myelitis (rLETM-onset NMO)., Main Outcomes and Measures: AQP4-IgG serostatus, clinical characteristics, and Expanded Disability Status Scale score., Results: Six patients with negative IIF results were reclassified as AQP4-IgG positive, yielding an overall AQP4-IgG seropositivity rate of 89%. Fluorescence-activated cell-sorting, cell-based, and enzyme-linked immunosorbent assays improved the detection rate to 89%, 85%, and 81%, respectively. The female to male ratio was 2:3 for AQP4-IgG-negative rLETM and 5:1 for AQP4-IgG-positive patients. The AQP4-IgG-positive patients with rLETM or rLETM-onset NMO were similar in age at onset, sex ratio, attack severity, relapse rate, and motor disability. From Kaplan-Meier analyses, 36% of AQP4-IgG-positive patients with rLETM are anticipated to need a cane to walk within 5 years after onset. For patients with rLETM-onset NMO, the median time from onset to first optic neuritis attack (54 months) was similar to the median disease duration for AQP4-IgG-positive patients with rLETM (59 months). The median number of attacks was 3 for AQP4-IgG-positive patients with rLETM (range, 2-22), and the first optic neuritis attack for those with rLETM-onset NMO followed a median of 3 myelitis attacks (range, 2-19). Immunosuppressant therapy reduced the relapse rate in both AQP4-IgG-positive and AQP4-IgG-negative patients with rLETM., Conclusions and Relevance: Recombinant antigen-based assays significantly increase AQP4-IgG detection in patients with rLETM, and AQP4-IgG-negative adults with rLETM are rare. Evolution to NMO can be anticipated in AQP4-IgG-positive patients. Early initiation of immunotherapy may result in a more favorable motor outcome.

Objective: To 1) determine, using contemporary recombinant antigen-based assays, the aquaporin-4 (AQP4)-immunoglobulin G (IgG) detection rate in sequential sera of patients assigned a clinical diagnosis of neuromyelitis optica (NMO) but initially scored negative by tissue-based indirect immunofluorescence (IIF) assay; and 2) evaluate the impact of serostatus on phenotype and outcome., Methods: From Mayo Clinic records (2005-2011), we identified 163 patients with NMO; 110 (67%) were seropositive by IIF and 53 (33%) were scored seronegative. Available stored sera from 49 "seronegative" patients were tested by ELISA, AQP4-transfected cell-based assay, and in-house fluorescence-activated cell sorting assay. Clinical characteristics were compared based on final serostatus., Results: Thirty of the 49 IIF-negative patients (61%) were reclassified as seropositive, yielding an overall AQP4-IgG seropositivity rate of 88% (i.e., 12% seronegative). The fluorescence-activated cell sorting assay improved the detection rate to 87%, cell-based assay to 84%, and ELISA to 79%. The sex ratio (female to male) was 1:1 for seronegatives and 9:1 for seropositives (p < 0.0001). Simultaneous optic neuritis and transverse myelitis as onset attack type (i.e., within 30 days of each other) occurred in 32% of seronegatives and in 3.6% of seropositives (p < 0.0001). Relapse rate, disability outcome, and other clinical characteristics did not differ significantly., Conclusions: Serological tests using recombinant AQP4 antigen are significantly more sensitive than tissue-based IIF for detecting AQP4-IgG. Testing should precede immunotherapy; if negative, later-drawn specimens should be tested. AQP4-IgG-seronegative NMO is less frequent than previously reported and is clinically similar to AQP4-IgG-seropositive NMO.

Objective: Small-cell lung carcinoma (SCLC) and limbic encephalitis are recognized γ-aminobutyric acid-B receptor (GABABR) autoantibody accompaniments. We sought to determine in a diagnostic serology laboratory the frequency and accompaniments (neurologic, oncologic, and serologic) of GABABR-immunoglobulin G (IgG)., Methods: We tested stored serum and CSF specimens from 3 patient groups for GABABR-IgG by indirect immunofluorescence on mouse brain tissue and transfected HEK293 cells. Group 1 included 3,989 patients tested for GABABR-IgG in service evaluation for suspected autoimmune encephalopathy. Group 2 included 49 patients with an unclassified CNS synaptic IgG detected (antedating descriptions of GABABR autoantibody). Group 3 included 384 patients in whom ≥1 SCLC-predictive autoantibodies had been detected., Results: GABABR-specific IgG was detected in 17 patients (serum, 14; CSF, 11). N-type calcium channel antibody coexisted with GABABR-IgG in all seropositive patients of groups 1 and 2. In group 1, 7 of 3,989 patients were positive (0.2%). All had limbic encephalitis; 5 had SCLC. Four patients received immunotherapy and improved neurologically. In group 2, 5 of 49 patients were positive (10%). Three had limbic encephalitis, 1 had rapidly progressive encephalomyelopathy, and 1 had cerebellar ataxia. Two patients had SCLC and 1 had multiple myeloma. In group 3, 5 of 384 patients were positive (1.3%); titers were low (detected only by transfected cell assay). The neurologic presentations were diverse and attributable to coexisting T-cell-mediated autoimmunity (indicated by CRMP-5 IgG [2], ANNA-1 [2], and ANNA-3 [2]), rather than to GABABR-IgG., Conclusion: GABABR autoantibody is a marker of an uncommon but treatable paraneoplastic neurologic disorder, usually occurring in the setting of limbic encephalitis and SCLC.

Background: Complement activation after binding of an IgG autoantibody to aquaporin 4 (AQP4) is thought to be a major determinant of CNS inflammation and astrocytic injury in neuromyelitis optica. The aim of this study was to investigate the use of eculizumab--a therapeutic monoclonal IgG that neutralises the complement protein C5--in neuromyelitis optica spectrum disorders., Methods: Between Oct 20, 2009, and Nov 3, 2010, we recruited patients from two US centres into an open-label trial. Patients were AQP4-IgG-seropositive, aged at least 18 years, had a neuromyelitis optica spectrum disorder, and had at least two attacks in the preceding 6 months or three in the previous 12 months. Patients received meningococcal vaccine at a screening visit and 2 weeks later began eculizumab treatment. They received 600 mg intravenous eculizumab weekly for 4 weeks, 900 mg in the fifth week, and then 900 mg every 2 weeks for 48 weeks. The coprimary endpoints were efficacy (measured by number of attacks [new worsening of neurological function lasting for more than 24 h and not attributable to an identifiable cause]) and safety. Secondary endpoints were disability (measured by expanded disability status scale), ambulation (Hauser score), and visual acuity. At follow-up visits (after 6 weeks and 3, 6, 9, and 12 months of treatment; and 3 and 12 months after discontinuation), complete neurological examination was undertaken and an adverse event questionnaire completed. This trial is registered with ClinicalTrials.gov, number NCT00904826., Findings: We enrolled 14 patients, all of whom were women. After 12 months of eculizumab treatment, 12 patients were relapse free; two had had possible attacks. The median number of attacks per year fell from three before treatment (range two to four) to zero (zero to one) during treatment (p<0·0001). No patient had worsened disability by any outcome measure. Median score on the expanded disability status scale improved from 4·3 (range 1·0-8·0) before treatment to 3·5 (0-8·0) during treatment (p=0·0078). Two patients improved by two points and three improved by one point on the Hauser score; no change was recorded for the other patients. Visual acuity had improved in at least one eye by one point in four patients, and by two points in one patient; no change was recorded for other patients. One patient had meningococcal sepsis and sterile meningitis about 2 months after the first eculizumab infusion, but resumed treatment after full recovery. No other drug-related serious adverse events occurred. Eight attacks in five patients were reported within 12 months of eculizumab withdrawal., Interpretation: Eculizumab seems to be well tolerated, significantly reduce attack frequency, and stabilise or improve neurological disability measures in patients with aggressive neuromyelitis optica spectrum disorders. The apparent effects of eculizumab deserve further investigation in larger, randomised controlled studies., Funding: Alexion Pharmaceuticals., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Objective: To determine the sex and age distribution of aquaporin-4 (AQP4) autoimmunity using data derived from clinical service laboratory testing of 56,464 patient samples., Design: Observational analysis., Setting: Mayo Clinic Neuroimmunology Laboratory., Patients: Between October 1, 2005, and January 4, 2011, 56,464 patients were tested for AQP4-IgG; 2960 (5.2%) patients were seropositive., Main Outcome Measure: Seropositivity for AQP4-IgG., Results: Patients seropositive for AQP4-IgG were older than seronegative patients (mean [SD] age, 46 [16] vs 42 [15] years, respectively; P < .001). More females than males were tested (37,662 vs 16,810, respectively; P < .001). Among 2743 seropositive patients, 146 (5.3%) were pediatric (aged ≤18 years) and 333 (12.1%) were elderly (aged ≥65 years). The sex distribution of seropositive patients was 2465 females and 306 males (absolute female:male ratio, 8.1:1; P < .001). After adjusting for the number of females tested, an excess of females persisted (adjusted female:male ratio, 3.6:1). Female predominance for AQP4-IgG was more striking in adults (absolute female:male ratio, 8.4:1; adjusted female:male ratio, 3.5:1) than in pediatric patients (absolute female:male ratio, 4.3:1; adjusted female:male ratio, 2.9:1) (P < .001). Elderly women were more likely to be seropositive than individuals in other age categories (13.1% vs 6.0%, respectively; P < .001). The proportion of AQP4-IgG-seropositive individuals (detection rate), defined by decade of age, increased exponentially in women after age 50 years., Conclusions: Seropositivity for AQP4-IgG occurs predominantly in females, particularly in individuals older than 18 years. Among seropositive patients, 1 in 6 is in the extremes of age. The detection rate of AQP4-IgG increased in women after age 50 years.

The astrocytic aquaporin-4 (AQP4) water channel is the target of pathogenic antibodies in a spectrum of relapsing autoimmune inflammatory central nervous system disorders of varying severity that is unified by detection of the serum biomarker neuromyelitis optica (NMO)-IgG. Neuromyelitis optica is the most severe of these disorders. The two major AQP4 isoforms, M1 and M23, have identical extracellular residues. This report identifies two novel properties of NMO-IgG as determinants of pathogenicity. First, the binding of NMO-IgG to the ectodomain of astrocytic AQP4 has isoform-specific outcomes. M1 is completely internalized, but M23 resists internalization and is aggregated into larger-order orthogonal arrays of particles that activate complement more effectively than M1 when bound by NMO-IgG. Second, NMO-IgG binding to either isoform impairs water flux directly, independently of antigen down-regulation. We identified, in nondestructive central nervous system lesions of two NMO patients, two previously unappreciated histopathological correlates supporting the clinical relevance of our in vitro findings: (i) reactive astrocytes with persistent foci of surface AQP4 and (ii) vacuolation in adjacent myelin consistent with edema. The multiple molecular outcomes identified as a consequence of NMO-IgG interaction with AQP4 plausibly account for the diverse pathological features of NMO: edema, inflammation, demyelination, and necrosis. Differences in the nature and anatomical distribution of NMO lesions, and in the clinical and imaging manifestations of disease documented in pediatric and adult patients, may be influenced by regional and maturational differences in the ratio of M1 to M23 proteins in astrocytic membranes.

Objective: To investigate the full extent of Purkinje cell cytoplasmic autoantibody type 1 autoimmunity (classically associated with paraneoplastic cerebellar degeneration) from clinical, immunohistochemical, and neuropathological perspectives., Design: Case series., Setting: Mayo Clinics, 3 sites (Minnesota, Arizona, and Florida)., Patients: Of 133,138 patients tested over a 21-year period, 83 (0.06%) were identified as seropositive for Purkinje cell cytoplasmic autoantibody type 1 IgG., Main Outcome Measures: The frequency of cerebellar and noncerebellar disorders and the clinical outcomes (neurological and oncological) of the patients., Results: All patients were women. At initial presentation, 64 patients (77%) had a cerebellar disorder, and 19 patients (23%) had an extracerebellar disorder. Over the clinical course, neurological symptoms and signs were multifocal in 50 patients (60%), and they involved the cerebellum (89% of patients), the pyramidal tract (30%), the brainstem (13%), and the spinal anterior horn cells or peripheral nerve (10%; frequently upper limb predominant); 11% of patients did not develop cerebellar ataxia. Serological and neuropathological findings were observed in the cerebellum, the brainstem, the spinal cord, the anterior horn, and the dorsal root ganglion that paralleled the diversity of clinical signs. After a median follow-up of 18 months, 1 or more carcinomas had been detected in 88% of patients: ovarian epithelial cancer (53%), breast cancer (22%), fallopian tubal cancer (11%), primary peritoneal cancer (5%), metastases of unknown primary cancer (4%), and other cancers (4%). Sustained improvement was reported in 15% of patients following oncological or immunological therapies. Voltage-gated calcium channel antibodies coexisted in 23 patients (28%)., Conclusions: Purkinje cell cytoplasmic autoantibody type 1 autoimmunity most commonly affects the cerebellum, but the spectrum of neurological symptoms and presentations is broad. Neurological outcomes are usually poor, even when cancer remission is achieved.

Introduction: Extratemporal involvement has been reported in ANNA-1 encephalitis, but the rate is unknown. EEG and MRI are used in the evaluation of these patients, but the relative value of each has not been determined. The study objectives were to measure the rate of extratemporal abnormalities, and to determine the relative value of MRI and EEG in an ANNA-1 encephalitis cohort., Methods: We selected from the neuroimmunology laboratory database ANNA-1 seropositive patients who underwent: (1) neurological evaluation at Mayo Clinic Rochester between 1990 and 2010 (2) comprehensive autoimmune paraneoplastic serological evaluation and (3) at least one EEG and MRI., Results: Of 28 identified patients, the EEG was abnormal in 24 (86%). Extratemporal abnormalities included slowing [12 (43%)], epileptiform discharges [eight (29%)], and epilepsia partialis continua [two (7%)]. In ten patients, only the MRI or EEG showed an abnormality but not both. Six patients had focal EEG abnormalities localized to regions other than those on MRI. In 13 patients with a negative MRI, the EEG showed a focal abnormality in seven (54%)., Conclusion: Extratemporal EEG abnormalities are present in nearly half of ANNA-1 seropositive patients, suggesting that extratemporal involvement is common. EEG and MRI are often complementary in determining lesional distribution in ANNA-1 seropositive patients., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Peripherin-IgG has been reported a pertinent autoantibody in non-obese type 1 diabetic (NOD) mice. However, it has not previously been recognized in any human disease. In blinded evaluation of serum for markers of neurological autoimmunity in a high-volume diagnostic laboratory, we incidentally identified 26 patients (61% female) with an IgG that bound selectively to neural elements in enteric ganglia, sympathetic nerve trunks and discrete nerve tracts in mid-brain and hind-brain. The target antigen was identified as peripherin, a 55kDa - type III intermediate filament protein. Review of clinical histories revealed that 54% of seropositive patients had dysautonomia (predominantly gastrointestinal dysmotility), 30% had neuropathies with varied sensory symptoms and 35% had clinical or serological evidence of endocrinopathy (type 1 diabetes, thyroiditis or premature ovarian failure). Collectively, 73% had autonomic dysfunction or endocrinopathy. None of 173 healthy subjects was seropositive. Subsequent western blot evaluation of archival sera from patients with small fiber/autonomic neuropathies (with or without endocrinopathy) revealed a 33% seropositivity rate for peripherin-IgG. Our further demonstration that peripherin-immunoreactive autonomic fibers in pancreas, thyroid and ovary are juxtaposed to endocrine epithelium, complement our clinical observations in suggesting that neuronal elements may be a pertinent initial target for immune attack in multiple forms of endocrine autoimmunity (intermolecular epitope spreading). It remains to be determined whether or not peripherin-IgG is predictive for development of small fiber neuropathy (autonomic or somatic).

Background: Recent reports support a pathogenic role in neuromyelitis optica (NMO) for the aquaporin-4 (AQP4)-specific autoantibody (NMO-IgG). Neuromyelitis optica is an inflammatory demyelinating central nervous system disease, usually relapsing, that causes variable degrees of attack-related disability. The NMO-IgG binds in vitro to the extracellular domain of AQP4, activates complement, and causes astrocyte lesioning., Objective: To compare the prognostic utility of NMO-IgG titer and quantitative measures of complement-mediated injury to AQP4-expressing cells in NMO attacks., Design, Setting, and Participants: A retrospective clinical-serological correlative study at Mayo Clinic's Neuroimmunology Laboratory was undertaken. Over an 18-month period, we identified NMO-IgG-seropositive patients in whom sufficient serum and adequate clinical information pertaining to NMO attacks (6 severe, 6 mild) were available to analyze clinical-serological correlations. Sera from 9 patients with multiple sclerosis and 9 healthy subjects (all NMO-IgG seronegative) served as controls. Complement activation was measured by quantifying the number of green fluorescent protein-AQP4-transfected HEK 293 cells permeable to the viability dye propidium iodide after exposure to patient serum and active complement., Main Outcome Measures: Attack severity (mild or severe), percentage of AQP4-transfected cells lesioned, and NMO-IgG titer., Results: The median percentage of AQP4-transfected cells lesioned by complement in the presence of serum from patients with NMO was 14% for patients with mild attacks and 54% for patients with severe attacks (P = .005). Median complement activation values for sera from healthy subjects and patients with multiple sclerosis were 8% and 12%, respectively. Patients with mild NMO attacks and patients with severe NMO attacks did not differ significantly with respect to NMO-IgG titer (P = .089)., Conclusions: A laboratory measure of complement-mediated cell injury may serve as a prognostic biomarker in NMO. Larger prospective studies are required to validate this observation.

Several autoimmune myelopathies are recognized clinically. We describe 57 patients in whom serological evaluation for myelopathy of uncertain cause demonstrated collapsin response-mediator protein 5 IgG. Most had spinal imaging and cerebrospinal fluid abnormalities and insidiously progressive presentation; some had acute monophasic or relapsing myelopathy. Initial diagnoses included multiple sclerosis, transverse myelitis, and unspecified neurodegenerative myelopathy. Most were smokers; neoplasia was discovered in 68% (most commonly small-cell lung carcinoma and after collapsin response-mediator protein-5 IgG detection). Collapsin response-mediator protein-5 autoimmune myelopathy and occult neoplasia are important considerations in patients with insidiously progressive myelopathy, especially with known cancer risk.

Objective: We investigated whether neuromyelitis optica (NMO) IgG seropositivity at the initial presentation of longitudinally extensive transverse myelitis (LETM) predicts relapse of myelitis or development of optic neuritis., Methods: Prospective study of patients with initial LETM who were tested for the presence of NMO-IgG., Results: Eleven of 29 patients (37.9%) were seropositive after a first attack of LETM spanning three or more vertebral segments on magnetic resonance imaging. Of 23 patients followed up for 1 year, none of 14 who were seronegative experienced a relapse or developed optic neuritis. Of 9 seropositive patients, 5 developed a second event: 4 of 9 (44%) developed recurrent transverse myelitis and 1 of 9 (11%) developed optic neuritis (p = 0.004)., Interpretation: LETM represents an inaugural or limited form of NMO in a high proportion of patients. The 40% of patients who are seropositive for NMO-IgG are at high risk for relapse.

Neuromyelitis optica (NMO) is an inflammatory demyelinating disease that principally targets the optic nerves and spinal cord and often leads to severe disability and occasionally life threatening respiratory failure. Although its clinical manifestations overlap with those of multiple sclerosis (MS), in established cases these two conditions can be distinguished on the basis of clinical, radiological, and routine spinal fluid studies. The diagnosis in early cases or limited forms of NMO is difficult. We recently discovered a unique IgG autoantibody (NMO-IgG) that is highly specific to patients with NMO and thus a valuable diagnostic aid. Its antigen, aquaporin-4 (AQP4), is the central nervous system's predominant water channel protein. This antibody has not yet been proven to be pathogenic, but several facts suggest that it might be, including the similarity of the immunohistochemical pattern of NMO-(AQP4) IgG binding to mouse CNS tissues to the pattern of immune complex deposition in autopsied patients' spinal cord tissue. The spectrum of diseases identified by NMO-IgG is broader than has previously been recognized clinically and includes incomplete forms of NMO, such as recurrent transverse myelitis without optic neuritis and recurrent optic neuritis without myelitis.

Neuromyelitis optica (NMO) is an inflammatory demyelinating disease that selectively affects optic nerves and spinal cord. It is considered a severe variant of multiple sclerosis (MS), and frequently is misdiagnosed as MS, but prognosis and optimal treatments differ. A serum immunoglobulin G autoantibody (NMO-IgG) serves as a specific marker for NMO. Here we show that NMO-IgG binds selectively to the aquaporin-4 water channel, a component of the dystroglycan protein complex located in astrocytic foot processes at the blood-brain barrier. NMO may represent the first example of a novel class of autoimmune channelopathy.

Autoantibodies have defined two paraneoplastic visual disorders related to small-cell lung carcinoma: retinopathy ("CAR"-IgG [23kDa, recoverin]) and optic neuritis collapsin response-mediated protein 5 (CRMP-5-IgG [62kDa]). Among 16 patients with CRMP-5-IgG and optic neuritis (aged 52-74 years; all smokers, 9 women), we documented coexisting retinitis in 5. None had CAR-IgG. Fifteen had subacute vision loss, swollen optic discs, and field defects. Vascular leakage was evident at and remote from the disc; 5/5 tested had abnormal electroretinograms. Nine had striking vitreous cells. Vitrectomy showed reactive lymphocytosis (4/4), predominantly CD4(+) (1/1). Most patients had multifocal neurological accompaniments. Cerebrospinal fluid contained lymphocytes (7-32), elevated protein, multiple oligoclonal immunoglobulin bands, and CRMP-5-IgG. Three patients superficially resembled Devic's disease at presentation. One autopsied patient had predominantly CD8(+) T lymphocytes infiltrating optic nerve and spinal cord. Eleven patients had confirmed small-cell carcinoma; 1 had imaging evidence of lung cancer; 3 had renal or thyroid carcinoma. Full-length CRMP-5 protein was identified in normal retina and optic nerve by Western blot analyses. Photoreceptor cells, retinal ganglion cells, and nerve fibers exhibited CRMP-5-specific immunoreactivity. In summary, CRMP-5-IgG defines a paraneoplastic ophthalmological entity of combined optic neuritis and retinitis with vitreous inflammatory cells. Positive serology obviates the need for vitreous biopsy and expedites the search for cancer.

We identified the IgG autoantibody ANNA-2 ("anti-Ri") in 34 patients in a 12-year period by immunofluorescence screening of sera from approximately 75000 patients with subacute neurological disorders that were suspected to be paraneoplastic. Detailed clinical information was available for 28 patients (10 men, 18 women). Cancer was diagnosed in 24 patients (86%); 21 had histologically proven carcinoma (10 lung, 9 breast, 1 cervical, 1 bladder), and 3 had an intrathoracic imaging abnormality. Cancer anteceded neurological symptoms in 4 of 28 patients. Cancer detection frequency increased with continued surveillance. Neurological disorders, in decreasing frequency, were brainstem syndrome (including opsoclonus, myoclonus, or both), cerebellar syndrome, myelopathy, peripheral neuropathy, cranial neuropathy, movement disorder, encephalopathy, Lambert-Eaton syndrome, and seizures. Four patients had laryngospasm and four had jaw opening dystonia (two with neck dystonia). Nine (32%) were wheelchair-bound 1 month after neurological symptom onset. Most improved neurologically after immunomodulatory or tumor-directed therapy. Accompanying autoantibodies, found in 73% of sera, included ANNA-1, ANNA-3, CRMP-5-IgG, P/Q-type and N-type Ca(2+) channel antibodies, and muscle-type acetylcholine receptor antibody. Some neurological accompaniments of ANNA-2 may reflect potentially pathogenic humoral or cell-mediated responses to coimmunogenic tumor antigens, for example, Lambert-Eaton syndrome (P/Q-type Ca(2+) channel antibody) and peripheral neuropathy (ANNA-1 effector T cells).

Objective:We sought to validate methods for detection and confirmation of GABAA receptor (R)-IgG and clinically characterize seropositive cases. Methods:Archived serum and CSF specimens (185 total) suspected to harbor GABAAR-IgG were evaluated by indirect immunofluorescence assay (IFA). Twenty-six specimens from 19 patients appeared suspicious for GABAAR-IgG positivity by IFA, based on prior reports and comparison with commercial GABAAR antibody staining. Aliquots of those specimens were tested at the University of Oxford, United Kingdom, and Euroimmun, Lubeck, Germany, for GABAAR-IgG by cell-based assays (CBAs) using HEK293-indicator cells transfected with plasmids encoding different GABAAR subunits. Results:Eight specimens (of 26 tested; 4 serums, 4 CSFs) from 5 patients were confirmed by CBA to be GABAAR-IgG positive. Patient IgGs were always reactive with α1β3 GABAAR subunits. One more patient was identified clinically after this validation study. Median age for the 6 patients at serologic diagnosis was 44 years (range, 1-71 years), and 4 of them were male. Among the 4 for whom clinical information was available (2 treated by the authors), all had encephalitis and antiepileptic drug refractory seizures. Three out of 4 patients treated with a combination of immunotherapies had good outcomes. The fourth, recognized to have an autoimmune cause late in the clinical course, had severe permanent neurologic sequelae and brain atrophy. Conclusions:Though not as common as NMDA-R encephalitis, GABAAR encephalitis generally has a characteristic clinical-radiologic presentation and is treatable, making accurate laboratory diagnosis critical.

Neuromyelitis optica (NMO) is a severe inflammatory autoimmune CNS disorder triggered by binding of an IgG autoantibody to the aquaporin 4 (AQP4) water channel on astrocytes. Activation of cytolytic complement has been implicated as the major effector of tissue destruction that secondarily involves myelin. We investigated early precytolytic events in the evolving pathophysiology of NMO in mice by continuously infusing IgG (NMO patient serum-derived or AQP4-specific mouse monoclonal), without exogenous complement, into the spinal subarachnoid space. Motor impairment and sublytic NMO-compatible immunopathology were IgG dose dependent, AQP4 dependent, and, unexpectedly, microglia dependent. In vivo spinal cord imaging revealed a striking physical interaction between microglia and astrocytes that required signaling from astrocytes by the C3a fragment of their upregulated complement C3 protein. Astrocytes remained viable but lost AQP4. Previously unappreciated crosstalk between astrocytes and microglia involving early-activated CNS-intrinsic complement components and microglial C3a receptor signaling appears to be a critical driver of the precytolytic phase in the evolving NMO lesion, including initial motor impairment. Our results indicate that microglia merit consideration as a potential target for NMO therapeutic intervention., Introduction Neuromyelitis optica (NMO) is an inflammatory autoimmune disorder of the central nervous system (CNS) with secondary myelin loss. It disproportionately affects women and non-White populations, typically presents as optic [...]

Objective: Determine the utility of aquaporin 4 IgG (AQP4-IgG) testing (live cell-based assay) for Neuromyelitis Optica Spectrum Disorders (NMOSD). Methods: We included Mayo Clinic patients (1/1/2018-12/31/2019) tested for serum AQP4-IgG by live cell-based flow-cytometric assay. Medical records were reviewed to assess if patients fulfilled 2015 NMOSD criteria. Results: Of 1371 patients tested, 41 were positive (3%) and all fulfilled NMOSD criteria with AQP4-IgG (specificity = 100%). Only 10/1330 testing negative met NMOSD criteria without AQP4-IgG (sensitivity = 80%) and seven of these 10 were MOG-IgG positive. Conclusions: AQP4-IgG by live cell-based assay was highly specific and without false positives in a high throughput setting. [ABSTRACT FROM AUTHOR]

Abstract: To determine whether CSF leucine‐rich glioma‐inactivated 1(LGI1)‐IgG titer, index or IgG subclass has prognostic significance, we tested serum and CSF specimens collected concomitantly from 39 seropositive patients. LGI1‐IgG index was elevated (>1) in 21 patients (54%), suggesting intrathecal synthesis. Patients with worse outcome at last follow‐up (modified Rankin Scale >2) had significantly higher index (median 6.57 vs. 0.5, P = 0.048) compared to those with better outcome. Higher CSF LGI1‐IgG4 subclass‐specific titer and index correlated with worse outcome (P < 0.005 for both). These data suggest that evidence of intrathecal LGI1‐IgG synthesis may correlate with neuronal injury and warrant consideration of aggressive immunotherapy. [ABSTRACT FROM AUTHOR]

Aquaporin-4 (AQP4) water channel-specific IgG distinguishes neuromyelitis optica (NMO) from multiple sclerosis and causes characteristic immunopathology in which central nervous system (CNS) demyelination is secondary. Early events initiating the pathophysiological outcomes of IgG binding to astrocytic AQP4 are poorly understood. CNS lesions reflect events documented in vitro following IgG interaction with AQP4: AQP4 internalization, attenuated glutamate uptake, intramyelinic edema, interleukin-6 release, complement activation, inflammatory cell recruitment, and demyelination. Here, we demonstrate that AQP4 internalization requires AQP4-bound IgG to engage an astrocytic Fcγ receptor (FcγR). IgG-lacking Fc redistributes AQP4 within the plasma membrane and induces interleukin-6 release. However, AQP4 endocytosis requires an activating FcγR's gamma subunit and involves astrocytic membrane loss of an inhibitory FcγR, CD32B. Interaction of the IgG-AQP4 complex with FcγRs triggers coendocytosis of the excitatory amino acid transporter 2 (EAAT2). Requirement of FcγR engagement for internalization of two astrocytic membrane proteins critical to CNS homeostasis identifies a complement-independent, upstream target for potential early therapeutic intervention in NMO. [ABSTRACT FROM AUTHOR]

Background & Aims: Antibodies against the water channel protein aquaporin (AQP)-4 cause a spectrum of inflammatory, demyelinating, central nervous system disorders called neuromyelitis optica spectrum disorders (NMOSDs); these primarily affect the optic nerves and spinal cord but also the brain. Symptoms of intractable nausea, vomiting, and hiccups reflect involvement of AQP4 in the brainstem area postrema and account for gastroenterological presentations. We investigated the frequency of intractable nausea, vomiting, or hiccups in patients with NMOSD who tested positive for immunoglobulin G against AQP4 (AQP4-IgG). We also analyzed sera from patients with idiopathic nausea or vomiting for the presence of AQP4-IgG. Methods: We reviewed the Mayo Clinic AQP4-IgG positive NMOSD database (n = 70) to identify patients who presented with vomiting, focusing on results from gastroenterological evaluations. We also tested serum samples (from the Gastroparesis Clinical Research Consortium repository) from patients who presented with idiopathic nausea or vomiting for AQP4-IgG (controls, n = 318 with gastroparesis and 117 without gastroparesis). Results: Ten AQP4-IgG–positive patients diagnosed with NMOSD (14% of patients in the database) initially presented with intractable vomiting. Extensive gastroenterological evaluation was noninformative. AQP4-IgG was not detected in any of the controls. Conclusions: Although NMOSDs are rare, tests for AQP4-IgG should be considered for patients who present with unexplained, intractable vomiting. Detection of the antibody before the development of optic neuritis or transverse myelitis allows patients to receive immunosuppressive therapy before the development of neurologic disabilities. [ABSTRACT FROM AUTHOR]

Collapsin response-mediator protein 5 (CRMP5) immunoglobulin G (IgG) has been associated with paraneoplastic optic neuritis, vitritis, retinitis, or a combination thereof, but few reports of these findings exist in the literature. We reviewed the neuro-ophthalmic findings and visual outcomes in a large series of CRMP5 IgG–positive patients to characterize further its clinical phenotype and response to treatment. Retrospective case series. Seventy-six patients with CRMP5 autoimmunity examined at the Mayo Clinic, Rochester, Minnesota. Single academic medical center chart review of all CRMP5 IgG–positive (serum titer, >1:240) patients seen between 2001 and 2017. Neuro-ophthalmic manifestations and outcomes of CRMP5 autoimmunity, coexisting neural autoantibody presence and paraneoplastic associations, and the impact of immunosuppressant therapy. Twenty-nine of 76 patients (38%) demonstrated neuro-ophthalmic manifestations. Of the 29 patients with neuro-ophthalmic findings, the median age was 67 years (range, 33–88 years) and 20 (69%) were women. Cancer was diagnosed in 62% of the patients (small-cell carcinoma in 83%). Neuro-ophthalmic symptoms occurred before the diagnosis of cancer in 72%. Seventeen of 29 patients (59%) showed ocular (i.e., anterior visual pathway or intraocular) manifestations; presenting median visual acuity was 20/50 (range, 20/20–counting fingers) and the final median visual acuity was 20/40 (range, 20/20–hand movements). Fourteen of 17 patients (82%) demonstrated optic neuropathy, with 12 of these patients also showing retinitis or uveitis. Three of 17 patients (18%) showed retinitis or uveitis without optic neuropathy. All 12 patients with optic neuropathy and a documented fundus examination at visual symptom onset demonstrated optic disc edema. No patients showed optic nerve enhancement on magnetic resonance imaging. Twelve of 29 patients (41%) demonstrated ocular motility dysfunction consisting of central nystagmus and diplopia. Among those receiving immunosuppressive therapy, visual function improved in 50%. In our cohort of 29 CRMP5 IgG–positive patients with neuro-ophthalmic manifestations, optic neuropathy presented with optic disc edema, often associated with uveitis, retinitis, or both. The combination of retinitis, vitritis, and optic disc edema without optic nerve enhancement should prompt serologic testing for CRMP5 IgG to expedite vision-sparing immunosuppressant therapy and a targeted search for a systemic cancer. [ABSTRACT FROM AUTHOR]

Abstract Recognition of autoimmunity as a cause of encephalopathy has increased. Recent studies have validated the use of Antibody-Prevalence-in-Epilepsy (APE) and Responsive-to-immunotherapy-in-Epilepsy (RITE) scores in the evaluation and management of autoimmune-epilepsy. We aim to assess the utility of these models for patients with cognitive dysfunction. Among the evaluated patients, 17% had antibodies universally associated with autoimmune-encephalopathy. NMDA-R-IgG and LGI1-IgG were the most common antibody specificities. Antibody-Prevalence-in-Epilepsy-and-Encephalopathy (APE2) score ≥ 4 was 99% sensitive and 93% specific for neural-specific-antibodies. Responsive-to-immunotherapy-in-Epilepsy-and-Encephalopathy (RITE2) score ≥ 7 had 96% sensitivity and 86% specificity for favorable initial immunotherapy response. Application of these models may optimize autoantibody evaluations and immunotherapeutic trials. Graphical abstract Unlabelled Image Highlights • Neural-specific antibodies associated with autoimmune-encephalopathy were detected in 17% of the patients evaluated. • NMDA-R IgG and LGI-1 IgG were the most common neural antibody specificities detected. • APE2 score ≥4 was 99% sensitive and 93% specific for neural-specific-antibodies. • RITE2 score ≥7 had 96% sensitivity and 86% specificity for favorable response to initial immunotherapy. • RITE2 score < 7 was associated with refractoriness to initial immunotherapy even among patients with neural-specific autoantibodies. [ABSTRACT FROM AUTHOR]

In this prospective evaluation of serum and CSF samples, all but two CSF GFAPα-IgG positive patients had autoimmune meningoencephalomyelitis while serum GFAPα-IgG positivity alone was less specific. Phenotypes were diverse among patients that were serum positive only. Adult and pediatric clinical presentations were similar. Most patients were immunotherapy responsive. Co-existing NMDA-R-IgG and cancer were associated with lack of response to first-line immunotherapy. Among patients with follow-up information, 18% had relapses. This study demonstrates CSF GFAPα-IgG is a specific autoimmune meningoencephalomyelitis biomarker, with favorable corticosteroid response. Lack of response should prompt evaluation for co-existing NMDA-R-IgG or malignancy. [ABSTRACT FROM AUTHOR]

Autoimmunity targeting voltage-gated potassium channel complexes have not been systematically documented in children. Identified in the Neuroimmunology Laboratory records of Mayo Clinic were 12 seropositive children, 7 among 252 Mayo Clinic pediatric patients tested on a service basis for serologic evidence of neurologic autoimmunity (June 2008-April 2010), 4 during the assay’s preimplementation validation (before June 2008) and 1 non-Mayo patient with available clinical information. Neurologic manifestations were subacute and multifocal. Three had global developmental regression, 6 movement disorders, 4 dysarthria, 3 seizures, 1 Satoyoshi syndrome, 1 painful red feet, 2 insomnia, 2 gastrointestinal dysmotility, and 2 small fiber neuropathy. Neoplasia was found in 1 child. Treating physicians recorded improvement in all 7 children who received immunotherapy. Neurologic symptom relapse occurred in 3 of 6 children after ceasing immunotherapy. These findings highlight a diverse clinical spectrum of neuronal potassium channel complex autoimmunity in children, and they illustrate benefit from early initiated immunotherapy, with a tendency to relapse when therapy ceases. Diagnosis is generally delayed in the process of eliminating neurodegenerative causes. Currently 2.7% of pediatric sera evaluated for neurologic autoimmunity are positive for neuronal potassium channel complex-reactive immunoglobulin G. The frequency and full spectrum of neurologic accompaniments remains to be determined. [ABSTRACT FROM AUTHOR]