Lennon, Vanda A.

The clinical phenotype of leucine‐rich glioma‐inactivated protein 1 (LGI1) and contactin‐associated proteinlike 2 (CASPR2) autoimmunity is well defined in adults. Data for children are limited (<10 cases). Among 13,319 pediatric patients serologically tested for autoimmune neurological disorders (2010–2017), 264 were seropositive for voltage‐gated potassium channel‐complex–IgG (radioimmunoprecipitation). Only 13 (4.9%) were positive by transfected cell‐binding assay for LGI1‐IgG (n = 7), CASPR2‐IgG (n = 3), or both (n = 3). This is significantly less than in adults. Encephalopathy, seizures, and peripheral nerve hyperexcitability were common, as was coexisting autoimmunity. No faciobrachial dystonic seizures or cancers were identified. Functional neurologic disorders were frequently the initial diagnosis, and immunotherapy appeared beneficial. Ann Neurol 2018;84:473–480

ABSTRACTIntroduction: Antitumor immune responses are postulated to initiate paraneoplastic neurological disorders when proteins that are normally restricted to neural cells are expressed as oncoproteins. Mutated oncopeptides could bypass self‐tolerant T cells to activate cytotoxic effector T lymphocytes and requisite helper T lymphocytes to stimulate autoantibody production by B lymphocytes. Methods: We investigated muscle‐type nicotinic acetylcholine receptor (AChR) antigen expression at transcriptional and protein levels in a small‐cell lung cancer line (SCLC) established from a patient with AChR‐immunoglobulin G (IgG)‐positive myasthenia gravis. Results: We identified messenger RNA transcripts encoding the 2 AChR α1‐subunit isoforms and 7 alternative‐splicing products, 3 of which yielded premature stop codons. Despite detecting native muscle‐type AChR pentamers in the tumor, we did not identify mutant α1‐peptides. However, we found α1‐subunit‐derived peptides bound to tumor major histocompatibility complex (MHC)1‐protein. In a control SCLC from an antineuronal nuclear autoantibody, type 1 (anti‐Hu)‐IgG‐positive patient, we identified MHC1‐complexed Hu protein‐derived peptides but not AChR peptides. Discussion: Our findings support onconeural protein products as pertinent immunogens initiating paraneoplastic neurological autoimmunity. Muscle Nerve 58: 600–604, 2018

AbstractTo 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.

Objective To evaluate the incidence and prevalence of autoimmune encephalitis and compare it to that of infectious encephalitis. Methods We performed a population‐based comparative study of the incidence and prevalence of autoimmune and infectious encephalitis in Olmsted County, Minnesota. Autoimmune encephalitis diagnosis and subgroups were defined by 2016 diagnostic criteria, and infectious encephalitis diagnosis required a confirmed infectious pathogen. Age‐ and sex‐adjusted prevalence and incidence rates were calculated. Patients with encephalitis of uncertain etiology were excluded. Results The prevalence of autoimmune encephalitis on January 1, 2014 of 13.7/100,000 was not significantly different from that of all infectious encephalitides (11.6/100,000; p = 0.63) or the viral subcategory (8.3/100,000; p = 0.17). The incidence rates (1995–2015) of autoimmune and infectious encephalitis were 0.8/100,000 and 1.0/100,000 person‐years, respectively ( p = 0.58). The number of relapses or recurrent hospitalizations was higher for autoimmune than infectious encephalitis ( p = 0.03). The incidence of autoimmune encephalitis increased over time from 0.4/100,000 person‐years (1995–2005) to 1.2/100,000 person‐years (2006–2015; p = 0.02), attributable to increased detection of autoantibody‐positive cases. The incidence (2.8 vs 0.7/100,000 person‐years, p = 0.01) and prevalence (38.3 vs 13.7/100,000, p = 0.04) of autoimmune encephalitis was higher among African Americans than Caucasians. The prevalence of specific neural autoantibodies was as follows: myelin oligodendrocyte glycoprotein, 1.9/100,000; glutamic acid decarboxylase 65, 1.9/100,000; unclassified neural autoantibody, 1.4/100,000; leucine‐rich glioma‐inactivated protein 1, 0.7/100,000; collapsin response‐mediator protein 5, 0.7/100,000; N‐methyl‐D‐aspartate receptor, 0.6/100,000; antineuronal nuclear antibody type 2, 0.6/100,000; and glial fibrillary acidic protein α, 0.6/100,000. Interpretation This study shows that the prevalence and incidence of autoimmune encephalitis are comparable to infectious encephalitis, and its detection is increasing over time. Ann Neurol 2018;83:166–177

ABSTRACTIntroduction: Neuronal calcium channel antibodies are a biomarker of Lambert‐Eaton syndrome (LES) and cerebellar ataxia. We have encountered several patients with LES and cerebellar ataxia coexisting, and we sought to further define this association. Methods: We reviewed records of patients at our institution with a diagnosis of “Lambert‐Eaton syndrome” and “cerebellar ataxia.” Results: Seventeen patients were identified with LES and ataxia. Presenting symptoms were weakness (8), concurrent weakness and ataxia (4), ataxia (4), and other (1). Nine patients had small‐cell lung carcinoma, 3 of whom had survival greater than 100 months. Immunotherapy responses were best among patients without cancer. Nine of 17 (53%) patients were alive at last follow‐up (median survival 62 months; range, 8–240). Discussion: Calcium channel autoimmunity should be considered in patients with coexisting cerebellar ataxia and myasthenic weakness. Affected patients may survive small‐cell carcinoma or have immunotherapy‐responsive neurological symptoms. Muscle Nerve 58: 29–35, 2018