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A growing spectrum of neurological manifestations are being recognized in association with IgLON5 autoimmunity, including recent reports of motor-neuron-disease-like phenotype. Here we describe four cases of IgLON5 autoimmunity with motor neuron involvement and evaluate an additional 109 probable or definite amyotrophic lateral sclerosis cases seen in our neuromuscular clinic for IgLON5-IgG seropositivity. The presence of parasomnias, vocal cord dysfunction or hyperkinetic movements in a patient with motor-neuron-disease-like phenotype should prompt evaluation for IgLON5-IgG autoantibodies. Recognition and treatment of this autoimmune disease with immunosuppressive agents may bring about significant neurological improvement in a minority of cases.

ObjectivesTo report the expanded neurological presentations and oncological associations of tripartite motif-containing protein 46 (TRIM46)-IgG seropositive patients.MethodsArchived sera/cerebrospinal fluid (CSF) were evaluated by tissue-based immunofluorescence assay to identify patients with identical axon initial segment (AIS)-specific staining pattern. Phage immunoprecipitation sequencing (PhIP-Seq) was used to identify the putative autoantigen.ResultsIgG in serum (17) and/or CSF (16) from 25 patients yielded unique AIS-specific staining on murine central nervous system (CNS) tissue. An autoantibody specific for TRIM46 was identified by PhIP-Seq, and autoantigen specificity was confirmed by transfected COS7 cell-based assay. Clinical information was available for 22 TRIM46-IgG seropositive patients. Fifteen were female (68%). Median age was 67 years (range 25–87). Fifteen (68%) patients presented with subacute cerebellar syndrome (six isolated; nine with CNS accompaniments: encephalopathy (three), brainstem signs (two), myelopathy (two), parkinsonism (one)). Other phenotypes included limbic encephalitis (three), encephalopathy with/without seizures (two), myelopathy (two). Eighteen (82%) had cancer: neuroendocrine carcinomas (9; pancreatic (3), small-cell lung (4), oesophagus (1), endometrium (1)), adenocarcinomas (6; lung (2), ovarian (2), endometrial (1), breast (1)), sarcoma (2) and gastrointestinal tumour (1). Neurological symptoms in three followed immune checkpoint inhibitor (ICI) administration.ConclusionsThis study supports TRIM46-IgG being a biomarker of paraneoplastic CNS disorders and expands the neurological phenotypes, oncological and ICI-related adverse event associations.

ObjectiveCochleovestibulopathy is a distinguishable paraneoplastic phenotype. In this study, we evaluate clinical presentation, serological/cancer associations and outcomes of paraneoplastic cochleovestibulopathy.MethodsRetrospective chart review of patients with hearing impairment and/or vestibulopathy who underwent serological evaluations for paraneoplastic antibodies between January 2007 and February 2021 was performed.ResultsTwenty-six patients were identified (men, n=23; median age, 45 years, range: 28–70). Biomarkers detected included: KLHL11-IgG‌ ‌(n=20,‌ ‌77% (coexisting LUZP4-IgG, n=8)),‌ ‌‌ANNA1-IgG‌ ‌ ‌(n=3,‌ ‌12%),‌ ‌amphiphysin-IgG‌‌ ‌(n=2,‌ ‌8%)‌ ‌and‌ ‌LUZP4-IgG‌‌ ‌(n=1,‌ ‌4%). Most common neoplastic association was ‌testicular‌/‌extra-testicular‌ ‌seminoma‌ ‌ (n=13,‌ ‌50%).‌‌ Hearing‌ impairment (bilateral, 62%) was ‌present‌ ‌in‌ ‌all‌ ‌patients.‌ ‌Fifteen patients (58%) had cochleovestibular dysfunction as their initial presentation before rhombencephalitis/encephalomyelitis manifestations (hearing loss, four; acute vertigo, eight; both, three). ‌Brain‌ ‌MRI‌ ‌demonstrated‌ ‌internal‌ ‌auditory‌ ‌canal‌ ‌enhancement‌ ‌in‌ ‌four ‌patients.‌ Audiometry commonly revealed severe-profound bilateral sensorineural hearing loss. Most patients ‌had‌ a refractory course ‌despite‌ ‌immunotherapy‌ ‌and/or‌ ‌cancer‌ ‌treatment‌.ConclusionCochleovestibulopathy commonly presents with rapidly progressive bilateral hearing loss and/or acute vertigo. However, in some patients, these symptoms present along with or following brainstem/cerebellar manifestations. KLHL11-IgG and seminoma are the most common serological and cancer associations, respectively. Recognition of this phenotype may aid in earlier diagnosis of paraneoplastic autoimmunity and associated cancer.

Immune-mediated rippling muscle disease (iRMD) is a rare myopathy characterized by wavelike muscle contractions (rippling) and percussion- or stretch-induced muscle mounding. A serological biomarker of this disease is lacking.To describe a novel autoantibody biomarker of iRMD and report associated clinicopathological characteristics.This retrospective cohort study evaluated archived sera from 10 adult patients at tertiary care centers at the Mayo Clinic, Rochester, Minnesota, and BrighamWomen's Hospital, Boston, Massachusetts, who were diagnosed with iRMD by neuromuscular specialists in 2000 and 2021, based on the presence of electrically silent percussion- or stretch-induced muscle rippling and percussion-induced rapid muscle contraction with or without muscle mounding and an autoimmune basis. Sera were evaluated for a common biomarker using phage immunoprecipitation sequencing. Myopathology consistent with iRMD was documented in most patients. The median (range) follow-up was 18 (1-30) months.Diagnosis of iRMD.Detection of a common autoantibody in serum of patients sharing similar clinical and myopathological features.Seven male individuals and 3 female individuals with iRMD were identified (median [range] age at onset, 60 [18-76] years). An IgG autoantibody specific for caveolae-associated protein 4 (cavin-4) was identified in serum of patients with iRMD using human proteome phage immunoprecipitation sequencing. Immunoassays using recombinant cavin-4 confirmed cavin-4 IgG seropositivity in 8 of 10 patients with iRMD. Results for healthy and disease-control individuals (n = 241, including myasthenia gravis and immune-mediated myopathies) were cavin-4 IgG seronegative. Six of the 8 individuals with cavin-4 IgG were male, and the median (range) age was 60 (18-76) years. Initial symptoms included rippling of lower limb muscles in 5 of 8 individuals or all limb muscles in 2 of 8 sparing bulbar muscles, fatigue in 9 of 10, mild proximal weakness in 3 of 8, and isolated myalgia in 1 of 8, followed by development of diffuse rippling. All patients had percussion-induced muscle rippling and half had percussion- or stretch-induced muscle mounding. Four of the 10 patients had proximal weakness. Plasma creatine kinase was elevated in all but 1 patient. Six of the 10 patients underwent malignancy screening; cancer was detected prospectively in only 1. Muscle biopsy was performed in 7 of the 8 patients with cavin-4 IgG; 6 of 6 specimens analyzed immunohistochemically revealed a mosaic pattern of sarcolemmal cavin-4 immunoreactivity. Three of 6 patients whose results were seropositive and who received immunotherapy had complete resolution of symptoms, 1 had mild improvement, and 2 had no change.The findings indicate that cavin-4 IgG may be the first specific serological autoantibody biomarker identified in iRMD. Depletion of cavin-4 expression in muscle biopsies of patients with iRMD suggests the potential role of this autoantigen in disease pathogenesis.

Background and ObjectivesDiagnostic criteria emphasize the use of sensitive and disease-specific tests to distinguish patients with rapidly progressive dementia (RPD) due to Creutzfeldt-Jakob disease (CJD) vs other causes (mimics). These tests are often performed in specialized centers, with results taking days to return. There is a need to leverage clinical features and rapidly reporting tests to distinguish patients with RPD due to CJD from those due to other causes (mimics) early in the symptomatic course.MethodsIn this case-control series, clinical features and the results of diagnostic tests were compared between mimics (n = 11) and patients with definite (pathologically proven, n = 33) or probable CJD (with positive real-time quaking-induced conversion [RT-QuIC], n = 60). Patients were assessed at Mayo Clinic Enterprise or Washington University from January 2014 to February 2021. Mimics were enrolled in prospective studies of RPD; mimics met the diagnostic criteria for probable CJD but did not have CJD.ResultsMimics were ultimately diagnosed with autoimmune encephalitis (n = 6), neurosarcoidosis, frontotemporal lobar degeneration with motor neuron disease, dural arteriovenous fistula, cerebral amyloid angiopathy with related inflammation, and systemic lupus erythematous with polypharmacy. Age at symptom onset, sex, presenting features, and MRI and EEG findings were similar in CJD cases and mimics. Focal motor abnormalities (49/93, 11/11), CSF leukocytosis (4/92, 5/11), and protein >45 mg/dL (39/92, 10/11) were more common in mimics (p< 0.01). Positive RT-QuIC (77/80, 0/9) and total tau >1149 pg/mL (74/82, 2/10) were more common in CJD cases (allp< 0.01). Protein 14-3-3 was elevated in 64/89 CJD cases and 4/10 mimics (p= 0.067). Neural-specific autoantibodies associated with autoimmune encephalitis were detected within the serum (5/9) and CSF (5/10) of mimics; nonspecific antibodies were detected within the serum of 9/71 CJD cases.DiscussionImmune-mediated, vascular, granulomatous, and neurodegenerative diseases may mimic CJD at presentation and should be considered in patients with early motor dysfunction and abnormal CSF studies. The detection of atypical features—particularly elevations in CSF leukocytes and protein—should prompt evaluation for mimics and consideration of empiric treatment while waiting for the results of more specific tests.

ObjectiveTo describe a novel autoantibody biomarker of Immune mediated rippling muscle disease (iRMD).BackgroundiRMD is a rare immunotherapy-responsive myopathy characterized by wave-like muscle contractions (rippling) and percussion/stretch-induced muscle mounding. However, serological biomarker of this disease is lacking.Design/MethodsA Retrospective review was done to identify iRMD patients with stored sera in Mayo Neuroimmunology laboratory. Archived sera from IRMD patients were evaluated for a common biomarker of IRMD using phage immunoprecipitation sequencing (PhIP-Seq).ResultsArchival sera from 10 patients with clinical diagnosis of iRMD were retrieved. Whole human proteome PhIP-Seq identified peptides corresponding to different regions of the cavin-4 in sera of iRMD patients. Eight of the ten iRMD cases were positive for cavin-4 IgG by immunofluorescent cell-based-assay (CBA) using cavin-4-transfected COS7 cells. The cavin-4-reactive IgG in all 8 positive sera was of IgG1 subclass. None of the disease control sera (98 immune-mediated myopathy/neuromuscular junction disorders, 20 autoimmune CNS diseases and 123 healthy subjects) contained cavin-4-reactive IgG. Furthermore, none of the iRMD patients' sera were positive for caveolin-3 IgG. The majority of seropositive cases were males (6/8, 75%) with median age of 51 years (range 18-76). Three seropositive patients had co-existing myasthenia gravis (38%). Creatine Kinase was elevated in 6/7 tested patients (median 771 U/L, range: 132-2625 U/L). Muscle biopsy was performed in 7 of the 8 cavin-4 IgG seropositive patients; 6/6 specimens analyzed immunohistochemically revealed a mosaic pattern of sarcolemmal cavin-4 immunoreactivity. Three of 6 seropositive patients who received immunotherapy had complete resolution of symptoms; one had mild improvement and two had no change.ConclusionsCavin-4 IgG is a novel and specific serological autoantibody biomarker identified in iRMD. Depletion of cavin-4 expression in iRMD patient muscle biopsies suggests the potential role of this autoantigen in disease pathogenesis.

e15593 Background: Metastatic colorectal cancer (mCRC) is a leading cause of cancer mortality. Few treatment options exist for patients who fail to respond to standard therapeutic agents. For patients with good performance status, phase I studies offer a valuable treatment option with a chance of clinical benefit. In this study, we report clinical characteristics, outcomes and survival of patients enrolled in phase I clinical trials at our institution. Methods: Medical records of patients with mCRC enrolled in phase I clinical trials between January 1999 to January 2022 at our institution were reviewed. Patient demographics, clinical characteristics, laboratory values, toxicities and survival time were analyzed. Overall survival (OS) was calculated as date of diagnosis of metastatic disease to death or last follow up. Phase 1 specific OS was analyzed from date of entry to first phase I trial to death. Results: 212 enrollments corresponding to 174 unique patients enrolled in 50 phase 1 clinical trials were reviewed. 53% (n = 112) were females with a median age of 60 years old [range 29-83]. 95% (n = 201) had an ECOG score of 0-1. The clinical benefit rate (stable disease plus partial response) was 35% and ORR was 4.3%. The median OS was 149 weeks, and the phase I OS was 23 weeks. Majority of the patients (53%, n = 110) received 3 or more lines of chemotherapy prior to phase I trial. In a univariable (UVA) model, the factors associated with better clinical outcome were WBC < 10.8 (P < 0.001), Hb > 12 (p = 0.011), ECOG score 0 or 1 (p = 0.005), baseline AST < 50 (p = 0.006), baseline albumin > 3.5 (p < 0.001), baseline LDH < 305 (p < 0.001). Conclusions: Phase I trials offer a reasonable option for patients with metastatic CRC. Our experience sheds light on the potential for improved outcomes in terms of survival. The survival of patients is at par with those used in late-stage disease including regorafenib and trifluridine/tipiracil. As expected, normal baseline lab parameters and better PS affect survival. Further modeling will be continued.

OBJECTIVE This study was undertaken to describe a novel biomarker of germ cell tumor and associated paraneoplastic neurological syndrome (PNS). METHODS Archival sera from patients with germ cell tumor-associated PNS were evaluated. We identified a common autoantigen in a human testicular cancer cell line (TCam-2) by Western blot and mass spectrometry. Its identity was confirmed by recombinant-protein Western blot, enzyme-linked immunosorbent assay (ELISA), and cell-based assay. Autoantibody specificity was confirmed by analyzing assorted control sera/cerebrospinal fluid. RESULTS Leucine zipper 4 (LUZP4)-immunoglobulin G (IgG) was detected in 28 patients' sera, 26 of whom (93%) were men. The median age at neurological symptom onset was 45 years (range = 28-84). Median titer (ELISA) was 1:300 (1:50 to >1:6,400, normal value