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  • Autoantibody-mediated disorders of the central nervous system.

    24 October 2018

    Autoimmunity has been demonstrated in a diverse range of peripheral neurological disorders, such as myasthenia gravis and acquired neuromyotonia. Serum antibodies found in these conditions are directed against ion channels and receptors situated on the cell surface and have been shown to produce pathogenic effects. The symptoms of these peripheral disorders have been transferred to animals by passive or active immunisation and, in humans, treated successfully with immunomodulatory therapy. Recently, a number of central nervous system disorders (CNS), such as limbic encephalitis, certain forms of epilepsy, neuromyelitis optica and cerebellar ataxia, have been hypothesised to associate with specific serum autoantibodies. In this article we consider this rapidly expanding field of CNS disorders, discuss evidence for their proposed autoimmune aetiology and review whether the antibodies detected have been shown to be pathogenic or if they are secondary to preceding neuronal damage.

  • HLA and smoking in prediction and prognosis of small cell lung cancer in autoimmune Lambert-Eaton myasthenic syndrome.

    24 October 2018

    Patients with small cell lung cancer (SCLC) survive longer if they have the antibody-mediated Lambert-Eaton myasthenic syndrome (LEMS), making this autoimmune disorder a prototype disease for studying cancer immunosurveillance. Patients with nontumor LEMS (NT-LEMS) never develop SCLC but are otherwise indistinguishable clinically. Therefore, we have compared immunogenetic factors in SCLC-LEMS and NT-LEMS and studied their role in the pathogenesis of LEMS and survival from SCLC. In 48 British and 29 Dutch Caucasian LEMS patients, we studied clinical symptoms, antibody titers, HLA types and alleles at six nearby located microsatellite loci. Highly significant associations were found in NT-LEMS, which appeared strongest with HLA-B8, but also involved HLA-DQ2, -DR3 and six flanking microsatellite alleles. SCLC-LEMS patients were not different from controls. Smoking was a strong predictor of SCLC. In contrast, HLA-B8 positivity correlated with a decreased risk of SCLC even among the smokers. Moreover, in SCLC-LEMS patients, HLA-B8 positivity correlated with prolonged survival after LEMS onset. We propose that two distinct immunopathogenetic routes can lead to one clinically and serologically indistinguishable autoimmune myasthenic syndrome. HLA-DR3-B8 is strongly associated with LEMS in nontumor patients only. In other LEMS patients, SCLC apparently provides a powerful autoimmunogenic stimulus that overrides HLA restrictions in breaking tolerance to calcium channels. Moreover, negativity for HLA-B8 combined with smoking behavior points more strongly to an underlying SCLC and predicts a worse prognosis in SCLC-LEMS patients.

  • A role for autoantibodies in some cases of acquired non-paraneoplastic gut dysmotility.

    24 October 2018

    BACKGROUND: Antibody-mediated autoimmunity underlies a diverse range of disorders, particularly in the nervous system where domains of ion channels and receptors are potential targets. The aetiology of many adult-onset conditions of severe gut dysmotility is not known. We looked for antibodies to neuronal antigens in patients with severe (slow-transit-type) constipation (STC). METHODS: Eleven sera from adult-onset STC patients and 18 from childhood onset cases were tested by routine immunoprecipitation assays for antibodies against neuronal antigens including voltage-gated potassium channels (VGKCs), calcium channels (VGCCs), both muscle and neuronal acetylcholine receptor and glutamic acid decarboxylase (GAD). Results were compared with positive and negative control populations. RESULTS: Two of the 11 sera from patients with adult-onset STC showed highly positive anti-VGKC antibodies. Both had onset of symptoms de novo in adulthood without evidence of autoimmune, neoplastic or neurological disease. One of these patients, and one other, had anti-GAD antibodies. None of the childhood-onset STC had evidence of anti-neuronal antibodies. CONCLUSIONS: Anti-neuronal antibodies are found in some patients with a condition of severe acquired gut dysmotility of previously unknown aetiology. Future studies may demonstrate an autoimmune role for such antibodies.

  • Long term outcome in Lambert-Eaton myasthenic syndrome without lung cancer.

    24 October 2018

    OBJECTIVES: To determine the prognosis in patients with Lambert-Eaton myasthenic syndrome (LEMS) without small cell lung cancer (SCLC), and to analyse longitudinal clinical, electrophysiological, and immunological data on each patient to establish prognostic factors for long term outcome. METHODS: The retrospective and part prospective study of 47 patients with LEMS was undertaken from data recorded during visits to a specialist neuromuscular clinic. Serial measurements of muscle strength score in shoulder abduction, elbow extension and hip flexion, compound muscle action potential (CMAP) amplitude, and postcontraction increment in abductor digiti minimi (ADM), and anti-P/Q-type voltage gated calcium channel (VGCC) antibody titre were made at each visit. RESULTS: Muscle strength scores were improved in 88% of patients after a median duration of immunosuppressive treatment of 6 years (range 1.3 to 17 years); anti-VGCC antibody titres fell in 52% after treatment; and mean resting CMAP amplitude improved from 2.7 mV initially to 8.8 mV after 2 years of treatment p<0.001). Initial pretreatment anti-VGCC antibody titre did not correlate significantly with either CMAP amplitude, CMAP increment, or clinical score: from serial measurements made during follow up, significant correlation between antibody titre and CMAP amplitude was seen in only two patients. Sustained clinical remission was achieved by 20 (43%) of whom only four remained in remission without the need for immunosuppression. Using a Cox proportional hazards model, the only independent predictor of sustained clinical remission was initial pretreatment clinical score (p=0.03). Lymphoma presented in three patients during the study. CONCLUSIONS: The prognosis in patients with LEMS without SCLC is favourable, although patients often need significant doses of immunosuppressive treatment to remain clinically stable. Only initial clinical muscle strength measurements and not anti-VGCC antibody titres or electrophysiological recordings are predictive of long term outcome.

  • Autoantibodies to neuronal surface antigens in thyroid antibody-positive and -negative limbic encephalitis.

    24 October 2018

    BACKGROUND: Thyroid antibodies (Thy-Abs) are frequently detected in various autoimmune disorders in coexistence with other systemic autoantibodies. In association with an encephalopathy, they are often taken as evidence of Hashimoto's encephalitis (HE). However, the presence of Thy-Abs in a cohort of limbic encephalitis (LE) patients and their association with anti-neuronal autoimmunity has not been explored. PATIENTS AND METHODS: We investigated thyroid and anti-neuronal antibodies in the sera of 24 LE patients without identified tumors by cell-based assay and radioimmunoassay and evaluated their clinical features. RESULTS: There was a female predominance in Thy-Ab-positive LE patients. Five of the eight Thy-Ab-positive patients and six of the 16 Thy-Ab-negative patients had antibodies to voltage-gated potassium channel (VGKC), N-methyl-D-aspartate receptor (NMDAR) or undefined surface antigens on cultured hippocampal neurons. There were trends towards fewer VGKC antibodies (1/8 vs. 5/16, P = 0.159) and more NMDAR antibodies (2/8 vs. 1/16, P = 0.095) among the Thy-Ab-positive LE patients; antibodies to undefined surface antigens were only identified in Thy-Ab-positive patients (2/8 vs. 0/16, P = 0.018). There were no distinguishing clinical features between Thy-Ab-positive patients with and without neuronal antibodies. However, patients with anti-neuronal antibodies showed a better treatment response. CONCLUSION: Thy-Abs can be found in a high proportion of patients with non-paraneoplastic LE, often in association with antibodies to specific or as yet undefined neuronal surface antigens. These results suggest that acute idiopathic encephalitis patients with Thy-Abs should be closely monitored for ion-channel antibodies and it should not be assumed that they have HE.

  • Prospective study into the incidence of Lambert Eaton myasthenic syndrome in small cell lung cancer.

    24 October 2018

    INTRODUCTION: The Lambert Eaton myasthenic syndrome (LEMS) is a paraneoplastic disorder associated with raised serum voltage-gated calcium channel (VGCC) antibodies in patients with small cell lung cancer (SCLC). VGCC can also be found in patients with SCLC and cerebellar ataxia. This was a prospective study to assess the incidence of clinical and subclinical LEMS or other neurologic disease in patients with SCLC. PATIENTS AND METHODS: Sixty-three unselected patients with cytologically or histologically confirmed SCLC consented to participate. Pretreatment assessment included a neurologic symptom questionnaire, examination for physical signs of LEMS or ataxia, measurement of serum titers of antibodies to P/Q-type VGCCs by radioimmunoassay in all patients and electrophysiological examination where appropriate. RESULTS: Neurologic symptoms unrelated to LEMS occurred in 26% of patients. Five patients (8%) had raised serum VGCC antibodies (range, 69-1553 pM/l) diagnostic of LEMS, two (3%) of whom had LEMS on clinical and electrophysiological grounds. Both also had mild cerebellar ataxia. There was no association between serum VGCC antibody titer and survival. CONCLUSION: Routine measurement of VGCC antibodies in patients without clinical LEMS is unlikely to assist either in management of SCLC or in assessment of prognosis.