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Rodrigues PRDVP, Kay CSK, Ducci RDP, Utiumi MAT, Fustes OJH, Werneck LC, Lorenzoni PJ, Scola RH. Triple-seronegative myasthenia gravis: clinical and epidemiological characteristics. ARQUIVOS DE NEURO-PSIQUIATRIA 2024; 82:1-7. [PMID: 38316426 PMCID: PMC10843919 DOI: 10.1055/s-0044-1779052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 10/04/2023] [Indexed: 02/07/2024]
Abstract
BACKGROUND Myasthenia gravis (MG) is an autoimmune disease usually caused by antibodies against the acetylcholine receptor (AChR-Abs), muscle-specific tyrosine kinase (MuSK-Abs), or low-density lipoprotein receptor-related protein 4 (LRP4-Abs). However, there are MG patients who do not have these antibodies and are thus said to have triple-seronegative (triple-SN) MG. OBJECTIVE This study aims to describe the frequency and clinical and epidemiological characteristics of patients with triple-SN MG. METHODS This was a retrospective cross-sectional study carried out through the analysis of medical records. Descriptive and analytical statistical analysis was performed comparing subgroups of myasthenic patients, classified according to serological profile. RESULTS The sample population consisted of 93 MG patients: 85 were positive for antibodies, 80 (86%) with AChR-Abs, 5 (5.4%) with MuSK-Abs, and no MG patients with LRP4-Abs. Eight patients (8.6%) had triple-SN MG; they had a median age at disease onset of 30 years (21-45). Their most common initial symptoms were ptosis, diplopia, and generalized weakness. Most patients presented with mild symptoms at their last visit, reflecting a median MG composite scale score of 4 (0-6), and 75% of patients had an adequate response to treatment. CONCLUSION Our study showed a low frequency of triple-SN MG in Brazilian MG patients. Triple-SN MG was predominant in females, who presented with ptosis, diplopia, and generalized weakness, and most patients had an adequate response to immunosuppressive treatment. There was no significant difference between triple-SN MG and the other subgroups.
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Affiliation(s)
- Paula Raquel do Vale Pascoal Rodrigues
- Universidade Federal do Paraná, Hospital de Clínicas, Departamento de Clínica Médica, Serviço de Neurologia, Serviço de Doenças Neuromusculares, Curitiba PR, Brazil.
- Universidade Federal do Paraná, Programa de Pós-Graduação em Medicina Interna, Curitiba PR, Brazil.
| | - Cláudia Suemi Kamoi Kay
- Universidade Federal do Paraná, Hospital de Clínicas, Departamento de Clínica Médica, Serviço de Neurologia, Serviço de Doenças Neuromusculares, Curitiba PR, Brazil.
| | - Renata Dal-Pra Ducci
- Universidade Federal do Paraná, Hospital de Clínicas, Departamento de Clínica Médica, Serviço de Neurologia, Serviço de Doenças Neuromusculares, Curitiba PR, Brazil.
| | | | - Otto Jesus Hernandez Fustes
- Universidade Federal do Paraná, Hospital de Clínicas, Departamento de Clínica Médica, Serviço de Neurologia, Serviço de Doenças Neuromusculares, Curitiba PR, Brazil.
| | - Lineu Cesar Werneck
- Universidade Federal do Paraná, Hospital de Clínicas, Departamento de Clínica Médica, Serviço de Neurologia, Serviço de Doenças Neuromusculares, Curitiba PR, Brazil.
- Universidade Federal do Paraná, Programa de Pós-Graduação em Medicina Interna, Curitiba PR, Brazil.
| | - Paulo José Lorenzoni
- Universidade Federal do Paraná, Hospital de Clínicas, Departamento de Clínica Médica, Serviço de Neurologia, Serviço de Doenças Neuromusculares, Curitiba PR, Brazil.
| | - Rosana Herminia Scola
- Universidade Federal do Paraná, Hospital de Clínicas, Departamento de Clínica Médica, Serviço de Neurologia, Serviço de Doenças Neuromusculares, Curitiba PR, Brazil.
- Universidade Federal do Paraná, Programa de Pós-Graduação em Medicina Interna, Curitiba PR, Brazil.
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Behbehani R. Ocular Myasthenia Gravis: A Current Overview. Eye Brain 2023; 15:1-13. [PMID: 36778719 PMCID: PMC9911903 DOI: 10.2147/eb.s389629] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 01/24/2023] [Indexed: 02/05/2023] Open
Abstract
Ocular myasthenia gravis (OMG) is a neuromuscular disease characterized by autoantibody production against post-synaptic proteins in the neuromuscular junction. The pathophysiological auto-immune mechanisms of myasthenia are diverse, and this is governed primarily by the type of autoantibody production. The diagnosis of OMG relies mainly on clinical assessment, the use of serological antibody assays for acetylcholine receptors (AchR), muscle-specific tyrosine kinase (MusK), and low-density lipoprotein 4 (LPR4). Other autoantibodies against post-synaptic proteins, such as cortactin and agrin, have been detected; however, their diagnostic value and pathogenic effect are not yet clearly defined. Clinical tests such as the ice test and electrophysiologic tests, particularly single-fiber electromyography, have a valuable role in diagnosis. The treatment of OMG is primarily through cholinesterase inhibitors (pyridostigmine), and steroids are frequently required in cases of ophthalmoplegia. Other immunosuppressive therapies include antimetabolites (azathioprine, mycophenolate mofetil, methotrexate) and biological agents such as B-cell depleting agents (Rituximab) and complement inhibitors (eculizumab). Evidence is scarce on the effect of immunosuppressive therapy on altering the natural course of OMG. Clinicians must be vigilant of a myasthenic syndrome in patients using immune-check inhibitors. Reliable and consistent biomarkers are required to assess disease severity and response to therapy to optimize the management of OMG. The purpose of this review is to summarize the current trends and the latest developments in diagnosing and treating OMG.
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Affiliation(s)
- Raed Behbehani
- Neuroophthalmology Unit, Ibn Sina Hospital, Kuwait City, Kuwait,Correspondence: Raed Behbehani, Ibn Sina Hospital, P.O Box 1180, Tel +965 2224 2999, Fax +965 2249 2406, Email
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3
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Jain R, Aulakh R, Banga A. Unusual presentation of uncommon cause of ptosis. J Paediatr Child Health 2023; 59:560-562. [PMID: 36633381 DOI: 10.1111/jpc.16321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2022] [Revised: 09/07/2022] [Accepted: 12/20/2022] [Indexed: 01/13/2023]
Affiliation(s)
- Reena Jain
- Department of Pediatrics, Government Medical College and Hospital, Chandigarh, India
| | - Roosy Aulakh
- Department of Pediatrics, Government Medical College and Hospital, Chandigarh, India
| | - Akshay Banga
- Department of Pediatrics, Government Medical College and Hospital, Chandigarh, India
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4
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Harsini S, Rezaei N. Autoimmune diseases. Clin Immunol 2023. [DOI: 10.1016/b978-0-12-818006-8.00001-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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5
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Vanoli F, Mantegazza R. Antibody Therapies in Autoimmune Neuromuscular Junction Disorders: Approach to Myasthenic Crisis and Chronic Management. Neurotherapeutics 2022; 19:897-910. [PMID: 35165857 PMCID: PMC9294078 DOI: 10.1007/s13311-022-01181-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/02/2022] [Indexed: 02/06/2023] Open
Abstract
Myasthenia gravis (MG) is a neurological autoimmune disorder characterized by muscle weakness and fatigue. It is a B cell-mediated disease caused by pathogenic antibodies directed against various components of the neuromuscular junction (NMJ). Despite the wide range of adverse effects, current treatment is still based on non-specific immunosuppression, particularly on long-term steroid usage. The increasing knowledge regarding the pathogenic mechanisms of MG has however allowed to create more target-specific therapies. A very attractive therapeutic approach is currently offered by monoclonal antibodies (mAbs), given their ability to specifically and effectively target different immunopathological pathways, such as the complement cascade, B cell-related cluster of differentiation (CD) proteins, and the human neonatal Fc receptor (FcRn). Up to now, eculizumab, a C5-directed mAb, has been approved for the treatment of generalized MG (gMG) and efgartigimod, a FcRn inhibitor, has just been approved by the U.S. Food and Drug Administration for the treatment of anti-acetylcholine receptor (AChR) antibody positive gMG. Other mAbs are currently under investigation with encouraging preliminary results, further enriching the new range of therapeutic possibilities for MG. This review article provides an overview of the present status of mAb-based therapies for MG, which offer an exciting promise for better outcomes by setting the basis of a precision medicine approach.
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Affiliation(s)
- Fiammetta Vanoli
- Neuroimmunology and Neuromuscular Disease Department, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
- Department of Human Neurosciences, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185, Rome, Italy
| | - Renato Mantegazza
- Neuroimmunology and Neuromuscular Disease Department, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy.
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6
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Punga AR, Maddison P, Heckmann JM, Guptill JT, Evoli A. Epidemiology, diagnostics, and biomarkers of autoimmune neuromuscular junction disorders. Lancet Neurol 2022; 21:176-188. [DOI: 10.1016/s1474-4422(21)00297-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 08/18/2021] [Accepted: 08/25/2021] [Indexed: 12/14/2022]
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Circulating Biomarkers in Neuromuscular Disorders: What Is Known, What Is New. Biomolecules 2021; 11:biom11081246. [PMID: 34439911 PMCID: PMC8393752 DOI: 10.3390/biom11081246] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 08/16/2021] [Accepted: 08/19/2021] [Indexed: 02/07/2023] Open
Abstract
The urgent need for new therapies for some devastating neuromuscular diseases (NMDs), such as Duchenne muscular dystrophy or amyotrophic lateral sclerosis, has led to an intense search for new potential biomarkers. Biomarkers can be classified based on their clinical value into different categories: diagnostic biomarkers confirm the presence of a specific disease, prognostic biomarkers provide information about disease course, and therapeutic biomarkers are designed to predict or measure treatment response. Circulating biomarkers, as opposed to instrumental/invasive ones (e.g., muscle MRI or nerve ultrasound, muscle or nerve biopsy), are generally easier to access and less “time-consuming”. In addition to well-known creatine kinase, other promising molecules seem to be candidate biomarkers to improve the diagnosis, prognosis and prediction of therapeutic response, such as antibodies, neurofilaments, and microRNAs. However, there are some criticalities that can complicate their application: variability during the day, stability, and reliable performance metrics (e.g., accuracy, precision and reproducibility) across laboratories. In the present review, we discuss the application of biochemical biomarkers (both validated and emerging) in the most common NMDs with a focus on their diagnostic, prognostic/predictive and therapeutic application, and finally, we address the critical issues in the introduction of new biomarkers.
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8
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Fc-Receptor Targeted Therapies for the Treatment of Myasthenia gravis. Int J Mol Sci 2021; 22:ijms22115755. [PMID: 34071155 PMCID: PMC8198115 DOI: 10.3390/ijms22115755] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 05/24/2021] [Accepted: 05/25/2021] [Indexed: 12/16/2022] Open
Abstract
Myasthenia gravis (MG) is an autoimmune disease in which immunoglobulin G (IgG) antibodies (Abs) bind to acetylcholine receptors (AChR) or to functionally related molecules in the postsynaptic membrane at the neuromuscular junction. IgG crystallizable fragment (Fc)-mediated effector functions, such as antibody-dependent complement deposition, contribute to disease development and progression. Despite progress in understanding Ab-mediated disease mechanisms, immunotherapy of MG remained rather unspecific with corticosteroids and maintenance with immunosuppressants as first choice drugs for most patients. More specific therapeutic IgG Fc-based platforms that reduce serum half-life or effector functions of pathogenic MG-related Abs are currently being developed, tested in clinical trials or have recently been successfully translated into the clinic. In this review, we illustrate mechanisms of action and clinical efficacies of emerging Fc-mediated therapeutics such as neonatal Fc receptor (FcRn)-targeting agents. Furthermore, we evaluate prospects of therapies targeting classical Fc receptors that have shown promising therapeutic efficacy in other antibody-mediated conditions. Increased availability of Fc- and Fc receptor-targeting biologics might foster the development of personalized immunotherapies with the potential to induce sustained disease remission in patients with MG.
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9
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Gastaldi M, Scaranzin S, Businaro P, Mobilia E, Benedetti L, Pesce G, Franciotta D. Improving laboratory diagnostics in myasthenia gravis. Expert Rev Mol Diagn 2021; 21:579-590. [PMID: 33970749 DOI: 10.1080/14737159.2021.1927715] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Introduction: Myasthenia gravis (MG) is a prototypical autoimmune disease, characterized by pathogenic autoantibodies targeting structures of the neuromuscular junction. Radioimmunoprecipitation assays (RIPAs) represent the gold standard for their detection. However, new methods are emerging to complement, or overcome RIPAs, also with the perspective of eliminating the use of radioactive reagents.Areas covered: We discuss advances in laboratory methods, prompted especially by cell-based assays (CBAs), for the detection of the autoantibodies of MG diagnostics, above all those to the nicotinic acetylcholine receptor (AChR), muscle-specific kinase (MuSK), and low molecular-weight receptor-related low-density lipoprotein-4 (LRP4).Expert opinion: CBA technology makes AChRs aggregate on cell membranes, thus allowing to detect autoantibodies to clustered AChRs, with reduction of seronegative MG cases. The diagnostic relevance of RIPA/CBA-measurable LRP4 antibodies is still unclear, in Caucasian patients at least. Live CBAs for the detection of AChR, MuSK, and LRP4 antibodies might represent an alternative to RIPAs, but first require full validation. CBAs could be used as screening tests, limiting RIPAs for antibody quantification. To this end, ELISAs might be an alternative.Fixation procedures preserving enough degree of antigen conformationality could yield AChR and MuSK CBAs suitable for a wide use in clinical-chemistry laboratories.
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Affiliation(s)
- Matteo Gastaldi
- Neuroimmunology Laboratory, IRCCS Mondino Foundation, Pavia, Italy
| | - Silvia Scaranzin
- Neuroimmunology Laboratory, IRCCS Mondino Foundation, Pavia, Italy
| | - Pietro Businaro
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Emanuela Mobilia
- Autoimmunity Laboratory, IRCCS Ospedale Policlinico San Martino, Genova, Italy
| | - Luana Benedetti
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova, Genova, Italy; IRCCS Ospedale Policlinico San Martino, Genova, Italy
| | - Giampaola Pesce
- Autoimmunity Laboratory, IRCCS Ospedale Policlinico San Martino, Genova, Italy.,Department of Internal Medicine (Dimi), University of Genova, Genova, Italy
| | - Diego Franciotta
- Autoimmunity Laboratory, IRCCS Ospedale Policlinico San Martino, Genova, Italy
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10
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Frykman H, Kumar P, Oger J. Immunopathology of Autoimmune Myasthenia Gravis: Implications for Improved Testing Algorithms and Treatment Strategies. Front Neurol 2020; 11:596621. [PMID: 33362698 PMCID: PMC7755715 DOI: 10.3389/fneur.2020.596621] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 11/19/2020] [Indexed: 12/13/2022] Open
Abstract
Myasthenia gravis (MG) is a heterogeneous condition, characterized by autoantibodies (Abs) that target functionally important structures within neuromuscular junctions (NMJ), thus affecting nerve-to-muscle transmission. MG patients are more often now subgrouped based on the profile of serum autoantibodies, which segregate with clinical presentation, immunopathology, and their response to therapies. The serological testing plays an essential role in confirming MG diagnosis and guiding disease management, although a small percentage of MG patients remain negative for antibodies. With the advancements in new highly effective pathophysiologically-specific immunotherapeutic options, it has become increasingly important to identify the specific Abs responsible for the pathogenicity in individual MG patients. There are several new assays and protocols being developed for the improved detection of Abs in MG patients. This review focuses on the divergent immunopathological mechanisms in MG, and discusses their relevance to improved diagnostic and treatment. We propose a comprehensive "reflex testing," algorithm for the presence of MG autoantibodies, and foresee that in the near future, the convenience and specificity of novel assays will permit the clinicians to consider them into routine systematic testing, thus stimulating laboratories to make these tests available. Moreover, adopting treatment driven testing algorithms will be crucial to identify subgroups of patients potentially benefiting from novel immunotherapies for MG.
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Affiliation(s)
- Hans Frykman
- Department of Medicine, University of British Columbia, Vancouver, BC, Canada.,BC Neuroimmunology Lab, University of British Columbia, Vancouver, BC, Canada
| | - Pankaj Kumar
- BC Neuroimmunology Lab, University of British Columbia, Vancouver, BC, Canada
| | - Joel Oger
- Department of Medicine, University of British Columbia, Vancouver, BC, Canada.,BC Neuroimmunology Lab, University of British Columbia, Vancouver, BC, Canada
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11
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Rodríguez Cruz PM, Cossins J, Beeson D, Vincent A. The Neuromuscular Junction in Health and Disease: Molecular Mechanisms Governing Synaptic Formation and Homeostasis. Front Mol Neurosci 2020; 13:610964. [PMID: 33343299 PMCID: PMC7744297 DOI: 10.3389/fnmol.2020.610964] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 10/30/2020] [Indexed: 12/28/2022] Open
Abstract
The neuromuscular junction (NMJ) is a highly specialized synapse between a motor neuron nerve terminal and its muscle fiber that are responsible for converting electrical impulses generated by the motor neuron into electrical activity in the muscle fibers. On arrival of the motor nerve action potential, calcium enters the presynaptic terminal, which leads to the release of the neurotransmitter acetylcholine (ACh). ACh crosses the synaptic gap and binds to ACh receptors (AChRs) tightly clustered on the surface of the muscle fiber; this leads to the endplate potential which initiates the muscle action potential that results in muscle contraction. This is a simplified version of the events in neuromuscular transmission that take place within milliseconds, and are dependent on a tiny but highly structured NMJ. Much of this review is devoted to describing in more detail the development, maturation, maintenance and regeneration of the NMJ, but first we describe briefly the most important molecules involved and the conditions that affect their numbers and function. Most important clinically worldwide, are myasthenia gravis (MG), the Lambert-Eaton myasthenic syndrome (LEMS) and congenital myasthenic syndromes (CMS), each of which causes specific molecular defects. In addition, we mention the neurotoxins from bacteria, snakes and many other species that interfere with neuromuscular transmission and cause potentially fatal diseases, but have also provided useful probes for investigating neuromuscular transmission. There are also changes in NMJ structure and function in motor neuron disease, spinal muscle atrophy and sarcopenia that are likely to be secondary but might provide treatment targets. The NMJ is one of the best studied and most disease-prone synapses in the nervous system and it is amenable to in vivo and ex vivo investigation and to systemic therapies that can help restore normal function.
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Affiliation(s)
- Pedro M. Rodríguez Cruz
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - Judith Cossins
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
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12
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Evoli A, Iorio R. Controversies in Ocular Myasthenia Gravis. Front Neurol 2020; 11:605902. [PMID: 33329368 PMCID: PMC7734350 DOI: 10.3389/fneur.2020.605902] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Accepted: 10/26/2020] [Indexed: 12/12/2022] Open
Abstract
Myasthenia gravis (MG) with symptoms limited to eye muscles [ocular MG (OMG)] is a rare disease. OMG incidence varies according to ethnicity and age of onset. In recent years, both an increase in incidence rate, particularly in the elderly, and a lower risk for secondary generalization may have contributed to the growing disease prevalence in Western countries. OMG should be considered in patients with painless ptosis and extrinsic ophthalmoparesis. Though asymmetric muscle involvement and symptom fluctuations are typical, in some cases, OMG can mimic isolated cranial nerve paresis, internuclear ophthalmoplegia, and conjugate gaze palsy. Diagnostic confirmation can be challenging in patients negative for anti-acetylcholine receptor and anti-muscle-specific tyrosine kinase antibodies on standard radioimmunoassay. Early treatment is aimed at relieving symptoms and at preventing disease progression to generalized MG. Despite the absence of high-level evidence, there is general agreement on the efficacy of steroids at low to moderate dosage; immunosuppressants are considered when steroid high maintenance doses are required. The role of thymectomy in non-thymoma patients is controversial. Prolonged exposure to immunosuppressive therapy has a negative impact on the health-related quality of life in a proportion of these patients. OMG is currently excluded from most of the treatments recently developed in generalized MG.
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Affiliation(s)
- Amelia Evoli
- Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy.,Department of Neuroscience, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Raffaele Iorio
- Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy.,Department of Neuroscience, Università Cattolica del Sacro Cuore, Rome, Italy
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13
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Lazaridis K, Tzartos SJ. Myasthenia Gravis: Autoantibody Specificities and Their Role in MG Management. Front Neurol 2020; 11:596981. [PMID: 33329350 PMCID: PMC7734299 DOI: 10.3389/fneur.2020.596981] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 10/30/2020] [Indexed: 12/11/2022] Open
Abstract
Myasthenia gravis (MG) is the most common autoimmune disorder affecting the neuromuscular junction, characterized by skeletal muscle weakness and fatigability. It is caused by autoantibodies targeting proteins of the neuromuscular junction; ~85% of MG patients have autoantibodies against the muscle acetylcholine receptor (AChR-MG), whereas about 5% of MG patients have autoantibodies against the muscle specific kinase (MuSK-MG). In the remaining about 10% of patients no autoantibodies can be found with the classical diagnostics for AChR and MuSK antibodies (seronegative MG, SN-MG). Since serological tests are relatively easy and non-invasive for disease diagnosis, the improvement of methods for the detection of known autoantibodies or the discovery of novel autoantibody specificities to diminish SN-MG and to facilitate differential diagnosis of similar diseases, is crucial. Radioimmunoprecipitation assays (RIPA) are the staple for MG antibody detection, but over the past years, using cell-based assays (CBAs) or improved highly sensitive RIPAs, it has been possible to detect autoantibodies in previously SN-MG patients. This led to the identification of more patients with antibodies to the classical antigens AChR and MuSK and to the third MG autoantigen, the low-density lipoprotein receptor-related protein 4 (LRP4), while antibodies against other extracellular or intracellular targets, such as agrin, Kv1.4 potassium channels, collagen Q, titin, the ryanodine receptor and cortactin have been found in some MG patients. Since the autoantigen targeted determines in part the clinical manifestations, prognosis and response to treatment, serological tests are not only indispensable for initial diagnosis, but also for monitoring treatment efficacy. Importantly, knowing the autoantibody profile of MG patients could allow for more efficient personalized therapeutic approaches. Significant progress has been made over the past years toward the development of antigen-specific therapies, targeting only the specific immune cells or autoantibodies involved in the autoimmune response. In this review, we will present the progress made toward the development of novel sensitive autoantibody detection assays, the identification of new MG autoantigens, and the implications for improved antigen-specific therapeutics. These advancements increase our understanding of MG pathology and improve patient quality of life by providing faster, more accurate diagnosis and better disease management.
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Affiliation(s)
| | - Socrates J Tzartos
- Tzartos NeuroDiagnostics, Athens, Greece.,Department of Neurobiology, Hellenic Pasteur Institute, Athens, Greece
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14
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Collagens at the vertebrate neuromuscular junction, from structure to pathologies. Neurosci Lett 2020; 735:135155. [PMID: 32534096 DOI: 10.1016/j.neulet.2020.135155] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 06/05/2020] [Accepted: 06/09/2020] [Indexed: 12/17/2022]
Abstract
The extracellular matrix at the neuromuscular junction is built upon components secreted by the motoneuron, the muscle cell and terminal Schwann cells, the cells constituting this specific synapse. This compartment contains glycoproteins, proteoglycans and collagens that form a dense and specialized layer, the synaptic basal lamina. A number of these molecules are known to play a crucial role in anterograde and retrograde signalings that are active in neuromuscular junction formation, maintenance and function. Here, we focus on the isoforms of collagens which are enriched at the synapse. We summarize what we know of their structure, their function and their interactions with transmembrane receptors and other components of the synaptic basal lamina. A number of neuromuscular diseases, congenital myastenic syndromes and myasthenia gravis are caused by human mutations and autoantibodies against these proteins. Analysis of these diseases and of the specific collagen knock-out mice highlights the roles of some of these collagens in promoting a functional synapse.
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15
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Takamori M. Myasthenia Gravis: From the Viewpoint of Pathogenicity Focusing on Acetylcholine Receptor Clustering, Trans-Synaptic Homeostasis and Synaptic Stability. Front Mol Neurosci 2020; 13:86. [PMID: 32547365 PMCID: PMC7272578 DOI: 10.3389/fnmol.2020.00086] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 04/28/2020] [Indexed: 12/18/2022] Open
Abstract
Myasthenia gravis (MG) is a disease of the postsynaptic neuromuscular junction (NMJ) where nicotinic acetylcholine (ACh) receptors (AChRs) are targeted by autoantibodies. Search for other pathogenic antigens has detected the antibodies against muscle-specific tyrosine kinase (MuSK) and low-density lipoprotein-related protein 4 (Lrp4), both causing pre- and post-synaptic impairments. Agrin is also suspected as a fourth pathogen. In a complex NMJ organization centering on MuSK: (1) the Wnt non-canonical pathway through the Wnt-Lrp4-MuSK cysteine-rich domain (CRD)-Dishevelled (Dvl, scaffold protein) signaling acts to form AChR prepatterning with axonal guidance; (2) the neural agrin-Lrp4-MuSK (Ig1/2 domains) signaling acts to form rapsyn-anchored AChR clusters at the innervated stage of muscle; (3) adaptor protein Dok-7 acts on MuSK activation for AChR clustering from “inside” and also on cytoskeleton to stabilize AChR clusters by the downstream effector Sorbs1/2; (4) the trans-synaptic retrograde signaling contributes to the presynaptic organization via: (i) Wnt-MuSK CRD-Dvl-β catenin-Slit 2 pathway; (ii) Lrp4; and (iii) laminins. The presynaptic Ca2+ homeostasis conditioning ACh release is modified by autoreceptors such as M1-type muscarinic AChR and A2A adenosine receptors. The post-synaptic structure is stabilized by: (i) laminin-network including the muscle-derived agrin; (ii) the extracellular matrix proteins (including collagen Q/perlecan and biglycan which link to MuSK Ig1 domain and CRD); and (iii) the dystrophin-associated glycoprotein complex. The study on MuSK ectodomains (Ig1/2 domains and CRD) recognized by antibodies suggested that the MuSK antibodies were pathologically heterogeneous due to their binding to multiple functional domains. Focussing one of the matrix proteins, biglycan which functions in the manner similar to collagen Q, our antibody assay showed the negative result in MG patients. However, the synaptic stability may be impaired by antibodies against MuSK ectodomains because of the linkage of biglycan with MuSK Ig1 domain and CRD. The pathogenic diversity of MG is discussed based on NMJ signaling molecules.
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Fichtner ML, Jiang R, Bourke A, Nowak RJ, O'Connor KC. Autoimmune Pathology in Myasthenia Gravis Disease Subtypes Is Governed by Divergent Mechanisms of Immunopathology. Front Immunol 2020; 11:776. [PMID: 32547535 PMCID: PMC7274207 DOI: 10.3389/fimmu.2020.00776] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 04/06/2020] [Indexed: 12/13/2022] Open
Abstract
Myasthenia gravis (MG) is a prototypical autoantibody mediated disease. The autoantibodies in MG target structures within the neuromuscular junction (NMJ), thus affecting neuromuscular transmission. The major disease subtypes of autoimmune MG are defined by their antigenic target. The most common target of pathogenic autoantibodies in MG is the nicotinic acetylcholine receptor (AChR), followed by muscle-specific kinase (MuSK) and lipoprotein receptor-related protein 4 (LRP4). MG patients present with similar symptoms independent of the underlying subtype of disease, while the immunopathology is remarkably distinct. Here we highlight these distinct immune mechanisms that describe both the B cell- and autoantibody-mediated pathogenesis by comparing AChR and MuSK MG subtypes. In our discussion of the AChR subtype, we focus on the role of long-lived plasma cells in the production of pathogenic autoantibodies, the IgG1 subclass mediated pathology, and contributions of complement. The similarities underlying the immunopathology of AChR MG and neuromyelitis optica (NMO) are highlighted. In contrast, MuSK MG is caused by autoantibody production by short-lived plasmablasts. MuSK MG autoantibodies are mainly of the IgG4 subclass which can undergo Fab-arm exchange (FAE), a process unique to this subclass. In FAE IgG4, molecules can dissociate into two halves and recombine with other half IgG4 molecules resulting in bispecific antibodies. Similarities between MuSK MG and other IgG4-mediated autoimmune diseases, including pemphigus vulgaris (PV) and chronic inflammatory demyelinating polyneuropathy (CIDP), are highlighted. Finally, the immunological distinctions are emphasized through presentation of biological therapeutics that provide clinical benefit depending on the MG disease subtype.
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Affiliation(s)
- Miriam L Fichtner
- Department of Neurology, School of Medicine, Yale University, New Haven, CT, United States.,Department of Immunobiology, School of Medicine, Yale University, New Haven, CT, United States
| | - Ruoyi Jiang
- Department of Immunobiology, School of Medicine, Yale University, New Haven, CT, United States
| | - Aoibh Bourke
- Trinity Hall, University of Cambridge, Cambridge, United Kingdom
| | - Richard J Nowak
- Department of Neurology, School of Medicine, Yale University, New Haven, CT, United States
| | - Kevin C O'Connor
- Department of Neurology, School of Medicine, Yale University, New Haven, CT, United States.,Department of Immunobiology, School of Medicine, Yale University, New Haven, CT, United States
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Lazaridis K, Tzartos SJ. Autoantibody Specificities in Myasthenia Gravis; Implications for Improved Diagnostics and Therapeutics. Front Immunol 2020; 11:212. [PMID: 32117321 PMCID: PMC7033452 DOI: 10.3389/fimmu.2020.00212] [Citation(s) in RCA: 112] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2019] [Accepted: 01/27/2020] [Indexed: 12/13/2022] Open
Abstract
Myasthenia gravis (MG) is an autoimmune disease characterized by muscle weakness and fatiguability of skeletal muscles. It is an antibody-mediated disease, caused by autoantibodies targeting neuromuscular junction proteins. In the majority of patients (~85%) antibodies against the muscle acetylcholine receptor (AChR) are detected, while in 6% antibodies against the muscle-specific kinase (MuSK) are detected. In ~10% of MG patients no autoantibodies can be found with the classical diagnostics for AChR and MuSK antibodies (seronegative MG, SN-MG), making the improvement of methods for the detection of known autoantibodies or the discovery of novel antigenic targets imperative. Over the past years, using cell-based assays or improved highly sensitive immunoprecipitation assays, it has been possible to detect autoantibodies in previously SN-MG patients, including the identification of the low-density lipoprotein receptor-related protein 4 (LRP4) as a third MG autoantigen, as well as AChR and MuSK antibodies undetectable by conventional methods. Furthermore, antibodies against other extracellular or intracellular targets, such as titin, the ryanodine receptor, agrin, collagen Q, Kv1.4 potassium channels and cortactin have been found in some MG patients, which can be useful biomarkers. In addition to the improvement of diagnosis, the identification of the patients' autoantibody specificity is important for their stratification into respective subgroups, which can differ in terms of clinical manifestations, prognosis and most importantly their response to therapies. The knowledge of the autoantibody profile of MG patients would allow for a therapeutic strategy tailored to their MG subgroup. This is becoming especially relevant as there is increasing progress toward the development of antigen-specific therapies, targeting only the specific autoantibodies or immune cells involved in the autoimmune response, such as antigen-specific immunoadsorption, which have shown promising results. We will herein review the advances made by us and others toward development of more sensitive detection methods and the identification of new antibody targets in MG, and discuss their significance in MG diagnosis and therapy. Overall, the development of novel autoantibody assays is aiding in the more accurate diagnosis and classification of MG patients, supporting the development of advanced therapeutics and ultimately the improvement of disease management and patient quality of life.
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Affiliation(s)
| | - Socrates J Tzartos
- Department of Neurobiology, Hellenic Pasteur Institute, Athens, Greece.,Tzartos NeuroDiagnostics, Athens, Greece
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Souto EB, Lima B, Campos JR, Martins-Gomes C, Souto SB, Silva AM. Myasthenia gravis: State of the art and new therapeutic strategies. J Neuroimmunol 2019; 337:577080. [PMID: 31670062 DOI: 10.1016/j.jneuroim.2019.577080] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 10/04/2019] [Indexed: 12/11/2022]
Abstract
Myasthenia Gravis (MG) - an autoimmune neuromuscular disease - is known by the production of autoantibodies against components of the neuromuscular junction mainly to the acetylcholine receptor, which cause the destruction and compromises the synaptic transmission. This disease is characterized by fluctuating and fatigable muscle weakness, becoming more intensive with activity, but with an improvement under resting. There are many therapeutic strategies used to alleviate MG symptoms, either by improving the transmission of the nerve impulse or by ameliorating autoimmune reactions with e.g. steroids, immunosuppressant drugs, or monoclonal antibodies (rituximab and eculizumab). Many breakthroughs in the discovery of new therapeutic targets have been reported, but MG remains to be a chronic disease where the symptoms are kept in the majority of patients. In this review, we discuss the different therapeutic strategies that have been used over the years to alleviate MG symptoms, as well as innovative therapeutic approaches currently under study.
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Affiliation(s)
- Eliana B Souto
- Department of Pharmaceutical Technology, Faculty of Pharmacy, University of Coimbra (FFUC), Pólo das Ciências da Saúde, 3000-548 Coimbra, Portugal; CEB - Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
| | - Bernardo Lima
- Department of Pharmaceutical Technology, Faculty of Pharmacy, University of Coimbra (FFUC), Pólo das Ciências da Saúde, 3000-548 Coimbra, Portugal
| | - Joana R Campos
- Department of Pharmaceutical Technology, Faculty of Pharmacy, University of Coimbra (FFUC), Pólo das Ciências da Saúde, 3000-548 Coimbra, Portugal
| | - Carlos Martins-Gomes
- Department of Biology and Environment, School of Life and Environmental Sciences, University of Trás-os-Montes and Alto Douro, Vila Real, Portugal; Centre for the Research and Technology of Agro-Environmental and Biological Sciences, University of Trás-os-Montes and Alto Douro, Vila Real, Portugal
| | - Selma B Souto
- Department of Endocrinology of S. João Hospital, Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal
| | - Amélia M Silva
- Department of Biology and Environment, School of Life and Environmental Sciences, University of Trás-os-Montes and Alto Douro, Vila Real, Portugal; Centre for the Research and Technology of Agro-Environmental and Biological Sciences, University of Trás-os-Montes and Alto Douro, Vila Real, Portugal.
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Beecher G, Putko BN, Wagner AN, Siddiqi ZA. Therapies Directed Against B-Cells and Downstream Effectors in Generalized Autoimmune Myasthenia Gravis: Current Status. Drugs 2019; 79:353-364. [PMID: 30762205 DOI: 10.1007/s40265-019-1065-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Myasthenia gravis is a rare, heterogeneous, classical autoimmune disease characterized by fatigable skeletal muscle weakness, which is directly mediated by autoantibodies targeting various components of the neuromuscular junction, including the acetylcholine receptor, muscle specific tyrosine kinase, and lipoprotein-related protein 4. Subgrouping of myasthenia gravis is dependent on the age of onset, pattern of clinical weakness, autoantibody detected, type of thymic pathology, and response to immunotherapy. Generalized immunosuppressive therapies are effective in all subgroups of myasthenia gravis; however, approximately 15% remain refractory and more effective treatments with improved safety profiles are needed. In recent years, successful utilization of targeted B-cell therapies in this disease has triggered renewed focus in unraveling the underlying immunopathology in attempts to identify newer therapeutic targets. While myasthenia gravis is predominantly B-cell mediated, T cells, T cell-B cell interactions, and B-cell-related factors are increasingly recognized to play key roles in its immunopathology, particularly in autoantibody production, and novel therapies have focused on targeting these specific immune system components. This overview describes the current understanding of myasthenia gravis immunopathology before discussing B-cell-related therapies, their therapeutic targets, and the rationale and evidence for their use. Several prospective studies demonstrated efficacy of rituximab in various myasthenia gravis subtypes, particularly that characterized by antibodies against muscle-specific tyrosine kinase. However, a recent randomized control trial in patients with acetylcholine receptor antibodies was negative. Eculizumab, a complement inhibitor, has recently gained regulatory approval for myasthenia gravis based on a phase III trial that narrowly missed its primary endpoint while achieving robust results in all secondary endpoints. Zilucoplan is a subcutaneously administered terminal complement inhibitor that recently demonstrated significant improvements in functional outcome measures in a phase II trial. Rozanolixizumab, CFZ533, belimumab, and bortezomib are B-cell-related therapies that are in the early stages of evaluation in treating myasthenia gravis. The rarity of myasthenia gravis, heterogeneity in its clinical manifestations, and variability in immunosuppressive regimens are challenges to conducting successful trials. Nonetheless, these are promising times for myasthenia gravis, as renewed research efforts provide novel insights into its immunopathology, allowing for development of targeted therapies with increased efficacy and safety.
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Affiliation(s)
- Grayson Beecher
- Division of Neurology, Department of Medicine, Faculty of Medicine and Dentistry, University of Alberta Hospital, 7-112 Clinical Sciences Building, 11350-83 Ave, Edmonton, AB, T6G 2G3, Canada
| | - Brendan Nicholas Putko
- Division of Neurology, Department of Medicine, Faculty of Medicine and Dentistry, University of Alberta Hospital, 7-112 Clinical Sciences Building, 11350-83 Ave, Edmonton, AB, T6G 2G3, Canada
| | - Amanda Nicole Wagner
- Division of Neurology, Department of Medicine, Faculty of Medicine and Dentistry, University of Alberta Hospital, 7-112 Clinical Sciences Building, 11350-83 Ave, Edmonton, AB, T6G 2G3, Canada
| | - Zaeem Azfer Siddiqi
- Division of Neurology, Department of Medicine, Faculty of Medicine and Dentistry, University of Alberta Hospital, 7-112 Clinical Sciences Building, 11350-83 Ave, Edmonton, AB, T6G 2G3, Canada.
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20
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Abstract
This article discusses antibodies associated with immune-mediated myasthenia gravis and the pathologic action of these antibodies at the neuromuscular junctions of skeletal muscle. To explain how these antibodies act, we consider the physiology of neuromuscular transmission with emphasis on 4 features: the structure of the neuromuscular junction; the roles of postsynaptic acetylcholine receptors and voltage-gated Na+ channels and in converting the chemical signal from the nerve terminal into a propagated action potential on the muscle fiber that triggers muscle contraction; the safety factor for neuromuscular transmission; and how the safety factor is reduced in different forms of autoimmune myasthenia gravis.
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Affiliation(s)
- Robert L Ruff
- Department of Neurology, Case Western University School of Medicine, The Metro Health System, 2500 Metro Health Drive, Cleveland, OH 44109, USA; Department of Neurosciences, Case Western Reserve University, Cleveland, OH, USA
| | - Robert P Lisak
- Department of Neurology, Wayne State University School of Medicine, 8D University Health Center, 4201 St Antoine, Detroit, MI 48201, USA; Department of Biochemistry, Microbiology and Immunology, Wayne State University, Detroit, MI, USA.
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21
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Myasthenia Gravis: Pathogenic Effects of Autoantibodies on Neuromuscular Architecture. Cells 2019; 8:cells8070671. [PMID: 31269763 PMCID: PMC6678492 DOI: 10.3390/cells8070671] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 06/26/2019] [Accepted: 06/28/2019] [Indexed: 12/13/2022] Open
Abstract
Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction (NMJ). Autoantibodies target key molecules at the NMJ, such as the nicotinic acetylcholine receptor (AChR), muscle-specific kinase (MuSK), and low-density lipoprotein receptor-related protein 4 (Lrp4), that lead by a range of different pathogenic mechanisms to altered tissue architecture and reduced densities or functionality of AChRs, reduced neuromuscular transmission, and therefore a severe fatigable skeletal muscle weakness. In this review, we give an overview of the history and clinical aspects of MG, with a focus on the structure and function of myasthenic autoantigens at the NMJ and how they are affected by the autoantibodies' pathogenic mechanisms. Furthermore, we give a short overview of the cells that are implicated in the production of the autoantibodies and briefly discuss diagnostic challenges and treatment strategies.
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22
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Zhang QL, Xu MJ, Wang TL, Zhu ZQ, Lai F, Zheng XC. Newly discovered COLQ gene mutation and its clinical features in patients with acetyl cholinesterase deficiency. J Integr Neurosci 2018; 17:439-446. [PMID: 29630557 DOI: 10.3233/jin-180080] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
To investigate the relationship between acetyl cholinesterase associated collagen gene (COLQ) mutation in patients with acetyl cholinesterase deficiency and its clinical characteristics. Serum and red blood cell acetyl cholinesterase from patients with acetyl cholinesterase deficiency (n=6) and normal controls (n=20) were measured by butyryl thiocholine substrate. COLQ gene variations were detected by sequencing. And the cholinesterase (ChE) genotypes were measured by dibucaine inhibition in vitro. The distributions of ChE surrounded the blood vessels and nerve fibers in lung or pancreas tissues were detected by immunohistochemical staining and indirect immunofluorescence. Serum lactic acid, ammonia and other clinical data were analyzed. Serum ChE in patients with acetyl cholinesterase deficiency were only 1/50 to 1/1000 fold of normal controls. Comparing to controls, dibucaine inhibition values of patients were significantly lower, while there were no differences in red blood cells acetyl cholinesterase. Serum lactic acid and ammonia in patients were significantly higher than controls. Inser 1281-1282 GC of COLQ gene was found in 2 patients, while IVS 6 + 21 T > A, IVS 6 + 30 G > T, IVS 6 + 34 T > C and IVS66 + 12 inser T mutations were found in the other 4 patients, respectively. In addition, the patients with COLQ gene mutation were resistant to regular doses of anesthetics. COLQ gene mutation may be an important reason for the lack of serum ChE in patients with acetyl cholinesterase deficiency.
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Affiliation(s)
- Qing-Lin Zhang
- Department of Anesthesiology, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Postcode: 100026, China. E-mails: , ,
| | - Ming-Jun Xu
- Department of Anesthesiology, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Postcode: 100026, China. E-mails: , ,
| | - Tian-Long Wang
- Department of Anesthesiology of Xuanwu Hospital, Capital Medical University, Postcode: 100053, China. E-mail:
| | - Zi-Qiong Zhu
- Department of Anesthesiology, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Postcode: 100026, China. E-mails: , ,
| | - Fancai Lai
- Department of Thoracic Surgery, 1st Affiliated Hospital, Fujian Medical University, Fuzhou, Fujian, China
| | - Xiao-Chun Zheng
- Department of Anesthesiology of Provincial Clinical College, Fujian Medical University, Postcode: 350001, China.,Department of Emergency, Fujian Provincial Hospital, Postcode: 350001, China. E-mail:
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23
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Trakas N, Tzartos SJ. Immunostick ELISA for rapid and easy diagnosis of myasthenia gravis. J Immunol Methods 2018; 460:107-112. [DOI: 10.1016/j.jim.2018.06.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Revised: 06/14/2018] [Accepted: 06/28/2018] [Indexed: 01/20/2023]
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24
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Abstract
PURPOSE OF REVIEW Myasthenia gravis, a rare disorder of the neuromuscular transmission, is increasingly acknowledged as a syndrome more than as a single disease. This review summarizes recent advances in pathophysiology which confirm the disease heterogeneity, and may help find disease-targeted and patient-targeted therapies. RECENT FINDINGS Antibodies to the acetylcholine receptor, the muscle-specific tyrosine kinase and the lipoprotein receptor protein 4, characterize disease subtypes with distinct clinical traits and immune-pathogenic mechanisms. Genome-wide approaches have identified susceptibility loci within genes that participate in the immune response. Regulatory T and B cells appear to be defective in myasthenia gravis. In patients with acetylcholine receptor antibodies, thymectomy associated with prednisone proved more effective than prednisone alone in a multicenter randomized trial. New therapeutic options target B cells, B-cell growth factors and complement inhibition, and are currently reserved for patients with refractory disease. SUMMARY In the recent past, there has been an active search for new antigens in myasthenia gravis, whereas clinical and experimental studies have provided new insights of crucial pathways in immune regulation, which might become the targets of future therapeutic interventions.
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Affiliation(s)
- Amelia Evoli
- Institute of Neurology, Catholic University, Fondazione Policlinico Gemelli, Roma, Italy
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25
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Catar O, Aubé-Nathier AC, Nadaj-Pakleza A. Myasthénie auto-immune séronégative. Med Sci (Paris) 2017; 33 Hors série n°1:34-38. [DOI: 10.1051/medsci/201733s107] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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26
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Yi JS, Guptill JT, Stathopoulos P, Nowak RJ, O'Connor KC. B cells in the pathophysiology of myasthenia gravis. Muscle Nerve 2017; 57:172-184. [PMID: 28940642 DOI: 10.1002/mus.25973] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/07/2017] [Indexed: 12/21/2022]
Abstract
Myasthenia gravis (MG) is an archetypal autoimmune disease. The pathology is characterized by autoantibodies to the acetylcholine receptor (AChR) in most patients or to muscle-specific tyrosine kinase (MuSK) in others and to a growing number of other postsynaptic proteins in smaller subsets. A decrease in the number of functional AChRs or functional interruption of the AChR within the muscle end plate of the neuromuscular junction is caused by pathogenic autoantibodies. Although the molecular immunology underpinning the pathology is well understood, much remains to be learned about the cellular immunology contributing to the production of autoantibodies. This Review documents research concerning the immunopathology of MG, bringing together evidence principally from human studies with an emphasis on the role of adaptive immunity and B cells in particular. Proposed mechanisms for autoimmunity, which take into account that different types of MG may incorporate divergent immunopathology, are offered. Muscle Nerve 57: 172-184, 2018.
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Affiliation(s)
- John S Yi
- Division of Surgical Sciences, Department of Surgery, Duke University Medical Center, Durham, North Carolina, USA
| | - Jeffrey T Guptill
- Department of Neurology, Neuromuscular Section, Duke University Medical Center, Durham, North Carolina, USA
| | - Panos Stathopoulos
- Department of Neurology, Yale School of Medicine, Room 353J, 300 George Street, New Haven, Connecticut, 06511, USA
| | - Richard J Nowak
- Department of Neurology, Yale School of Medicine, Room 353J, 300 George Street, New Haven, Connecticut, 06511, USA
| | - Kevin C O'Connor
- Department of Neurology, Yale School of Medicine, Room 353J, 300 George Street, New Haven, Connecticut, 06511, USA
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27
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Romi F, Hong Y, Gilhus NE. Pathophysiology and immunological profile of myasthenia gravis and its subgroups. Curr Opin Immunol 2017; 49:9-13. [PMID: 28780294 DOI: 10.1016/j.coi.2017.07.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 07/07/2017] [Indexed: 01/11/2023]
Abstract
Myasthenia gravis (MG) is an autoimmune antibody-mediated disease characterized by muscle weakness and fatigability. It is believed that the initial steps triggering humoral immunity in MG take place inside thymic tissue and thymoma. The immune response against one or several epitopes expressed on thymic tissue cells spills over to neuromuscular junction components sharing the same epitope causing humoral autoimmunity and antibody production. The main cause of MG is acetylcholine receptor antibodies. However, many other neuromuscular junction membrane protein targets, intracellular and extracellular proteins are suggested to participate in MG pathophysiology. MG should be divided into subgroups based on clinical presentation and immunology. This includes onset age, clinical characteristics, thymic pathology and antibody profile. The immunological profile of these subgroups is determined by the antibodies present.
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Affiliation(s)
- Fredrik Romi
- Department of Neurology, Haukeland University Hospital, Norway.
| | - Yu Hong
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
| | - Nils Erik Gilhus
- Department of Neurology, Haukeland University Hospital, Norway; Department of Clinical Medicine, University of Bergen, Bergen, Norway
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28
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Lee JI, Jander S. Myasthenia gravis: recent advances in immunopathology and therapy. Expert Rev Neurother 2016; 17:287-299. [PMID: 27690672 DOI: 10.1080/14737175.2017.1241144] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- John-Ih Lee
- Department of Neurology, Heinrich-Heine-University, Medical Faculty, Duesseldorf, Germany
| | - Sebastian Jander
- Department of Neurology, Heinrich-Heine-University, Medical Faculty, Duesseldorf, Germany
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29
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Myasthenia gravis — autoantibody characteristics and their implications for therapy. Nat Rev Neurol 2016; 12:259-68. [DOI: 10.1038/nrneurol.2016.44] [Citation(s) in RCA: 209] [Impact Index Per Article: 26.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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30
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Stergiou C, Lazaridis K, Zouvelou V, Tzartos J, Mantegazza R, Antozzi C, Andreetta F, Evoli A, Deymeer F, Saruhan-Direskeneli G, Durmus H, Brenner T, Vaknin A, Berrih-Aknin S, Behin A, Sharshar T, De Baets M, Losen M, Martinez-Martinez P, Kleopa KA, Zamba-Papanicolaou E, Kyriakides T, Kostera-Pruszczyk A, Szczudlik P, Szyluk B, Lavrnic D, Basta I, Peric S, Tallaksen C, Maniaol A, Gilhus NE, Casasnovas Pons C, Pitha J, Jakubíkova M, Hanisch F, Bogomolovas J, Labeit D, Labeit S, Tzartos SJ. Titin antibodies in "seronegative" myasthenia gravis--A new role for an old antigen. J Neuroimmunol 2016; 292:108-15. [PMID: 26943968 DOI: 10.1016/j.jneuroim.2016.01.018] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 01/25/2016] [Indexed: 12/11/2022]
Abstract
Myasthenia gravis (MG) is an autoimmune disease caused by antibodies targeting the neuromuscular junction of skeletal muscles. Triple-seronegative MG (tSN-MG, without detectable AChR, MuSK and LRP4 antibodies), which accounts for ~10% of MG patients, presents a serious gap in MG diagnosis and complicates differential diagnosis of similar disorders. Several AChR antibody positive patients (AChR-MG) also have antibodies against titin, usually detected by ELISA. We have developed a very sensitive radioimmunoprecipitation assay (RIPA) for titin antibodies, by which many previously negative samples were found positive, including several from tSN-MG patients. The validity of the RIPA results was confirmed by western blots. Using this RIPA we screened 667 MG sera from 13 countries; as expected, AChR-MG patients had the highest frequency of titin antibodies (40.9%), while MuSK-MG and LRP4-MG patients were positive in 14.6% and 16.4% respectively. Most importantly, 13.4% (50/372) of the tSN-MG patients were also titin antibody positive. None of the 121 healthy controls or the 90 myopathy patients, and only 3.6% (7/193) of other neurological disease patients were positive. We thus propose that the present titin antibody RIPA is a useful tool for serological MG diagnosis of tSN patients.
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Affiliation(s)
- C Stergiou
- Hellenic Pasteur Institute, Athens, Greece; Tzartos NeuroDiagnostics, Athens, Greece
| | | | - V Zouvelou
- Neurology Department, Aeginition Hospital, Athens, Greece
| | - J Tzartos
- Hellenic Pasteur Institute, Athens, Greece; Tzartos NeuroDiagnostics, Athens, Greece
| | - R Mantegazza
- Neurological Institute "C. Besta", Milano, Italy
| | - C Antozzi
- Neurological Institute "C. Besta", Milano, Italy
| | - F Andreetta
- Neurological Institute "C. Besta", Milano, Italy
| | - A Evoli
- Institute of Neurology, Catholic University, Rome, Italy
| | - F Deymeer
- Istanbul University, Istanbul, Turkey
| | | | - H Durmus
- Istanbul University, Istanbul, Turkey
| | - T Brenner
- Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | - A Vaknin
- Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | | | - A Behin
- UPMC and INSERM, Paris, France
| | - T Sharshar
- Raymond Poincaré Hospital, Garches, France
| | - M De Baets
- School for Mental Health and Neuroscience, Maastricht University, The Netherlands
| | - M Losen
- School for Mental Health and Neuroscience, Maastricht University, The Netherlands
| | - P Martinez-Martinez
- School for Mental Health and Neuroscience, Maastricht University, The Netherlands
| | - K A Kleopa
- The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
| | | | - T Kyriakides
- The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
| | | | - P Szczudlik
- Department of Neurology, Medical University of Warsaw, Poland
| | - B Szyluk
- Department of Neurology, Medical University of Warsaw, Poland
| | - D Lavrnic
- Neurology Clinic, Clinical Center of Serbia, School of Medicine, University of Belgrade, Belgrade, Serbia
| | - I Basta
- Neurology Clinic, Clinical Center of Serbia, School of Medicine, University of Belgrade, Belgrade, Serbia
| | - S Peric
- Neurology Clinic, Clinical Center of Serbia, School of Medicine, University of Belgrade, Belgrade, Serbia
| | - C Tallaksen
- Norway Department of Neurology, Ullevaal University Hospital, Oslo, Norway; Faculty of Medicine, Olso University, Norway
| | - A Maniaol
- Norway Department of Neurology, Ullevaal University Hospital, Oslo, Norway
| | - N E Gilhus
- Department of Clinical Medicine, University of Bergen, Norway
| | | | - J Pitha
- Department of Neurology and Clinical Neuroscience Center, 1st Faculty of Medicine, Charles University and General Teaching Hospital, Prague, Czech Republic
| | - M Jakubíkova
- Department of Neurology and Clinical Neuroscience Center, 1st Faculty of Medicine, Charles University and General Teaching Hospital, Prague, Czech Republic
| | - F Hanisch
- Universitätsklinikum Halle, Halle, Germany
| | - J Bogomolovas
- Faculty of Clinical Medicine Manheim, University of Heidelberg, Germany
| | - D Labeit
- Faculty of Clinical Medicine Manheim, University of Heidelberg, Germany; Myomedix GmbH, 69151 Neckargemuend, Germany
| | - S Labeit
- Faculty of Clinical Medicine Manheim, University of Heidelberg, Germany
| | - S J Tzartos
- Hellenic Pasteur Institute, Athens, Greece; Tzartos NeuroDiagnostics, Athens, Greece.
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31
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Binks S, Vincent A, Palace J. Myasthenia gravis: a clinical-immunological update. J Neurol 2015; 263:826-34. [PMID: 26705120 PMCID: PMC4826656 DOI: 10.1007/s00415-015-7963-5] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 10/06/2015] [Indexed: 12/13/2022]
Abstract
Myasthenia gravis (MG) is the archetypic disorder of both the neuromuscular junction and autoantibody-mediated disease. In most patients, IgG1-dominant antibodies to acetylcholine receptors cause fatigable weakness of skeletal muscles. In the rest, a variable proportion possesses antibodies to muscle-specific tyrosine kinase while the remainder of seronegative MG is being explained through cell-based assays using a receptor-clustering technique and, to a lesser extent, proposed new antigenic targets. The incidence and prevalence of MG are increasing, particularly in the elderly. New treatments are being developed, and results from the randomised controlled trial of thymectomy in non-thymomatous MG, due for release in early 2016, will be of particular clinical value. To help navigate an evidence base of varying quality, practising clinicians may consult new MG guidelines in the fields of pregnancy, ocular and generalised MG (GMG). This review focuses on updates in epidemiology, immunology, therapeutic and clinical aspects of GMG in adults.
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Affiliation(s)
- Sophie Binks
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DU, UK
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DU, UK
| | - Jacqueline Palace
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DU, UK.
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Evoli A, Iorio R, Bartoccioni E. Overcoming challenges in the diagnosis and treatment of myasthenia gravis. Expert Rev Clin Immunol 2015; 12:157-68. [PMID: 26675896 DOI: 10.1586/1744666x.2016.1110487] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In recent years, the discovery of new autoantigens and the use of sensitive assays have expanded the clinical spectrum of myasthenia gravis (MG). In particular, antibodies binding to clustered acetylcholine receptors and to the low-density lipoprotein receptor-related protein 4 have not only bridged a significant gap in diagnosis but also have relevant clinical implications. MG management includes different therapeutic options, from symptomatic agents as the only therapy in mildly affected cases to combined long-term immunosuppression and thymectomy in patients with severe disabling disease. MG biological diversity can influence the response to therapies and should be taken into account when planning treatment. Biologic agents are promising, though their use is currently limited to patients with refractory disease.
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Affiliation(s)
- Amelia Evoli
- a Institute of Neurology , Catholic University , Roma , Italy
| | - Raffaele Iorio
- a Institute of Neurology , Catholic University , Roma , Italy.,b Don Gnocchi ONLUS Foundation , Milan , Italy
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