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Belimezi M, Kalliaropoulos A, Jiménez J, Garcia I, Mentis AFA, Chrousos GP. Age at sampling and sex distribution of AChRAb vs. MuSKAb myasthenia gravis in a large Greek population. Clin Neurol Neurosurg 2021; 208:106847. [PMID: 34343914 DOI: 10.1016/j.clineuro.2021.106847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 07/22/2021] [Accepted: 07/24/2021] [Indexed: 10/20/2022]
Abstract
OBJECTIVE Myasthenia gravis (MG) is a typical B-cell-mediated neuromuscular junction disease that can be classified into seropositive and seronegative subtypes. Association of patients' age at sampling and sex with the two major seropositive MG subcategories, i.e., MGs linked to antibodies directed against the acetylcholine receptor (AChRAb) and against the muscle-specific kinase (MuSKAb), has not been compared in a large population. METHODS We performed a retrospective analysis of samples from patients with MG in Greece who underwent neurochemical diagnostic evaluation between January 2, 2013, and August 31, 2016. RESULTS Overall, 1620 adult (623 male and 997 female patients; male-to-female ratio = 0.62) and 51 pediatric patients were found to be seropositive for MG. The distributions in both male and female patients were bimodal in the total and AChRAb MG cases but not in the total MuSKAb MG cases. Significant differences in the age at sampling distribution between the male and female adult patients were observed only in the AChRAb MG subtype. Significant differences between the AChRAb and MuSKAb MG categories were noted in the mean age values (60.10 and 51.49 years, respectively, for female and 65.69 and 56.19 years, respectively, for male adult patients). CONCLUSION Our findings confirm an uneven profile of age at sampling and sex between the AChRAb and MuSKAb MG cases in a large population. Future mechanistic studies can elucidate the cause of these differences. Moreover, clinical studies can explore how such differences can affect MG treatment and prognosis.
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Affiliation(s)
- Maria Belimezi
- Diagnostic Services Laboratory, Hellenic Pasteur Institute, Athens, Greece
| | | | - Juan Jiménez
- ADEMA Universitary School, University of the Balearic Islands (UIB), Palma, Balearic Islands, Spain
| | - Irene Garcia
- Department of Mathematical Sciences and Informatics, and Health Research Institute (IdISBa), University of the Balearic Islands (UIB), Palma, Balearic Islands, Spain
| | - Alexios-Fotios A Mentis
- Diagnostic Services Laboratory, Hellenic Pasteur Institute, Athens, Greece; University Research Institute of Maternal and Child Health and Precision Medicine, National and Kapodistrian University of Athens, Levadias, Athens, Greece.
| | - George P Chrousos
- University Research Institute of Maternal and Child Health and Precision Medicine, National and Kapodistrian University of Athens, Levadias, Athens, Greece
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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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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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Cao M, Koneczny I, Vincent A. Myasthenia Gravis With Antibodies Against Muscle Specific Kinase: An Update on Clinical Features, Pathophysiology and Treatment. Front Mol Neurosci 2020; 13:159. [PMID: 32982689 PMCID: PMC7492727 DOI: 10.3389/fnmol.2020.00159] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Accepted: 08/03/2020] [Indexed: 12/24/2022] Open
Abstract
Muscle Specific Kinase myasthenia gravis (MuSK-MG) is an autoimmune disease that impairs neuromuscular transmission leading to generalized muscle weakness. Compared to the more common myasthenia gravis with antibodies against the acetylcholine receptor (AChR), MuSK-MG affects mainly the bulbar and respiratory muscles, with more frequent and severe myasthenic crises. Treatments are usually less effective with the need for prolonged, high doses of steroids and other immunosuppressants to control symptoms. Under physiological condition, MuSK regulates a phosphorylation cascade which is fundamental for the development and maintenance of postsynaptic AChR clusters at the neuromuscular junction (NMJ). Agrin, secreted by the motor nerve terminal into the synaptic cleft, binds to low density lipoprotein receptor-related protein 4 (LRP4) which activates MuSK. In MuSK-MG, monovalent MuSK-IgG4 autoantibodies block MuSK-LRP4 interaction preventing MuSK activation and leading to the dispersal of AChR clusters. Lower levels of divalent MuSK IgG1, 2, and 3 antibody subclasses are also present but their contribution to the pathogenesis of the disease remains controversial. This review aims to provide a detailed update on the epidemiological and clinical features of MuSK-MG, focusing on the pathophysiological mechanisms and the latest indications regarding the efficacy and safety of different treatment options.
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Affiliation(s)
- Michelangelo Cao
- Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Inga Koneczny
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
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Vergoossen DLE, Augustinus R, Huijbers MG. MuSK antibodies, lessons learned from poly- and monoclonality. J Autoimmun 2020; 112:102488. [PMID: 32505442 DOI: 10.1016/j.jaut.2020.102488] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 04/28/2020] [Accepted: 05/06/2020] [Indexed: 11/25/2022]
Abstract
Muscle-specific kinase (MuSK) plays a critical role in establishing and maintaining neuromuscular synapses. Antibodies derived from immunizing animals with MuSK were important tools to help detect MuSK and its activity. The role of antibodies in MuSK-related research got an extra dimension when autoantibodies to MuSK were found to cause myasthenia gravis (MG) in 2001. Active immunization with MuSK or passive transfer of polyclonal purified IgG(4) fractions from patients reproduced myasthenic muscle weakness in a range of animal models. Polyclonal patient-purified autoantibodies were furthermore found to block agrin-Lrp4-MuSK signaling, explaining the synaptic disassembly, failure of neuromuscular transmission and ultimately muscle fatigue observed in vivo. MuSK autoantibodies are predominantly of the IgG4 subclass. Low levels of other subclass MuSK antibodies coexist, but their role in the pathogenesis is unclear. Patient-derived monoclonal antibodies revealed that MuSK antibody subclass and valency alters their functional effects and possibly their pathogenicity. Interestingly, recombinant functional bivalent MuSK antibodies might even have therapeutic potential for a variety of neuromuscular disorders, due to their agonistic nature on the MuSK signaling cascade. Thus, MuSK antibodies have proven to be helpful tools to study neuromuscular junction physiology, contributed to our understanding of the pathophysiology of MuSK MG and might be used to treat neuromuscular disorders. The source of MuSK antibodies and consequently their (mixed) polyclonal or monoclonal nature were important confounding factors in these experiments. Here we review the variety of MuSK antibodies described thus far, the insights they have given us and their potential for the future.
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Affiliation(s)
- Dana L E Vergoossen
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, the Netherlands
| | - Roy Augustinus
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, the Netherlands
| | - Maartje G Huijbers
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, the Netherlands; Department of Neurology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, the Netherlands.
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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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Poursadeghfard M, Azhdari S. Simultaneous Presence of Acetylcholine Receptor and Muscle Specific Tyrosine Kinase Antibodies in Myasthenia Gravis. INTERNATIONAL JOURNAL OF BASIC SCIENCE IN MEDICINE 2019. [DOI: 10.34172/ijbsm.2019.01] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Myasthenia gravis (MG) is known as an autoimmune disorder which affects transmission in neuromuscular junction. The serologic tests used for diagnosis include acetylcholine receptor and muscle specific receptor tyrosine kinase antibodies. Studies often have reported that patients with formal antibody are negative for the latter one. However, very limited studies have reported positive anti-muscle specific receptor tyrosine kinase antibody in a small percentage of patients with acetylcholine receptor antibody. Here, we reported a young woman who was diagnosed with MG and had a rapid and progressive course of the disease. She was seropositive for both acetylcholine receptor and muscle-specific receptor tyrosine kinase antibodies simultaneously. However, she discharged from the hospital with good condition after treatment.
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Affiliation(s)
- Maryam Poursadeghfard
- Clinical Neurology Research Center, Department of Neurology, Medical School, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Sara Azhdari
- Department of Neurology, Medical School, Shiraz University of Medical Sciences, Shiraz, Iran
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8
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Roda RH, Doherty L, Corse AM. Stopping oral steroid-sparing agents at initiation of rituximab in myasthenia gravis. Neuromuscul Disord 2019; 29:554-561. [DOI: 10.1016/j.nmd.2019.06.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 05/31/2019] [Accepted: 06/03/2019] [Indexed: 11/25/2022]
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Serological Immunoglobulin-Free Light Chain Profile in Myasthenia Gravis Patients. J Immunol Res 2018; 2018:9646209. [PMID: 29765992 PMCID: PMC5889870 DOI: 10.1155/2018/9646209] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 01/29/2018] [Indexed: 12/12/2022] Open
Abstract
Background Serological levels of free immunoglobulin light chains (FLCs), produced in excess of heavy chains during synthesis of immunoglobulins by plasma cells, can be considered a direct marker of B cell activity in different systemic inflammatory-autoimmune conditions and may represent a useful predictor of rituximab (RTX) therapeutic efficacy, as reported for rheumatoid arthritis and systemic lupus erythematosus. Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction with antibodies (abs) targeting the acetylcholine receptor (AChR) or the muscle-specific tyrosine kinase (MuSK), inducing muscle weakness and excessive fatigability. As MG course may be remarkably variable, we evaluated the possible use of FLCs as biomarkers of disease activity. Subjects and Methods We assessed FLC levels in 34 sera from 17 AChR-MG and from 13 MuSK-MG patients, in comparison with 20 sera from patients with systemic autoimmune rheumatic diseases and 18 from healthy blood donors, along with titers of specific auto-abs and IgG subclass distribution. Results We found a statistically significant increase in free κ chains in both AChR- and MuSK-MG patients, while free λ chain levels were increased only in AChR-MG. We also observed a significant reduction of both free κ and λ chains in 1/4 MuSK-MG patients along with specific abs titer, two months after RTX treatment. Conclusions From our data, FLCs appear to be a sensitive marker of B cell activation in MG. Further investigations are necessary to exploit their potential as reliable biomarkers of disease activity.
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Rodríguez Cruz PM, Al-Hajjar M, Huda S, Jacobson L, Woodhall M, Jayawant S, Buckley C, Hilton-Jones D, Beeson D, Vincent A, Leite MI, Palace J. Clinical Features and Diagnostic Usefulness of Antibodies to Clustered Acetylcholine Receptors in the Diagnosis of Seronegative Myasthenia Gravis. JAMA Neurol 2015; 72:642-9. [PMID: 25894002 DOI: 10.1001/jamaneurol.2015.0203] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
IMPORTANCE Cell-based assays (CBAs) were shown to improve detection of acetylcholine receptor (AChR) antibodies in patients with myasthenia gravis (MG). Herein, we asked whether these assays were able to help determine the diagnosis in patients studied in routine clinical practice. OBJECTIVES To determine the diagnostic usefulness of CBAs in the diagnosis of MG and to compare the clinical features of patients with antibodies only to clustered AChRs with those of patients with seronegative MG (SNMG). DESIGN, SETTING, AND PARTICIPANTS All patients with clinical suspicion of MG who were seen within the Division of Clinical Neurology at the John Radcliffe Hospital in Oxford, England, between November 1, 2009, and November 30, 2013. Their serum antibodies and clinical features were studied. EXPOSURES Radioimmunoprecipitation assay (RIPA) and CBA were used to test for standard AChR antibodies and antibodies to clustered AChRs in 138 patients. All available samples from patients with SNMG were retrospectively tested for lipoprotein receptor-related protein 4 (LRP4) antibodies. MAIN OUTCOMES AND MEASURES Demographic, clinical, neurophysiological, and laboratory data. RESULTS In total, 138 patients were tested for antibodies to clustered AChRs, and 42 had a final diagnosis of MG. The clustered AChR CBA detected antibodies in 38.1% (16 of 42) of RIPA-negative patients with MG with 100% specificity. All patients with SNMG who were tested for LRP4 antibodies (21 of 26) were negative by CBA. Compared with patients with SNMG, patients with antibodies only to clustered AChRs had frequent prepubertal onset (62.5% [median age, 6 years; age range, 1-52 years] vs 11.5% [median age, 38 years; age range, 2-72 years], P ≤ .05), high prevalence of ocular MG (62.5% vs 42.3%), milder disease severity with less bulbar involvement (25.0% vs 46.2%), and absence of respiratory symptoms (0% vs 23.1%). Response to treatment and prognosis was good, with a reduced need for thymectomy (6.3% vs 19.2%) and a high proportion of patients going into remission (50.0% vs 8.3%, P ≤ .05). These observations also apply to the classic AChR MG phenotype seen in large series. CONCLUSIONS AND RELEVANCE Cell-based assay is a useful procedure in the routine diagnosis of RIPA-negative MG, particularly in children. Patients with antibodies only to clustered AChRs appear to be younger and have milder disease than other patients with MG. These observations will have implications in planning treatment.
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Affiliation(s)
- Pedro M Rodríguez Cruz
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, England2Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, England
| | - Michal Al-Hajjar
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, England
| | - Saif Huda
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, England
| | - Leslie Jacobson
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, England
| | - Mark Woodhall
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, England
| | - Sandeep Jayawant
- Department of Paediatric Neurology, Children's Hospital, John Radcliffe Hospital, Oxford, England
| | - Camilla Buckley
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, England
| | - David Hilton-Jones
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, England
| | - David Beeson
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, England
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, England
| | - Maria Isabel Leite
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, England
| | - Jacqueline Palace
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, England
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MuSK autoantibodies in myasthenia gravis detected by cell based assay--A multinational study. J Neuroimmunol 2015; 284:10-7. [PMID: 26025053 DOI: 10.1016/j.jneuroim.2015.04.015] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 04/21/2015] [Accepted: 04/24/2015] [Indexed: 12/21/2022]
Abstract
Seronegative myasthenia gravis (MG) presents a serious gap in MG diagnosis and understanding. We applied a cell based assay (CBA) for the detection of muscle specific kinase (MuSK) antibodies undetectable by radioimmunoassay. We tested 633 triple-seronegative MG patients' sera from 13 countries, detecting 13% as positive. MuSK antibodies were found, at significantly lower frequencies, in 1.9% of healthy controls and 5.1% of other neuroimmune disease patients, including multiple sclerosis and neuromyelitis optica. The clinical data of the newly diagnosed MuSK-MG patients are presented. 27% of ocular seronegative patients were MuSK antibody positive. Moreover, 23% had thymic hyperplasia suggesting that thymic abnormalities are more common than believed.
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Marino M, Maiuri MT, Di Sante G, Scuderi F, La Carpia F, Trakas N, Provenzano C, Zisimopoulou P, Ria F, Tzartos SJ, Evoli A, Bartoccioni E. T cell repertoire in DQ5-positive MuSK-positive myasthenia gravis patients. J Autoimmun 2014; 52:113-21. [DOI: 10.1016/j.jaut.2013.12.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Accepted: 12/08/2013] [Indexed: 11/26/2022]
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CTLA4 variants and haplotype contribute genetic susceptibility to myasthenia gravis in northern Chinese population. PLoS One 2014; 9:e101986. [PMID: 25003519 PMCID: PMC4086970 DOI: 10.1371/journal.pone.0101986] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Accepted: 06/13/2014] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Cytotoxic T lymphocyte-associated antigen-4 (CTLA4), a critical negative regulator of the T-cell response, has been considered a candidate for many autoimmune diseases. Evidence from Caucasians supported a genetic predisposition of CTLA4 to myasthenia gravis (MG), but the contribution in East Asians has not been established. OBJECTIVES To investigate the role of CTLA4 variants in the susceptibility to MG and the contribution to subtypes of MG. METHODS Six autoimmune disease-related risk alleles of CTLA4 (rs1863800, rs733618, rs4553808, rs5742909, rs231775, and rs3087243) were investigated for MG in northern Chinese. 168 patients with MG (mean age 37.1±20.5 years, 64 men and 104 women) and 233 healthy controls (mean age 53.3±8.7 years, 96 men and 137 women) were screened, and the contribution of CTLA4 to the general risk of MG and each subgroup was explored. RESULTS rs1863800*C, rs733618*C, and rs231775*G were significantly associated with the whole cohort of patients with MG after permutation correction for multiple-testing adjustment (P = 0.027, 0.001, and 0.032, respectively). A risk haplotype (CCACG) [odds ratio (OR) = 1.535, range = 1.150-2.059, P = 0.004)] was also identified. The stratified subtype analysis indicated that the positive contribution was possibly derived from early onset MG (EOMG), seropositive MG (SPMG), female patients, and MG without thymoma. No association was observed in juvenile MG/LOMG, and MG coupled with thymoma. CONCLUSION A predisposing effect of rs1863800*C, rs733618*C, and rs231775*G of CTLA4 gene to general risk of MG in Chinese was demonstrated for the first time, which was likely derived from EOMG, SPMG, MG without thymoma and the female patients.
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George S, Paulick S, Knütter I, Röber N, Hiemann R, Roggenbuck D, Conrad K, Küpper JH. Stable expression of human muscle-specific kinase in HEp-2 M4 cells for automatic immunofluorescence diagnostics of myasthenia gravis. PLoS One 2014; 9:e83924. [PMID: 24416182 PMCID: PMC3886972 DOI: 10.1371/journal.pone.0083924] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Accepted: 11/11/2013] [Indexed: 12/22/2022] Open
Abstract
Muscle-specific kinase (MuSK) belongs to the nicotinic acetylcholine receptor complex which is targeted by pathogenic autoantibodies causing Myasthenia gravis. While up to 95% of patients with generalized Myasthenia gravis were shown to be positive for acetylcholine receptor-specific autoantibodies, up to 70% of the remaining patients develop autoantibodies against MuSK. Discrimination of the autoantibody specificity is important for therapy of Myasthenia gravis. Recently, the new automatic fluorescence assessment platform AKLIDES has been developed for immunofluorescence-based diagnostics of autoimmune diseases. In order to establish an AKLIDES procedure for the detection of MuSK-specific autoantibodies (anti-MuSK), we developed a recombinant HEp-2 cell clone expressing the human MuSK cDNA. Here we show at the mRNA and protein level that the cell clone HEp-2 M4 stably expresses human MuSK. We provide evidence for a localization of MuSK at the cell membrane. Using cell clone HEp-2 M4 on the AKLIDES system, we investigated 34 patient sera that were previously tested anti-MuSK positive by radioimmunoassay as positive controls. As negative controls, we tested 29 acetylcholine receptor-positive but MuSK-negative patient sera, 30 amytrophic lateral sclerosis (ALS) patient sera and 45 blood donors. HEp-2 M4 cells revealed a high specificity for the detection of MuSK autoantibodies from 25 patient sera assessed by a specific pattern on HEp-2 M4 cells. By using appropriate cell culture additives, the fraction of cells stained positive with anti-MuSK containing sera can be increased from 2-16% to 10-48%, depending on the serum. In conclusion, we provide data showing that the novel recombinant cell line HEp-2 M4 can be used to screen for anti-MuSK with the automatic AKLIDES system.
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Affiliation(s)
- Sandra George
- Faculty of Science, Brandenburg University of Technology Cottbus-Senftenberg, Senftenberg, Germany
- Institute of Immunology, Technical University Dresden, Dresden, Germany
| | - Silvia Paulick
- Faculty of Science, Brandenburg University of Technology Cottbus-Senftenberg, Senftenberg, Germany
| | - Ilka Knütter
- GA Generic Assays GmbH, Dahlewitz/Berlin, Germany
| | - Nadja Röber
- Institute of Immunology, Technical University Dresden, Dresden, Germany
| | - Rico Hiemann
- GA Generic Assays GmbH, Dahlewitz/Berlin, Germany
| | - Dirk Roggenbuck
- Faculty of Science, Brandenburg University of Technology Cottbus-Senftenberg, Senftenberg, Germany
- GA Generic Assays GmbH, Dahlewitz/Berlin, Germany
| | - Karsten Conrad
- Institute of Immunology, Technical University Dresden, Dresden, Germany
| | - Jan-Heiner Küpper
- Faculty of Science, Brandenburg University of Technology Cottbus-Senftenberg, Senftenberg, Germany
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15
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Yi JS, Guidon A, Sparks S, Osborne R, Juel VC, Massey JM, Sanders DB, Weinhold KJ, Guptill JT. Characterization of CD4 and CD8 T cell responses in MuSK myasthenia gravis. J Autoimmun 2013; 52:130-8. [PMID: 24378287 DOI: 10.1016/j.jaut.2013.12.005] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Accepted: 12/08/2013] [Indexed: 01/22/2023]
Abstract
Muscle specific tyrosine kinase myasthenia gravis (MuSK MG) is a form of autoimmune MG that predominantly affects women and has unique clinical features, including prominent bulbar weakness, muscle atrophy, and excellent response to therapeutic plasma exchange. Patients with MuSK MG have predominantly IgG4 autoantibodies directed against MuSK on the postsynaptic muscle membrane. Lymphocyte functionality has not been reported in this condition. The goal of this study was to characterize T cell responses in patients with MuSK MG. Intracellular production of IFN-gamma, TNF-alpha, IL-2, IL-17, and IL-21 by CD4+ and CD8+ T cells was measured by polychromatic flow cytometry in peripheral blood samples from 11 Musk MG patients and 10 healthy controls. Only one MuSK MG patient was not receiving immunosuppressive therapy. Regulatory T cells (Treg) were also included in our analysis to determine if changes in T cell function were due to altered Treg frequencies. CD8+ T cells from MuSK MG patients had higher frequencies of polyfunctional responses than controls, and CD4+ T cells had higher IL-2, TNF-alpha, and IL-17. MuSK MG patients had a higher percentage of CD4+ T cells producing combinations of IFN-gamma/IL-2/TNF-gamma, TNF-alpha/IL-2, and IFN-gamma/TNF-alpha. Interestingly, Treg numbers and CD39 expression were not different from control values. MuSK MG patients had increased frequencies of Th1 and Th17 cytokines and were primed for polyfunctional proinflammatory responses that cannot be explained by a defect in CD39 expression or Treg number.
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Affiliation(s)
- J S Yi
- Division of Surgical Sciences, Department of Surgery, Duke University Medical Center, 204 SORF (Bldg. 41), 915 S. LaSalle Street, Box 2926, Durham, NC 27710, USA
| | - A Guidon
- Neuromuscular Division, Department of Neurology, Duke University Medical Center, DUMC Box 3403, Durham, NC 27710, USA
| | - S Sparks
- Division of Surgical Sciences, Department of Surgery, Duke University Medical Center, 204 SORF (Bldg. 41), 915 S. LaSalle Street, Box 2926, Durham, NC 27710, USA
| | - R Osborne
- Division of Surgical Sciences, Department of Surgery, Duke University Medical Center, 204 SORF (Bldg. 41), 915 S. LaSalle Street, Box 2926, Durham, NC 27710, USA
| | - V C Juel
- Neuromuscular Division, Department of Neurology, Duke University Medical Center, DUMC Box 3403, Durham, NC 27710, USA
| | - J M Massey
- Neuromuscular Division, Department of Neurology, Duke University Medical Center, DUMC Box 3403, Durham, NC 27710, USA
| | - D B Sanders
- Neuromuscular Division, Department of Neurology, Duke University Medical Center, DUMC Box 3403, Durham, NC 27710, USA
| | - K J Weinhold
- Division of Surgical Sciences, Department of Surgery, Duke University Medical Center, 204 SORF (Bldg. 41), 915 S. LaSalle Street, Box 2926, Durham, NC 27710, USA
| | - J T Guptill
- Neuromuscular Division, Department of Neurology, Duke University Medical Center, DUMC Box 3403, Durham, NC 27710, USA.
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16
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Koneczny I, Cossins J, Vincent A. The role of muscle-specific tyrosine kinase (MuSK) and mystery of MuSK myasthenia gravis. J Anat 2013; 224:29-35. [PMID: 23458718 DOI: 10.1111/joa.12034] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/05/2013] [Indexed: 11/28/2022] Open
Abstract
MuSK myasthenia gravis is a rare, severe autoimmune disease of the neuromuscular junction, only identified in 2001, with unclear pathogenic mechanisms. In this review we describe the clinical aspects that distinguish MuSK MG from AChR MG, review what is known about the role of MuSK in the development and function of the neuromuscular junction, and discuss the data that address how the antibodies to MuSK lead to neuromuscular transmission failure.
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Affiliation(s)
- Inga Koneczny
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
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17
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Cossins J, Belaya K, Zoltowska K, Koneczny I, Maxwell S, Jacobson L, Leite MI, Waters P, Vincent A, Beeson D. The search for new antigenic targets in myasthenia gravis. Ann N Y Acad Sci 2013; 1275:123-8. [PMID: 23278587 DOI: 10.1111/j.1749-6632.2012.06833.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Around 80% of myasthenia gravis patients have antibodies against the acetylcholine receptor, and 0-60% of the remaining patients have antibodies against the muscle-specific tyrosine kinase, MuSK. Another recently identified antigen is low-density lipoprotein receptor-related protein 4 (Lrp4). To improve the existing assays and widen the search for new antigenic targets, we have employed cell-based assays in which candidate target proteins are expressed on the cell surface of transfected cells and probed with patient sera. These assays, combined with use of myotube cultures to explore the effects of the antibodies, enable us to begin to identify new antigenic targets and test antibody pathogenicity in vitro.
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Affiliation(s)
- Judith Cossins
- Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford, United Kingdom.
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18
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Abstract
Juvenile myasthenia gravis is an uncommon autoimmune disorder. Its management is not standardized. Juvenile myasthenia gravis is pathophysiologically similar to myasthenia gravis in adults. However, a number of significant particularities related to race, age at onset, severity, and antibody status complicate the management. We summarize the unique clinical features of juvenile myasthenia gravis and review the therapeutic options.
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Affiliation(s)
- Cristian M Ionita
- Connecticut Children's Medical Center, Department of Pediatrics, and Division of Pediatric Neurology, Department of Neurology, University of Connecticut School of Medicine, Hartford, CT 06106, USA.
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19
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Zanin A, Sartori S, Salandin M, Laverda AM, Fenicia L, Anniballi F, Cogo PE. A descending cranial nerve palsy during the christmas holidays. Neurohospitalist 2012; 2:66-70. [PMID: 23983866 DOI: 10.1177/1941874412438903] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Affiliation(s)
- Anna Zanin
- Department of Pediatrics Salus Pueri, University of Padua, Italy
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20
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Köhler W, Bucka C, Klingel R. A randomized and controlled study comparing immunoadsorption and plasma exchange in myasthenic crisis. J Clin Apher 2011; 26:347-55. [DOI: 10.1002/jca.20317] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Accepted: 09/13/2011] [Indexed: 11/06/2022]
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21
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Pevzner A, Schoser B, Peters K, Cosma NC, Karakatsani A, Schalke B, Melms A, Kröger S. Anti-LRP4 autoantibodies in AChR- and MuSK-antibody-negative myasthenia gravis. J Neurol 2011; 259:427-35. [PMID: 21814823 DOI: 10.1007/s00415-011-6194-7] [Citation(s) in RCA: 203] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Revised: 06/27/2011] [Accepted: 07/14/2011] [Indexed: 11/25/2022]
Abstract
Myasthenia gravis (MG) is an autoimmune disorder characterized by a defect in synaptic transmission at the neuromuscular junction causing fluctuating muscle weakness with a decremental response to repetitive nerve stimulation or altered jitter in single-fiber electromyography (EMG). Approximately 80% of all myasthenia gravis patients have autoantibodies against the nicotinic acetylcholine receptor in their serum. Autoantibodies against the tyrosine kinase muscle-specific kinase (MuSK) are responsible for 5-10% of all myasthenia gravis cases. The autoimmune target in the remaining cases is unknown. Recently, low-density lipoprotein receptor-related protein (LRP4) has been identified as the agrin receptor. LRP4 interacts with agrin, and the binding of agrin activates MuSK, which leads to the formation of most if not all postsynaptic specializations, including aggregates containing acetylcholine receptors (AChRs) in the junctional plasma membrane. In the present study we tested if autoantibodies against LRP4 are detectable in patients with myasthenia gravis. To this end we analyzed 13 sera from patients with generalized myasthenia gravis but without antibodies against AChR or MuSK. The results showed that 12 out of 13 antisera from double-seronegative MG patients bound to proteins concentrated at the neuromuscular junction of adult mouse skeletal muscle and that approximately 50% of the tested sera specifically bound to HEK293 cells transfected with human LRP4. Moreover, 4 out of these 13 sera inhibited agrin-induced aggregation of AChRs in cultured myotubes by more than 50%, suggesting a pathogenic role regarding the dysfunction of the neuromuscular endplate. These results indicate that LRP4 is a novel target for autoantibodies and is a diagnostic marker in seronegative MG patients.
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Affiliation(s)
- Alexandra Pevzner
- Department of Physiological Genomics, Institute for Physiology, Ludwig-Maximilians University, Pettenkoferstrasse 12, 80336, Munich, Germany
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22
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Anti-MuSK-Positive Myasthenia Gravis in a Patient with Parkinsonism and Cognitive Impairment. Neurol Res Int 2011; 2011:859802. [PMID: 21822490 PMCID: PMC3148447 DOI: 10.1155/2011/859802] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 04/06/2011] [Accepted: 05/02/2011] [Indexed: 11/22/2022] Open
Abstract
Muscle-specific tyrosine kinase- (MuSK-) antibodies-positive Myasthenia Gravis accounts for about one third of Seronegative Myasthenia Gravis and is clinically characterized by early onset of prominent bulbar, neck, shoulder girdle, and respiratory weakness. The response to medical therapy is generally poor. Here we report a case of late-onset MuSK-antibodies-positive Myasthenia Gravis presenting with signs of cognitive impairment and parkinsonism in addition to bulbar involvement and external ophthalmoplegia. The pattern of involvement of both peripheral and central nervous system dysfunction might suggest a common pathogenic mechanism, involving impaired cholinergic transmission.
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23
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24
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Zouvelou V, Rentzos M, Toulas P, Evdokimidis I. MRI evidence of early muscle atrophy in MuSK positive myasthenia gravis. J Neuroimaging 2009; 21:303-5. [PMID: 20002967 DOI: 10.1111/j.1552-6569.2009.00456.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Muscle atrophy, particularly of facial and bulbar muscles, seems to be a relatively common long-term consequence of musclespecific tyrosine kinase-myasthenia gravis (MuSK-MG), perhaps reflecting the chronic state of disease or long-term therapy with corticosteroids. We performed magnetic resonance imaging (MRI) to assess muscle wasting in the facial and bulbar muscles in two female MuSK-MG patients, with short duration of symptoms prior to diagnosis and prior to commencement of steroid therapy. The study revealed marked atrophy of temporalis, masseters, and lingual muscles with fatty replacement. MRI evidence of early muscle atrophy in MuSK-MG may indicate that MuSK antibodies per se may predispose to muscle atrophy.
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Affiliation(s)
- Vasiliki Zouvelou
- Neurology Department, University of Athens, Eginition Hospital, Athens, Greece.
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25
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Aubert S, Salort-Campana E, Franques J, Uzenot D, Pouget J. Myasthénie séronégative et myasthénie avec anticorps anti-MuSK : une série rétrospective de 20 cas. Rev Neurol (Paris) 2009; 165:901-10. [DOI: 10.1016/j.neurol.2009.01.049] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2008] [Revised: 11/28/2008] [Accepted: 01/15/2009] [Indexed: 11/30/2022]
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26
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Littleton E, Dreger M, Palace J, Vincent A. Immunocapture and identification of cell membrane protein antigenic targets of serum autoantibodies. Mol Cell Proteomics 2009; 8:1688-96. [PMID: 19332416 PMCID: PMC2716719 DOI: 10.1074/mcp.m800563-mcp200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2008] [Revised: 03/26/2009] [Indexed: 11/08/2022] Open
Abstract
There is increasing interest in the role of antibodies targeting specific membrane proteins in neurological and other diseases. The target(s) of these pathogenic antibodies is known in a few diseases, usually when candidate cell surface proteins have been tested. Approaches for identifying new antigens have mainly resulted in the identification of antibodies to intracellular proteins, which are often very useful as diagnostic markers for disease but unlikely to be directly involved in disease pathogenesis because they are not accessible to circulating antibodies. To identify cell surface antigens, we developed a "conformational membrane antigen isolation and identification" strategy. First, a cell line is identified that reacts with patient sera but not with control sera. Second, intact cells are exposed to sera to allow the binding of presumptive autoantibodies to their cell surface targets. After washing off non-bound serum components, the cells are lysed, and immune complexes are precipitated. Third, the bound surface antigen is identified by mass spectrometry. As a model system we used a muscle cell line, TE671, that endogenously expresses muscle-specific tyrosine receptor kinase (MuSK) and sera or plasmas from patients with a subtype of the autoimmune disease myasthenia gravis in which patients have autoantibodies against MuSK. MuSK was robustly detected as the only membrane protein in immunoprecipitates from all three patient samples tested and not from the three MuSK antibody-negative control samples processed in parallel. Of note, however, there were many intracellular proteins found in the immunoprecipitates from both patients and controls, suggesting that these were nonspecifically immunoprecipitated from cell extracts. The conformational membrane antigen isolation and identification technique should be of value for the detection of highly relevant antigenic targets in the growing number of suspected antibody-mediated autoimmune disorders. The approach would also be very suitable for the analysis of human or experimental antitumor responses.
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Affiliation(s)
- Edward Littleton
- From the ‡Neurosciences Group, Weatherall Institute of Molecular Medicine and
| | - Mathias Dreger
- ¶Proteomics Laboratory, Henry Wellcome Centre for Gene Function, South Parks Road, Oxford OX3 7BN, United Kingdom
| | - Jackie Palace
- **Department of Clinical Neurology, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom and
| | - Angela Vincent
- From the ‡Neurosciences Group, Weatherall Institute of Molecular Medicine and
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27
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Lebrun C, Bourg V, Tieulie N, Thomas P. Successful treatment of refractory generalized myasthenia gravis with rituximab. Eur J Neurol 2009; 16:246-50. [DOI: 10.1111/j.1468-1331.2008.02399.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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28
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Abstract
Circulating antibodies of the acetylcholine receptor (AchRAb) are detectable in most patients with generalized myasthenia gravis (MG). A newly discovered antibody against muscle-specific kinase (MuSKAb) has been detected in 40-70% of AchRAb-negative MG patients. We report a series of Taiwanese MuSKAb-positive patients, and compare their clinical features with MuSKAb-negative patients and also with MuSKAb-positive Caucasians. Five out of 44 seronegative generalized MG patients (11.4%) were positive for MuSKAb. Patients with MuSKAb tended to have severe disability and bulbar involvement, and more often experienced crisis or impending crisis. Although all of these patients showed an initial response to immunosuppressant therapy, they had greater disability at follow-up. The clinical features of Taiwanese MuSKAb-positive patients were not different from those of Caucasians, except for a lower prevalence.
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29
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Hubball A, Martin JE, Lang B, De Giorgio R, Knowles CH. The role of humoral autoimmunity in gastrointestinal neuromuscular diseases. Prog Neurobiol 2008; 87:10-20. [PMID: 18929621 DOI: 10.1016/j.pneurobio.2008.09.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Revised: 07/25/2008] [Accepted: 09/19/2008] [Indexed: 02/08/2023]
Abstract
Dysfunction of the gastrointestinal neuromuscular apparatus (including interstitial cells of Cajal) is presumed to underlie a heterogeneous group of disorders collectively termed gastrointestinal neuromuscular diseases (GINMDs). There is increasing experimental and clinical evidence that some GINMDs are immune-mediated, with cell-mediated dysfunction relatively well studied. Humoral (antibody)-mediated autoimmunity is associated with several well-established acquired neuromuscular diseases and is now implicated in an increasing number of less well-characterised disorders, particularly of the central nervous system. The role of autoimmunity in GINMDs has been less studied. Whilst most work has focused on the presence of antibodies directed to nuclear antigens, particularly in the context of secondary disorders such as paraneoplastic intestinal pseudo-obstruction, the possibility that 'functional' anti-neuronal antibodies directed to membrane-bound ion channels may cause disease (channelopathy) is now also being realised. The evidence for humoral autoimmunity as an etiologic factor in primary (idiopathic) and secondary GINMDs is systematically presented using the original paradigms previously applied to established autoimmune neuromuscular disorders. The presence of anti-enteric neuronal antibodies, although repeatedly demonstrated, still requires the identification of specific neuronal autoantigens and validated evidence of pathogenicity.
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Affiliation(s)
- Andrew Hubball
- Neurogastroenterology Group, Centres for Academic Surgery and Pathology, Institute of Cellular and Molecular Science, Barts and the London, Queen Mary's School of Medicine and Dentistry, Whitechapel, London, UK
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30
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Atassi N, Amato AA. Muscle-specific kinase (MuSK) antibody-associated myasthenia gravis after bone marrow transplantation. Muscle Nerve 2008; 38:1074-5. [DOI: 10.1002/mus.21023] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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31
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Illa I, Diaz-Manera J, Rojas-Garcia R, Pradas J, Rey A, Blesa R, Juarez C, Gallardo E. Sustained response to Rituximab in anti-AChR and anti-MuSK positive Myasthenia Gravis patients. J Neuroimmunol 2008; 201-202:90-4. [PMID: 18653247 DOI: 10.1016/j.jneuroim.2008.04.039] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Revised: 04/15/2008] [Accepted: 04/18/2008] [Indexed: 11/24/2022]
Abstract
We report the results of treatment with Rituximab in six severe, non-responder MG patients. We treated three AChR+MG and three MuSK+MG patients, representing 2% and 20% of the respective groups of our series. Patients were assessed according to the Myasthenia Gravis Foundation of America (MGFA) recommendations. Antibody titers to AChR and MuSK, Ig levels, and IgG subclasses, were tested before treatment and during a follow-up of 9-22 months. All patients, one class V and five class IVB, improved dramatically, with no side effects. Antibody titers declined in all patients (p=0.006). The decline was significantly better in MuSK+MG patients at 9 months (p=0.046) and correlated with a more sustained clinical improvement. We did not find any significant changes in IgG4 that could explain the different outcome observed between these two groups.
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Affiliation(s)
- Isabel Illa
- Department of Neurology, Neuromuscular Unit, Hospital Santa Creu i Sant Pau, Universitat Autònoma Barcelona, Barcelona, Spain.
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32
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Shigemoto K, Kubo S, Jie C, Hato N, Abe Y, Ueda N, Kobayashi N, Kameda K, Mominoki K, Miyazawa A, Ishigami A, Matsuda S, Maruyama N. Myasthenia Gravis Experimentally Induced with Muscle-specific Kinase. Ann N Y Acad Sci 2008; 1132:93-8. [DOI: 10.1196/annals.1405.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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33
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Punga AR, Sawada M, Stålberg EV. Electrophysiological signs and the prevalence of adverse effects of acetylcholinesterase inhibitors in patients with myasthenia gravis. Muscle Nerve 2008; 37:300-7. [PMID: 18069667 DOI: 10.1002/mus.20935] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The aim of this prospective study was to assess whether extra discharges (EDs), sometimes following the compound muscle action potential, could be used as a neurophysiological indicator of overdose of acetylcholinesterase inhibitors (AChEIs) in patients with myasthenia gravis (MG). The characteristics and frequency of EDs were explored and the correlation of EDs with cholinergic side effects was also determined. Twenty-two MG patients (14 women, 8 men; 61 +/- 16 years of age) with daily AChEI treatment were examined. The mean disease duration was 10 years (range 2-62 years) and all patients had been treated with AChEI since MG onset. Both single and repetitive stimulation of the ulnar and accessory nerves were performed before and 60 min after oral pyridostigmine bromide (PB) administration and after additional edrophonium injection. Fatigue, side effects, and AChE activity in blood were assessed before and 60 min after PB intake. The daily dose of PB ranged from 150 to 900 mg/day. Fourteen patients (64%) experienced daily cholinergic adverse effects, and muscarinic side effects correlated with AChE activity. Eleven patients (50%) developed EDs after oral PB. Among the eight patients with daily nicotinic side effects, EDs were significantly (P < 0.05) more common. Additionally, older patients were more prone to develop cholinergic side effects and EDs. Thus, when EDs are found, patients should be asked about daily muscular symptoms, which may be related to AChEI treatment and not solely to MG.
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Affiliation(s)
- Anna Rostedt Punga
- Department of Clinical Neurophysiology, Uppsala University Hospital, 751 85 Uppsala, Sweden.
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34
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Chan KH, Lachance DH, Harper CM, Lennon VA. Frequency of seronegativity in adult-acquired generalized myasthenia gravis. Muscle Nerve 2008; 36:651-8. [PMID: 17654558 DOI: 10.1002/mus.20854] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We determined the prevalence of muscle acetylcholine receptor (AChR) antibodies in patients with adult-acquired generalized myasthenia gravis (MG), the seroconversion rate at 12 months, and the prevalence of muscle-specific tyrosine kinase (MuSK) antibody among persistently seronegative patients. We identified 562 consecutive Mayo Clinic patients with MG based on clinical and electrophysiological criteria. At presentation, 508 patients (90.4%) tested positive for AChR binding or AChR modulating antibodies. After 12 months, 15.2% of initially seronegative patients had become seropositive, yielding a seronegativity rate of 8.2% (95% confidence interval: 6.2-9.6%). Among seronegative patients not receiving immunosuppressants, 38% were MuSK antibody-positive and 43% were seropositive for nonmuscle autoantibodies. Classification as seronegative MG should be reserved for nonimmunosuppressed patients with generalized MG who lack muscle AChR binding, AChR modulating, or MuSK antibodies at presentation and at follow-up of at least 12 months.
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Affiliation(s)
- Koon Ho Chan
- Department of Laboratory Medicine & Pathology, Mayo Clinic, College of Medicine, 200 First Street S.W., Rochester, Minnesota 55905, USA
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35
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Vincent A. Autoantibodies in different forms of myasthenia gravis and in the Lambert-Eaton syndrome. HANDBOOK OF CLINICAL NEUROLOGY 2008; 91:213-227. [PMID: 18631844 DOI: 10.1016/s0072-9752(07)01506-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Affiliation(s)
- Angela Vincent
- Department of Clinical Neurology, University of Oxford, Oxford, UK.
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Yeh JH, Chen WH, Chiu HC, Bai CH. MuSK antibody clearance during serial sessions of plasmapheresis for myasthenia gravis. J Neurol Sci 2007; 263:191-3. [PMID: 17602704 DOI: 10.1016/j.jns.2007.05.033] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2007] [Revised: 05/12/2007] [Accepted: 05/25/2007] [Indexed: 11/23/2022]
Abstract
To evaluate the relationship of antibody clearance and clinical improvement for myasthenia gravis (MG) patients with MuSK antibody (MuSKAb) receiving one course of double-filtration plasmapheresis (DFP) treatment, we prospectively recorded their MG scores and measured MuSKAb concentrations before and after each DFP treatment session in two MuSKAb-positive patients. The clinical improvement trends roughly paralleled the reductions of MG score, except for the late rebound of MuSKAb in the 6th DFP treatment session, without concomitant clinical worsening in one patient. Longitudinal analysis on the serological changes during the serial sessions revealed that the levels of MuSKAb fell by 44%, 59%, 79%, 82%, 92%, and 71% in patient 1 and 52%, 70%, 78%, 87%, and 90% in patient 2. The titers of MuSKAb decreased constantly during the first 5 DFP treatment sessions. MuSKAb clearance per session for the 11 sessions ranged from 19% to 56%, with a mean of 45%. In conclusion, DFP was effective for MuSKAb removal and amelioration of clinical weakness for our two patients with MuSKAb. A 5-session protocol cleared 90% of serum MuSKAb.
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Affiliation(s)
- Jiann-Horng Yeh
- Department of Neurology, Shin Kong Wu Ho-Su Memorial Hospital, 95 Wen Chang Road, Shih Lin district, Taipei, Taiwan.
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Abstract
Myasthenia gravis (MG) is a rare, autoimmune neuromuscular junction disorder. Contemporary prevalence rates approach 1/5,000. MG presents with painless, fluctuating, fatigable weakness involving specific muscle groups. Ocular weakness with asymmetric ptosis and binocular diplopia is the most typical initial presentation, while early or isolated oropharyngeal or limb weakness is less common. The course is variable, and most patients with initial ocular weakness develop bulbar or limb weakness within three years of initial symptom onset. MG results from antibody-mediated, T cell-dependent immunologic attack on the endplate region of the postsynaptic membrane. In patients with fatigable muscle weakness, the diagnosis of MG is supported by: 1. pharmacologic testing with edrophonium chloride that elicits unequivocal improvement in strength; 2. electrophysiologic testing with repetitive nerve stimulation (RNS) studies and/or single-fiber electromyography (SFEMG) that demonstrates a primary postsynaptic neuromuscular junctional disorder; and 3. serologic demonstration of acetylcholine receptor (AChR) or muscle-specific tyrosine kinase (MuSK) antibodies. Differential diagnosis includes congenital myasthenic syndromes, Lambert Eaton syndrome, botulism, organophosphate intoxication, mitochondrial disorders involving progressive external ophthalmoplegia, acute inflammatory demyelinating polyradiculoneuropathy (AIDP), motor neuron disease, and brainstem ischemia. Treatment must be individualized, and may include symptomatic treatment with cholinesterase inhibitors and immune modulation with corticosteroids, azathioprine, cyclosporine, and mycophenolate mofetil. Rapid, temporary improvement may be achieved for myasthenic crises and exacerbations with plasma exchange (PEX) or intravenous immunoglobulin (IVIg). Owing to improved diagnostic testing, immunotherapy, and intensive care, the contemporary prognosis is favorable with less than five percent mortality and nearly normal life expectancy.
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Affiliation(s)
- Vern C Juel
- Division of Neurology, Box 3403, Duke University Medical Center, Durham, North Carolina, 27710, USA
| | - Janice M Massey
- Division of Neurology, Box 3403, Duke University Medical Center, Durham, North Carolina, 27710, USA
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Chan KH, Cheung RTF, Mak W, Ho SL. Nonthymoma early-onset- and late-onset-generalized myasthenia gravis—A retrospective hospital-based study. Clin Neurol Neurosurg 2007; 109:686-91. [PMID: 17644246 DOI: 10.1016/j.clineuro.2007.05.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Revised: 05/28/2007] [Accepted: 05/30/2007] [Indexed: 11/20/2022]
Abstract
OBJECTIVE Acquired myasthenia gravis (MG) is predominantly due to nicotinic acetylcholine receptor (AChR) autoantibodies (Ab). Differences between nonthymoma early-onset and late-onset MG were reported. We studied the clinical and serological characteristics of nonthymoma AChR Ab-positive-generalized MG patients. PATIENTS AND METHODS Chinese AChR Ab-positive-generalized MG patients who had generalized disease for 3 years or longer were studied. RESULTS Among 41 such patients, 25 (61%) were female. The mean onset age was 43.5 years (range 9-78 years) and the mean follow-up duration was 7.8 years (range 3-20 years). Sixteen (39%) patients had late-onset disease (onset age >or=50 years). Compared to early-onset patients (onset age <50 years), late-onset patients were characterized by male predominance (p=0.002), absence of thymic lymphofollicular hyperplasia (p=0.036), and a higher striated muscle Ab seropositivity rate (94% versus 4%, p<0.001). Although there was no statistically significant difference in clinical severity and outcome or response to treatment between late-onset and early-onset patients, 50% and 75% of late-onset patients had moderate or severe disease at onset and worst status, respectively, compared to 28% and 52% for early-onset patients at onset and worst status, respectively. Also 63% of late-onset patients had disease progressed within first 3 years compared to only 40% of early-onset patients did. CONCLUSION Nonthymoma late-onset-generalized MG patients were common among Hong Kong Chinese, with a statistically non-significant trend that it was clinically more severe than early-onset MG but with similar clinical outcome or response to treatment; >90% of these patients were seropositive for striated muscle Ab.
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Affiliation(s)
- K H Chan
- Department of Medicine, Queen Mary Hospital, The University of Hong Kong, Hong Kong, China.
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Hayashi A, Shiono H, Ohta M, Ohta K, Okumura M, Sawa Y. Heterogeneity of immunopathological features of AChR/MuSK autoantibody-negative myasthenia gravis. J Neuroimmunol 2007; 189:163-8. [PMID: 17706794 DOI: 10.1016/j.jneuroim.2007.07.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2007] [Revised: 07/05/2007] [Accepted: 07/06/2007] [Indexed: 11/22/2022]
Abstract
We compared B cells and germinal centers in thymus from myasthenia gravis (MG) patients either with anti-acetylcholine receptor (AChR) autoantibodies or with neither anti-muscle-specific tyrosine kinase (MuSK) nor anti-AChR (seronegative MG: SN-MG). The numbers and frequencies of total and germinal center B cells varied in the SN-MG thymi, some of which were normal/atrophic. Others were clearly hyperplastic, their B cell parameters overlapping with those in AChR-positive MG, which implicates the thymus in pathogenesis. Indeed, some SN-MG patients apparently benefited from thymectomy, which should be considered a management option.
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Affiliation(s)
- Akio Hayashi
- Department of Surgery, Osaka University Graduate School of Medicine, Japan
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Zhang X, Yang M, Xu J, Zhang M, Lang B, Wang W, Vincent A. Clinical and serological study of myasthenia gravis in HuBei Province, China. J Neurol Neurosurg Psychiatry 2007; 78:386-90. [PMID: 17088330 PMCID: PMC2077769 DOI: 10.1136/jnnp.2006.100545] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND Ocular and childhood myasthenia gravis (MG) cases seem relatively more common in Oriental than in Caucasian populations, but there have been no comprehensive serological studies on patients from mainland China. METHODS 391 unselected patients with MG attending Tongji Hospital in WuHan (the largest hospital in the province of HuBei, China) were studied during a 15-month period; most had already received treatment for their condition. RESULTS The male to female ratio was 0.8. 50% of the patients were children (<15 years), and age at onset showed a single peak at between 5 and 10 years of age. 64% of the children and 66% of the adults were positive for acetylcholine receptor (AChR) antibodies but the antibody titres were lower than in similar Caucasian studies, although this was partly due to the high incidence of ocular MG. Of the 43 patients with generalised MG without AChR antibodies, only 1 had muscle-specific kinase antibodies (2.5%) and 2 had voltage-gated calcium channel antibodies indicating probable Lambert-Eaton myasthenic syndrome. 75% of the children, compared with only 28% of the adults, had ocular MG. Thymoma was evident by MRI in 1.5% of children and in 20% of adults. Despite most patients having received prednisone, very few had obtained full clinical remission. CONCLUSION This study emphasises the frequency of early childhood onset with ocular symptoms and shows that many of these patients have AChR antibodies. By contrast, patients presenting in later age seem to be very uncommon in comparison with recent studies in Caucasian populations.
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Affiliation(s)
- Xiaofan Zhang
- Department of Neurology, Tongji Hospital, Huazhong University of Science and Technology, WuHan, China
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Farrugia ME, Kennett RP, Hilton-Jones D, Newsom-Davis J, Vincent A. Quantitative EMG of facial muscles in myasthenia patients with MuSK antibodies. Clin Neurophysiol 2007; 118:269-77. [PMID: 17157556 DOI: 10.1016/j.clinph.2006.10.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2005] [Revised: 09/28/2006] [Accepted: 10/03/2006] [Indexed: 01/08/2023]
Abstract
OBJECTIVE Our aim was to study the pathophysiological process leading to facial muscle atrophy in 13 patients with MuSK antibody positive myasthenia gravis (MuSK-MG), and to compare with findings from 12 acetylcholine receptor antibody positive myasthenia patients (AChR-MG), selected because they suffered from the same degree of disease severity and required similar treatment. METHODS Motor unit action potential (MUAP) and interference pattern analysis from orbicularis oculi (O oculi) and orbicularis oris (O oris) muscles were studied using a concentric needle electrode, and compared with findings in 20 normal subjects, 6 patients receiving botulinum toxin injections (representing a neurogenic model) and 6 patients with a muscle dystrophy (representing a myopathic model). The techniques and control data have been reported previously. RESULTS The mean MUAP durations for O oculi and O oris were significantly reduced (p<0.001) in both MG cohorts when compared with healthy subjects, and were similar to those in the myopathic control group. They were significantly different from those obtained from the neurogenic control group (p<0.001 for both O oculi and O oris). The MUAP findings in O oculi occurred independently from neuromuscular blocking on single fibre EMG (SFEMG) in the same muscle. On turns amplitude analysis (TAA), 50% of MuSK-MG patients and 42% of AChR-MG patients had a pattern in O oculi which was similar to that in the myopathic control group, and 62% of MuSK-MG patients and 50% of AChR-MG patients had a pattern in O oris that was also similar to that in the myopathic control group. The TAA findings for O oculi and O oris in both MG cohorts were different from those obtained from the neurogenic control group. CONCLUSIONS Facial muscle atrophy in MuSK-MG patients is not neurogenic and the pathophysiological changes are akin to a myopathic process. The selected AChR-MG patients also show evidence of a similar pathophysiological process in the facial muscles albeit to a lesser degree. SIGNIFICANCE We propose that muscle atrophy in MuSK-MG is a myopathic process consisting of either muscle fibre shrinkage or loss of muscle fibres from motor units. The duration of disease and long-term steroid treatment may be further contributory factors.
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Affiliation(s)
- Maria E Farrugia
- Department of Clinical Neurophysiology, The Radcliffe Infirmary, Oxford OX2 6HE, UK.
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Abstract
BACKGROUND Although myasthenia gravis (MG) is often considered the best-understood autoimmune disorder and effective treatments have controlled life-threatening complications, the pathogenesis of ocular myasthenia (OM) remains enigmatic, and its clinical consequences offer therapeutic challenges. REVIEW SUMMARY About half of patients with MG present with visual complaints of droopy eyelids or double vision, and many will remain with purely ocular muscle weakness without generalized weakness, defined as OM. OM may be confused with disorders of the brainstem, ocular motor nerves, and eye muscles. Frustrating for the clinician, confirmatory tests such as the edrophonium test, serum acetylcholine receptor antibodies, and standard electrodiagnostic evaluations may fail to positively identify the clinical suspicion of OM. Patients may derive relief from nonpharmacologic interventions and cholinesterase inhibitors, but most will desire better symptom control with corticosteroids or need other immunosuppression. Early corticosteroid therapy may reduce the probability of generalization of the disease. The reasons for ocular muscle involvement by OM include physiologic and cellular properties of the ocular motor system and the unique immunology of OM, which, when better understood, will lead to novel treatments. CONCLUSIONS OM is a challenging disorder for the clinician and scientist, with both learning from the other for the betterment of the patient. The future requires answers to why the ocular muscles are so frequently involved by MG, whether the generalization of the disease may be limited by early corticosteroid treatment, and what treatment options may be developed which will improve symptoms without long-term complications.
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Affiliation(s)
- Linda L Kusner
- Department of Neurology, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio, USA
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Abstract
Ion channels are crucial elements in neuronal signaling and synaptic transmission, and defects in their function are known to underlie rare genetic disorders, including some forms of epilepsy. A second class of channelopathies, characterized by autoantibodies against ligand- and voltage-gated ion channels, cause a variety of defects in peripheral neuromuscular and ganglionic transmission. There is also emerging evidence for autoantibody-mediated mechanisms in subgroups of patients with central nervous system disorders, particularly those involving defects in cognition or sleep and often associated with epilepsy. In all autoimmune channelopathies, the relationship between autoantibody specificity and clinical phenotype is complex. But with this new information, autoimmune channelopathies are detected and treated with increasing success, and future research promises new insights into the mechanisms of dysfunction at neuronal synapses and the determinants of clinical phenotype.
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Affiliation(s)
- Angela Vincent
- Neurosciences Group, Department of Clinical Neurology, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford OX3 9DS, United Kingdom.
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Toth C, McDonald D, Oger J, Brownell K. Acetylcholine receptor antibodies in myasthenia gravis are associated with greater risk of diabetes and thyroid disease. Acta Neurol Scand 2006; 114:124-32. [PMID: 16867036 DOI: 10.1111/j.1600-0404.2006.00649.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Myasthenia gravis (MG) may be associated with the presence of acetylcholine receptor antibodies (AChRAb) [seropositive MG (SPMG)] or their absence [seronegative MG (SNMG)]. Along with features of MG, the presence of the AChRAb may relate to the existence of other immune-mediated diseases. We sought to determine the association of SPMG with other potential autoimmune diseases. METHODS A retrospective evaluation of prospectively identified MG patients at a tertiary care center was performed, with patients separated into SPMG and SNMG. Prevalence of other immune-mediated disorders, as well as the epidemiology, sensitivity of diagnostic testing, and thymic pathology, was contrasted between both patient groups. RESULTS Of the 109 MG patients identified, 66% were SPMG. SPMG was associated with a greater likelihood of significant repetitive stimulation decrement, the presence of either thymoma or thymic hyperplasia, and the presence of thyroid disease. In addition, all patients with a diagnosis of diabetes, concurrent with MG, were found to be SPMG. CONCLUSIONS AChRAb and SPMG impart not only a distinctive clinical and electrophysiological phenotype of MG, but are also associated with the heightened presence of endocrinological disease.
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Affiliation(s)
- C Toth
- Department of Clinical Neurosciences, University of Calgary and the Calgary Health Region, Calgary, Alberta, Canada.
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Boneva N, Frenkian-Cuvelier M, Bidault J, Brenner T, Berrih-Aknin S. Major pathogenic effects of anti-MuSK antibodies in myasthenia gravis. J Neuroimmunol 2006; 177:119-31. [PMID: 16857268 DOI: 10.1016/j.jneuroim.2006.05.017] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2006] [Revised: 05/17/2006] [Accepted: 05/23/2006] [Indexed: 12/19/2022]
Abstract
MG with anti-MuSK antibodies (MuSK+) is often characterized with muscle atrophy and excellent response to plasma exchanges. To elucidate some MuSK+ MG features, we analyzed the functional effects of anti-MuSK Abs in human TE 671 muscle cells. We found that some MuSK+ sera induced a striking inhibition of proliferation, accompanied by: 1) cell cycle arrest, 2) atrogin-1 overexpression, 3) AChR subunits, rapsyn, Rho A and cdc42 downregulation. These effects correlated to disease severity and to anti-MuSK Abs titer and vanished following PE. Altogether, these results indicate that anti-MuSK Abs could be pathogenic by contributing to the muscle atrophy in MuSK+ MG patients.
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Affiliation(s)
- Neli Boneva
- CNRS-UMR 8162, IPSC, Université Paris XI, Hôpital Marie Lannelongue, 133 Avenue de la Résistance, 92350 Le Plessis-Robinson, France
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Rostedt Punga A, Ahlqvist K, Bartoccioni E, Scuderi F, Marino M, Suomalainen A, Kalimo H, Stålberg EV. Neurophysiological and mitochondrial abnormalities in MuSK antibody seropositive myasthenia gravis compared to other immunological subtypes. Clin Neurophysiol 2006; 117:1434-43. [PMID: 16737845 DOI: 10.1016/j.clinph.2006.03.028] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2005] [Revised: 03/21/2006] [Accepted: 03/30/2006] [Indexed: 11/19/2022]
Abstract
OBJECTIVE To compare the electrophysiological and histopathological features of immunological myasthenia gravis (MG) subtypes. METHODS Fifty MG patients underwent clinical examination, MuSK-Ab and AChR-Ab analysis. The majority underwent quantitative and single-fiber electromyography (QEMG, SFEMG), repetitive nerve stimulation and deltoid muscle biopsy. From muscle specimens with histological mitochondrial dysfunction, we amplified mitochondrial DNA (mtDNA). In specimens with mtDNA deletions, the nuclear gene POLG1 was sequenced. RESULTS Five AChR-Ab seropositive [AChR(+)] and 5 seronegative [AChR(-)] patients were MuSK-Ab seropositive [MuSK(+)]. Five of 7 neurophysiologically examined MuSK(+) patients (71%) had proximal myopathic pattern, compared to 7 of 31 MuSK(-)/AChR(+) patients (23%) (P=0.012). SFEMG was abnormal in all examined MuSK(+) patients. All 7 biopsied MuSK(+) and 32 MuSK(-) patients (89%) had cytochrome c oxidase (COX) negative fibers. Three of five MuSK(+) and 13 of 20 MuSK(-) patients analyzed had multiple mtDNA deletions but no POLG1 mutations. CONCLUSIONS Similar degree of SFEMG abnormalities was present in proximal muscles among MuSK(+) and AChR(+) patients. Proximal myopathy was over-represented in MuSK(+) patients; however, both MuSK(+) and MuSK(-) patients had mild myopathy with frequent mitochondrial abnormalities. SIGNIFICANCE The weakness in MuSK(+) patients is most likely due to disturbed neuromuscular transmission. The frequently encountered mitochondrial dysfunction in MG warrants further study.
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Affiliation(s)
- A Rostedt Punga
- Department of Clinical Neurophysiology, University Hospital, S-75185 Uppsala, Sweden.
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Jha S, Xu K, Maruta T, Oshima M, Mosier DR, Atassi MZ, Hoch W. Myasthenia gravis induced in mice by immunization with the recombinant extracellular domain of rat muscle-specific kinase (MuSK). J Neuroimmunol 2006; 175:107-17. [PMID: 16697051 DOI: 10.1016/j.jneuroim.2006.03.016] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2005] [Revised: 02/08/2006] [Accepted: 03/10/2006] [Indexed: 11/23/2022]
Abstract
UNLABELLED Myasthenia gravis (MG) is mostly caused by anti-acetylcholine receptor (AChR) auto-antibodies (Abs). Such Abs are undetectable in 10-15% of MG patients, but many have anti-muscle-specific kinase (MuSK) Abs. We injected recombinant rat-MuSK extracellular domain in H-2(a), H-2(b), H-2(bm12) and H-2(d) mice. Certain strains exhibited exercise-induced fatigue, tremors, weight loss, and some died after 2-3 injections. Compound muscle action potentials showed decrement with low-frequency repetitive nerve stimulation. Miniature endplate potentials decreased, suggesting lower numbers of endplates functional AChRs. Myasthenic sera inhibited agrin-induced AChR aggregation in C2C12 myotubes. CONCLUSION Anti-MuSK Abs induce MG, which might also result from blocking the agrin-signaling pathway.
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Affiliation(s)
- Smita Jha
- Department of Biology and Biochemistry, University of Houston, TX 77204, USA
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Abstract
The neuromuscular junction (NMJ) is a prototype synapse and myasthenia gravis is the prototypic antibody-mediated disorder. There are now three other disorders of neuromuscular transmission caused by antibodies to other essential components of the NMJ. Antibodies to the muscle-specific kinase, MuSK, are defining a new form of myasthenia that can be associated with muscle atrophy. Antibodies to voltage-gated calcium channels are responsible for muscle weakness and autonomic dysfunction in the Lambert Eaton myasthenic syndrome. Antibodies to voltage-gated potassium channels are found in patients with a range of disorders affecting the NMJ, the autonomic system or the central nervous system. The pathogenic mechanisms probably depend on the IgG subclass of the antibodies and are only partly shared between the diseases.
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Affiliation(s)
- A Vincent
- Neurosciences Group, Department of Clinical Neurology, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford, UK.
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Hain B, Jordan K, Deschauer M, Zierz S. Successful treatment of MuSK antibody-positive myasthenia gravis with rituximab. Muscle Nerve 2006; 33:575-80. [PMID: 16323216 DOI: 10.1002/mus.20479] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We report on a 56-year-old woman with muscle-specific receptor tyrosine kinase (MuSK) antibody-positive myasthenia with predominant bulbar symptoms and respiratory insufficiency. Conventional immunosuppression (prednisolone, azathioprine, mycophenolate mofetil) could not maintain the clinical improvement initially achieved by repeated plasma exchanges. Therefore, treatment with rituximab was initiated. After 2 months of rituximab treatment, remarkable clinical improvement correlating with a reduction of MuSK serum antibodies was seen. The patient continued to remain stable 12 months after initiation of therapy. This case report demonstrates that rituximab may be an effective and tolerable treatment in MuSK antibody-positive myasthenia gravis.
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Affiliation(s)
- Berit Hain
- Department of Neurology, Martin Luther University of Halle-Wittenberg, Ernst-Grube-Strasse 40, 06120 Halle/Saale, Germany.
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