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Hayashi M. Pathophysiology of Childhood-Onset Myasthenia: Abnormalities of Neuromuscular Junction and Autoimmunity and Its Background. PATHOPHYSIOLOGY 2023; 30:599-617. [PMID: 38133144 PMCID: PMC10747330 DOI: 10.3390/pathophysiology30040043] [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: 10/28/2023] [Revised: 11/28/2023] [Accepted: 11/29/2023] [Indexed: 12/23/2023] Open
Abstract
The pathophysiology of myasthenia gravis (MG) has been largely elucidated over the past half century, and treatment methods have advanced. However, the number of cases of childhood-onset MG is smaller than that of adult MG, and the treatment of childhood-onset MG has continued to be based on research in the adult field. Research on pathophysiology and treatment methods that account for the unique growth and development of children is now desired. According to an epidemiological survey conducted by the Ministry of Health, Labour and Welfare of Japan, the number of patients with MG by age of onset in Japan is high in early childhood. In recent years, MG has been reported from many countries around the world, but the pattern of the number of patients by age of onset differs between East Asia and Western Europe, confirming that the Japanese pattern is common in East Asia. Furthermore, there are racial differences in autoimmune MG and congenital myasthenic syndromes according to immunogenetic background, and their pathophysiology and relationships are gradually becoming clear. In addition, treatment options are also recognized in different regions of the world. In this review article, I will present recent findings focusing on the differences in pathophysiology.
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Affiliation(s)
- Masatoshi Hayashi
- Department of Pediatrics, Uwajima City Hospital, Uwajima 798-8510, Japan
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2
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Sanadze AG, Sidnev DV, Tumurov DA, Afanasieva OI. [Ocular myasthenia gravis]. Zh Nevrol Psikhiatr Im S S Korsakova 2023; 123:116-120. [PMID: 37796078 DOI: 10.17116/jnevro2023123091116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/06/2023]
Abstract
The article describes an urgent medical and social problem - the diagnosis and treatment of the ocular myasthenia gravis. Despite recent advances in the study of synaptic pathology, the diagnosis of the ocular form of myasthenia gravis remains a challenging problem. This is due to the poor information content of laboratory and electromyographic methods in the diagnosis of ocular myasthenia gravis, and the generalized myasthenia gravis manifests in 90% of cases by external ophthalmoplegia and ptosis. The article highlights the features of the diagnosis and differential diagnosis of ocular myasthenia gravis. Data on the course and features of the clinical presentation of the disease are presented. The importance of analyzing anamnestic data and clinical manifestations of the disease is emphasized. The article discusses modern approaches to the treatment of the ocular myasthenia gravis. The authors present clinical observations of 2 patients with ocular myasthenia gravis.
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Affiliation(s)
- A G Sanadze
- Buyanov City Clinical Hospital, Moscow, Russia
- Scientific and Practical Psychoneurological Center, Moscow, Russia
- Pirogov Russian National Research Medical University, Moscow, Russia
| | - D V Sidnev
- Scientific and Practical Psychoneurological Center, Moscow, Russia
| | - D A Tumurov
- Buyanov City Clinical Hospital, Moscow, Russia
- Scientific and Practical Psychoneurological Center, Moscow, Russia
- Pirogov Russian National Research Medical University, Moscow, Russia
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3
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Abstract
Eye movements are indispensable for visual image stabilization during self-generated and passive head and body motion and for visual orientation. Eye muscles and neuronal control elements are evolutionarily conserved, with novel behavioral repertoires emerging during the evolution of frontal eyes and foveae. The precise execution of eye movements with different dynamics is ensured by morphologically diverse yet complementary sets of extraocular muscle fibers and associated motoneurons. Singly and multiply innervated muscle fibers are controlled by motoneuronal subpopulations with largely selective premotor inputs from task-specific ocular motor control centers. The morphological duality of the neuromuscular interface is matched by complementary biochemical and molecular features that collectively assign different physiological properties to the motor entities. In contrast, the functionality represents a continuum where most motor elements contribute to any type of eye movement, although within preferential dynamic ranges, suggesting that signal transmission and muscle contractions occur within bands of frequency-selective pathways.
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Affiliation(s)
- Anja K E Horn
- Institute of Anatomy and Cell Biology I, Ludwig-Maximilians-University Munich, 80336 Munich, Germany;
| | - Hans Straka
- Department Biology II, Ludwig-Maximilians-University Munich, 82152 Planegg, Germany
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4
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Cetin H, Beeson D, Vincent A, Webster R. The Structure, Function, and Physiology of the Fetal and Adult Acetylcholine Receptor in Muscle. Front Mol Neurosci 2020; 13:581097. [PMID: 33013323 PMCID: PMC7506097 DOI: 10.3389/fnmol.2020.581097] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 08/13/2020] [Indexed: 12/31/2022] Open
Abstract
The neuromuscular junction (NMJ) is a highly developed synapse linking motor neuron activity with muscle contraction. A complex of molecular cascades together with the specialized NMJ architecture ensures that each action potential arriving at the motor nerve terminal is translated into an action potential in the muscle fiber. The muscle-type nicotinic acetylcholine receptor (AChR) is a key molecular component located at the postsynaptic muscle membrane responsible for the generation of the endplate potential (EPP), which usually exceeds the threshold potential necessary to activate voltage-gated sodium channels and triggers a muscle action potential. Two AChR isoforms are found in mammalian muscle. The fetal isoform is present in prenatal stages and is involved in the development of the neuromuscular system whereas the adult isoform prevails thereafter, except after denervation when the fetal form is re-expressed throughout the muscle. This review will summarize the structural and functional differences between the two isoforms and outline congenital and autoimmune myasthenic syndromes that involve the isoform specific AChR subunits.
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Affiliation(s)
- Hakan Cetin
- Department of Neurology, Medical University of Vienna, Vienna, Austria.,Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Richard Webster
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
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5
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Myasthénies oculaires : diagnostic et traitement. Rev Neurol (Paris) 2010; 166:987-97. [DOI: 10.1016/j.neurol.2010.08.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2010] [Revised: 07/10/2010] [Accepted: 08/31/2010] [Indexed: 11/18/2022]
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6
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Gattenlöhner S, Jörißen H, Huhn M, Vincent A, Beeson D, Tzartos S, Mamalaki A, Etschmann B, Muller-Hermelink HK, Koscielniak E, Barth S, Marx A. A human recombinant autoantibody-based immunotoxin specific for the fetal acetylcholine receptor inhibits rhabdomyosarcoma growth in vitro and in a murine transplantation model. J Biomed Biotechnol 2010; 2010:187621. [PMID: 20204062 PMCID: PMC2829619 DOI: 10.1155/2010/187621] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Accepted: 11/18/2009] [Indexed: 11/28/2022] Open
Abstract
Rhabdomyosarcoma (RMS) is the most common malignant soft tissue tumor in children and is highly resistant to all forms of treatment currently available once metastasis or relapse has commenced. As it has recently been determined that the acetylcholine receptor (AChR) gamma-subunit, which defines the fetal AChR (fAChR) isoform, is almost exclusively expressed in RMS post partum, we recombinantly fused a single chain variable fragment (scFv) derived from a fully human anti-fAChR Fab-fragment to Pseudomonas exotoxin A to generate an anti-fAChR immunotoxin (scFv35-ETA). While scFv35-ETA had no damaging effect on fAChR-negative control cell lines, it killed human embryonic and alveolar RMS cell lines in vitro and delayed RMS development in a murine transplantation model. These results indicate that scFv35-ETA may be a valuable new therapeutic tool as well as a relevant step towards the development of a fully human immunotoxin directed against RMS. Moreover, as approximately 20% of metastatic malignant melanomas (MMs) display rhabdoid features including the expression of fAChR, the immunotoxin we developed may also prove to be of significant use in the treatment of these more common and most often fatal neoplasms.
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Affiliation(s)
- S. Gattenlöhner
- Institute of Pathology, University of Würzburg, 97080 Würzburg, Germany
| | - H. Jörißen
- Department of Pharmaceutical Product Development, Fraunhofer Institute for Molecular Biology and Applied Ecology, Forckenbeckstraße 6, 52074 Aachen, Germany
| | - M. Huhn
- Neurosciences Group, Department of Clinical Neurology, Weatherall Institute of Molecular Medicine, University of Oxford, OX3 9DU Oxford, UK
| | - A. Vincent
- Neurosciences Group, Department of Clinical Neurology, Weatherall Institute of Molecular Medicine, University of Oxford, OX3 9DU Oxford, UK
| | - D. Beeson
- Neurosciences Group, Department of Clinical Neurology, Weatherall Institute of Molecular Medicine, University of Oxford, OX3 9DU Oxford, UK
| | - S. Tzartos
- Hellenic Pasteur Institute, 127, Vas. Sofias Avenue 11521, Athens, Greece
| | - A. Mamalaki
- Hellenic Pasteur Institute, 127, Vas. Sofias Avenue 11521, Athens, Greece
| | - B. Etschmann
- Institute of Pathology, University of Würzburg, 97080 Würzburg, Germany
| | | | - E. Koscielniak
- Department of Pediatric Oncology, Olga Hospital, 70176 Stuttgart, Germany
| | - S. Barth
- Department of Pharmaceutical Product Development, Fraunhofer Institute for Molecular Biology and Applied Ecology, Forckenbeckstraße 6, 52074 Aachen, Germany
- Department of Experimental Medicine and Immunotherapy, Helmholtz-Institute for Biomedical Engineering, University Hospital RWTH Aachen, Pauwelsstraße 20, 52074 Aachen, Germany
| | - A. Marx
- Institute of Pathology, University of Würzburg, 97080 Würzburg, Germany
- Institute of Pathology, University Medical Center Mannheim, University of Heidelberg, Theodor-Kutzer Ufer 1-3, 68135 Mannheim, Greece
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7
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Eymard B. Anticorps dans la myasthénie. Rev Neurol (Paris) 2009; 165:137-43. [DOI: 10.1016/j.neurol.2008.11.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2008] [Revised: 11/14/2008] [Accepted: 11/24/2008] [Indexed: 11/28/2022]
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8
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Abstract
Craniofacial skeletal muscles (CskM), including the masticatory (MM), extraocular (EOM) and laryngeal muscles (LM), have a number of properties that set them apart from the majority of skeletal muscles (SkM). They have embryological origins that are distinct from musculature elsewhere in the body, they express a number of immature myosin heavy chain isoforms and maintain increased and distinct expression of a number of myogenic growth factors and their receptors from other adult SkMs. Furthermore, it has recently been demonstrated that unlike limb SkM, normal adult EOM and LM retain a population of activated satellite cells, the regenerative cell in adult SkM. In order to maintain this proliferative pool throughout life, CSkM may contain more satellite cells and/or more multipotent precursor cells that may be more resistant to apoptosis than those found in limb muscle. A further exciting question is whether this potentially more active muscle precursor cell population could be utilized not only for SkM repair, but be harnessed for repair or reconstruction of other tissues, such as nervous tissue or bone. This is a highly attractive speculation as the innate regenerative capacity of craniofacial muscles would ensure the donor tissue would not have compromised future function.
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Affiliation(s)
- L K McLoon
- Department of Ophthalmology, University of Minnesota, Minneapolis, MN, USA
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9
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Lantsova VB, Sepp EK. Differential diagnosis of various forms of myasthenia and endocrine ophthalmopathy by immunoblotting. Bull Exp Biol Med 2006; 140:473-5. [PMID: 16671584 DOI: 10.1007/s10517-005-0522-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Immunoblotting can be used for screening a population of antibodies to acetylcholine receptor subunits circulating in the blot of patients with myasthenia. Torpedo Californica acetylcholine receptor served as the antigen. We found that in generalized myasthenia autoantibodies bind to alpha1- or alpha1- and gamma-subunits, while in ophthalmic form they bind only gamma-subunit of acetylcholine receptor. No antibodies to any of the acetylcholine receptor subunits were detected in patients with endocrine ophthalmopathy and in healthy volunteers. This method can be used for differential diagnosis of ophthalmic myasthenia and endocrine ophthalmopathy and for predicting generalization of the pathological process in patients with myasthenia.
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Affiliation(s)
- V B Lantsova
- Department of Human Neuromuscular Diseases, Institute of Pathology and Pathophysiology, Russian Academy of Medical Sciences, Moscow.
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10
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Wakata N, Iguchi H, Sugimoto H, Nomoto N, Kurihara T. Relapse of ocular symptoms after remission of myasthenia gravis--a comparison of relapsed and complete remission cases. Clin Neurol Neurosurg 2003; 105:75-7. [PMID: 12691794 DOI: 10.1016/s0303-8467(02)00104-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Extended thymectomy and high-dose alternate-day prednisolone administration may increase the chance of remission in myasthenia gravis (MG) patients. In cases of remission, ocular symptoms sometimes reappear after a gradual decrease or discontinuation of prednisolone administration. We compared relapsed patients with those who experienced complete remission. We found that the period from onset of MG to thymectomy and initiation of prednisolone administration was longer in the relapsed cases, which suggests that early thymectomy and administration of prednisolone can lead to a superior outcome in MG patients.
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Affiliation(s)
- Nobuo Wakata
- The Fourth Department of Internal Medicine, Toho University School of Medicine, 2-17-6 Oohashi, Meguro-ku, Tokyo 153-8515, Japan.
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11
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Weizer JS, Lee AG, Coats DK. Myasthenia gravis with ocular involvement in older patients. CANADIAN JOURNAL OF OPHTHALMOLOGY 2001; 36:26-33. [PMID: 11227387 DOI: 10.1016/s0008-4182(01)80063-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
BACKGROUND There has been little previous study reporting the eye findings and presentation of elderly patients with myasthenia gravis. The purpose of this study was to review the findings and course of myasthenia gravis after the sixth decade of life. METHODS Retrospective observational case series. The authors reviewed the clinical records of 27 patients with onset of myasthenia gravis at age 60 years or more who were seen at a tertiary care academic ophthalmology centre in Houston between January 1992 and March 1999. The diagnosis of myasthenia gravis was based on conventional clinical and laboratory criteria. RESULTS Twenty patients (74%) were men. Of the 16 patients who underwent testing for anti-acetylcholine receptor antibodies, 11 (69%) were seropositive. Concurrent thyroid disease was found in seven patients (26%), including five (71%) of the seven women. No patient had thymoma. Sixteen patients (59%) manifested generalized symptoms during follow-up; 12 did so within 1 year of disease onset. Patients responded well to both anticholinesterase and corticosteroid therapy. At the most recent follow-up visit 18 patients (67%) were clinically improved, and no patient was clinically worse. INTERPRETATION Myasthenia gravis in this study was characterized by a male predominance, high rate of concurrent thyroid disease, high rate of progression to mild generalized symptoms, absence of thymoma, good response to medical therapy and minimal life-threatening complications. Clinicians should consider the diagnosis of myasthenia gravis in an older patient presenting with diplopia or ptosis.
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Affiliation(s)
- J S Weizer
- Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Texas Children's Hospital, Houston, Tex., USA
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12
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Abstract
Extraocular muscle weakness is the most common presenting sign of myasthenia gravis (MG). More than half of patients presenting with symptoms isolated to these muscles (OMG) develop generalized myasthenia gravis (GMG) over the course of their illness. No clinical, laboratory, or electrophysiological features are recognized that identify these high-risk patients. We have therefore assessed the ability of single-fiber electromyography (SFEMG) to predict the development of GMG in patients presenting with OMG. Thirty-nine consecutive patients presenting with OMG underwent SFEMG of the extensor digitorum communis muscle as well as a battery of other laboratory and imaging studies at the time of diagnosis. All patients were followed prospectively for a minimum of 24 months or until they developed GMG. Two patients were excluded, leaving 37 for assessment. Twenty remained with pure OMG for the entire follow-up period (mean, 55 months). Twenty-six of the 37 had abnormal SFEMG studies at presentation. Eleven of these remained with OMG and 15 developed GMG. Fifty-eight percent of patients with an abnormal SFEMG developed GMG, whereas 82% of those with a normal study remained with OMG. Thus, a normal SFEMG was associated with MG remaining restricted to the extraocular muscles. (P = 0.036, Fisher's exact test), but an abnormal SFEMG was not predictive of subsequent development of GMG.
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Affiliation(s)
- D H Weinberg
- Department of Neurology, St. Elizabeth's Medical Center and Tufts University School of Medicine, Boston, Massachusetts 02135, USA
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13
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Affiliation(s)
- H J Kaminski
- Department of Neurology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
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14
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Buchwald B, Weishaupt A, Toyka KV, Dudel J. Pre- and postsynaptic blockade of neuromuscular transmission by Miller-Fisher syndrome IgG at mouse motor nerve terminals. Eur J Neurosci 1998; 10:281-90. [PMID: 9753137 DOI: 10.1046/j.1460-9568.1998.00053.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Miller-Fisher syndrome, a variant of an acute inflammatory neuropathy is often associated with serum antibodies to the ganglioside GQ1b, but the pathogenic role of these antibodies and other serum factors is unclear. We here investigated the effect of highly purified immunoglobulin G (IgG) from patients with typical Miller-Fisher syndrome, recording quantal endplate currents by means of a perfused macro-patch-clamp electrode on hemidiaphragms of adult mice. The GQ1b-positive and the GQ1b-negative Miller-Fisher IgG as well as its monovalent Fab-fragments depressed evoked quantal release in a fast and fully reversible, concentration and voltage dependent manner. The time-course of quantal release was changed with the late releases becoming more frequent. The extent of depression of release followed a Michaelis-Menten kinetic and depended on the extracellular calcium concentration. In addition the amplitude of quanta was reduced postsynaptically. IgG and sera from healthy subjects had no effect. Our results indicate that in Miller-Fisher syndrome, IgG antibodies to an undetermined antigen depress the release process, most likely by interfering with the presynaptic Ca2+ inflow or by interacting with proteins of the exocytotic apparatus, and prevent the activation of postsynaptic channels. Antibodies thus seem to be one pathogenic factor for muscle weakness in Miller-Fisher syndrome and our findings may explain why muscle strength recovers rapidly after therapeutical plasmapheresis.
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Affiliation(s)
- B Buchwald
- Physiologisches Institut der Technischen Universität München, Germany
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15
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Ferrero B, Aimo G, Pagni R, Bergamasco B, Bongioanni MR, Bergamini L, Durelli L. Modified and improved anti-acetylcholine receptor (AChR) antibody assay: comparison of analytical and clinical performance with conventional anti-AChR antibody assay. Clin Chem 1997. [DOI: 10.1093/clinchem/43.5.824] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
We developed a modified anti-acetylcholine receptor (AChR) antibody (Ab) assay based on a radioreceptor assay and a calibration curve. We compared the analytical and clinical performances of this modified assay with those of the conventional anti-AChR Ab radioreceptor assay. Serum specimens were from patients with myasthenia gravis (MG) (n = 156) and from control subjects (n = 106). The modified assay demonstrated lower within-assay (4.0–6.6%) and between-assay (5.3–7.8%) CVs, greater linearity, lower cost, and shorter assay time than the conventional method. ROC curve analysis indicated almost identical specificity and sensitivity (>0.92) for these two anti-AChR Ab assays. The modified and conventional assays were also equivalent for blocking anti-AChR Ab assay. Moreover, the modified anti-AChR Ab assay, differently from the conventional assay, allowed us to reveal anti-AChR Ab concentration differences among different clinical grades of MG.
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Affiliation(s)
- Bruno Ferrero
- Department of Neurosciences, University Hospital “Molinette”, Via Cherasco 15, I-10126, Turin, Italy
| | - Giuseppe Aimo
- Department of Laboratory “Baldi e Riberi”, University Hospital “Molinette”, Via Cherasco 15, I-10126, Turin, Italy
| | - Roberto Pagni
- Department of Laboratory “Baldi e Riberi”, University Hospital “Molinette”, Via Cherasco 15, I-10126, Turin, Italy
| | - Bruno Bergamasco
- Department of Neurosciences, University Hospital “Molinette”, Via Cherasco 15, I-10126, Turin, Italy
| | - Maria R Bongioanni
- Department of Neurosciences, University Hospital “Molinette”, Via Cherasco 15, I-10126, Turin, Italy
| | - Lodovico Bergamini
- Department of Neurosciences, University Hospital “Molinette”, Via Cherasco 15, I-10126, Turin, Italy
| | - Luca Durelli
- Department of Neurosciences, University Hospital “Molinette”, Via Cherasco 15, I-10126, Turin, Italy
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16
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MacLennan C, Beeson D, Buijs AM, Vincent A, Newsom-Davis J. Acetylcholine receptor expression in human extraocular muscles and their susceptibility to myasthenia gravis. Ann Neurol 1997; 41:423-31. [PMID: 9124798 DOI: 10.1002/ana.410410404] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In myasthenia gravis (MG), extraocular muscle (EOM) weakness is often an initial and persisting symptom. It has been proposed that acetylcholine receptor (AChR) from EOM is antigenically different from AChR of other innervated muscles and that the presence of antibodies to fetal AChR expressed in EOM causes their weakness. We have (1) studied mRNA expression for each of the AChR subunits (alpha, beta, gamma, delta, and epsilon) in human muscle, including EOM, and (2) compared the binding of sera from ocular myasthenia gravis (OMG) patients with fetal (alpha2 beta gamma delta) and adult (alpha2 beta epsilon delta) human AChRs. RNase protection assays showed that expression of the AChR gamma-subunit (fetal-type) mRNA in EOM was comparable with that in other innervated muscle types. By contrast, epsilon-subunit (adult-type) mRNA was expressed at much higher levels in EOM than in other muscles studied. Moreover, some OMG sera bound specifically to adult AChR. These results do not support the contention that susceptibility of EOM in MG results from expression of fetal AChR and indicate that the inclusion of antigen from a source rich in adult AChR in the MG diagnostic assay will increase the yield of positive results in OMG patients.
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MESH Headings
- Adolescent
- Adult
- Aged
- Base Sequence
- Cells, Cultured
- Child
- Child, Preschool
- DNA, Complementary/analysis
- Gene Amplification
- Humans
- Infant
- Middle Aged
- Muscle, Skeletal/chemistry
- Muscle, Skeletal/embryology
- Myasthenia Gravis/complications
- Ocular Motility Disorders/diagnosis
- Ocular Motility Disorders/immunology
- Oculomotor Muscles/chemistry
- RNA, Messenger/analysis
- Receptors, Cholinergic/analysis
- Receptors, Cholinergic/genetics
- Receptors, Cholinergic/immunology
- Transcription, Genetic
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Affiliation(s)
- C MacLennan
- Neurosciences Group, Institute of Molecular Medicine, John Radcliffe Hospital, Oxford, UK
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17
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Porter JD, Baker RS. Muscles of a different 'color': the unusual properties of the extraocular muscles may predispose or protect them in neurogenic and myogenic disease. Neurology 1996; 46:30-7. [PMID: 8559415 DOI: 10.1212/wnl.46.1.30] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The rules that govern many aspects of skeletal muscle structure and function are very different for the extraocular muscle allotype. The myoblast lineages present in the extraocular muscle primordia are permissive for generation of an unusually wide range of fiber types. The balance that is struck between genetic specification and activity dependent factors in shaping fiber phenotype to suit the demands of complex visuomotor systems is not yet well defined. Because skeletal muscle has high energy demands, diversity in fiber types is needed to maximize efficiency; greater diversity in fiber composition then indicates a more diverse functional repertoire. Together, the characteristics of small motor unit size, precise dependence of muscle force upon motor neuron discharge rate, high contractile speed but low tension development, and contractile protein heterogeneity contribute toward the high precision and diversity that is required for eye movements. Finally, the structural and functional characteristics and plasticity of the individual extraocular muscle fiber types play an important role in determining their response to disease or manipulation. The lack of uniform responses across the muscle allotypes in disease, or in response to pharmaceutical or surgical interventions, requires that we obtain a better understanding of the fundamental differences that exist between muscle groups.
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Affiliation(s)
- J D Porter
- Department of Anatomy and Neurobiology, University of Kentucky Medical Center, Lexington 40536-0084, USA
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18
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Abstract
Ocular myasthenia is a localized form of myasthenia clinically involving only the extraocular, levator palpebrae superioris, and/or orbicularis oculi muscles. Ocular manifestations can masquerade as a variety of ocular motility disorders, including cranial nerve and gaze palsies. A history of variable and fatiguable muscle weakness suggests this diagnosis, which may be confirmed by the edrophonium (Tensilon) test and acetylcholine receptor antibody titer. Anticholinesterases, corticosteroids and other immunosuppressive agents, and other therapeutic modalities, including thymectomy and plasmapheresis, are used in treatment. As the pathophysiology of myasthenia has been elucidated in recent years, newer treatment strategies have evolved, resulting in a much more favorable prognosis than several decades ago. This review provides historical background, pathophysiology, immuno-genetics, diagnostic testing, and treatment options for ocular myasthenia, as well as a discussion of drug-induced myasthenic syndromes.
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Affiliation(s)
- D A Weinberg
- Neuro-Ophthalmology Service, Wills Eye Hospital, Philadelphia, Pennsylvania
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19
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Vincent A. Aetiological factors in development of myasthenia gravis. ADVANCES IN NEUROIMMUNOLOGY 1994; 4:355-71. [PMID: 7719616 DOI: 10.1016/0960-5428(94)00041-l] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- A Vincent
- Department of Clinical Neurology, University of Oxford, UK
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20
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Conti-Tronconi BM, McLane KE, Raftery MA, Grando SA, Protti MP. The nicotinic acetylcholine receptor: structure and autoimmune pathology. Crit Rev Biochem Mol Biol 1994; 29:69-123. [PMID: 8026215 DOI: 10.3109/10409239409086798] [Citation(s) in RCA: 110] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The nicotinic acetylcholine receptors (AChR) are presently the best-characterized neurotransmitter receptors. They are pentamers of homologous or identical subunits, symmetrically arranged to form a transmembrane cation channel. The AChR subunits form a family of homologous proteins, derived from a common ancestor. An autoimmune response to muscle AChR causes the disease myasthenia gravis. This review summarizes recent developments in the understanding of the AChR structure and its molecular recognition by the immune system in myasthenia.
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Affiliation(s)
- B M Conti-Tronconi
- Department of Biochemistry, College of Biological Sciences, University of Minnesota, St. Paul 55108
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