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This paper provides a thorough overview of the current advances in diagnosis and therapy of myasthenia gravis (MG). Nowadays the term 'myasthenia gravis' includes heterogeneous autoimmune diseases, with a postsynaptic defect of neuromuscular transmission as the common feature. Myasthenia gravis should be classified according to the antibody specificity [acetylcholine, muscle-specific receptor tyrosine kinase (MuSK), low-density lipoprotein receptor-related protein 4 (LRP4), seronegative], thymus histology (thymitis, thymoma, atrophy), age at onset (in children; aged less than or more than 50 years) and type of course (ocular or generalized). With optimal treatment, the prognosis is good in terms of daily functions, quality of life and survival. Symptomatic treatment with acetylcholine esterase inhibition is usually combined with immunosuppression. Azathioprine still remains the first choice for long-term immunosuppressive therapy. Alternative immunosuppressive options to azathioprine include cyclosporin, cyclophosphamide, methotrexate, mycophenolate mofetil and tacrolimus. Rituximab is a promising new drug for severe generalized MG. Emerging therapy options include belimumab, eculizumab and the granulocyte- macrophage colony-stimulating factor. One pilot study on etanercept has given disappointing results. For decades, thymectomy has been performed in younger adults to improve non-paraneoplastic MG. However, controlled prospective studies on the suspected benefit of this surgical procedure are still lacking. In acute exacerbations, including myasthenic crisis, intravenous immunoglobulin, plasmapheresis and immunoadsorption are similarly effective., (© 2013 British Society for Immunology.)

Introduction: For more than 50 years the acetylcholinesterase inhibitor pyridostigmine bromide has been the drug of choice in the symptomatic therapy for myasthenia gravis. The sustained-release dosage form of pyridostigmine (SR-Pyr) is only available in a limited number of countries (e.g. in the United States and Germany). Astonishingly, the therapeutic usefulness of SR-Pyr has not yet been evaluated., Methods: In this non-interventional prospective open-label trial, 72 patients with stable myasthenia gravis were switched from instant-release dosage forms of pyridostigmine bromide to SR-Pyr. The results from the 37 patients younger than 60 years were separately analyzed., Results: The initial daily dose of SR-Pyr was 288.1 ± 171.0mg. The drug switch was unproblematic in all patients. The number of daily doses was significantly reduced from 4.3 to 3.6 (p=0.011). The switch to SR-Pyr ameliorated the total quantified myasthenia gravis (QMG) score from 0.9 ± 0.5 to 0.6 ± 0.4 (p<0.001) in all patients and in the younger subgroup. This was accompanied by a significant improvement in the quality of life parameters. The health status valued by EuroQoL questionnaire improved from 0.626 ± 0.286 to 0.782 ± 0.186 (p<0.001). After switching to SR-Pyr, 28 adverse reactions disappeared and 24 adverse reactions occurred less frequent or weaker, however, 17 new adverse reactions were documented., Conclusions: Our results support the usefulness of SR-Pyr in an individualized therapeutic regimen to improve quality of life regardless of the patient's age in myasthenia gravis., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Neuromuscular transmission is compromised in a variety of disorders due to immunological, toxic or congenital mechanisms. Myasthenia gravis (MG) is the most frequent among these disorders. In about 15% of cases, MG is associated with a second autoimmune disorder mainly seen in rheumatologists. Some of the drugs used in rheumatology can exacerbate MG or even trigger immunologically the occurrence of MG. In most MG patients, antibodies to the acetylcholine receptor (AChR) are present, but around 10% have AChR antibodies that are only identified by novel methods, and up to 5% have muscle-specific kinase antibodies which define a different subgroup of myasthenia. Among those MG patients with anti-AChR antibodies, a number of clinical subtypes can be identified including early-onset MG (onset

Myasthenia gravis is probably the most thoroughly understood of all human autoimmune diseases. The basic mechanism of the disease is an antibody-mediated autoimmune attack that decreases the acetylcholine receptor density at the neuromuscular junction. Current therapies aim to restore the available acetylcholine receptors, deplete the autoantibodies or suppress the immune system. Prolonged drug treatment is required, but this carries a potential risk of severe adverse effects. Therefore, the ideal treatment for myasthenia would eliminate the abnormal autoimmune response without interfering with the immune system.

A 57-year-old woman suffered from generalized muscular weakness without diplopia or dysphagia for about 2 years. An abnormal decremental response on low frequency nerve stimulation and improvement upon administration of edrophonium chloride suggested a diagnosis of myasthenia gravis. However, this diagnosis remained uncertain, since repeated tests for antiacetylcholine receptor antibodies were negative. In addition, the patient reported that she was never able to keep up with peers in prolonged physical activities since childhood. For this reason, a congenital myasthenic syndrome was suspected and an intercostal muscle biopsy performed for special end-plate studies. Immunohistochemistry of the muscle biopsy revealed membrane attack complex deposits at the end-plates. This finding definitely confirmed the diagnosis of autoimmune myasthenia gravis. In conclusion, immunohistochemistry for complement deposits at the end-plates is a simple and reliable method of confirming the diagnosis of myasthenia gravis in uncertain cases.

We studied two families with five affected members suffering from ptosis and slowly progressive limb-girdle muscle weakness. All patients had abnormal decremental response on low-frequency nerve stimulation, but there were no repetitive responses to single stimuli. The patients improved on anti-acetylcholinesterase drugs. Intercostal muscle was obtained for special studies from one patient of each family. In vitro microelectrode studies were done in Patient 1. Miniature end-plate potentials were of low amplitude, and the quantal content of the evoked end-plate potentials was normal. Light microscopy revealed a marked type 1 fiber predominance. Acetylcholinesterase reactivity was dispersed over increased length of individual fibers in Patient 2. On morphometry of the end-plate ultrastructure, the number of secondary synaptic clefts per neuromuscular junction and the expansion of the postsynaptic area were markedly reduced. In Patient 1, but not in Patient 2, the envelopment of the nerve terminal by Schwann cell was increased. Acetylcholine-receptor (AChR) density was reduced as judged by the reduced immunoreactivity to antibodies against different receptor subunits. Immunohistochemical analysis of proteins known to be involved in orchestrating the end-plate structure showed deficiency of the AChR-associated protein utrophin. These patients appear to have a defect in the development or maintenance of the postsynaptic clefts; whether this defect results from or causes a reduced expression of utrophin or AChR is unclear.

Mutations in genes encoding the epsilon, delta, beta and alpha subunits of the end plate acetylcholine (ACh) receptor (AChR) are described and functionally characterized in three slow-channel congenital myasthenic syndrome patients. All three had prolonged end plate currents and AChR channel opening episodes and an end plate myopathy with loss of AChR from degenerating junctional folds. Genetic analysis revealed heterozygous mutations: epsilon L269F and delta Q267E in Patient 1, beta V266M in Patient 2, and alpha N217K in Patient 3 that were not detected in 100 normal controls. Patients 1 and 2 have no similarly affected relatives; in Patient 3, the mutation cosegregates with the disease in three generations. epsilon L269F, delta Q267E and beta V266M occur in the second and alpha N217K in the first transmembrane domain of AChR subunits; all have been postulated to contribute to the lining of the upper half of the channel lumen and all but delta Q267E are positioned toward the channel lumen, and introduce an enlarged side chain. Expression studies in HEK cells indicate that all of the mutations express normal amounts of AChR. epsilon L269F, beta V266M, and alpha N217K slow the rate of channel closure in the presence of ACh and increase apparent affinity for ACh; epsilon L269F and alpha N217K enhance desensitization, and epsilon L269F and beta V266M cause pathologic channel openings in the absence of ACh, rendering the channel leaky, delta Q267E has none of these effects and is therefore a rare polymorphism or a benign mutation. The end plate myopathy stems from cationic overloading of the postsynaptic region. The safety margin of neuromuscular transmission is compromised by AChR loss from the junctional folds and by a depolarization block owing to temporal summation of prolonged end plate potentials at physiologic rates of stimulation.

We studied a Libyan family in which five out of seven siblings have had slowly progressive limb-girdle weakness accentuated by exercise since childhood. Ptosis or ophthalmoplegia were not observed. Pronounced decremental electromyographic responses on 3 Hz stimulation indicated the presence of a defect of neuromuscular transmission. Repeated testing for acetylcholine receptor antibodies was negative. Muscle biopsy revealed tubular aggregates in 34% of the type 2 muscle fibers. Our observation illustrates the wide clinical spectrum of congenital myasthenic syndromes.

The congenital myasthenic syndrome constitute a group of genetic disorders affecting neuromuscular transmission. This group includes presynaptic as well as postsynaptic defects. In several congenital myasthenic syndromes, it was possible to characterize the underlying mechanism by applying modern in vitro electrophysiological methods, like single-channel recordings. These genetic disorders include defects of acetylcholine release, absence of the endplate-specific form of acetylcholinesterase, and kinetic abnormalities of the acetylcholine receptor. Recently several mutations of the acetylcholine receptor have been characterized. Clinical features of these syndromes, diagnostic work-up, and treatment are described in detail. These diseases present usually within the first 2 years of life, however, in some syndromes manifestation during adulthood is possible. The clinical spectrum ranges from mild muscle weakness to severe disability with lifethreatening episodes. Only some syndromes respond to acetylcholinesterase inhibitors. Further elucidation of these syndromes will not only lead to improved treatment, but should contribute to our understanding of synaptic transmission.