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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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PMID:Myasthenia gravis. 1798 28

Glycogen storage disease type Ib (GSD Ib, OMIM 232220) is an inborn disorder of glucose metabolism, caused by mutations in the G6PT gene, encoding a glucose 6-phosphate transporter (G6PT). GSD Ib is mainly associated with fasting hypoglycaemia and hepatomegaly. Most GSD Ib patients also show neutropenia and neutrophil dysfunction and therefore are at risk of developing severe infections and inflammatory bowel disease (IBD). An increased risk for autoimmune disorders, such as thyroid autoimmunity and Crohn-like disease, has also been demonstrated, but no systematic study on the prevalence of autoimmune disorders in GSD Ib patients has ever been performed. We describe a 25-year-old patient affected by GSD Ib who developed 'seronegative' myasthenia gravis (MG), presenting with bilateral eyelid ptosis, diplopia, dysarthria, severe dysphagia, dyspnoea and fatigue. The repetitive stimulation of peripheral nerves test showed signs of exhaustion of neuromuscular transmission, particularly evident in the cranial area. Even in the absence of identifiable anti-acetylcholine receptor antibodies, seronegative MG is considered an autoimmune disorder and may be related to the disturbed immune function observed in GSD Ib patients.
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PMID:Myasthenia gravis in a patient affected by glycogen storage disease type Ib: a further manifestation of an increased risk for autoimmune disorders? 1843 26

Myotonic dystrophy type 1 (DM1) is an autosomal-dominant multisystemic disorder that may rarely be associated with benign and malignant neoplasms. Cases of both thymoma and myasthenia gravis in association with DM1 are extremely rare. A literature review revealed only three prior reports. We present a 51-year-old man with a family history of DM1 and fluctuating diplopia and ptosis, who was found to have acetylcholine receptor-binding antibodies, thymoma, and a clinical presentation compatible with ocular myasthenia gravis as well as positive genetic testing for DM1. Needle electromyographic (EMG) study demonstrated diffuse runs of myotonic discharges in multiple muscles, consistent with the diagnosis of DM1. Single-fiber EMG showed both increased jitter and blocking. Due to somatic instability, which has been shown previously in DM1, the myotonin protein kinase (DMPK) gene appears to act as a tumor suppressor. Therefore, abnormal CTG repeat expansions in the gene could lead to the development of thymoma and myasthenia gravis.
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PMID:Myotonic dystrophy type 1 coexisting with myasthenia gravis and thymoma. 1856 24

We have defined myasthenia gravis (MG) in the elderly as onset after the age of 50 years. MG is diagnosed more often today than previously. The increase is mainly found in patients over the age of 50 years. Neurologists therefore see more old patients with MG now than before. Prevalence of the early-onset form of MG seems to be unchanged. Recent data indicate that MG may still be substantially underdiagnosed in very old people. Ptosis, diplopia, weakness of the facial muscles, and problems of articulation are important clinical signs in MG and are easier to detect in a youthful appearance. Since ageing causes a decrease in the total eyelid area with sagging of the lower eyelids, a ptosis may be more difficult to diagnose in the elderly. In addition, diplopia may not be detected because of reduced vision due to macular degeneration or cataract formation. Ocular symptoms of MG are therefore more easily missed in the elderly. Thymomatous MG is more common among older patients than it is in younger onset. The mean age at onset of MG for thymoma cases is 50-60 years. Approximately 10-15% of all MG patients have a thymoma, and around 40% of all thymoma cases are associated with MG. During normal aging, the thymus tissue becomes atrophic and replaced with fat. Recent data on MG thymus pathology suggest that lymphocyte accumulation indicating residual thymus may also be found in the elderly, and that there is little qualitative difference between the young and the old thymus from MG patients. The mean concentration of antibodies to acetylcholine receptor (AChR) is lower in MG in the elderly than in early-onset or thymoma-associated MG. Seronegative MG is less common among older patients. Approximately 30% of patients with late-onset, nonthymoma MG have antibodies to titin, while such antibodies are extremely scarce in early-onset MG. Titin antibodies in MG patients seem to be associated with a higher frequency of DR7 antigen and a decrease of DR3 antigen. The antibody response in MG may therefore be influenced by the genetic background.
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PMID:Myasthenia gravis in the elderly: Is it different? 1856 74

Myasthenia gravis (MG) is a chronic neuromuscular disease which leads to varying degrees of weakness in the skeletal muscles. Some of the symptoms of the disorder include weakness of the eye muscles, difficulty in swallowing and slurred speech. When only the muscles of the eyes are affected, the illness is termed ocular myasthenia, which is often characterized by abrupt onset of diplopia and ptosis of the eyelid. In most patients with ocular-onset MG, there is a progression to involvement of other muscle groups within the first two years (generalized myasthenia). In the case reported here, a 39-year-old male of Ecuadorian descent complained of difficulty seeing, double vision, dizziness, unsteady gait, difficulty maintaining balance and fatigue for the previous two days. Neurological examination was remarkable for total external ophthalmoplegia. There was no external bulbar muscle paralysis, motor weakness, muscle wasting, sensory deficits or sphincter dysfunction. His laboratory workup was significant for elevated acetylcholine receptor antibody. He was diagnosed with ocular MG after differential diagnoses were ruled out based on the onset and presentation of symptoms, the patient's age and a normal magnetic resonance imaging exam. No signs of generalized myasthenia were detected. His symptoms improved dramatically after treatment with Acetyl cholinesterase (AchE) inhibitors and steroids, regaining much of his ocular mobility and ability to walk without gait imbalance. At follow-up visits, the patient remained healthy with no evidence development of other myasthenic signs. This case is atypical since ocular MG does not normally occur in the absence of other myasthenic forms.
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PMID:An atypical course of myasthenia gravis. 1860 52

A-58-year old man presented with fluctuating ptosis and dysphagia. When he was 53 years old, he developed oral candidiasis and serum human immunodeficiency virus (HIV) RNA was detected. After starting highly active antiretroviral therapy, serum HIV RNA became undetectable. Neurological examination revealed ptosis and bulbar symptoms. Myasthenia gravis was comfirmed by a positive edrophonium test, showing 20% decrement of the compound muscle action potential on repetitive stimulation. Anti-acetylcholine receptor antibodies were negative and anti-muscle specific tyrosine kinase (MuSK) antibodies were positive. The chest CT scan was normal. He experienced transient clinical remission with pyridostigmine bromide and prednisolone. However relapse occurred after he returned to work. Persistent clinical remission was first observed after cyclosporin administration. There are eleven reports in which patients had concomitant myasthenia gravis and HIV infection. Most of those cases were benign in clinical course and required only anticholinesterase therapy. In our case, however, anti-MuSK antibodies were positive, and symptoms of myasthenia gravis remained despite prednisolone administration. Cyclosporin is directly active against HIV, and thus, cyclosporine therapy may be helpful in patients with concomitant myasthenia gravis and HIV infection.
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PMID:[Anti-MuSK antibody positive myasthenia gravis with HIV infection successfully treated with cyclosporin: a case report]. 1904 51

Congenital myasthenic syndromes (CMS) are rare heterogeneous disorders of neurotransmission caused by genetic defects of neuromuscular junction molecules. While CMS patients have been reported worldwide, in Japan there have been only a few descriptions of adult CMS patients with acetylcholinesterase (AChE) deficiency and slow channel syndrome. Herein, we report a Japanese CMS patient with acetylcholine receptor (AChR) deficiency, diagnosed during childhood, and our treatment approach to the patient. This 13-year-old Japanese boy had had severe myasthenic symptoms since infancy. Ptosis, his first symptom, appeared at 5 months and nasal voice was recognized at 2 years of age. AchR and anti-muscle-specific tyrosine kinase (Musk) antibody remained negative. A positive tensilon test and decremental response on electromyogram supported the diagnosis of sero-negative myasthenia gravis. Despite thymectomy and strong immunosuppressive therapy including steroid pulse and FK 506, he gradually deteriorated and became wheelchair bound. Genetic analyses for AchR, Rapsyn, Musk and AChE were negative. At age 11 years, a muscle biopsy was performed in the deltoid muscle for neuromuscular junction sampling. Electron microscopic and confocal microscopic analysis of endplates showed almost complete loss of AChR and the diagnosis of CMS with AChR deficiency was confirmed. All immunosuppressive therapies were discontinued. Instead, we started Ubretide and 3,4-diaminopyridine (DAP) after obtaining informed consent. Although not approved in Japan for this use, 3,4-DAP is reportedly effective in refractory cases of CMS. The patient experienced no side effects. Despite all of the objective data were improving, his subjective symptoms and ADL remained poor. There are still many challenges in the treatment of the patient.
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PMID:[Treatment approach to congenital myasthenic syndrome in a patient with acetylcholine receptor deficiency]. 1917 15

Congenital myasthenic syndromes are a clinically and genetically heterogeneous group of hereditary disorders affecting neuromuscular transmission. We have identified mutations within the acetylcholine receptor (AChR) epsilon-subunit gene underlying congenital myasthenic syndromes in nine patients (seven kinships) of Dutch origin. Previously reported mutations epsilon1369delG and epsilonR311Q were found to be common; epsilon1369delG was present on at least one allele in seven of the nine patients, and epsilonR311Q in six. Phenotypes ranged from relatively mild ptosis and external ophthalmoplegia to generalized myasthenia. The common occurrence of epsilonR311Q and epsilon1369delG suggests a possible founder for each of these mutations originating in North Western Europe, possibly in Holland. Knowledge of the ethnic or geographic origin within Europe of AChR deficiency patients can help in targeting genetic screening and it may be possible to provide a rapid genetic diagnosis for patients of Dutch origin by screening first for epsilonR311Q and epsilon1369delG.
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PMID:AChR deficiency due to epsilon-subunit mutations: two common mutations in the Netherlands. 1954 78

We report the case of a 17.5-year old girl with generalized myasthenia gravis (MG). When she was 13, she started to complain of episodic diplopia, ptosis and mild fatigability of upper and lower extremity muscles. She was diagnosed with MG 3 years later, after exacerbation of her limb muscle weakness. Acetylcholine receptor antibody was positive (2.56 nmol/l, n < 0.4 nmol/l), anti-MuSK antibodies were not tested at that time. She was treated with a thymectomy. After the operation a gradual worsening of her MG was seen; she reported pirydostygmine intolerance. On retesting, acetylcholine receptor antibodies were negative and she was positive for anti-MuSK antibodies. She received immunosuppressive treatment with prednisone and azathioprine with clinical improvement. She is the third reported patient diagnosed with acetylcholine receptor antibody-positive MG, who became MuSK-positive after thymectomy. Recognition of such clinical patterns may be important for decision making in myasthenia gravis patients.
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PMID:Juvenile seropositive myasthenia gravis with anti-MuSK antibody after thymectomy. 1954 60

A 63-year-old male experienced sudden diplopia after 9 weeks of administration of pegylated interferon (IFN) alpha-2b and ribavirin for chronic hepatitis C (CHC). Ophthalmologic examinations showed ptosis on the right upper lid and restricted right eye movement without any other neurological signs. A brain imaging study and repetitive nerve stimulation test indicated no abnormality. The acetylcholine receptor antibody titer and response to acetylcholinesterase inhibitors were negative, and the results of thyroid function tests were normal. The patient's ophthalmological symptoms improved rapidly 3 weeks after discontinuation of pegylated IFN alpha-2b and ribavirin. The ocular myasthenia associated with combination therapy of pegylated IFN alpha-2b and ribavirin for CHC is very rarely reported; therefore, we present this case with a review of the various eye complications of IFN therapy.
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PMID:Development of ocular myasthenia during pegylated interferon and ribavirin treatment for chronic hepatitis C. 1958 73


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