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PubMed1996

Ocular myasthenia gravis.

Ocular myasthenia gravis may mimic any pupil-spared, painless, nonproptotic ophthalmoplegia with or without ptosis. This review references recent papers regarding clinical features, diagnostic techniques, and treatment for ocular myasthenia gravis.

Combined Modality Therapy↗
PubMedDate not supplied

[False negatives in the diagnosis of myasthenia gravis].

INTRODUCTION: Myasthenia gravis is an uncommon disorder with very variable clinical findings. This often leads to errors in diagnosis. OBJECTIVE: To study the main errors leading to false negatives in the diagnosis of myasthenia gravis. PATIENTS AND METHODS: We carried out a questionnaire to determine all the doctors and diagnoses made by them in relation to symptoms of myasthenia graves in 109 patients in whom this diagnosis was later confirmed when a specialist was consulted. RESULTS: Most of the patients went to a general practitioner first. During this initial consultation the disease was only diagnosed in 10 cases (9.2%) and neurosis was the most frequent diagnosis (27.5%). Although most patients had to see from two to four doctors before diagnosis was made, there was no major delay in this. In 84 of the 109 cases the diagnosis was established within the first six months, generally by a neurologist (86.2%) and less frequently by a general physician (11.0%). CONCLUSION: General practitioners, ophthalmologists, psychiatrists and otorhinolaryngologists are often involved in the evaluation of these cases although they made little contribution to the diagnosis.

Adult↗
PubMed1990

Vecuronium dose-response and maintenance requirements in patients with myasthenia gravis.

Eleven myasthenia gravis and seven control patients were studied during N2O/O2-fentanyl anesthesia to determine the ED50, ED95, and maintenance requirement of vecuronium using both mechanomyography and electromyography. The ED95 of vecuronium was 17 (range 8-34) micrograms/kg in patients with myasthenia gravis, and this was significantly related to patient's acetylcholine receptor antibody titer (r = -0.75, P less than 0.01). The average ED95 value was 250% greater in control than in myasthenic patients (P less than 0.01). The hourly requirement of vecuronium to maintain an 80-90% neuromuscular blockade was 38 +/- 10 micrograms/kg in myasthenic and 120 +/- 27 micrograms/kg in control patients (P less than 0.001). When these requirements were related to individual ED95 doses, they were comparable indicating similar time durations of effect of vecuronium following an equipotent dose in myasthenic and in control patients.

Adult↗
PubMed1992

T-cell epitopes on the human acetylcholine receptor alpha-subunit residues 10-84 in myasthenia gravis.

In myasthenia gravis the production of anti-acetylcholine receptor antibodies is modulated by acetylcholine receptor-specific T cells. Most B- and T-cell epitopes are located on the alpha-subunit of the receptor. In order to map the fine specificity of the antigen-specific T cells in myasthenia gravis, T-cell stimulation in response to 70 hexapeptides was studied in 24 patients and 24 healthy individuals. The hexapeptides overlapped with one amino acid and represented residues 10-84 of the NH2-terminal part of the alpha-subunit of the receptor. The IFN-gamma secretion from single T cells was used to detect T-cell stimulation. A significant difference in the T-cell response to several of the peptides was found between patients and healthy controls. The majority of the hexapeptides induced T-cell stimulation in at least one of the patients. Peptide-induced T-cell stimulation was evident in all but one of the patients. The results indicate that different epitopes and multiple T-cell clones are involved in the T-cell recognition of the acetylcholine receptor.

Adult↗
PubMed1997

Acetylcholine receptor expression in human extraocular muscles and their susceptibility to myasthenia gravis.

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.

Adolescent↗
PubMed2001

Thyroid gland tumour, pemphigus foliaceus and myasthenia gravis in the daughter of a woman with myasthenia gravis.

We describe a rare case of pemphigus foliaceus associated with familial myasthenia gravis (MG). A 35-year-old woman developed MG during oral corticosteroid treatment for pemphigus foliaceus. She had been operated on for a thyroid gland tumour that was confirmed histopathologically to be papillary carcinoma without metastasis. At the time of treatment, her mother had had MG for 30 years and undergone thymectomy 22 years ago. A specific ELISA technique showed that antidesmoglein 1 antibody was present in the daughter. There are many reports of multiple diseases such as pemphigus, thymoma, malignancy, and other autoimmune diseases associated with MG. However, familial MG following pemphigus foliaceus has not been reported previously.

Adult↗
PubMed1997

TCR V beta usage by acetylcholine receptor-specific CD4+ T cells in myasthenia gravis.

In myasthenia gravis the muscle acetylcholine receptor (AChR) is the target of an autoimmune response. AChR epitopes recognized by CD4+ T cells in myasthenic patients have been identified. AChR-specific CD4+ cell lines can be propagated by stimulation of blood lymphocytes with synthetic or biosynthetic AChR sequences. We analysed, using a semi-quantitative PCR assay, the T cell receptor (TCR) V beta usage of 16 anti-AChR polyclonal CD4+ T cell lines of known epitope specificity, propagated from myasthenic patients using pools of overlapping peptides corresponding to the sequence of an AChR subunit, or individual synthetic AChR sequences. Twelve lines had been propagated for less than 2 months, four lines for 3.5-5 months. Most lines had limited V beta usage, but in most cases different V beta regions were used for different epitopes in the same patient, and for the same epitope in different patients. In a few patients, the same V beta regions were used for recognition of different epitopes. The V beta 4 and V beta 6 regions were used most frequently. These findings suggest that the potentially autoimmune T cells that survive clonal deletion have a limited TCR repertoire. Although the present data do allow conclusions on the role of a superantigen in triggering the anti-AChR autoimmune response, the finding that different V beta regions were used in different patients does not support an important role of a superantigen in the maintenance of the CD4+ response in myasthenia gravis.

Amino Acid Sequence↗
PubMed1977

Myasthenia gravis: steroid-induced effects on lymphocyte subpopulations in myasthenia gravis.

Lymphocyte subpopulations from patients with myasthenia gravis were evaluated during chronic steroid therapy. A marked lymphocytopenia (10-70%) was initially (day 3-21) noticed as well as a preferential depletion of thymus-derived cells which paralleled the clinical deterioration. Thus there was a relative increase in B cells, although their absolute number remained rather constant. These changes were reverted within 2-4 weeks in spite of continuous treatment. These findings are compatible with a release of myasthenic factors (anti-acetylcholine receptor antibodies?) during the initial steroid-induced cell damage, the long-term beneficial effects being due to loss or suppression of autoreactive helper t cells.

Adolescent↗
PubMed1987

Increased binding of anti-acetylcholine receptor antibodies to thymic antigen in patients with myasthenia gravis and other autoimmune diseases, as compared to those with myasthenia gravis alone.

We compared the binding activity against acetylcholine receptors solubilized from human muscle (AChRM) and human thymus (AChRT), of sera from patients with myasthenia gravis (MG) alone, to those of sera from patients with myasthenia gravis and associated autoimmune diseases (MG AD). The sera of the MG AD group bound relatively better to thymic antigen (86% vs. 62%). This group was found to contain a higher proportion of women over 40 years of age (more than 50% of the group). The expression of a particular AChR antigen in normal human thymus may be one of the factors involved in the pathogenesis of MG, especially when this disease is associated with other autoimmune disorders.

Adolescent↗
PubMed2003

Development of generalized disease at 2 years in patients with ocular myasthenia gravis.

BACKGROUND: Generalized myasthenia gravis will develop in more than 50% of patients who present with ocular myasthenia gravis, typically within 2 years. The optimal treatment of ocular myasthenia gravis, including the use of corticosteroids, remains controversial. In addition, the prevalence of thymoma and the optimal performance of the edrophonium chloride test for ocular myasthenia remain unknown. OBJECTIVE: To assess the effect of oral corticosteroid therapy on the frequency of development of generalized myasthenia gravis within 2 years, the incidence of thymoma, and the amount of edrophonium needed for a positive test result in patients with ocular myasthenia gravis. METHODS: We reviewed an ocular myasthenia gravis database of 147 patients. Patients underwent measurement of acetylcholine receptor (AChR) antibody levels and chest computed tomography. Unless contraindicated, patients with diplopia were recommended for therapy with prednisone, up to 40 to 60 mg/d, with the dosage tapered for 5 to 6 weeks. Most continued to receive daily or alternate-day doses of 2.5 to 10 mg to prevent diplopia. Patients not given prednisone (untreated group) received pyridostigmine bromide or no medication. After the diagnosis, we documented the signs and symptoms of ocular and generalized myasthenia gravis and performed 2-year follow-up in 94 patients. RESULTS: The mean dose of edrophonium chloride to give a positive response was 3.3 mg (SD, 1.6 mg) for ptosis and 2.6 mg (SD, 1.1 mg) for ocular motor dysfunction. Thymoma occurred in 1 patient (0.7%). Generalized myasthenia gravis developed within 2 years in 4 of 58 treated and 13 of 36 untreated patients. The odds ratio (OR) for development of generalized disease in the treated group was 0.13 (95% confidence interval [CI], 0.04-0.45) compared with the untreated group. The AChR antibody level was not predictive of development of generalized myasthenia gravis at 2 years, but the risk was greater in patients with abnormal AChR antibody levels (OR, 6.33; 95% CI, 1.71-23.42). Logistic regression that included age, abnormal AChR antibody level, and prednisone therapy yielded significance only for abnormal AChR antibody level (OR, 7.03; 95% CI, 1.35-36.64) and treatment (OR, 0.06; 95% CI, 0.01-0.30). CONCLUSIONS: At 2 years, prednisone treatment appears to reduce the incidence of generalized myasthenia gravis to 7% in contrast to 36% of patients who did not receive prednisone. Thymoma, although uncommon, occurs in ocular myasthenia gravis. Only small amounts of edrophonium are needed to diagnose ocular myasthenia gravis.

Administration, Oral↗
PubMed1991

The thymus in myasthenia gravis. Changes typical for the human disease are absent in experimental autoimmune myasthenia gravis of the Lewis rat.

In human myasthenia gravis (MG) formation of autoantibodies against acetylcholine receptor (AChR) is commonly associated with thymic changes termed lymphofollicular hyperplasia (LFH). To learn whether the thymic lesions of human MG are primary changes in the autoimmune pathogenesis, or rather secondary events caused by peripheral autoimmunization, the authors compared the pathologic changes of MG thymuses with the thymuses of Lewis rats with experimental autoimmune myasthenia gravis (EAMG). EAMG was induced either actively by immunization with AChR, or transferred passively with monoclonal antibodies (mAb) binding to AChR. The clinical diagnosis of EAMG was confirmed by electromyography. Germinal centers, which are typical for human MG thymuses, were not detectable in the thymus of EAMG rats. Scattered B cells were seen as normal components of the thymic medulla. In EAMG their number was not augmented, nor were they accumulated focally. The perivascular spaces (PVS) were not distended and the amount of reticulin was not increased. Thymic myoid cells were identified in EAMG as well as in control thymuses; their cellular microenvironment was inconspicuous. Both in normal and in EAMG thymuses, a subpopulation of myoid cells expressed the main immunogenic region of the AChR. Heavily affected rats showed a severe cortical involution, but no specific changes of the medulla. The fact that none of the thymic lesions characteristic for human MG was found in EAMG is compatible with the concept that the thymic changes in MG are primary events in the autoimmune pathogenesis of this disease.

Animals↗
PubMed1978

The immunopathology of myasthenia gravis.

Experimental autoimmune myasthenia gravis, induced by immunization with solubilized acetylcholine receptors, has proven an excellent animal model for the study of myasthenia gravis. The role of the thymus in myasthenia gravis is not yet known. Its content of skeletal muscle elements and acetylcholine receptors and the presence of germinal centers in myasthenia gravis suggest that the thymus could be a site of autoimmunization. An effector role has not been demonstrated for T cells in the pathogenesis of experimental autoimmune or clinical myasthenia gravis, but helper T cells participate in the rat's autoantibody response to acetylcholine receptors. Antibodies and lymphocytes reactive with acetylcholine receptors are demonstrable in the peripheral blood of patients with myasthenia gravis and appear to be specific for this disease. Parallel studies of both experimental autoimmune and clinical myasthenia gravis have provided evidence for an autoimmune basis for the pathophysiology in myasthenia gravis. Antiacetylcholine receptor antibodies appear to play a central role in impairing neuromuscular transmission. Numerous antibody specificities have been described, but none seems to be directed at the acetylcholine binding site of the receptor. Addition of antiacetylcholine receptor antibodies to cultured muscle cells, in the absence of complement, causes redistribution of the receptors on the membranes of myotubes, accelerated receptor degradation, apparent impairment of ionophore function, and loss of sensitivity to acetylcholine. In vivo complement appears to be an important mediator of antiacetylcholine receptor antibody pathogenicity. Its presence is essential for the passive transfer of experimental autoimmune myasthenia gravis with antibodies. In muscle biopsy specimens from patients with myasthenia gravis, IgG and C3 have been demonstrated on the postsynaptic membrane and on degenerated fragments of membrane in the synaptic cleft. This suggests that complement activation in vivo is associated with focal lysis of the postsynaptic membrane. A causal relationship appears to exist between the binding of antibody to acetylcholine receptors, the reduction in muscle acetylcholine receptors, and impairment of neuromuscular transmission.

Animals↗