Treatment of myasthenia gravis based on its immunopathogenesis.
ABSTRACT The prognosis of myasthenia gravis (MG) has improved dramatically due to advances in critical-care medicine and symptomatic treatments. Its immunopathogenesis is fundamentally a T-cell-dependent autoimmune process resulting from loss of tolerance toward self-antigens in the thymus. Thymectomy is based on this immunological background. For MG patients who are inadequately controlled with sufficient symptomatic treatment or fail to achieve remission after thymectomy, remission is usually achieved through the addition of other immunotherapies. These immunotherapies can be classified into two groups: rapid induction and long-term maintenance. Rapid induction therapy includes intravenous immunoglobulin (IVIg) and plasma exchange (PE). These produce improvement within a few days after initiation, and so are useful for acute exacerbation including myasthenic crisis or in the perioperative period. High-dose prednisone has been more universally preferred for remission induction, but it acts more slowly than IVIg and PE, commonly only after a delay of several weeks. Slow tapering of steroids after a high-dose pulse offers a method of maintaining the state of remission. However, because of significant side effects, other immunosuppressants (ISs) are frequently added as "steroid-sparing agents". The currently available ISs exert their immunosuppressive effects by three mechanisms: 1) blocking the synthesis of DNA and RNA, 2) inhibiting T-cell activation and 3) depleting the B-cell population. In addition, newer drugs including antisense molecule, tumor necrosis factor alpha receptor blocker and complement inhibitors are currently under investigation to confirm their effectiveness. Until now, the treatment of MG has been based primarily on experience rather than gold-standard evidence from randomized controlled trials. It is hoped that well-organized studies and newer experimental trials will lead to improved treatments.
Acta veterinaria Scandinavica. Supplementum 02/1989; 86:68-75.
Article: Clinical trial of plasma exchange and high-dose intravenous immunoglobulin in myasthenia gravis. Myasthenia Gravis Clinical Study Group.[show abstract] [hide abstract]
ABSTRACT: We have conducted a trial to randomly assess the efficacy and tolerance of intravenous immunoglobulin (i.v.Ig) or plasma exchange (PE) in myasthenia gravis (MG) exacerbation and to compare two doses of i.v.Ig. Eighty-seven patients with MG exacerbation were randomized to receive either three PE (n = 41), or i.v.Ig (n = 46) 0.4 gm/kg daily further allocated to 3 (n = 23) or 5 days (n = 23). The main end point was the variation of a myasthenic muscular score (MSS) between randomization and day 15. The MSS variation was similar in both groups (median value, +18 in the PE group and +15.5 in the i.v.Ig group, p = 0.65). Similar efficacy, although slightly reduced in the 5-day group was observed with both i.v.Ig schedules. The tolerance of i.v.Ig was better than that of PE with a total of 14 side effects observed in 9 patients, 8 in the PE group and 1 in the i.v.Ig group (p = 0.01). Although our trial failed to show a pronounced difference in the efficacy of both treatments, it exhibited a very limited risk for i.v.Ig. i.v.Ig is an alternative for the treatment of myasthenic crisis. The small sample sizes in our trial, however, could explain why a difference in efficacy was not observed. Further studies are needed to compare PE with i.v.Ig and to determine the optimal dosage of i.v.Ig.Annals of Neurology 07/1997; 41(6):789-96. · 11.09 Impact Factor
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ABSTRACT: Although widely accepted as an appropriate immunosuppressive therapy, the efficacy of glucocorticosteroid treatment has only rarely been tested in controlled studies. To assess the efficacy of glucocorticosteroids or adrenocorticotrophic hormone (ACTH) medication in autoimmune myasthenia gravis. We searched the Cochrane Neuromuscular Disease Group Trials Register in July 2004, MEDLINE (from January 1966 to June 2004) and EMBASE (from January 1980 to June 2004). We also checked the bibliographies in reviews and the randomised trials and contacted their authors to identify additional published and unpublished data. From the articles identified we selected those open or controlled studies which allowed us to assess the outcome of treated and untreated patients at definite endpoints. Types of studies: quasi-randomised or randomised controlled trials. Types of participants: patients with myasthenia gravis of all ages and all degrees of severity. Types of interventions: any form of glucocorticosteroids or adrenocorticotrophic hormone treatment. Types of outcome measures:Primary outcome(1) improvement after at least three months in either the weakest muscles or all muscles. Secondary outcomes(1) proportion of patients improved after at least six months(2) proportion of patients in remission(3) number of episodes of worsening during the first six months(4) acetylcholine receptor antibody titres after at least three months of therapy. Three authors extracted the data from the selected articles and one other checked them. A trial of adrenocorticotrophic hormone (43 patients) did not show any advantage compared with placebo for the treatment of ocular myasthenia gravis. Two double-blind trials compared prednisone with placebo for generalised myasthenia gravis. In the first (13 patients), the improvement was slightly greater in the prednisone group at six months. In the second (20 patients) which was a short-term trial, the improvement was significantly greater at two weeks. Two trials compared glucocorticosteroids with azathioprine (41 and 10 patients respectively). In one of these the rate of treatment failure was greater in the prednisone group. In a trial of glucocorticosteroids versus intravenous immunoglobulin (33 patients) no differences in treatment responses were encountered during a treatment period of 14 days. An open trial (39 patients) evaluating different corticosteroid doses revealed a shorter time to improvement in the high-dose group. However only limited evidence can be drawn from the available randomised controlled trials due to numerous and important methodological flaws. Limited evidence from randomised controlled trials suggests that corticosteroid treatment offers significant short-term benefit in myasthenia gravis compared with placebo. This supports the conclusions of observational studies and expert opinion. Limited evidence from randomised controlled trials does not show any difference in efficacy between corticosteroids and either azathioprine or intravenous immunoglobulin.Cochrane database of systematic reviews (Online) 02/2005; · 5.72 Impact Factor