Plasma exchange alone as therapy for myasthenia gravis

Clinical trials for myasthenia gravis: a historical perspective

Symposia dedicated to myasthenia gravis and related disorders date back to 1947 and serve as markers of the progress for the field. We provide a brief historical review of therapy development through the lens of the publications that arose from the close to quinquennial meetings that have been supported nearly since their inception by the Myasthenia Gravis Foundation of America and the New York Academy of Sciences. One can appreciate great advances, false starts, and dead ends that are found in all fields of medicine. We tally up the score card for MG and find points scored, but the win is not yet close.

Mycophenolate Mofetil Treatment of Myasthenia Gravis

Objective:

To review published literature evaluating the effectiveness of mycophenolate mofetil for the treatment of myasthenia gravis (MG).

Data Sources:

Searches of MEDLINE (1966–August 2005) and Cochrane Database (1993–August 2005) were conducted. Studies conducted in humans and published in English were retrieved. Additional data were identified through subsequent bibliographic reviews.

Data Synthesis:

Interruption of T- and B-lymphocyte proliferation in various autoimmune diseases has been investigated. Mycophenolate is known to inhibit lymphocyte proliferation and has shown improved clinical responses in several autoimmune diseases including lupus erythematosus, rheumatoid arthritis, and systemic vasculitis. Data suggesting similar benefits in MG treatment have been reported in case reports, retrospective analyses, an open-label trial, and a randomized, double-blind trial.

Conclusions:

Limited evidence from retrospective analyses and clinical trials suggests that mycophenolate is a possible treatment option for patients with MG. Improvement in clinical symptoms and a steroid-sparing effect have been reported when mycophenolate is used in this patient population. Larger, randomized, controlled, and comparative trials are needed to establish optimal dose, time to effect, specific therapeutic role, and long-term safety for mycophenolate when used for treating MG.

Treatment of Acquired Autoimmune Myasthenia Gravis: a Topic Review

We propose a new approach to staging the disease based on clinical and immunological response to treatment. We oppose clinical remission to immunological remission and define total clinical remission as the goal of therapy. We describe the use, side effects and indications of established therapies. Acetycholine esterase inhibitors are only a symptomatic treatment as is plasma exchange. Usefulness and limits of thymectomy, corticosteroids and immunosuppressants are described here. Their goal is to reduce the auto-immune process. Long-term hazards from these medications are described and methods to reduce their potential risks are suggested. We suggest the number of patients having life threatening complications while undergoing aggressive immunosuppression can be reduced by a systematic approach to follow-up. In the second part of this review article, adapting management to specific situations is emphasized in refractory disease, respiratory failure, neonatal and juvenile forms of the disease. The special situation of seronegative myasthenia is discussed.

Acute lower motor neuron tetraparesis

Flaccid nonambulatory tetraparesis or tetraplegia is an infrequent neurologic presentation; it is characteristic of neuromuscular disease (lower motor neuron [LMN] disease) rather than spinal cord disease. Paresis beginning in the pelvic limbs and progressing to the thoracic limbs resulting in flaccid tetraparesis or tetraplegia within 24 to 72 hours is a common presentation of peripheral nerve or neuromuscular junction disease. Complete body flaccidity develops with severe decrease or complete loss of spinal reflexes in pelvic and thoracic limbs. Animals with acute generalized LMN tetraparesis commonly show severe motor dysfunction in all limbs and severe generalized weakness in all muscles.

Clinical evaluation and management of myasthenia gravis

Myasthenia gravis (MG) is a syndrome of fluctuating skeletal muscle weakness that worsens with use and improves with rest. Eye, facial, oropharyngeal, axial, and limb muscles may be involved in varying combinations and degrees of severity. Its etiology is heterogeneous, divided initially between those rare congenital myasthenic syndromes, which are genetic, and the bulk of MG, which is acquired and autoimmune. The autoimmune conditions are divided in turn between those that possess measurable serum acetylcholine receptor (AChR) antibodies and a smaller group that does not. The latter group includes those MG patients who have serum antibodies to muscle-specific tyrosine kinase (MuSK). Therapeutic considerations differ for early-onset MG, late-onset MG, and MG associated with the presence of a thymoma. Most MG patients can be treated effectively, but there is still a need for more specific immunological approaches.

Treatment of refractory myasthenia: "rebooting" with high-dose cyclophosphamide

Patients with myasthenia gravis (MG) who do not respond to conventional immunotherapeutic agents, or cannot tolerate their side effects, are considered "refractory." Ablation of the immune system followed by bone marrow transplant has been shown to cure experimental MG in rats. It is now known that immunoablative treatment with high-dose cyclophosphamide does not damage hematopoietic "stem cells," permitting repopulation of the immune system without bone marrow transplant. Recent evidence indicates that this treatment can induce durable remissions in autoimmune diseases. We treated three myasthenic patients, for whom treatment with thymectomy, plasmapheresis, and conventional immunotherapeutic agents failed, by using high-dose cyclophosphamide (50mg/kg/day intravenously for 4 days) followed by granulocyte colony stimulating factor. All three patients tolerated the treatment well and have had marked improvement in myasthenic weakness, permitting reduction of immunosuppressive medication to minimal levels. Acetylcholine receptor (AChR) antibody levels decreased in two AChR antibody-positive patients, and anti-MuSK antibody levels decreased in one "AChR antibody-negative" patient. The patients have been followed for up to 3.5 years, with no recurrence of symptoms. High-dose cyclophosphamide treatment appears to be an effective and safe treatment for selected patients with refractory MG. Further follow-up of these and additional patients will be needed to determine whether the benefit is durable.

Plasma exchange for treatment of myasthenia gravis: pathophysiologic basis and clinical experience

Myasthenia gravis is an autoimmune disease characterized by production of antibodies to acetylcholine receptors located at the motor end plate in skeletal muscles. The antibodies bind and subsequently induce degeneration of these receptors. Loss of acetylcholine receptors results in inadequate contraction of muscle fibers in response to acetylcholine released from nerve terminals and clinically apparent muscle weakness. Plasma exchange removes the circulating antibodies in myasthenic patients with short-term clinical improvement. Plasma exchange may be indicated in patients with acute exacerbation of neuromuscular weakness with bulbar or respiratory compromise, preoperative optimization prior to thymectomy, and postoperative deterioration following thymectomy or other surgical procedures. Long-term, intermittent plasma exchange for patients who do not adequately respond to standard treatment is another evolving indication.

Predictable recovery from myasthenia gravis crisis with plasma exchange: thirty-six cases and review of current management

Adult, acquired, idiopathic, autoimmune myasthenia gravis has a well-characterized IgG anti-acetylcholine striated-muscle receptor antibody. Removal by plasma exchange is effective, established therapy to augment anti-cholinesterase and immunosuppressive therapy and is the treatment of choice for myasthenia gravis crisis. We report 36 consecutive patients referred and accepted for plasma exchange, 32 of whom were in or entering myasthenia crisis, over a 10 year period. An average of 7.8 (range 1 to 16) plasma exchange procedures were done, with uniform, significant improvement, including extubation of 13 in myasthenic crisis and discharge from hospital in all. We conclude that this is the best treatment for myasthenia gravis crisis in hospital. From recent cases, most, if not all, crises can be prevented by IVIgG or plasma exchange as out-patients with use of corticosteroid and or azathioprine.

Immunoglobulin treatment in refractory Myasthenia gravis

Failure to induce and maintain remission in severe exacerbations of myasthenia gravis (MG), despite optimal care, is a common problem. We evaluated the efficacy and safety of high-dose intravenous immunoglobulin (IVIg) therapy in an open-label study of 10 patients with severe generalized myasthenia and an acute deterioration unresponsive to conventional therapy including high-dose corticosteroids, cyclosporine, and azathioprine. Intravenous Ig at a loading dose of 400 mg/kg was administered daily for 5 consecutive days, with maintenance IVIg treatment at a dose of 400 mg/kg, once every 6 weeks. Significant improvement occurred in all patients, beginning at 6 +/- 2 days of treatment as measured by the Osserman scale, fatigue variables, muscle strength, and respiratory function tests. No side effects were observed during induction of remission. Further IVIg treatments were highly efficacious in maintaining the remission. The severity of the disease decreased by 2.5 +/- 0.8 grades of the Osserman scale over a period of 1 year (P <0.001), in parallel with reduction of immunosuppressive therapy as well as a decrease in acetylcholine receptor antibody titers (P < 0.01). Intravenous Ig therapy seems to be highly potent for inducing rapid improvement in refractory myasthenia during acute deterioration as well as for maintaining remission.

Plasmapheresis in myasthenia gravis. A survey

Plasmapheresis plays an important role in the acute management of patients with severe myasthenia gravis. Although plasmapheresis is now in use for more than 20 years, some controversies remain about the indication and the place in the therapy. It is generally found that the effect starts one week after the start of PP and lasts about 2-4 weeks after the last exchange; because of this temporary effect use of concomitant immunosuppressive medication is recommended. Compilation of data from 13 large series shows that about 75% of the patients react favourably. The relation between fluctuations of antibodies and the effect of PP is poor; even seronegative patients may improve as well.

Plasmapheresis in severe forms of myasthenia gravis

In this study we introduce a new combination treatment of plasma exchange (PE) and high daily doses of prednisone for severe forms of myasthenia gravis (MG). The clinical efficacy of the combined therapy has been tested in 18 patients suffering from severe forms of MG. The protocol included 5 sessions of PE, performed in a range of 15 days, 1 session every 3 days, with concurrent administration of oral prednisone (1 mg/kg of body weight), starting at the first session of PE and given daily for at least 3 months. At the end of the entire cycle of PE, almost complete recovery (more than 90% of the initial clinical score) was obtained in 8 of 18 patients while an improvement between 60 and 90% of the initial score was achieved in 9 of 18 patients. An early improvement was noted 24 h after the beginning of plasmapheresis in 11 of 18 patients. No recurrence of symptoms was reported after 36 months of follow-up for 17 patients. The administration of steroid therapy was never followed by an early exacerbation of myasthenic symptoms as reported when it is administered in the absence of concomitant PE. According to our results, we can conclude that high doses of oral prednisone therapy in simultaneous association with PE lead to successful control of severe forms of MG, significantly superior to the therapeutic strategies until now adopted and reported in literature.

Remission of myasthenia gravis caused by proteinuria in nephrotic syndrome

Myasthenia gravis is caused by antibodies against acetylcholine receptors and is treated with inhibition or elimination of antibody production. We report a 43-year-old myasthenic female who was symptomatic until she developed proteinuria from nephrotic syndrome, which caused a marked drop in acetylcholine receptor antibody titer with remission of myasthenia. Treatment of the nephrotic syndrome produced exacerbation of her myasthenia and a rise in antibody level. This patient's improvement is the result of antibody elimination during proteinuria in nephrotic syndrome.

Oral tolerance in myasthenia gravis

Because of the antibody-mediated pathogenesis of MG, it is of particular interest to understand the effects of oral administration of the autoantigen AChR on the disease process. It is now clear that feeding AChR prior to immunization can prevent clinical manifestation of EAMG. It initially primed, then inhibited, antibody responses to foreign (Torpedo) AChR and self (rat) AChR, with a delayed onset. Cellular responses to AChR, evaluated by lymphocyte proliferation and IL-2 production, were markedly inhibited. The effects were dependent on the dose and purity of the fed antigen. Tolerance to an orally administered unrelated antigen, OVA, was more prompt in development and more profound, illustrating the influence of the nature of the antigen on tolerance. The tolerance induced was antigen specific. Oral administration of AChR after immunization resulted in inhibition of the clinical manifestation of EAMG, concomitant with a paradoxical enhancement of the AChR-antibody responses. Both the clinical benefit and the antibody response appear to be dependent on the feeding protocol. These findings suggest that a molecule with less immunogenic potential than native AChR may be required for safe and effective oral treatment of ongoing disease.

Plasmapheresis as preparatory method for thymectomy in myasthenia gravis

To study the effects of plasmapheresis in preparation for thymectomy, two groups of 40 patients were selected from a sample of 286 patients with myasthenia gravis examined by the first author Group 1 included patients (15 male and 25 female; age range 8-64 yrs) who underwent thymectomy without previous plasmapheresis, whereas patients in group 2 (17 male and 23 female; age range 11-61 yrs) were thymectomized after plasmapheresis. We required patients to have a minimum follow-up period of 12 months to be included in the study. A clinical evaluation protocol composed of 76 items was developed for the study. We found significant improvement in respiratory function and muscular strength in patients thymetomized after plasmapheresis. Furthermore, the combined treatment reduced cost and length of hospital stay. Therefore, we conclude that plasmapheresis should be considered as a coadjuvant to thymectomy in the treatment of myasthenia gravis.

Reliable disability scale for myasthenia gravis sensitive to clinical changes

INTRODUCTION

we developed a disability scale to monitor myasthenia gravis (MG) patients, based on degree of function impairment and daily frequency of each symptom.

MATERIAL & METHODS

the scale was based on standardized questions and clinical examination. The scale was administered to 12 patients, one or more times, for a total of 22 interviews. Each observation was recorded on videotape and reviewed by five independent observers. The ability of our scale to discriminate clinical changes was also compared with the Osserman classification.

RESULTS

our scale showed from substantial to almost perfect inter and intraobserver agreement. Our findings showed that clinically relevant changes not detected by Osserman staging were disclosed by our scale.

CONCLUSION

our scale is simple and easy to use in clinical practice. It offers an accurate means of evaluating disability in MG patients and may detect clinically relevant changes in disability. It would therefore be useful to monitor the effects of therapy.

Myasthenia gravis: immunological mechanisms and immunotherapy

This review of the immunological aspects of myasthenia gravis and the immunotherapy of the disease emphasizes the current state of knowledge of the immunological events at the neuromuscular junction, and the immunoregulatory abnormalities noted in myasthenic patients. The treatment modalities available to the clinician are discussed in an attempt to provide information that will allow for a rational approach to therapy.

Ocular myasthenia: a protean disorder

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.

A short plasma exchange protocol is effective in severe myasthenia gravis

Plasma exchange has been reported to be a successful therapeutic procedure for the treatment of severely compromised myasthenic patients, but the optimal regimen in terms of costs or clinical benefit has not so far been determined. We have investigated the efficacy of a short plasmapheresis protocol of two exchanges 1 day apart in a series of 70 patients with severe forms of myasthenia gravis. Patients were evaluated before and 7 days after the first exchange. A positive outcome was observed in 70% of the plasma exchange cycles performed. Disease severity did not seem to be a negative prognostic factor for the efficacy of this short protocol, which was well tolerated by patients. In only 1 case were major side-effects observed. In spite of its short duration, the exchange treatment plus concomitant immunosuppressive drug therapy was not followed by early clinical deterioration.

Azathioprine as a single drug or in combination with steroids in the treatment of myasthenia gravis

Azathioprine (Aza) has been used alone or in combination with steroids for two groups of myasthenic patients. Positive responses were noted in 75% of patients on Aza alone and in 70% receiving the combined regimen. The clinical course of the two groups differed in terms of respiratory crisis and need for plasma exchange. With an appropriate Aza administration schedule side-effects were not a limiting factor to its use. Aza treatment induced a reduction in anti-AchR-antibody level that was correlated with clinical improvement and greatly decreased the need for steroids.

Myasthenia gravis and myasthenic syndromes

More than a decade ago myasthenic symptoms were observed in rabbits immunized with acetylcholine receptor (AChR) [119] and AChR deficiency was found at the neuromuscular junction in human myasthenia gravis (MG) [36]. By 1977 the autoimmune character of MG and the pathogenic role of AChR antibodies had been established by several measures. These included the demonstration of circulating AChR antibodies in nearly 90% of patients with MG [87], passive transfer with IgG of several features of the disease from human to mouse [149], localization of immune complexes (IgG and complement) on the postsynaptic membrane [30], and the beneficial effects of plasmapheresis [20, 123]. Substantial subsequent progress has occurred in understanding the structure and function of AChR and its interaction with AChR antibodies. The relationships of the concentration, specificities, and functional properties of the antibodies to the clinical state in MG have been carefully analyzed, and the mechanisms by which AChR antibodies impair neuromuscular transmission have been further investigated. The clinical classification of MG has been refined, the role of the thymus gland in the disease has been further clarified, and new information has become available on transient neonatal MG. The prognosis for generalized MG is improving, but there is still no consensus on its optimal management. Novel therapeutic approaches to MG are now being explored in animal models. Recognition of the autoimmune origin of acquired MG also implied that myasthenic disorders occurring in a genetic or congenital setting had a different cause. As a result, a number of congenital myasthenic syndromes have come to be recognized and investigated. Finally, an acquired disorder of neuromuscular transmission different from MG, the Lambert-Eaton myasthenic syndrome, has also been shown to have an autoimmune basis. In this syndrome, active zone particles of the presynaptic membrane are direct or indirect targets of the pathogenic autoantibodies.

Aphresis

Therapeutic apheresis is a relatively new modality. Its absolute indications are few and include hyperviscosity syndrome, cryoglobulinemia, thrombotic thrombocytopenic purpura, Goodpasture's syndrome, and life-threatening complications of immunologic disorders refractory to conventional management. The use of apheresis in most of the other disorders discussed in this monograph is experimental and should not be employed unless all the mitigating therapeutic considerations clearly suggest an overwhelming advantage of apheresis. The promise of apheresis is much greater than its current use, and the research applications of specific component separation and antibody removal are of great importance. It is hoped that these new developments will shortly make current devices obsolete and improve the clinical management of patients as well as increase our knowledge of disease etiopathogenesis.

Anti-acetylcholine receptor antibodies in myasthenia gravis. Part 2. Clinical and serological follow-up of individual patients

Circulating antibodies to acetylcholine receptor protein (anti-AChR) were measured in the sera collected from 75 patients (53 women, 22 men, ages 9-83 year, 20 with a thymoma) with myasthenia gravis (MG) during 5-44 (mean 25) months. The clinical state of each patient was graded on a 6-point scale. Anti-AChR concentrations were measured by a radioimmunoassay with human antigen. We analysed the relation between the change in clinical state and the change in anti-AChR concentration in 155 periods (1-7, mean 2.1 per patient). The change in clinical state is given as the difference in score at the onset and at the end of this period. The change in anti-AChR concentration is expressed as the percentage of the original concentration at the onset of the period. The results were analysed in relation to the therapy and to the severity of the MG at the onset of each period. A strong correlation between a change in anti-AChR concentration and a change in clinical condition existed during treatment with prednisone or immunosuppression and in the period after thymectomy, while a weaker correlation was present in periods without immunosuppression. In only 3 patients did the changes in anti-AChR concentration precede the clinical change. No changes in anti-AChR concentrations were found if improvement was due to the effect of anticholinesterases or if deterioration was caused by infection or emotion. The serial measurement of anti-AChR may be a valuable method of following the basic trend of the MG in severely affected patients.

Immunopathology of acetylcholine receptors in myasthenia gravis

It is now clear that the muscular weakness and fatigability seen in MG result from an antibody-mediated immune response to AChR. The mechanisms by which antibodies impair transmission are moderately well understood and detection of antibodies in patient's sera is a reliable diagnostic test for the disease. The spectrum of antibody specificities produced in MG is also beginning to be understood, largely through the use of antibodies produced in the experimental model EAMG. Treatment for MG continues to rely heavily on the symptomatic relief afforded by acetylcholinesterase inhibitors. However, the recent recognition of the autoimmune nature of MG has led to increased emphasis on immunosuppression and antibody removal with some beneficial effects. Despite all that has been learned, the level of ignorance has just been pushed back one step--from the neuromuscular junction to the immune system. What initiates the immune response to AChR in MG and how to specifically suppress this aberrant response remain completely unknown.