Course and prognosis of myasthenia gravis: a systematic review.

The clinical course of myasthenia gravis (MG) is variable, and spontaneous remission is still uncommon. Knowledge of the prognostic factors may help understand the course of MG and thus optimize its management. A systematic review search was conducted in MEDLINE and EMBASE for English language studies from 1985 through 2009. We identified additional studies by reviewing bibliographies of retrieved articles and hand search main journal of neurology. Studies evaluating variables associated with or predictive of remission in adult patients with MG were included. Because of methodological heterogeneity, we refrained from statistical pooling, instead, a best evidence synthesis was used for summarizing the results. From 1810 potentially relevant studies, 13 cohort studies met the inclusion criteria. The included studies were heterogeneous considerably in sample size, disease duration, follow-up years, definition of remission, and analysis. Study quality was limited by retrospective design in most studies and lack of multivariate analysis. Time of diagnosis from onset (<1 year) showed strong evidence of predicting a better remission. In studies using completely stable remission outcomes, there was strong evidence that age at onset (<40 years) was of prognostic importance. Furthermore, gender showed no association with remission. Time of diagnosis from onset and age at onset were found to be predictors of remission. Gender does not seem to predict the course of MG. Our findings should be interpreted with caution because of the clinical and methodological heterogeneity of included studies.

Anti-presynaptic membrane receptor antibodies in myasthenia gravis.

Myasthenia gravis (MG) is considered as an autoimmune disease of neuromuscular junction resulting from antibodies directed to acetylcholine receptors (AChR). We describe the use of beta-bungarotoxin (beta-BuTx) and alpha-bungarotoxin (alpha-BuTx) to capture their corresponding proteins from preparation of crude human muscle receptor. beta-BuTx binds to presynaptic membrane receptor (PsmR) of the whole receptor fraction, while alpha-BuTx binds to AchR. The captured proteins were used as antigen in ELISA to detect antibodies to PsmR and to AchR in sera from 82 Chinese patients with MG and in controls. In MG, antibodies to PsmR only were detected in 13%, to AchR only in 11% and both to PsmR and AchR in 54%. Only 3 of 50 patients with other neurological diseases and none of 50 healthy subjects had these antibodies. Specificity tests for antibodies showed that the detection systems which we used are specific and confident. No correlation was found between antibody levels and clinical status. The significance of the PsmR antibodies in the pathogenesis of MG is unknown. We suggest that myasthenia gravis is not only due to damage of the postsynaptic membrane, but of presynaptic structures as well.