Myasthenia gravis is characterised by fluctuating muscle weakness and muscles that tire easily. An acute increase in symptoms can be life-threatening because of swallowing difficulties or respiratory failure. Myasthenia gravis is an autoimmune disorder in which the body's own antibodies block the transmission of nerve impulses to muscles and damage the neuromuscular junction (where the nerve meets the muscle). With optimal treatment, including thymectomy, corticosteroids, immunosuppressive drugs and plasma exchange, most people with myasthenia gravis go into remission or improve but these treatments can cause many adverse events. Intravenous immunoglobulin (IVIg) (antibodies purified from human blood), is effective in other autoimmune diseases. The objective of this review was to examine the efficacy of IVIg for treating acute exacerbations or for chronic long-term, persistent myasthenia. We identified seven randomised controlled trials (RCTs), all of which investigated short-term benefit. Other than where study limitations are mentioned the risk of bias was generally low. Adverse events due to IVIg were observed in all trials. They were moderate (fever, nausea, headache), self-limiting and are subjectively less severe than those with plasma exchange (although no statistical comparison was possible).
Five of the RCTs evaluated the efficacy of IVIg for the treatment of exacerbations or worsening (the former being usually more severe than the latter). One RCT of IVIg versus placebo, which included 51 participants, showed some evidence of the efficacy of IVIg for treating myasthenia gravis with worsening weakness. Two trials, the first of which included the first 87 and the second 84 participants, showed no significant difference between IVIg and plasma exchange. In the first of these trials there was a high risk of bias because the assigned treatments were not hidden. A trial including 33 participants showed no difference in efficacy between IVIg and a corticosteroid (methylprednisolone) but did not recruit enough participants to detect an effect, so there is insufficient evidence to favour IVIg over corticosteroids in moderate exacerbations. Another trial, which included 168 participants, showed no evidence of superiority of IVIg 2 g/kg over IVIg 1 g/kg on the change of myasthenic muscle score (MMS) after 15 days (MD 3.84; 95% CI -0.98 to 8.66).
Two RCTs evaluated the efficacy of IVIg for the treatment of moderate or severe myasthenia gravis. One compared, in 12 participants, IVIg and plasma exchange. The second, with 15 participants included, compared IVIg and a placebo. Both are underpowered and the first at some risk of bias, so no conclusion could be drawn from these two trials. There is no evidence from RCTs nor from other trials to determine whether IVIg improves function or reduces the need for steroids.