Controlled studies with high-dose intravenous immunoglobulin in the treatment of dermatomyositis, inclusion body myositis, and polymyositis.

There are three major subsets of the inflammatory myopathies: polymyositis (PM), dermatomyositis (DM), and inclusion-body myositis (IBM). High-dose intravenous immunoglobulin (IVIg) has been tried in controlled clinical trials in patients with DM and IBM but not with PM. In patients with DM that is resistant or partially responsive to conventional therapies, IVIg was very effective. The treated patients experienced dramatic improvement not only in muscle strength but also of their skin rash. Repeated muscle biopsies with quantitative histologic studies showed the IVIg-treated patients had a statistically significant improvement of the muscle cytoarchitecture, with resolution of the aberrant immunopathologic parameters. In two controlled clinical trials conducted in IBM patients, IVIg showed marginal improvements in muscle strength which were nonsignificant. However, a few IBM patients had a definite clinical improvement with increased activities of daily living, but when analyzed within the entire IVIg-treated group, their total gains in muscle strength did not reach statistical significance compared to the placebo-treated group. Of interest is that certain muscle groups in the IVIg-treated patients, such as the muscles of swallowing, showed significant improvement compared to those of the placebo-treated patients, implying mild regional effects. In PM, uncontrolled trials have shown improvements in muscle strength, but the controlled clinical trial is still ongoing.