Plasma exchange and intravenous immunoglobulin treatment of neuromuscular disease.

Removal of immunoglobulin by plasma exchange and administration of immunoglobulin by intravenous infusion each improve selected neuromuscular diseases. Both treatments are expensive and relatively brief in their duration of action, but they benefit both self-limited neuromuscular diseases such as the Guillain-Barré syndrome and acute exacerbations of more chronic neuromuscular diseases including myasthenia gravis and chronic inflammatory demyelinating polyneuropathy. It is likely that plasma exchange acts by removing pathogenic antibodies. The mechanism by which intravenous immunoglobulin acts is less clear. Possibilities include (1) antiidiotypic antibody effect, (2) complement absorption, (3) downregulation of immunoglobulin production, (4) receptor blockade, (5) virus neutralization, (6) enhancement of suppressor cells, and (7) inhibition of lymphocyte proliferation. Although plasma exchange and intravenous immunoglobulin have major side effects, severe reactions are uncommon with plasma exchange and rare with intravenous immunoglobulin. Because of their low incidence of life-threatening complications, both treatments have major appeal to clinicians. Because of their brief action and high cost as well as the uncertainty as to whether either or both should be employed, their role in the therapeutic armamentarium of the neurologist requires further study.