Monoclonal gammopathy and antibody activity against the acetylcholine receptor.

A 50-year-old woman with muscular fatigue and monoclonal gammopathy of unknown significance was shown to have high levels of antibodies against the acetylcholine receptor of the skeletal muscle endplate. The specific antibody activity was exclusively associated with the monoclonal component. There were no objective signs of myasthenia gravis. This is the first reported case with antibody activity against the acetylcholine receptor found in a monoclonal immunoglobulin fraction.