Muscle antibodies in myasthenia gravis.

The existence of a second type of antibody to the striations of skeletal muscle is confirmed. This antibody, which reacts with the I bands, is found both in subjects with myasthenia gravis and in normal subjects, but is present in higher titres in the former. The relative frequency of the two types of muscle antibody was estimated in a small group of subjects in whom the thymic changes were known; the possible implications of an association between A band antibody and thymic neoplasia are discussed.