Arthritis in myasthenia gravis.

Seven patients with myasthenia gravis developed clinical signs of arthropathy. In two patients, the symptoms were due to a deforming rheumatoid arthritis and the myasthenic symptoms appeared as a transitory phase during the course of the disease. Muscle antibodies of IgG class were demonstrated with sera from both patients. Autoreactivity between muscle antibodies and rheumatoid factor was detected in one patient. Both patients died from sudden cardiac failure. Necropsy was performed in one and revealed a spotty myocardial necrosis. One patient had juvenile rheumatoid arthritis. Two patients had mild articular symptoms with indices of multivisceral disease and serological findings indicating a systemic lupus erythematous. One patient had classical ankylosing spondylitis, and one, unspecified arthropathy.