Anti-skeletal muscle and anti-acetylcholine receptor antibodies in patients with thymoma without myasthenia gravis: relation to the onset of myasthenia gravis.

We measured the anti-skeletal muscle (SM) antibody titers in sera from 46 patients with thymoma but without Myasthenia gravis (MG) in order to determine whether the presence of anti-SM antibody is linked to the combination of thymoma-MG, or to thymoma alone. We detected anti-SM antibodies in 18 of these sera, of which 15 had concomitantly elevated titers of anti-AChR antibodies. Moreover, 9 of whom had experienced the onset of MG after surgery. In contrast, no patient without elevations in both antibodies developed MG during the followup. We conclude that the presence of anti-SM antibodies is linked strongly with thymoma associated with MG, but not with thymoma alone.