The thymus gland sits in the chest behind the breastbone. Myasthenia gravis is a chronic autoimmune disease that causes muscle weakness and degeneration. About 15 percent of people with this condition have a tumor in their thymus gland. Symptoms of myasthenia gravis include:
If a tumor is present, or if a patient does not respond to medication, a thymectomy may be recommended. In this surgery, the thymus is removed. This operation can sometimes be performed as a minimally-invasive procedure.