What are the signs and symptoms of the disease?

Myasthenia gravis causes muscle weakness that is worsened by use and improved with rest. For this reason, a person may have few or no symptoms right after awakening or resting. As the person goes about his or her daily activities, the symptoms may become obvious.

Eye muscle involvement may cause drooping eyelids and double vision. The person may have a masklike expression if the facial nerves are affected. Head control, chewing, swallowing, and speech may also be affected by muscle weakness.

Approximately 15% to 20% of people who have myasthenia gravis have muscle weakness in the arms and hands. Weakness in the leg muscles is less common. Increasing weakness of the muscles in the chest may lead to difficulty breathing. Respiratory distress, which is an emergency, can occur.