Myasthenia means muscle weakness. This is confined to the voluntary muscles, muscles whose action is normally controlled by an individual's will such as the arm and leg muscles, and does not affect either the autonomic system or sensation. The autonomic system regulates the functions of the heart, stomach and intestines. People with myasthenia have characteristically fatigable muscles and the harder people with myasthenia try, the weaker they get. They are often strongest in the mornings and get weaker during the day. Myasthenia affects all ages and genders. It is treatable and can be brought under good control with medication. In some circumstances, it can be fatal.
Myasthenia gravis (MG) is an autoimmune condition. When you have MG the antibodies that normally fight infections go wrong and end up attacking the communications system between your brain and your muscle movements. This results in muscle weakness, muscle fatigue and generally making you feel weak.