Myasthenia gravis occurs when the immune system produces antibodies that damage or block the receptor cells of the muscles, notes Mayo Clinic. The muscles get fewer signals due to fewer receptor cells, leading to fatigue and weakness.
As of 2015, the origin of these antibodies is unknown, explains WebMD. The antibodies block the function of a protein called tyrosine kinase. There is no cure for the condition, but treatments are available to control its symptoms, according to NHS Choices. A doctor prescribes medication to improve communication between the muscles and the nerves, to limit the production of antibodies and to enhance muscle strength.