Myasthemia gravis is the neuromuscular disease and is chronic. Its main symptom is the weakening of the muscles resulting in the weakness of arms, legs etc. It happens when the body immune system produces antibodies that destroy its own healthy tissues. It reduces the formation of the neurotransmitter acetylcholine (chemicals responsible for the formation of nerve impulses), this leads to communication loss between muscles and neurons. Due to a decrease in acetylcholine, there is loss in the strength of muscles, hence muscles weaken.