According to Medilexicon's medical dictionary:
Myasthenia gravis is " a disorder of neuromuscular transmission marked by fluctuating weakness and fatigue of certain voluntary muscles, including those innervated by brainstem motor nuclei; caused by a marked reduction in the number of acetylcholine receptors in the postsynaptic membrane of the neuromuscular junction, resulting from an autoimmune mechanism."(8)
Myasthenia gravis comes from the Greek and Latin words meaning "grave muscular weakness."(1) Myasthenia gravis is an autoimmune disease that causes weakness in the voluntary muscle of the body. This muscle weakness usually occurs during periods of activity and improves after periods of ...view middle of the document...
Once they arrive at the junction, they will release a neurotransmitter called acetylcholine. Acetylcholine will travel to the muscle side of the neuromuscular junction and binds to the receptors. Hence, muscle contraction occurs.
Myasthenia gravis occurs when the normal communication between the nerve system and the muscles are blocked at the junction. Human body immune system which is normally help to fight infections, sometimes is found to turn against body for some unknown reason. The immune system produces antibodies which circulate around the body through blood. The antibodies produced tends to destroy or block the acetylcholine receptors found on the post-synaptic neuromuscular junction. The neurotransmitters now have less binding sites, leading to less impulses being transmitted, thus resulting weakness in muscle contraction.(1,3,4)
In addition, the auto-antibodies also attack muscle specific tyrosine kinase receptors. These receptors involved in formation of neuromuscular junction and organization of acetylcholine receptors.(3,5) Hence, muscle contraction will be weaken.
Pregnant mothers with Myasthenia gravis who give birth later tends to transmit the auto-antibodies to their babies. This is so called neonatal Myasthenia which babies have 12% chance to be infected. However, as the antibody level in the babies go down, thus, the babies can recover in a few weeks.(2)
There are also some people with Myasthenia gravis which do not have the auto-antibodies to attack the acetylcholine receptors. It is believed that presence of antibodies in these people which will interrupt with enzymes which required in the acetylcholine receptor function.(2)
Moreover, people with Myasthenia gravis often have abnormally large thymus gland. Therefore, it is believed that thymus may trigger the production of the antibodies that block the acetylcholine receptors. 15% of the infected people suffer from thymus tumor, thymoma.(2,5,6,7) Other causes such as antibodies against lipoprotein-related protein 4 and genetic factors may also lead to Myasthenia gravis. (7)
To deal with Myasthenia gravis, one of the ways...