Myasthenia gravis

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Myasthenia Gravis (MG) is an autoimmune disorder[1].in which antibodies belonging to the sufferer inhibit acetylcholine (ACh - a neurotransmitter) from binding to their target receptor proteins (AChR)[2].in the neuromuscular junction. By preventing communication at synapses, muscular contraction is inhibited in the affected individual causing muscle weakness in the sufferer, often leading to characteristic symptoms such as drooping eye lids (ptosis) and a "snarling" smile. Acetylcholine is a neurotransmitter that allows the transmission of signals across synapses in a neuromuscular junction by diffusing across the synaptic cleft and binding to receptor proteins. If the ACh can not bind to it's complementary binding sites on the motor end plate, the transmission of the action potential ceases and contraction does not take place.The disease is relatively rare affecting 1 in every 10,000 people in the United Kingdom[3]. and may be triggered by particular viruses or medicines, though certain individuals may be more prone to developing such an autoimmune disease due to their genetic background[4].

Due to the safety factor, transmission at the neuromuscular junction does not fail until many receptors have accumulated and are destroyed. The EPPs are not large enough to stimulate an action potential in the muscle which can lead to paralysis of the respiratory muscles, or worse - death.

Symptoms [5].

  1. Drooping of the eyelids (ptosis) and face.
  2. Blurred or double vision. (Due to a weakening of the eye muscles)
  3. Muscle fatigue in the neck. (Caused by the strain of holding the head up)
  4. Difficulty swallowing.
  5. Difficulty breathing.
  6. Progressive weakening of the leg and arm muscles.

References

  1. Alberts B., Johnson A., Lewis J., Raff M., Roberts K., Waltzer P.(2008) Molecular Biology of THE CELL, 5th edition, New York: Garland Science. p1549
  2. J. Clin. Invest. 116:2843–2854 (2006). doi:10.1172/JCI29894.
  3. NHS, Myasthenia Gravis.(2011)Available at http://www.nhs.uk/Conditions/Myasthenia-gravis/Pages/Introduction.aspx (last accessed 30.11.12)
  4. Genetic factors in autoimmune myasthenia gravis.fckLRAnn N Y Acad Sci. 2008;1132:180-92. doi: 10.1196/annals.1405.027.fckLRGiraud M1, Vandiedonck C, Garchon HJ.
  5. NHS, Myasthenia Gravis.(2011)Available at http://www.nhs.uk/Conditions/Myasthenia-gravis/Pages/Introduction.aspx (last accessed 30.11.12)
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