Myasthenia Gravis
Myasthenia gravis is a condition where we develop antibodies to the places, called receptors, on the muscle end plates where the nerves exert their effects. It is here that the nerves release the transmitter, the chemical called acetylcholine, that binds to the receptor and makes the muscle contract. In most cases of myasthenia gravis (the words mean a grave case of weak muscles) the antibodies attack the receptors, reducing their number. Since we need to activate a number of receptors before the muscles work this means they are weak and rapidly become fatigued. It can start at any age, and may affect just one group of muscles, such as those responsible for moving the eyes and the eyelids, causing a squint, or many, causing difficulties with such activities as running or dancing. In a proportion of cases - about 10% - there is a tumour of the thymus gland in the front of the chest, a gland which usually atrophies and disappears after adolescence. This may be responsible for producing the antibodies and while surgical removal may not improve the symptoms it may be necessary to prevent local spread of the tumour.
The management of myasthenia gravis is aimed at increasing the effectiveness of acetylcholine by increasing its concentration using chemicals which block the enzyme responsible for its breakdown (called acetyl cholinesterase, and so these chemicals are called anti cholinesterases), or by using immunosuppressants to block the production of antibodies.
|
