Question

I would like some information on the disease called myasthenia gravis.

Answer

Myasthenia gravis is characterised by weakness of the muscles, which show fatigability. This means that the more they are used, the weaker they become. For muscles to work, they need to receive stimulation from the nerves. These release a neurotransmitter called acetylcholine, which crosses the junction between the end of the nerve and the beginning of the muscle. When it gets to the muscle, it causes the muscle to contract. Myasthenia gravis is an autoimmune disease, which means that there is an antibody produced within the person themselves, which attacks the muscular side of where the nerve and the muscles meet - called the neuromuscular junction. The management of the condition includes tablets to increase the amount of neurotransmitter between the nerve and the muscle, and plasma exchange (which means removing the antibody in the blood stream). Because the condition is an immunological one, removal of the thymus may help. Increasing use of immunological treatments has greatly improved the outlook.

There is no pain associated with the muscle weakness, and the first attack may follow infection or the use of muscle relaxants during a general anaesthetic. The weakness of the muscles may present with double vision, and indeed in some patients, the symptoms remain confined to the eye.

More commonly, symptoms are generalised, with perhaps an odd sort of nasal speech or difficulty in chewing and swallowing that increases during the meal. There may be difficulty in holding the head up. There is weakness of the limbs, particularly the arms and the muscles of the leg nearest the pelvis. Spontaneous remission does occur, and the disease can also go into relatively quiet periods.