What is Myasthenia Gravis?

Myasthenia Gravis (MG) is an auto-immune disease in which the immune system attacks and damages the nerve signal reception areas.  This causes a breakdown between nerves and muscles and results in loss of effectiveness in the muscles of the arms, legs and eyes.  The name ‘Myasthenia Gravis’ comes from the Greek and Latin words for ‘grave muscular weakness’.

Who gets MG?

MG occurs in all races, in both genders and at any age.  It is not thought to be directly inherited, nor is it contagious.  Occasionally, it occurs in more than one member of the same family.  It most commonly affects young adult women (under 40) and older men (over 60), but it can occur at any age.  Research shows that 80 per cent of MG sufferers are over 55; 13 per cent are between 21 and 55 and seven per cent are under 21.

One in 10,000 people suffer from MG and many more go undiagnosed and misdiagnosed due to a lack of awareness of the condition.  In Ireland, there are almost 400 diagnosed sufferers of MG, but it is estimated that for every diagnosed sufferer there are at least two to three others whose condition is undetected.

What are the symptoms?

The onset of MG may be sudden and may affect any voluntary muscle, although muscles that control eye and eyelid movement, facial expression and swallowing are the most frequently affected. 

In most cases, the first noticeable symptom of the disease is weakness of the eye muscles.  In others, difficulty in swallowing and slurred speech may be the first signs.  The degree of muscle weakness varies greatly among patients, ranging from a form of MG that is limited to eye muscles to a severe form in which many muscles – sometimes including those that control breathing – are affected.  Symptoms, which vary in type and severity, may include a drooping of one or both eyelids; blurred or double vision due to weakness of the muscles that control eye movements; an unstable or waddling gait; weakness in the arms, hands, fingers, legs and neck; a change in facial expression; difficulty in swallowing; shortness of breath and impaired speech.

MG is not a painful disease, but it can be debilitating if not treated.

How is MG treated?

There is no known cure for MG, but effective treatments are available that allow many – though not all – people with MG to lead full lives.  Common treatments include medications, thymectomy (surgical removal of the thymus gland) and plasmapheresis (plasma exchange).  In some people, muscle weakness may completely disappear as a result of treatments.  This is called a remission.

The effectiveness of current treatments for MG means that the outlook for most patients is bright.  Although they will not be cured, treatments will lead to significant improvements in the muscle weakness of most patients.  In some cases, MG may go into remission for a time, during which time no treatment is necessary.