Myasthenia Gravis is a chronic autoimmune disease that causes muscle weakness and excessive muscle fatigue. The severity of the disease can vary hugely between individuals, and in any one patient the symptoms fluctuate with relapses and remissions. Myasthena Gravis can resolve spontaneously but, for most people it persists for life.

Myasthena Gravis is usually caused by a faulty immune system and can affect anybody and develop at any age. It is thought that those who inherit a tendency to develop other autoimmune disease, such as a thyroid problem, are more likely to develop MG. 'Autoimmune' means that the immune system, which produces antibodies to protect against bacteria and viruses, starts producing antibodies against its own proteins ('self' proteins). Congenital Myasthena Gravis is, however, a genetic condition.

There are two main forms of Myasthena Gravis - ocular Myasthena Gravis and generalised Myasthena Gravis. Ocular Myasthena Gravis affects the eye muscles only. Symptoms are drooping of the eyelid and double vision. Generalised Myasthena Gravis usually causes symptoms of ocular Myasthena Gravis and it also affects the face, throat, neck, limb and breathing muscles.

Myasthena Gravis is uncommon, affecting approximately 15 in every 100,000 people in the UK.

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