Myasthenia gravis is a postsynaptic disorder of the neuromuscular junction in which antibodies are produced against components of the acetylcholine receptors on muscle. These antibodies are most commonly against the acetylcholine receptor itself, leading to blocking and destruction of these receptors.
Myasthenia gravis is the most common autoimmune disease affecting the neuromuscular junction and is characterised by painless fatigable muscle weakness. It is caused by autoantibodies against neuromuscular junction proteins, either the nicotinic acetylcholine receptor (AChR) or the muscle specific tyrosine kinase (MuSK). Mutations in neuromuscular junction proteins cause congenital myasthenic syndromes. Other antibody mediated conditions affecting the neuromuscular junction include Lambert Eaton myasthenic syndrome and neuromyotonia.
Epidemiology of myasthenia gravis
Myasthenia gravis affects approximately 100 patients per million population.
It has a bimodal age of onset—early and late onset myasthenia gravis.
Early onset myasthenia gravis typically affects women less than 40 years of age whereas the later onset form is more common in older men.
With improved diagnosis and survival, the prevalence is increasing, especially in the elderly.
