Disorders of the neuromuscular junction

This chapter looks at how two fundamentally different pathological processes are associated with disease at the neuromuscular junction: acquired disorders in which autoantibodies are directed against nerve or muscle receptor or ion channels; rare inherited conditions in which the defect may be pre- or postsynaptic. The acquired neuromuscular junction disorders are associated with antibodies directed against one of the ion channels. The fact that there are three autoimmune disorders known to affect such a small region may be explained by the neuromuscular junction, unlike the peripheral nerve, not being contained within the blood–nerve barrier, which stops just short of the nerve terminal, and thus being potentially exposed to circulating humoral attack. The inherited disorders may affect presynaptic processes (acetylcholine resynthesis, packaging, or release), acetylcholinesterase binding, or postsynaptic function (acetylcholine receptor numbers or localization). Pathogenic mechanisms are considered in more detail when discussing individual disorders.