The neuromuscular junction disorders.

Neuromuscular junction (NMJ) disorders result from destruction, malfunction or absence of one or more key proteins involved in neuromuscular transmission, illustrated diagrammatically in fig 1. The most common pathology is antibody mediated damage or down regulation of ion channels or receptors, resulting in myasthenia gravis (MG), Lambert-Eaton myasthenic syndrome (LEMS), and acquired neuromyotonia (Isaac’s syndrome). Not surprisingly these three conditions share many common features (table 1). A second important group of disorders are the congenital myasthenic syndromes caused by mutations in NMJ proteins. Detailed discussion of these rare conditions is beyond the scope of this short review but interested readers are referred to a recent review by Engel and Ohno.