Neuromuscular Junction Disorders NMJ

Please start with the section on neuromuscular disease patterns for an introduction. Also see the section on the approach to weakness. Here are some notes on neuromuscular junction diseases that may be of interest prior to reading about the individual diseases.

Clinical features of neuromuscular junction disorders:

  • No atrophy
  • Normal or reduced tone
  • Weakness: patchy i.e. doesn’t conform to an anatomic structure, fluctuation with time & exercise i.e. fatigability
  • Normal or depressed reflexes
  • No sensory changes
  • Fatigability of weakness or facilitation of power. Weakness that gets worse or better with muscle exertion.


Causes of weakness due to interruption of the neuromuscular junction:

Autoimmune Myasthenic syndromes :

Congenital myasthenic syndromes, rare :

  • Presynaptic:
    • Choline Acetyltransferase
  • Synaptic:
    • Endplate acetylcholinesterase AChE deficiency
  • Postsynaptic:
    • AChR deficiencies
    • AChR kinetic abnormalities (slow & fast channel syndromes)
    • Rapsyn mutation

Infective NMJ disorders:

Toxic NMJ disorders:

  • Aminoglycosides