Myasthenia gravis

 Disease class:  Autoimmune diseases of the nervous system
Disease class: Neuromuscular junction diseases 

Also known as MG.

Pathophysiology

1. There is production of autoantibodies. 
2. These autoantibodies target acetylcholine receptors on the post-synaptic membrane of the neuromuscular junction.
3. The antibody binding on the axon prevents acetylcholine binding. 
4. There is reduced acetylcholine signalling. 
5. There is a decrease in skeletal muscle contractility and autonomic function (e.g. gland secretions).

 

Symptoms and signs

• Distal muscle weakness, which is usually worse after exertion or at the end of the day.
• The muscles of the arms and head are usually the worst affected.
• The muscles of the eyes are often affected. This often causes double vision.
• Dysfunction of the autonomic nervous system
• Dry mouth
• Constipation
• Blurred vision 

 

Management

• Acetylcholinesterase inhibitors
• Immunosuppression (therapeutic)
• Airway management
• Tracheal intubation
• Mechanical ventilation

 

Compare with 

• Botulism
• Guillain–Barré syndrome
• Lambert–Eaton myasthenic syndrome
• Organophosphate poisoning