Myasthenia Gravis Flashcards
What type of condition is myasthenia gravis?
Autoimmune condition
What does myasthenia gravis cause?
Muscle weakness
What causes muscle weakness to worsen?
Activity
What causes muscle weakness to improve?
Rest
What type of reaction is myasthenia gravis?
Type 2 hypersensitivity reaction
What age of women are affected?
20-30
What age of men are affected?
60-70
What do the B and T cell autoantibodies attack?
Postsynaptic acetylcholine receptors
What happens to the signal for the muscle to contract?
It is blocked
What do the B and T cell autoantibodies also activate?
The complement system
What happens when the complement system is activated?
Muscle cell destruction
What is the main antibody?
Acetylcholine receptor antibody
What are the other 2 antibodies?
Muscle specific kinase antibody
LRP4 antibody
what is the importance of Muscle specific kinase antibody and LRP4 antibody?
They’re responsible for the formation of acetylcholine receptors
What is the main characteristic of myasthenia gravis?
Muscle weakness that gets worse as the day goes on
What are the 4 main sets of muscles affected?
Ocular
Bulbar
Proximal
Axial
What are the ocular signs?
Ptosis and diplopia
What are the bulbar signs?
Dyphasia, Dysarthria, Dysphonia
What are the proximal muscles affected?
Shoulders and thighs
What are the axial muscles affected?
Neck and respiratory muscles
Additional symptoms?
Slurred speech and fatigue when chewing
How can you exacerbate ptosis?
Repetitive blinking
Worsened on sustained upward gaze
What are 2 things you should look for?
Thymectomy scars
Forced Vital Capacity
Why would you check forced vital capacity?
Due to the effect of myasthenia gravis on respiratory muscles
What is the first line test?
Blood test- serum acetylcholine receptor antibodies
Why would you do a CT of thorax?
Check for thymoma
What is the TENSILON/ edrophonium test?
Give IV edrophonium
What does edrophonium do?
Prevents the breakdown of acetylcholine providing temporary relief of weakness
What is the first line treatment?
Acetylcholinesterase inhibitor (Cholinesterase)
What are 2 examples of acetylcholinesterase inhibitors?
Pyridostigmine (main)
Neostigmine
What additional medical treatment can you give?
Steroid- Prednisolone
What surgical procedure may you need to carry out?
Thymectomy
What is myasthenic crisis?
Acute worsening of symptoms
What type of illness is myasthenic crisis usually triggered by?
Respiratory illness
What can myasthenic crisis lead to?
Respiratory failure
What is the main management of myasthenic crisis?
IV immunoglobulins
What would you give if IV immunoglobulins fail?
Plasmapheresis (plasma exchange)
Which type of drug should be avoided in someone with myasthenia gravis?
Beta-blockers
