Myasthenia Gravis

Question 1

What is MG?

Answer 1

Autoimmune disease mediated by antibodies to nicotinic acetylcholine receptors (AChR), which interfere with the neuromuscular junction via the depletion of working post-synaptic receptor sites.

Question 2

What are the 2 main peaks of presentation?

Answer 2

• Females in their 20-30s

- Males in their 60-70s.

Question 3

How can muscle fatiguability be examined clinically?

Answer 3

Ask the patient to do a repetitive task (e.g. abduct shoulder 20 times) and check muscle strength before and after.

Question 4

What are the reflexes like in someone with MG?

Answer 4

Normal

Question 5

Which 2 antibodies would you investigate for?

Answer 5

• AChR antibody levels

- Muscle-specific tyrosine kinase (MuSK) antibodies

Question 6

Which scanning modality should be performed for all new patients?

Answer 6

CT; to assess the thymus (thymoma occurs in 15%, thymic hyperplasia in 75%)

Question 7

What would be used for symptom control in MG?

Answer 7

Acetylcholinesterase inhibitor (e.g. pyridostigmine)

Question 8

What is a myasthenic crisis and how would it be managed?

Answer 8

Weakness of the respiratory muscles during a relapse; plasmapheresis or IV Ig whilst identifying the trigger for the relapse (e.g. infection, medications).