Myasthenia Gravis Investigations and Management (BMJ Best Practice)

Question 1

What is the first antibody tested for in myasthenia gravis?

Answer 1

Acetylcholine receptor antibodies

Question 2

What antibodies are tested if acetylcholine receptor antibodies are negative?

Answer 2

Muscle specific tyrosine kinase (MuSK) antibodies

Question 3

What population of people are more likely to have negative acetylcholine receptor antibodies but positive MuSK antibodies?

Answer 3

Black people in the US (esp women)

Question 4

What investigation is used in myasthenic crisis?

Answer 4

Serial pulmonary function testing
Specifically FVC and negative inspiratory force (NIF)

Question 5

What is used to treat significantly reduced FVC/NIF in myasthenic crisis?

Answer 5

Mechanical ventilation

Question 6

When is electrophysiological testing done in MG?

Answer 6

When antibodies are negative

Question 7

What scan should be done in patients with new onset MG in adulthood and why?

Answer 7

CT scan
Look for thymoma or thymic hyperplasia

Question 8

Other than respiratory support, what can be done for patients in myasthenic crisis?

Answer 8

Plasma exchange or IVIG
Consider steroid

Question 9

What is first line treatment in MG?

Answer 9

Pyridostigmine

Question 10

When would you add a steroid/immunosuppressant in MG?

Answer 10

If severe/refractory disease
Pyridostigmine not working

Question 11

What monoclonal antibody can be given if other treatments don’t work?

Answer 11

Rituximab