Myasthenia Gravis

Question 1

What is myasthenia gravis?

Answer 1

Autoimmune disorder which results in antibodies against acetylcholine receptors.

Question 2

What are the features of myasthenia gravis?

Answer 2

Muscle fatigability. This can present as extraocular muscle weakness, proximal muscle weakness, ptosis and dysphagia

Question 3

What conditions are associated with myasthenia gravis?

Answer 3

Thymic hyperplasia
Other autoimmune disorders eg, pernicious anaemia, autoimmune thyroid disorders, rheumatoid
Thymomas

Question 4

What are the investigations for myasthenia gravis?

Answer 4

1. Single fibre electromyography (high sensitivity)
2. Antibodies to acetylcholine receptors
3. CT thorax to exclude thymoma
   Creatinine kinase will be normal

Question 5

What is the management of myasthenia gravis?

Answer 5

First line - Pyridostigmine (Long acting acetylcholinesterase inhibitors)
Many patient’s later require immunosuppression with prednisolone or azathioprine.

Question 6

What is the management of a myasthenic crisis?

Answer 6

Plasmapheresis and IV immunoglobulins

Question 7

What are the investigations for a myasthenic crisis?

Answer 7

Lung function tests (spirometry_, if FVC is less than 15 then patient should be considered for mechanical ventilation

Question 8

What are the differential diagnosis for myasthenia gravis?

Answer 8

1. Lambert eaton syndrome (fluctuating muscle weakness which improves with exercise),
2. Brainstem glioma,
3. MS,
4. Botulism,
5. Polymyositis,

Question 9

What are some drugs which can exacerbate MG?

Answer 9

Penicillamine, quinidine, beta blockers, lithium, phenytoin and antibiotics