Myasthenia gravis

Question 1

What is myasthenia gravis?

Answer 1

An autoimmune disease mediated by antibodies to nicotinic acetylcholine receptors on the post-synaptic side of the NMJ.

Question 2

What are Sx of myasthenia gravis?

Answer 2

• Slowly increasing or relapsing muscular fatigue
• Muscle groups affected chronologically:
○ Bulbar
○ Face
○ Neck
○ Limb girdle
Trunk

Ptoasis, diplopia, voice fading when counting to 50, orbicularis fatgiue

Patients will have normal reflexes

Thymoma

Question 3

What can trigger symptoms in patients with myasthenia gravis?

Answer 3

• Pregnancy
	• Hypokalaemia
	• Exercise 
	• Emotion
Certain drugs

Question 4

What are differentials for myasthenia gravis?

Answer 4

• Polymyositis
	• Other myopathies 
	• Takayasu's arteritis 
	• Botulism
SLE

Question 5

What Ix in myasthenia gravis/

Answer 5

Anti-Ach antibodies

EMG shows decreases response to repetitive nerve stimulation

CT for thymoma

Question 6

How is myasthenia gravis treated?

Answer 6

Symptom control: Anticholinesterase, e.g. pyridostigmine

Immunosuppression: relapses with prednisolone

Thymectomy can help symptoms even in patients without thymoma