Myasthenia gravis

Question 1

What is MG

Answer 1

autoimmune disorder resulting in insufficient functioning acetylcholine receptors

Antibodies to Ach receptors are seen in 85-90% of cases

Question 2

What is the epidemiology of MG

Answer 2

more common in women
2:1

Question 3

What is the most common exacerbating factor of MG

Answer 3

exertion resulting in fatigability - hallmark of MG

Question 4

What drugs may exacerbate MG

Answer 4

pencilliamine
quinidine, procainamide- anti arrythmic drugs

beta blockers

lithium

phenytoin

antibiotics- gentamicin, macrolides, quinolones, tetracyclines

Question 5

What may someone with MG present with

Answer 5

key feature is muscle fatigability - worse during exertion and slowly improve after rest

extraocular muscle weakness- diplopia

proximal muscle weakness - face, neck, limb girdle

ptosis

dysphagia

Question 6

What conditions are associated with MG

Answer 6

thymomas
autoimmune disorders - pernicious anemia , autoimmune thyroid disorders, RA, SLE

Question 7

What investigations are required

Answer 7

single fibre electromyography - high sensitivity ( 92-100%)

CT thorax to exclude thymoma

CK normal

ANTIBODIES TO ACH RECEPTORS
- positive in around 90%

• of remaining , 40% positive for anti-muscle -specific tyrosine kinase antibodies

Question 8

What is the management

Answer 8

Pyridostigmine - long acting Acetylcholinesterase inhibitor

immunosuppression - not initial but will be eventually given
Prednisolone intial
Azathioprine, cyclosporine etc

Thymectomy