Myasthenia Gravis

Question 1

Pathophysiology

Answer 1

Decrease in the number of nicotinic AChRs at NMJ

Increase in gap at NMJ

Question 2

Associations

Answer 2

Autoimmune Conditions
Graves' disease
RA
SLE
Addison's disease
Vitiligo
NMO

Question 3

Clinical Features

Answer 3

Painless muscle weakness increased with exercise

FATIGUABILITY

Question 4

Ocular Muscles affected causing

Answer 4

Ptosis

Diplopia

Question 5

Exacerbated by

Answer 5

Hyperthyroidism
Occult infection
Drugs:
- aminoglycosides

Question 6

Investifations

Answer 6

Serum AChR antibody test
Repetitive nerve stimulation
Single fibre EMG studies
Tensilon (edrophonium) test
Post contrast CT/MRI- mediastinu looking for thymoma

Question 7

DD of Generalised MG

Answer 7

Lambert-Eaton Syndrome
Botulism
Penicillamine induced myasthenia
MND (bulbar onset)

Question 8

DD of Ocular MG

Answer 8

Thyroid opthalmopathy
Mitochondrial disease
Intracranial mass lesion (Cavernous sinus)
Wernicke’s encephalopathy

Question 9

Management

Answer 9

Cholinesterase Inhibitors
Steroids
Azathioprine
Thymectomy

Question 10

Cholinesterase inhibitors

Answer 10

1st Line
Pyridostimine bromide
SE: Abdo pain and Diarrhoea

Question 11

How can Cholinesterase inhbitors SE be treated?

Answer 11

Propantheline

Question 12

When are steroids indicated?

Answer 12

Not adequately controlled by cholinesterase
Prednisolone
Carry a steroid card
Osteoporosis prevention- bisphosphonate, HRT

Question 13

When is azothioprine indicated?

Answer 13

With steroids

FBC and LFT necessary

Question 14

MuSK antibodies causing MG- clin features

Answer 14

Affects bulbar, ocular, facial muscles

Question 15

DD of MuSK MG

Answer 15

MND

IBM

Question 16

Investigations of MuSK MG

Answer 16

MuSK antibody (+)
ACh receptor antibody (-)
Edrophonium test- weakly positive
EMJ- abnormality in NMJ facial muscles
CT chest- no thymic enlargement

Question 17

Management of MuSK MG

Answer 17

Plasmapheresis