muscle diseases

Question 1

Myasthenia gravis (MG) - weakness in what muscles?

Answer 1

acquired
characterised by weakness of ocular, bulbar and proximal limb muscles
heart not affected

Question 2

predominant feature of muscle disease

Answer 2

weakness
reflexes and sensation = normal, unlike in muscle disease
wasting of muscle occurs late
acquired or congenital

Question 3

When does MG peak

Answer 3

3rd and 6th decade

2 x more common in F than M

Question 4

MG aetiology

Answer 4

autoantibodies to acetylcholine receptors at the postsynaptic membrane of the neuromuscular junction cause receptor loss

Question 5

MG associated with

Answer 5

thymic hyperplasia

10% thymic tumour found

Question 6

clinical features MG

Answer 6

fatiguability of muscle on sustained or repeated activity that improves after rest
ocular muscles first to be involved = ptosis
weakness works its way down: difficulty talking, chewing, swallowing and resp dif

Question 7

what is ptosis

Answer 7

drooping or falling of upper eyelid

Question 8

investigations MG

Answer 8

anti-AChR antibodies 90%

Question 9

management
first line
second line
crisis

Answer 9

first line - anticholinesterases eg pyridostigmine - inc availability of ACh at the receptor = mainstay of rx
second line - immunosuppressants and corticosteroids
myasthenic crisis: plasmapheresis and iv immunoglobilin