Disorders Of The NMJ

Question 1

What Rs are attacked in Myasthenia Gravis?

Answer 1

Nicotinic ACh Rs on the post-synaptic/muscular side

Question 2

What genetic predisposition is seen in MG?

Answer 2

HLA-B8/DR3

Question 3

Pts w/ MG also often have abnormalities in what organ?

Answer 3

Thyroid gland

Question 4

What sxs does a pt w/ MG c/o?

Answer 4

Ptosis
Double vision/diplopia
Limb and/or neck weakness
Dysarthria/dysphagia

Question 5

What antibodies are found in MG?

Answer 5

Anti-AChR antibodies (10% of pts won’t have)

MUSK antibodies (clusters Rs)

Question 6

What does repetitive stimulation cause in MG?

Answer 6

Decremental response

Question 7

What test can be used to confirm MG? What are possible SE?

Answer 7

Tensilon/Edrophonium test

Bradycardia, arrhythmias

Question 8

MG tx?

Answer 8

ACh-esterase inh

Thymectomy

Question 9

What’s a popular drug that can exacerbate/unmask MG?

Answer 9

Aminoglycoside ATB

Question 10

If a pt comes in w/ MG sxs but doesn’t have the MG serology, what’s likely? What’s the tx?

Answer 10

MUSK syndrome

ACh-esterase meds don’t work well, nor a thymectomy

Rituximab

Question 11

What is Lambert-Eaton Myasthenic Syndrome (LEMS)? It’s associated w/ CA!!!!!! Which one?

Answer 11

Autoimmune attack on Ca channels along the pre-synaptic side, prevents Ca influx and thus vesicle mobilization/ACh release into the synapse > weakness

Squamous Cell carcinoma of the lung

Question 12

What’s the activity of botulism? What does it cause? What’s the tx?

Answer 12

Toxin from the bacteria inh ACh release

Descending paralysis, flaccid

Antitoxin
Guanidine Hydrochloride

Question 13

What is the MOA of Sarin? How is Sarin intoxication treated?

Answer 13

It’s an organophosphate, it binds ACh-esterase covalently causing an inc in synaptic ACh (and thus ACh activity) aka cholinergic crisis > flaccid paralysis

Atropine + Praladoxine + benzodiazapine (for seizures)