Myasthenia Gravis Flashcards
what type of disease is myasthenia gravis?
autoimmune
Cause?
autoantibodies block Acetylcholine (Ach)
what is the main overall symptom?
muscle weakness
which receptor does Ach bind to at the muscle?
nicotinic acetylcholine receptor
small proportion of patients also have antibodies against a post-synaptic protein.
what is this protein called?
muscle-specific kinase, MuSK
60% of MG cases get reactive hyperplasia of what cell and in what organ?
intrathymic B cell
thyroid
how many myasthenia gravis pts get thymoma?
-% wise
12%
ptosis is due to weakness of what muscle?
levator palpebrae superioris muscle
weak swallowing muscles causes what symptom?
dysphagia
weak facial muscles leads to what symptoms?
-2
slurred speech + snarl smile
why is there head drop?
Neck extensor muscles weak
why is there SOB?
Resp muscles weak
what is worldwide prevalence?
-%wise
0.02%
which gender is a risk factor?
females
do younger or older people get onset of this disease?
younger onset
which complication has increased risk due to the dysphagia?
↑aspiration pneumonia
Weak respiratory muscles can cause what complication?
how do you treat this?
-2
myasthenic crisis
plasmapheresis + intubation
how does the muscle weakness vary during the day?
worse at end of day
Risk Factors for MG?
-6
Female young FHx Autoimmune disorder Thymoma Thymic hyperplasia
which imaging do you use to exclude thymoma?
exclude thymoma
what test is appropriate for checking nerve behaviour in MG?
result on this test?
Electromyography
nerves show a decremental response to repetitive stimulation
what is 1st line blood test ?
2nd line blood test?
how many pts will be postiive for the above two test?
if not positive in above test but they have a strong history what is the 2nd line Ix you do?
check blood for anti-AChR antibodies - 85%
anti-muSK antibodies - 40%
Electromyography
how does exercise affect symptoms?
makes it worse
pt has positive Hx but nothing abnormal in blood tests.
what Ix should you do now?
positive result on said Ix?
how sensitive is said test?
Electromyography
nerves show a decremental response to repetitive stimulation
95%
1st line drug?
group of this drug?
PYRIDOSTIGMINE
acetylcholinesterase inhibitor
if thymoma is seen on imaging.
what Mx do you do?
Thymectomy
1st line drug fails.
what is 2nd line drug?
class of this drug? group of this drug?
Prednisolone
corticosteroids
immunosuppression
what is 2nd line drug?
2nd line drug fails.
what is 3rd line drug?
class of this drug? group of this drug?
Prednisolone
azathioprine
purine synthesis inhibitor
immunosuppression
what is nutshell Mx?
-2 things
boost ACh (&downregulate immune system)
on examination how can you exacerbate ptosis?
ask pt to look up
symptoms?
-7
Lethargy Muscle weakness, worse at end of day Double vision Slurred speech Dysphagia SOB Head drop
does rest make symptoms better or worse?
better
signs on examination?
-4
muscle weakness
muscles fatigue on use
Ptosis
Myasthenic snarl
what is 1st line blood test ?
2nd line blood test?
how many pts will be postiive for the above two test?
if not positive in above test but they have a strong history what is the 2nd line Ix you do?
check blood for anti-AChR antibodies - 85%
anti-muSK antibodies - 40%
Electromyography
