Myasthenia Gravis

Question 1

Define myasthenia Gravis

Answer 1

Autoimmune inflamatory disorder attacking your post synaptic Nictonic ACh

Question 2

Aetiology and risk factors of Myasthenia Gravs

Answer 2

Organ specific, Antibody based disease against Nicotnic Ash (at neuromuscular junction)
AB binding to Ach reduces action potentials

Risk factors:
FHx of autoimmune disorders
Some HLA markers are associated with MG
Cancer treatment

Question 3

Signs and symptoms of Mysathenia Gravis

Answer 3

Classically-
Proximal limb weakness
And Muscle fatiguability (tired as use-improve on rest)–double vision develop as reading, or eyelid drops as you ask for them to look up

Ptosis and double Vision-very common early signs
Eyeballs face different direction and droopy eyelids

Also common but bit later-dysphagia (swallowing bad), Dysarthia (speaking changes) and facial paresis

MG crisis-Shortness of breath-need mechanical ventilation

Question 4

Investigations for myasthenia Gravis

Answer 4

Serum ACh antibodies-high

Muscle specific tyrosine Kinase AB test-Positive test in up to 70% of AChR-seronegative generalised MG

Pulmonary studies-in MG crisis -low FVC and NIF

EMG-latency or complete blcoks

CT chest-thymus enlargement

Question 5

Management of acute mysasthenia crisis

Answer 5

always A-E -if lung support needed NIV or endotracheal tube

Plasma exchange gets a better response, in 2-3 sessions, but IVIG is usually easier to give (respond in 5days, max at 2 weeks)

can give steroids too for cover after IVIG/plasma

Question 6

Management of chronic MG

Answer 6

Depends on severity/class
Class I-III-
Cholinesterase inhibitor- Pyridostigmine oral,
and consider steroids if pyrido not enough

if cant physo- azathioprine

severe -class IV-V
Pyridostigmine + steroids

can use cyclophosphamide in severe with intolerance
Thymectomy if refractory

and IVIG/Plasma exchange maintenance therapy can be considered

Question 7

complications and long term MG

Answer 7

Pyridostigmine SE- like severe diarrhoea-give loperamide

can get cardiac complications, and ofc crisises-cant breath/swallow
high risk of aspiration pneumoniae

BUT long term usually pt have good QOL and life expectancy with treatment- not progressive disease