myasthenia graves Flashcards
1
Q
what is myasthenia graves
A
an autoimmune condition that causes muscle weakness that gets progressively worse with activity and improves with rest
2
Q
pathophysiology of MG
A
- initiating event
- self reactive B cells activated by nAchR subunits in secondary lymphoid tissue
- plasma cell differentiation
- secretion of IgG antibodies that bind to nAchRs
- decreased stimulation of nAchRs by endogenous ACh
- decreased muscle contraction
3
Q
why does muscle contraction return to normal in MG patients after a period of rest?
A
Antibody-bound receptors are transiently internalised into muscle cells by endocytosis
The bound antibody is released in acidic environment of the endo-lysosomal compartment
Early on in the disease, nAchRs are returned to the cell membrane, ready and able to bind to endogenous Ach.
Long term: internalised nAchRs are degraded leading to permanent muscle weakness
4
Q
symptoms of MG
A
- double vision
- drooping of eyelids
- weak facial movements
- difficulty swallowing
- fatigue in jaw when chewing
- slurred speech
- progressive weakness with repetitive movements
4
Q
symptoms of MG
A
- double vision
- drooping of eyelids
- weak facial movements
- difficulty swallowing
- fatigue in jaw when chewing
- slurred speech
- progressive weakness with repetitive movements
5
Q
investigations for MG
A
- lab tests - presence of autoreactive antibodies in serum
- scan thymus gland for thymoma
- repetitive nerve stimulation -reduced response
- edrophonium test
6
Q
treatment of MG
A
- increase neurotransmission
- surgery if needed
- immunosuppressants
7
Q
what do you do in an MG crisis
A
- oxygen and/or ventilator
- plasmapheresis
- IVIG
