Myasthenia Gravis Flashcards
Pathophysiology
Autoimmune blockage and destruction of the acetylcholine receptor
Other antibodies in myasthenia gravis
Muscle - specific kinase (MuSK)
Low density lipoprotein receptor related protein 4 (LRP4)
Ineffective creation and organisation of acetylcholine receptors
Age of onset for myasthenia gravis
Women - under 40 yo
Men - over 60 yo
Condition associated with myasthenia gravis
Thymoma (tumours of the thymus gland)
Presentation of myasthenia gravis
Weakness that gets worse with muscle use and improves with rest
Minimal in the morning and worse at night
Affect proximal muscles and small muscles of the head:
- diplopia - extraocular muscles
- ptosis
- weakness in facial movements
- fatigue in jaw when chewing
- slurred speech - dysarthria
- progressive weakness with repetitive movements
Myasthenia Gravis examination
Repeated blinking - exacerbate ptosis
Prolonged upward gazing - diplopia
Repeated abduction of 1 arm - unilateral weakness when compared to both sides
Check thymectomy scar
Test FVC
How to diagnose myasthenia gravis
Antibody testing:
- acetylcholine receptor antibodies
- Muscle specific kinase
- low density lipoprotein receptor related protein 4
CT or MRI of the thymus gland - thymoma
Edrophonium test
Edrophonium test
IV edrophonium chloride (neostigmine) inhibits acetylcholinesterase therefore temporary relieves weakness
Treatment of myasthenia gravis
Reversible acetylcholinesterase inhibitor - pyridostigmine or neostigmine
Immunosuppression- Prednisolone or azathioprine
Thymectomy
Monoclonal antibodies - rituximab, eculizimab (complement C5)
Myasthenia crisis
Life threatening, acute worsening of symptoms
Triggered by another illness like a respiratory tract infection
Can lead to respiratory failure due to weak muscles of respiration
Myasthenia gravis crisis treatment
Require non invasive ventilation - BiPAP or full intubation and ventilation
IV immunoglobulins and plasma exchange
