Myasthenia Gravis

Question 1

What is myasthenia gravis?

Answer 1

• An autoimmune condition affecting the neuromuscular junction

Question 2

What is the pathophysiology of MG?

Answer 2

• Acetylcholinesterase receptor antibodies bind to the postsynaptic AcH receptors which blocks them and prevents muscle activity
• These antibodies also activate the complement system
• Also may have anti-muscle-specific tyrosine-kinase antibodies

Question 3

How does MG present?

Answer 3

• More common in women
• Muscle weakness which worsens with use and improves with rest
• Proximal muscles of limbs and muscles of head and neck most affected
• Can also cause slurred speech, double vision, ptosis, diplopia, weakness in facial movements

Question 4

How is MG investigated?

Answer 4

• EMG
• Antibody testing
• CT thorax
• Tensilon test

Question 5

How is MG managed?

Answer 5

• Pyridostigmine is an cholinesterase inhibitor which prolongs action of ACh
• Immunosuppressants e.g prednisolone/azathioprine
• Thymectomy

Question 6

What is MG associated with?

Answer 6

• Thymoma
• Other autoimmune disorders e.g. pernicious anaemia

Question 7

How is myasthenic crisis managed?

Answer 7

• Acute worsening of symptoms often triggered by another infection e.g respiratory
• Treated with IV Immunoglobulins/Plasmapheresis
• Patients may need NIV/Mechanical ventilation