Myaesthenia Gravis Flashcards
What is myaesthenia Gravis?
Ai disorder of neuromuscular junction transmission
What antibodies are present in MG?
ABs to acetylcholine receptor protein are present and these form complexes which cause destruction of ACh receptors which blocks binding of Ach to the post synaptic membrane
When do symptoms start for MG?
When ACh receptors are reduced to 30% of normal
What is their a strong association between with Myaesthenia gravis?
Thymic abnormalities and thymic hyperplasia
(Found in 70% of MG patients under the age of 40)
Also an association between MG and other AI diseases
Peaks of occurrence for MG in gender and age?
3rd decade females
6th-7th decade males
What gender is more likely to have MG?
Females
Presentation of MG?
- Weakness that worsens throughout the day
- Extraocular, facial and bulbar weakness
- Drooping eye lids
- Usually eye movement abnormalities and patient may complain of double vision that comes and goes
Investigations for MG?
-Check for +ve serum anti-AchR and anti-MuSK antibodies
- Repetitive nerve stimulation tests show decrements in evoked muscle action potential during repetitive stimulation
- Imaging to look for thymic abnormalities
Acute management of MG?
- Lifelong illness
- Acetylcholinesterase inhibitors, IV immunoglobin
Treatment given at initial diagnosis?
Steroids, then slowly moved to steroid sparing agents (azathioprine and mycophenolate)
What drugs should be avoided in MG?
Gentamicin
What is a myasthenic crisis?
- Sudden worsening of symptoms
- Often involves acute respiratory failure due to weakness of the muscles of respiration
- Characterised by FVC below 1L, -ve inspiratory force (NIF) of 2ocm H20 and need for ventilatory support
Main treatments for myasthenic crisis?
IV Immunoglobin
Plasma exchange
