Myasthenia gravis
Jump to navigation
Jump to search
Clinic
- MG is an autoimmune disease characterized by muscle weakness and fatigue
- It results from antibodies that block or destroy nicotinic acetylcholine receptors at neuro-muscular junction.
- This prevents nerve impulses from triggering muscle contractions.
- The Initial / Main symptom is painless weakness of specific muscles, not fatigue.
- The muscle weakness becomes progressively worse during periods of physical activity and amel by rest.
- Typically, the weakness and fatigue agg toward the end of the day.
Sign / Symptoms
MG generally starts with ocular weakness then progress to weakness in the extremities. (Opposed to ascending paralysis of GBS)
- Ptosis due to weakness of levator palpebrae superioris
- Diplopia due to weakness of the extraocular muscles
- Weakness of mastication
- Hanging jaw sign and as a snarling expression when attempting to smile.
- Difficulty in holding the head upright
- Dysarthria and Hypophonia (Slow / Slurred / Nasal Speech)
- Dyspnea and limb movements
- Dysphagia
Pathology
- MG is an autoimmune synaptopathy.
- The antibodies attack the nicotinic acetylcholine receptor, or a related protein called MuSK, a muscle-specific kinase.
- Other, less frequent antibodies are found against LRP4, agrin, and titin proteins.
- Thymus gland cells form part of the body's immune system. In MG, Thymus is large and abnormal. It sometimes contains clusters of immune cells that indicate lymphoid hyperplasia, and the thymus gland may give wrong instructions to immune cells.
Entity / Miasms
| PLV | CJD | FFI | MTB | |
|---|---|---|---|---|
| Diplopia / Ophtalmoplegia | +++ | +++ | +++ | +++ |
| Dysphagia | +++ | +++ | +++ | +++ |
| Soft palate paralysis | +++ | |||
| Dysartheria | +++ | +++ | ||
| Massification difficult | ||||
| Face, palsy | +++ | +++ |
Note that MG paralysis is symmetric so face palsy is used instead of Bel's palsy.
Related disease
- Guillain-Barré syndrome
- Miller Fisher syndrome (MFS) is an immune-mediated neuropathy that involves the triad of symptoms of acute ophthalmoplegia, ataxia and areflexia, also with positive GQ1b antibody.