Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction caused by antibodies that attack components of the postsynaptic membrane, impair neuromuscular transmission, and lead to weakness and fatigue of skeletal (voluntary) muscles. This can be generalised or localised to certain muscle groups, and involvement of the bulbar and respiratory muscles can be life threatening.
The exact cause of myasthenia gravis is unknown. In some cases, it is linked to tumours of the thymus.
Myasthenia gravis can affect people at any age. It is most common in young women and older men. Current estimates place the prevalence at a high value of about 20 per 100,000.
Myasthenia gravis can affect people at any age. It is most common in young women and older men. Current estimates place the prevalence at a high value of about 20 per 100,000.
Myasthenia gravis can be classified according to the type, age of onset, antibody specificity and thymus histology.
1. course type:
- ocular (in approximately 15-20% of MG patients)
- oropharyngeal or generalized
2. age of onset:
- start before puberty
- early onset before the age of 50 years
- late onset after the age of 50 years
3. antibody specificity:
- anti-AChR
- anti-muscle-specific receptor tyrosine kinase (MuSK)
- anti-low-density lipoprotein receptor-related protein 4 (LRP4)
- seronegative MG
4. pathology of the thymus
- normal/atrophic thymus pathology
- thymitis
- paraneoplastic occurrence associated with thymoma