Myasthenia gravis is a chronic autoimmune neuromuscular disease characterized by weakness of the skeletal muscles. Common symptoms include weakness of the muscles that control the eye and eyelid, facial expressions, chewing, talking, and swallowing. Weakness tends to increase during periods of activity and improve after periods of rest. The condition results from a defect in the transmission of nerve impulses to muscles, which is due to the presence of antibodies against acetylcholine. The exact reason this occurs is not known. Some cases have been linked to tumors in the thymus gland. Researchers believe that variations in certain genes may increase a person’s risk to develop myasthenia gravis, but other factors likely also play a role. There is no cure for myasthenia gravis at this time, but treatment can significantly improve muscle weakness. Some cases may go into remission temporarily, and muscle weakness may disappear so that medications can be discontinued.
Pathophysiology and Epidemiology
The exact cause of myasthenia gravis is unknown, but it is likely that a number of factors contribute to the risk of developing this disorder.
Myasthenia gravis is not directly inherited, nor is it contagious. However, a genetic predisposition to autoimmune disease can run in families. Occasionally, myasthenia gravis may occur in more than one member of the same family.
Signs and Symptoms
Common symptoms of myasthenia gravis include:
- Abnormality of the thymus
- Acetylcholine receptor antibody positivity
- Bulbar palsy
- Muscle specific kinase antibody positivity
- Single fiber EMG abnormality
Management and Treatment
The following have been approved by the FDA as orphan drugs for myasthenia gravis:
- Eculizumab (Brand name: Soliris)
For a full list of clinical trials relating to myasthenia gravis, go here.