Myasthenia Gravis is a rare condition resulting in the rapid weakness of any group of muscles that are under voluntary control. It is caused by a communication breakdown between the nerves and the muscles, usually due to the abnormal production of antibodies, and it tends to worsen as the muscle is used more frequently. While weakness will usually improve with a bit of rest, the condition itself will progress over a period of time, with symptoms being at their worst a few years after the disease first appears.
Myasthenia gravis can impact any group of muscles, but some are more commonly affected than others. Most cases see symptoms appearing in the muscles of the eyes, face, throat, limbs, and neck. If left untreated, the disorder can lead to life-threatening complications. Thymus tumors, myasthenic crisis, overactive or underactive thyroid, and autoimmune conditions have all been seen in patients with myasthenia gravis.
Exact symptoms will vary, as will severity and location.
Myasthenia gravis is an autoimmune disorder that is caused by an immune system reaction that destroys the receptor sites in the muscles that receive neurotransmitters. When nerves fire, they release a substance into the muscles called acetylcholine. This substance triggers movement in the muscles. In patients with myasthenia gravis, these receptor sites are destroyed or damaged by a malfunction of the immune system which views them as a foreign substance.
In some patients, a different neurotransmitter is blocked. Tyrosine kinase helps the nerves and muscles work together properly. When this neurotransmitter is destroyed by the immune system, myasthenia gravis is the result.
Another cause of myasthenia gravis in some patients is a benign tumor located in the thymus gland. This gland helps to regulate the body’s immune system. The tumor causes the immune system to malfunction and destroy the neurotransmitter receptor sites.
In a few very rare cases, myasthenia gravis is present from birth. It is not believed that it is directly inherited, but more research must be done to determine this.
There are a few drugs known to cause myasthenia gravis. Beta blockers used for heart problems, phenytoin used to control seizures and drugs used to treat malaria are the most common offending drugs.
Symptoms of myasthenia gravis can be treated with a variety of therapies, either in combination or alone. Doctors will determine which therapies have the best chance of success based on the patient’s age, disease severity, if other medical conditions are present, and which muscles are being affected.
Oral medications like immunosuppressants and corticosteroids inhibit the immune system and reduce antibody production, while cholinesterase inhibitors work to improve communication between the muscles and nerves. Other drugs can be given intravenously to remove excess antibodies, provide normal antibodies, or deplete white blood cells. Patients may require surgery if the condition has led to a thymus tumor or to remove the thymus gland to improve symptoms.
There is no known way to prevent most cases of myasthenia gravis. In those few cases that are caused by taking certain medications, myasthenia gravis will be prevented from recurring if the patient never takes the drug in question again.
As there is no direct genetic link known to cause myasthenia gravis, genetic testing of parents would be of little use.
There are a few diseases whose sufferers are more susceptible to myasthenia gravis. People with hypothyroidism, rheumatoid arthritis and lupus sometimes develop myasthenia gravis. Those with these conditions should report any muscle weakness symptoms to their doctor.