Myasthenia gravis is a neuromuscular autoimmune disease that manifests as variable muscle weakness, primarily affecting muscles under voluntary control.
The muscles commonly affected include those that control eye movement, eyelid movement, chewing, swallowing, coughing, and facial expression.
It is more common in young women and older men. Women usually develop the disease before age 30, while men typically develop it after age 50. It is rare in children.
The main characteristic of myasthenia gravis is a progressive loss of muscle strength with use, until the muscle becomes completely fatigued. After a period of rest, the muscle regains all or part of its strength.
The primary symptoms are due to weakness of voluntary muscles and include:
Muscles that control breathing and movement of the arms and legs may also be affected. Weakness in the muscles required for breathing can lead to respiratory difficulties and impair the ability to cough.
The muscles involved in myasthenia gravis vary greatly between patients. If the weakness affects only the muscles controlling eye and eyelid movement, it is called ocular myasthenia and is considered the mildest form of the disease.
The most severe form involves the muscles needed for breathing. Most patients fall somewhere between these two extremes.
Myasthenia gravis is caused by a defect in the transmission of nerve impulses to the muscles at the junction between nerve fibers and muscle fibers.
This occurs because the body produces autoantibodies—meaning it attacks its own tissues as if they were foreign agents. In myasthenia gravis, these autoantibodies destroy or block receptors at the neuromuscular junction.
The exact reason why the body produces these autoantibodies is still unknown.
There is also an association between myasthenia gravis and tumors of the thymus gland. The thymus is an immune system gland located in the chest that decreases in size throughout life.
Some patients may experience worsening of symptoms after a viral infection.
Myasthenia gravis is not directly inherited, although it can occasionally occur in more than one family member. Family members may have other autoimmune diseases, such as lupus erythematosus.
It is not contagious.
The diagnosis of myasthenia gravis should be made by an experienced neurologist, considering several factors:
There are numerous options for treating myasthenia gravis. There is no one-size-fits-all treatment, and patients may respond differently to various therapies.
Some treatments may be more suitable depending on the patient’s age, the presence of other conditions, or potential side effects. Often, a combination of treatments is optimal.
When muscle weakness is severe and involves the respiratory muscles, hospitalization is usually necessary.
The main treatments for myasthenia gravis include:
Some medications can worsen myasthenia gravis. Always consult your doctor before starting or stopping any medication.
Myasthenia gravis varies greatly from person to person. Some individuals experience rapid progression of paralysis affecting breathing, while others have only mild symptoms for many years, with or without worsening.
The disease may improve significantly for months or years, only to suddenly relapse, often triggered by an infection.
The highest risk of death occurs during the first year after diagnosis, with a mortality rate just under 5%. The risk then stabilizes but increases again between the fourth and seventh years after symptom onset.
The leading cause of death in myasthenia gravis is aspiration pneumonia, which is preventable with proper treatment in most patients.
Special care is required when a person with myasthenia gravis undergoes anesthesia for surgery.
Pregnant women with the disease may face delivery complications and worsening symptoms postpartum. Up to 20% of babies born to these women may show symptoms such as weak sucking and a weak cry for up to two months; however, severe disease in newborns is rare.
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