Welcome to the Rare Classroom, a new series from Patient Worthy. Rare Classroom is designed for the curious reader who wants to get informed on some of the rarest, most mysterious diseases and conditions. There are thousands of rare diseases out there, but only a very small number of them have viable treatments and regularly make the news. This series is an opportunity to learn the basics about some of the diseases that almost no one hears much about or that we otherwise haven’t been able to report on very often.
Eyes front and ears open. Class is now in session.
In recognition of Myasthenia Gravis Awareness Month, which is recognized in June, we will be re-running this story about myasthenia gravis, which was originally published in March 2021.
The rare disease that we will be learning about today is:
Myasthenia Gravis
What is Myasthenia Gravis?
- Myasthenia gravis is a chronic autoimmune neuromuscular disease that causes weakness in the skeletal muscles, which are responsible for breathing and moving parts of the body, including the arms and legs. The name myasthenia gravis, which is Latin and Greek in origin, means “grave, or serious, muscle weakness.”
- Myasthenia gravis is caused by an error in the transmission of nerve impulses to muscles. It occurs when normal communication between the nerve and muscle is interrupted at the neuromuscular junction—the place where nerve cells connect with the muscles they control.
- Myasthenia gravis affects about 20 per 100,000 people worldwide. The prevalence has been increasing in recent decades, which likely results from earlier diagnosis and better treatments leading to longer lifespans for affected individuals.
- There is no cure for myasthenia gravis, but it is treated with medications and sometimes surgery.
- Myasthenia gravis affects both males and females and occurs across all racial and ethnic groups.
How Do You Get It?
- Myasthenia gravis is caused by an error in the transmission of nerve impulses to muscles.
- It occurs when normal communication between the nerve and muscle is interrupted at the neuromuscular junction—the place where nerve cells connect with the muscles they control.
- Neurotransmitters are chemicals that neurons, or brain cells, use to communicate information.
- Normally when electrical signals or impulses travel down a motor nerve, the nerve endings release a neurotransmitter called acetylcholine.
- Acetylcholine travels from the nerve ending and binds to acetylcholine receptors on the muscle. The binding of acetylcholine to its receptor activates the muscle and causes a muscle contraction.
- It most commonly impacts young adult females (under 40) and older males (over 60), but it can occur at any age, including childhood. Myasthenia gravis is not inherited nor is it contagious. Occasionally, the disease may occur in more than one member of the same family.
- Although myasthenia gravis is rarely seen in infants, the fetus may acquire antibodies from a mother affected with myasthenia gravis—a condition called neonatal myasthenia.
- In myasthenia gravis, antibodies (immune proteins) block, alter, or destroy the receptors for acetylcholine at the neuromuscular junction, which prevents the muscle from contracting.
- In most individuals with myasthenia gravis, this is caused by antibodies to the acetylcholine receptor itself. However, antibodies to other proteins, such as MuSK (Muscle-Specific Kinase) protein, can also lead to impaired transmission at the neuromuscular junction.
- These antibodies are produced by the body’s own immune system. Myasthenia gravis is an autoimmune disease because the immune system—which normally protects the body from foreign organisms—mistakenly attacks itself.
What Are The Symptoms?
- Although myasthenia gravis may affect any skeletal muscle, muscles that control eye and eyelid movement, facial expression, and swallowing are most frequently affected.
- The onset of the disorder may be sudden, and symptoms often are not immediately recognized as myasthenia gravis.
- In most cases, the first noticeable symptom is weakness of the eye muscles. In others, difficulty swallowing, and slurred speech may be the first signs.
- The degree of muscle weakness involved in myasthenia gravis varies greatly among individuals, ranging from a localized form limited to eye muscles (ocular myasthenia), to a severe or generalized form in which many muscles—sometimes including those that control breathing—are affected.
- Common symptoms include:
- drooping of one or both eyelids (ptosis)
- blurred or double vision (diplopia) due to weakness of the muscles that control eye movements
- a change in facial expression
- difficulty swallowing/chewing
- shortness of breath
- impaired speech (dysarthria)
- weakness in the arms, hands, fingers, legs, and neck.
- Myasthenic crisis
- A myasthenic crisis is a medical emergency that occurs when the muscles that control breathing weaken to the point where individuals require a ventilator to help them breathe.
- Approximately 15 to 20 percent of people with myasthenia gravis experience at least one myasthenic crisis.
- This condition usually requires immediate medical attention and may be triggered by infection, stress, surgery, or an adverse reaction to medication.
- However, up to one-half of people may have no obvious cause for their myasthenic crisis. Certain medications have been shown to cause myasthenia gravis.
- However, sometimes these medications may still be used if it is more important to treat an underlying condition.
How Is It Treated?
- There is no cure for MG.
- Today, myasthenia gravis can generally be controlled. There are several therapies available to help reduce and improve muscle weakness
- Health Care team-doctors trained in nervous system conditions (neurologists), chest surgeons (thoracic surgeons) and other specialists have extensive experience in diagnosing and treating myasthenia gravis.
- Treatments for myasthenia gravis include:
- Cholinesterase inhibitors. Medications such as pyridostigmine (Mestinon, Regonal) and neostigmine (Bloxiverz) enhance communication between nerves and muscles. These medications aren’t a cure, but they can improve muscle contraction and muscle strength in some people.
- Possible side effects include gastrointestinal upset, diarrhea, nausea, and excessive salivation and sweating.
- Corticosteroids. Corticosteroids such as prednisone inhibit the immune system, limiting antibody production. Prolonged use of corticosteroids, however, can lead to serious side effects, such as bone thinning, weight gain, diabetes and increased risk of some infections.
- Immunosuppressants. Your doctor might also prescribe other medications that alter your immune system, such as azathioprine (Azasan,, Imuran) mycophenolate mofetil (Cellcept), cyclosporine (Sandimmune) methotrexate (Trexall) or tacrolimus (Astrograf XL, Prograf). These drugs, which can take months to work, might be used with corticosteroids.
- Side effects of immunosuppressants, such as increased risk of infection and liver or kidney damage, can be serious.
- Intravenous therapy
- The following therapies are usually used in the short term to treat a sudden worsening of symptoms or before surgery or other therapies.
- Plasmapheresis. This procedure uses a filtering process similar to dialysis. Your blood is routed through a machine that removes the antibodies that block transmission of signals from your nerve endings to your muscles’ receptor sites. However, the good effects usually last only a few weeks, and repeated procedures can lead to difficulty accessing veins for the treatment.
- Risks associated with plasmapheresis include a drop in blood pressure, bleeding, heart rhythm problems or muscle cramps. Some people develop an allergic reaction to the solutions used to replace the plasma.
- Intravenous immunoglobulin (IVIg). This therapy provides your body with normal antibodies, which alters your immune system response. Benefits are usually seen in less than a week and can last three to six weeks.
- Side effects, which usually are mild, can include chills, dizziness, headaches and fluid retention.
- Monoclonal antibody. Rituximab (Rituxan) and the more recently approved eculizumab (Soliris) are intravenous medications used in some cases of myasthenia gravis. These drugs are usually used for people who don’t respond to other treatments. They can have serious side effects.
- Surgery
- Some people with myasthenia gravis have a tumor in their thymus gland. If you have a tumor, called a thymoma, doctors will surgically remove your thymus gland (thymectomy).
- Even if you don’t have a tumor in the thymus gland, removing the gland might improve your myasthenia gravis symptoms. However, the benefits of thymectomy can take years to develop.
- A thymectomy can be performed as an open surgery or as a minimally invasive surgery. In open surgery, your surgeon splits the central breastbone (sternum) to open your chest and remove your thymus gland.
- Cholinesterase inhibitors. Medications such as pyridostigmine (Mestinon, Regonal) and neostigmine (Bloxiverz) enhance communication between nerves and muscles. These medications aren’t a cure, but they can improve muscle contraction and muscle strength in some people.
Where Can I Learn More???
- Learn more about this disease from the Myasthenia Gravis Foundation of America.
- Check out our cornerstone on this disease here.
