Myasthenia Gravis Treatments and Medications

No two snowflakes are alike. And no two cases of myasthenia gravis, popularly nicknamed the “snowflake disease,” are alike either. The result of an overactive immune system, myasthenia gravis causes bouts of muscle weakness and fatigue. There’s more than one cause, so symptoms and treatment can vary. Although it takes some trial and error, most people with myasthenia gravis will find treatments that dramatically, if not completely, alleviate the weakness.

What is myasthenia gravis?

Myasthenia gravis is an autoimmune disorder characterized by fluctuating muscle weakness that worsens with exertion and improves with rest. Myasthenia gravis is a rare condition. About two in every 10,000 people live with the condition. Most experience only mild or moderate symptoms.

The weakness concentrates on one or more muscle groups, typically the eyes and eyelids. However, the jaw muscles, throat, upper extremities (thighs and biceps), and, in some cases, the respiratory muscles are affected

Like other autoimmune disorders, the symptoms of myasthenia gravis are caused by an overactive immune system. The body mistakenly produces antibodies that attach to receptors at the neuromuscular junction, the place where nerves pass signals to muscle cells and stimulate muscle contractions. Nerves communicate to muscle cells through a chemical called acetylcholine, but the antibodies attack the receptors that allow these signals to get through. Weakened nerve signals cause the fluctuating weakness typical of myasthenia gravis.

Several types of autoantibodies cause myasthenia gravis, named after the receptor to which they attach: AChR antibodies, MuSK antibodies, or LRP4 antibodies. Symptoms and treatment will vary depending on the type of autoantibody causing the disease.

No cause has been discovered, but the thymus gland is often involved. Around 10%–15% of cases involve tumors of the thymus gland. This organ, located in the upper chest, produces immune cells that generate antibodies. Again, both symptoms and treatment can vary depending on the involvement of the thymus.

Finally, myasthenia gravis is classified based on the age of onset and the extent to which it affects the body, either limited to the eyes (ocular myasthenia gravis) or muscle groups elsewhere (generalized myasthenia gravis). Again, symptoms and treatment may vary.

The most serious complication of myasthenia gravis is a myasthenic crisis, a medical emergency that happens when respiratory muscles become too weak to allow for sufficient breathing. Patients will require hospitalization and may need to be put on a mechanical ventilator. Other complications include neonatal myasthenia gravis. Pregnant women with myasthenia gravis can pass antibodies to the fetus, and the baby may be born with myasthenia gravis. It is, however, only a temporary condition and resolves in a few weeks or months.

Myasthenia gravis is highly treatable. Most patients will experience significant, if not total, remission of symptoms from a variety of medications or procedures. About 10%–15% of patients with generalized myasthenia gravis, however, have severe symptoms that cannot be adequately controlled by medications, a condition called refractory myasthenia gravis.

How is myasthenia gravis diagnosed?

Myasthenia gravis is diagnosed mainly from the symptoms and patient’s history, but testing is required to determine the type and severity of the condition. Testing, final diagnosis, and treatment will primarily be managed by a neurologist.

The characteristic symptom of myasthenia gravis is weakness that comes and goes, gets worse with exertion or repetitive activities, and improves with rest.

Other typical symptoms depend on which muscle groups are affected and include:

• Blurred vision

• Double vision

• Drooping eyelid (ptosis)

• Impaired speech

• Difficulty chewing or swallowing

• Choking

• Expressionless face or drooping head

• Weak upper arms or legs

• Difficulty breathing

Because myasthenia gravis is diagnosed by the type of autoantibodies attacking the neuromuscular junctions, blood tests will be required to identify those antibodies. In patients who do not have myasthenia gravis autoantibodies, other tests may be required:

• Electrophysiological tests such as repetitive nerve stimulation (RNS) or electromyography (EMG) can diagnose delays in nerve interactions with muscles

• Edrophonium tests are used when electrophysiologic tests can’t be performed, for instance, when the weakness is limited to the eyes. Edrophonium is a drug that rapidly improves the ability of nerves to communicate with muscles. The neurologist will monitor the patient for improvements in double vision or droopy eyelids

• If none of these tests can be administered, an ice pack test works in much the same way as an edrophonium test. Cold typically improves nerve conduction in myasthenia gravis, so an ice pack is placed over the eye for two to five minutes to see if it improves double vision or drooping eyelid

A CT scan of the chest will be performed if the doctor suspects cancer of the thymus gland (thymoma).

Myasthenia gravis treatment options

Myasthenia gravis is an autoimmune disorder that cannot be cured. The goal of long-term treatment is to achieve a partial or total remission of symptoms with the least amount of unwanted side effects. This is achieved by drugs that increase the ability of nerves to pass signals to the muscles, drugs that suppress the immune system, or surgery to remove an overactive thymus. Emergency treatment for a myasthenic crisis involves plasma exchange or intravenous immunoglobulins to rapidly remove autoantibodies and relieve symptoms.

Medications

The first-line treatment for myasthenia gravis is to increase the ability of nerves to pass signals to the muscles. Acetylcholinesterase inhibitors allow the neurotransmitter acetylcholine to linger at the junctions between nerves and muscles, giving the nerves more time to get signals through to the muscles. If these drugs do not control symptoms, patients will be put on drugs that dial back or suppress the immune system.

Surgery

The thymus, a small organ in the chest between your collar bones, produces immune system cells (lymphocytes) that fight infections and make antibodies such as the ones that cause myasthenia gravis. Problems with the thymus, such as cancer (thymoma) or overactive growth (hyperplasia), can produce an excess of immune cells and myasthenia gravis antibodies. In these cases, a thoracic surgeon will remove the thymus, a procedure known as thymectomy. This often produces complete and permanent symptom remission, but the effects may take months or years after the surgery to become noticeable.

Intravenous immunoglobulin (IVIg)

For a myasthenic crisis, surgical operations, or severe myasthenia gravis, an intravenous infusion of human antibodies (immunoglobulins) can rapidly reduce symptoms. These are essentially antibodies to the autoantibodies that cause myasthenia gravis. They attach to the harmful autoantibodies, and the immune system then clears them from the bloodstream. A single infusion may be necessary for a medical emergency or before an operation, but patients with severe myasthenia gravis will require regular infusions.

Plasmapheresis (PLEX)

Plasmapheresis “cleans” antibodies from the bloodstream. Also called plasma exchange (PLEX), a needle in one arm removes blood from the body. The blood is sent to a device that separates the blood cells from the plasma, the mix of water and proteins, including antibodies. The red blood cells are combined with new plasma without harmful antibodies, and the blood is returned to the patient. Plasmapheresis is usually used to treat a myasthenic crisis, but patients with uncontrolled symptoms may require regular plasma exchange.

Rehabilitation

Rehabilitation is a critical and often overlooked component of myasthenia gravis treatment. The goal is to relieve symptoms, improve daily function, and increase the quality of life. Physical therapy, strength training, respiratory therapy, occupational therapy, speech therapy, or vocational counseling can help bring back or maintain the ability to carry on everyday tasks.

Myasthenia gravis medications

First-line drugs for myasthenia gravis are intended to reduce symptoms. If they don’t work, however, second-line treatment focuses on suppressing the immune system. By suppressing the immune system, these medications attack the root of the problem: an overactive immune system.

Acetylcholinesterase inhibitors

Acetylcholinesterase inhibitors are the first-line treatment for myasthenia gravis. They relieve MG symptoms by increasing the amount of acetylcholine at the junctions between nerves and muscles. This increases muscle strength and reflex times but does not address the underlying autoimmune condition. The only acetylcholinesterase inhibitor approved for myasthenia gravis is pyridostigmine, but similar drugs may be prescribed if pyridostigmine does not sufficiently work. Symptoms noticeably improve in about 15 minutes and will last for three to four hours. However, their effectiveness depends on the type of autoantibodies responsible, so some patients may need higher doses.

Corticosteroids

When acetylcholinesterase inhibitors do not adequately relieve weakness and fatigue, the second-line drugs for myasthenia gravis are corticosteroids. Normally used to reduce swelling, corticosteroids also suppress the immune system and decrease the number of autoantibodies generated by immune cells. Oral or injected prednisone, prednisolone, or methylprednisolone are given in high doses that are steadily decreased to a maintenance dose over time.

Immune suppressants

Immunosuppressants are the next step if corticosteroids are not effective or their side effects are intolerable. Azathioprine, mycophenolate mofetil, methotrexate, cyclophosphamide, cyclosporine, and tacrolimus all work in different ways to either reduce the number of immune cells (lymphocytes) or prevent them from producing autoantibodies.

Monoclonal antibodies

Monoclonal antibodies are synthetic antibodies that attach to the surface of lymphocytes (immune cells). Once attached, they either stop lymphocytes from growing or block chemical activities at the neuromuscular junction that provoke the autoimmune processes (Soliris). Soliris (eculizumab) is well-studied and the only drug other than pyridostigmine and methotrexate that is FDA-approved for treating myasthenia gravis. Rituxan (rituximab) is either used alone or with other immune suppressants. Both significantly reduce symptoms over the long-term but are reserved for more severe cases that have not responded to other drugs.

What is the best medication for myasthenia gravis?

Myasthenia gravis is nicknamed the “snowflake disease” because it varies so much from person to person. Successful treatments will also vary between people, so there is no “best” medication for myasthenia gravis. The goal is to find a medication that provides dramatic or complete symptom relief with the fewest side effects. It may take a few tries to discover just the right medication that fits the patient’s situation.

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