Disease Information

What is Myasthenia Gravis?

Myasthenia gravis (MG) is a neuromuscular disorder that causes weakness in the skeletal muscles, which are the muscles your body uses for movement. MG happens when communication between nerve cells and muscles becomes impaired. This impairment prevents crucial muscle contractions from occurring, causing muscle weakness.

According to the Myasthenia Gravis Foundation of America, more than 70,000 people in the United States have received a diagnosis of myasthenia gravis. Learn more about the symptoms and causes of MG and what treatment options are available for this neuromuscular disorder.

Symptoms of Myasthenia Gravis

The main symptom of MG is weakness in the voluntary skeletal muscles, which are muscles under your control.

Muscles typically fail to contract if they can’t respond to nerve impulses. When communication between nerve and muscle is blocked, weakness results. The degree of weakness can change daily, and symptom severity typically increases over time if left untreated.

Symptoms of myasthenia gravis may include:

• Muscle weakness in your arms, hands, fingers,
• legs and neck
• Fatigue
• Weakening of eye muscles
• Slurred speech
• Difficulty in swallowing
• Droopy eyelids (ptosis)
• Blurry or double vision
• Limited facial expressions
• Difficulty speaking, swallowing or chewing
• Trouble walking

Initial symptoms of myasthenia gravis happen suddenly. Your muscles usually get weaker when you’re active. Muscle strength returns when you rest. The intensity of muscle weakness often changes from day to day. Most people feel strongest at the start of the day and weakest at the end of the day.

Causes of Myasthenia Gravis

Myasthenia gravis (autoimmune type) happens when your body’s immune system mistakenly attacks itself. Researchers aren’t sure why this happens. Studies suggest that certain immune system cells in your thymus gland have trouble identifying what’s a threat to your body (like bacteria or viruses) versus healthy components.

A genetic change causes congenital myasthenia. Antibodies passed from a birthing parent to a fetus during pregnancy cause neonatal myasthenia.

How Does Myasthenia Gravis Affect My Body?

Myasthenia gravis affects communication between nerves and muscles.

When your immune system is working as expected, nerves and muscles work together. It’s similar to a baseball game:

• Nerves (the pitcher) send signals to muscles (the catcher) across a synapse (field) called the neuromuscular junction. To communicate, nerves release a molecule called acetylcholine (the baseball).
• Muscles have sites called acetylcholine receptors (the catcher’s glove). The acetylcholine binds to its receptors in the muscle tissue, like a ball landing in a glove.
• When the acetylcholine binds to its receptor, it triggers the muscle fiber to contract.
  Nerves signal muscles effortlessly, like one ball player catching a ball and throwing it to a teammate.
• If you have myasthenia gravis, antibodies destroy the receptor sites, blocking nerve-muscle communication. The “catcher” can’t catch the ball, and communication becomes sluggish or doesn’t work at all.

Is Myasthenia Gravis Inherited?

It’s rare to inherit autoimmune myasthenia gravis. You can inherit congenital myasthenia or neonatal myasthenia. Types where inheritance happens usually occur in an autosomal recessive pattern where you need two genes, one from each biological parent, to experience symptoms.

How do Doctors Diagnose Myasthenia Gravis?

A doctor typically performs a complete physical exam and takes a detailed history of your symptoms. They’ll also do a neurological exam.

This may consist of:

• Checking your reflexes
• Looking for muscle weakness
• Checking for muscle tone
• Seeing how your eyes move
• Testing sensation in different areas of your body
• Testing motor functions, like touching your finger to your nose

Other tests that can help diagnose the condition include:

• Repetitive nerve stimulation and single-fiber EMG tests
• Blood testing for antibodies associated with MG
  an edrophonium (Tensilon) test
• Imaging using CT scans or MRI to rule out a tumor

What are the Complications of Myasthenia Gravis?

Weakness and fatigue from myasthenia gravis can keep you from participating in activities you enjoy. This may lead to stress and depression. However, studies also show that most people with myasthenia gravis can tolerate light activities and exercises on a routine basis.

Up to 1 in 5 people with myasthenia gravis experience a myasthenic crisis or severe respiratory muscle weakness. You may need a respirator or other treatments to help you breathe. This is a life-threatening medical emergency. An estimated 20% of people with myasthenia gravis experience at least one myasthenic crisis in their lifetime.

Lifestyle Changes

Some things you can do at home may help alleviate symptoms of MG include:

• Get plenty of rest to help minimize muscle weakness.
• If you’re bothered by double vision, talk with a doctor about wearing an eye patch.
• Avoid stress and heat exposure since both can worsen symptoms.
• If a doctor recommends it, regular low impact exercise may help strengthen your muscles.

You may also go into remission, during which treatment is not necessary.

Some medications and supplements can make MG symptoms worse. Before taking any new medication, check with a doctor or pharmacist to ensure it does not interact with your other medications.

What’s the Outlook for Myasthenia Gravis?

Myasthenia gravis is a treatable condition. Symptoms range from mild to severe. Symptoms tend to reach their peak in severity within one to three years of initial diagnosis.

Most people with the condition live full and active lives with treatment.

Some cases go into remission. Remission is when your symptoms stop for a period of time. This could be temporary or permanent. If remission happens, your healthcare provider may adjust your treatment plan.

What is the Life Expectancy of a Person with Myasthenia Gravis?

Most people have a normal life expectancy with myasthenia gravis. Life-threatening outcomes may happen during a myasthenic crisis, which affects your ability to breathe.

How is Myasthenia Gravis Treated?

There’s no cure for myasthenia gravis. But effective treatment is available to help manage your symptoms. Treatments may include:

• Medications: Certain medications can reduce your symptoms.
• Monoclonal Antibodies: You’ll receive intravenous (IV) or subcutaneous (SQ) infusions of biologically engineered proteins. These proteins suppress an overactive immune system.
• Plasma Exchange (plasmapheresis): An IV connected to a machine removes harmful antibodies from your blood plasma and replaces them with donor plasma or a plasma solution.
• IV or SQ Immunoglobulin (IVIG or SCIG): You’ll receive IV infusions of donor antibodies over two to five days. IVIG or SCIG can treat myasthenia crisis, as well as generalized myasthenia gravis.
• Surgery: A thymectomy is surgery to remove the thymus gland.

Reference:

https://www.healthline.com/health/myasthenia-gravis

https://my.clevelandclinic.org/health/diseases/17252-myasthenia-gravis-mg