Myasthenia gravis is an autoimmune disorder that disrupts communication between nerve cells and muscles. It can cause muscle weakness and other symptoms depending on the affected areas.
Myasthenia gravis (MG) is a neuromuscular disorder that causes weakness in the skeletal muscles, which are the muscles your body uses for movement.
MG is an autoimmune condition, which means your immune system mistakenly attacks healthy cells in your body. This can impair communication between nerve cells and muscles, which can prevent crucial muscle contractions from occurring and lead to muscle weakness.
Researchers estimate that approximately
Learn more about the symptoms and causes of MG and what treatment options are available for this neuromuscular disorder.
MG causes weakness in the voluntary skeletal muscles, which are those you can control.
In particular, MG typically affects certain muscles in the face and throat. This can impact eye movements, facial expressions, swallowing, chewing, and speaking.
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. MG weakness typically worsens with activity and improves with rest.
People with MG may experience symptoms affecting different parts of the body, such as:
Eyes
When affecting the eyes, MG can cause:
- drooping eyelids (ptosis)
- blurry or double vision (diplopia)
- issues with eye and eyelid movement
Face
MG can affect your control of your facial muscles. This can cause:
- facial paralysis
- changes in your facial expressions
- difficulties chewing
Throat
When MG affects the muscles of the throat, you may experience:
- difficulty speaking (dysarthria)
- difficulty swallowing or chewing
- hoarse voice
- neck weakness, which can make it difficult to hold up your head
Chest
When MG affects the muscles of the chest area, you may experience:
- shortness of breath
- difficulty breathing
- weakness in the diaphragm and chest muscles
This can lead to myasthenic crisis and respiratory failure. A myasthenic crisis is life threatening and requires emergency medical treatment.
Arms and legs
MG can also affect muscles in your arms and legs, which may cause:
- fatigue
- weakness in your fingers, hands, and arms
- overall weakness in your legs
- problems walking up stairs or lifting objects
There are two main types of MG, which vary based on which antibodies are present, the muscles affected, and the type and severity of symptoms you experience.
According to the Muscular Dystrophy Association (MDA), the two types of MG are:
- Ocular MG: Weakness affects the muscles that control the movements of your eyes and eyelids.
- General MG: Weakness may affect the ocular muscles and those in other parts of the body, such as the arms, legs, and throat. This is also referred to as systemic weakness.
Healthcare professionals may further classify MG into
- Class 1: Weakness of the ocular muscles.
- Class 2: Ocular muscle weakness and mild systemic weakness.
- Class 3: Ocular muscle weakness and moderate systemic weakness.
- Class 4: Ocular muscle weakness and severe systemic weakness.
- Class 5: Severe muscular weakness that causes respiratory failure and the need for immediate medical intervention.
Classes 2, 3, and 4 may be further categorized into two subtypes, depending on which systemic muscles are affected:
- Subtype 1: More commonly affects the muscles in the limbs (arms and legs), trunk, and neck.
- Subtype 2: More commonly affects the respiratory muscles and those in the throat, ears, and nose.
In MG, irregular antibodies can interfere with nerve transmission. Problems with the thymus gland may lead to the production of these antibodies.
The causes and risk factors can include:
An autoimmune reaction
Autoimmune disorders occur when your immune system mistakenly targets healthy tissue. In MG, these antibodies, which usually target harmful substances in the body, instead damage nerve cells.
The antibodies block or attack acetylcholine receptors, which makes muscles unable to respond to acetylcholine and contract. This results in muscle weakness.
The exact cause of this autoimmune reaction is unclear. The MDA suggests specific viral or bacterial proteins may prompt the body to target acetylcholine.
A family history of autoimmune diseases may increase your risk of developing an autoimmune disorder like MG.
Thymus gland irregularities
The thymus gland typically grows until puberty and controls healthy immune functions throughout your life. After puberty, the gland shrinks in size.
In
Developing benign or cancerous thymus gland tumors is also possible, which may interfere with crucial immune cell production. The enlarged thymus gland also produces antibodies that block the action of acetylcholine.
About 75% of people with MG have thymus gland irregularities (thymic hyperplasia), and another 15% have tumors.
As a result, the thymus gland may provide your immune system with incorrect instructions, which researchers believe may lead to the destruction of immune cells that cause MG.
Age
While MG may develop at any age, the
About 10% to 15% of MG cases develop in childhood.
Flare-ups are periods when symptoms reappear or worsen, while remission is a period when symptoms settle down or disappear completely.
Some common triggers of MG flare-ups may
- having an infection
- undergoing surgery
- getting vaccinated
- experiencing stress
- being exposed to high temperatures
- being pregnant
- taking certain medications, such as aminoglycosides, fluoroquinolones, and beta-blockers
- having a chronic condition
Consider speaking with a primary care doctor if you experience unusual symptoms affecting your eyes, face, throat, or overall body movements.
You should be especially aware of possible MG symptoms if you’re an older adult with a personal or family history of autoimmune disorders.
If you have MG, you may go into remission, or a period where your symptoms may get better or go away. But since remission may be temporary, it’s important to keep track of your symptoms and talk with a doctor if they return.
A doctor typically performs a complete physical exam and takes a detailed history of your symptoms. They’ll also do a neurological exam, which 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:
Is myasthenia gravis a form of MS?
While both MG and MS can affect muscle control, they are separate diseases. They both have an autoimmune component, but the specific cause is different.
Learn more: What’s the difference between MG and MS?
There’s currently no cure for MG, but treatments can help manage symptoms and the activity of your immune system. Treatment options can include:
- medications, such as corticosteroids, immunosuppressants, and monoclonal antibodies
- thymectomy (thyroid gland removal)
- plasmapheresis (plasma exchange)
- intravenous immune globulin (IVIG)
- lifestyle changes, such as resting, managing stress, and wearing an eye patch
A healthcare professional can help develop an appropriate treatment plan tailored to your needs.
If left untreated, MG may lead to complications.
One of the most dangerous potential complications of MG is a myasthenic crisis, which causes severe muscle weakness that may lead to respiratory failure. Up to
Treatments for MG may also increase the risk of complications,
- osteoporosis
- hyperglycemia (high blood sugar)
- cataracts
- hypertension (high blood pressure)
- bone tissue death in the hip
- bacterial and fungal infections
How does myasthenia gravis affect pregnancy?
Several factors associated with MG can impact the health of the birthing person before, during, and after pregnancy, as well as the health of the baby.
For instance, hormonal fluctuations and stressors associated with pregnancy can exacerbate MG symptoms, usually within 6 months after delivering the baby. Myasthenic crisis is rare, but it’s still possible.
Researchers also estimate that 1 in 10 babies born to a person with MG may experience short-term muscle weakness that could last up to 4 weeks. This condition, known as neonatal myasthenia, occurs when the mother has MG and passes the antibodies to a fetus.
If you have MG and are concerned about the condition itself or how your treatment plan may affect pregnancy, speak with a healthcare professional. They can provide you with information, guidance, and support.
What is the life expectancy of a person with myasthenia gravis?
The life expectancy of a person with MG is
The long-term outlook for MG depends on several factors. Some people may experience only mild symptoms, while others may have more severe ones. Remission is also possible.
Early and proper treatment can help limit disease progression and improve quality of life.
Learn more: Progression, outlook, and life expectancy of MG
Myasthenia gravis is an autoimmune disorder that causes muscle loss and weakness. It most commonly affects the muscles in the eyes, face, and throat, but could also affect other muscles.
Consider speaking with a healthcare professional if you experience symptoms like drooping eyelids, general weakness, or difficulty chewing, swallowing, or speaking.
They can assess your symptoms and develop an appropriate treatment plan for you.