Symptoms of myasthenia gravis

Last updated Nov. 19, 2024, by Lindsey Shapiro, PhD
Fact-checked by Joana Carvalho, PhD

Muscle weakness and fatigue are the hallmark symptoms of myasthenia gravis (MG), an autoimmune disorder in which self-reactive antibodies mistakenly attack proteins in the body necessary for the communication between nerve and muscle cells.

MG symptoms may come and go. For many patients, symptoms get worse with repetitive activity and ease with rest, but they can also worsen with other disease triggers.

MG can be diagnosed at any age, but symptoms typically start manifesting in adulthood. Men often develop MG symptoms later in life — after the age of 60 — whereas symptoms usually emerge in younger women, specifically those younger than 40.

While MG can affect any muscles in the body, some specific muscle groups are more commonly affected than others. There is no cure for MG, but certain treatments can help manage its symptoms.

Eyes and eyelids

For most MG patients, the earliest symptoms involve the muscles that control eye and eyelid movements. Common early signs of MG related to the loss of muscle strength in those muscles include:

• partial paralysis of eye movements
• upper eyelid droopiness, or droopy eyes, called ptosis
• double vision, known as diplopia
• difficulty focusing.

These symptoms typically get worse with activity and improve with rest, and thus are usually more severe at the end of the day.

There are a few possible explanations for why eye muscles are most commonly affected in MG. For one, eye muscles have fewer acetylcholine receptors, which are the target of the self-reactive antibodies that drive MG in about 85% of patients.

Acetylcholine receptors are found at the neuromuscular junction, the point of contact between nerve and muscle cells, and are essential for nerve-muscle communication. Because there are fewer of those receptors in eye muscle tissue, their damage or loss may have more profound effects.

Another possible explanation lies in the fact that eye muscles contract more than other muscles in the body, making them more susceptible to fatigue.

In about 20% of MG patients, symptoms are limited to eye and eyelid muscles for the entire course of the disease. This specific form of the disease is known as ocular MG. For other patients, muscle weakness spreads to other parts of the body, giving rise to a form of the disease known as generalized myasthenia gravis, often called gMG.

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Face, neck, and throat

In about 15% of people with MG, early disease manifestations are related to weakness in the face, neck, and throat muscles, which can lead to difficulties in swallowing, speech, and sometimes holding the head upright.

Importantly, patients may experience some symptoms and not others, and their severity can also vary from person to person.

• Speech difficulties may come as a consequence of muscle weakness in the throat, tongue, jaw, and mouth. Patients may have difficulties speaking, called dysarthria, or experience speech alterations, including a weak, hoarse, or nasal voice.
• Eating problems can occur when patients develop difficulties in swallowing, known as dysphagia, due to weakness of the mouth, jaw, and tongue. These symptoms may make a person more prone to choking. Difficulties chewing also are possible, and jaw muscles may tire out during meals, sometimes before the person has finished eating.
• Facial expressions may be affected as a result of muscle weakness in the face. For instance, a smile may look like a snarl.

Holding one’s head up can become more difficult due to weakness in neck muscles. For some patients, trying to keep the head upright can lead to fatigue and soreness.

Respiratory symptoms

MG can cause weakness in the respiratory muscles used for breathing and the throat muscles needed to keep the airways open. That can lead to abnormal breathing patterns and breathing problems.

When respiratory muscles become too weak to move air in and out of the lungs, patients may experience a myasthenic crisis, a potentially life-threatening medical emergency that usually requires hospitalization and ventilation support.

Patients most likely to experience a myasthenic crisis are those who have issues with swallowing and talking. If patients start to experience shortness of breath or other signs that could indicate an imminent myasthenic crisis, it’s recommended they visit their doctor or the emergency room to receive immediate treatment.

While respiratory symptoms are not commonly the first type of symptom people with MG will experience, it is possible that a myasthenic crisis is the initial sign of the disease for some patients.

Limbs

In gMG, weakness tends to spread sequentially from the face and neck to the upper limbs, hands, and then to the lower limbs.

Limb weakness may manifest as numbness, heaviness, muscle spasms, loss of limb control, or a feeling of loss of balance. These symptoms are often not symmetrical, with one side of the body being weaker than the other.

While the mechanisms of MG itself are not thought to cause pain, weakness in the arms and legs may lead to aches and pains over time.

Upper limbs

Muscle weakness tends to be worse in the upper limbs, including the arms, hands, shoulders, and chest, than in the lower limbs.

When upper limbs are affected, patients may have:

• trouble lifting and holding up their arms
• a weak grip, with difficulty opening jars and medicine bottles and grabbing heavier objects
• trouble opening the hands fully to an extended palm.

Lower limbs

Weakness in a person’s lower limbs — the hips, legs, ankles, and feet — can also lead to a number of functional difficulties, particularly mobility problems.

Examples of symptoms linked to lower limb involvement include:

• difficulty climbing stairs
• problems walking long distances
• trouble rising from a sitting position.

Complications

The most serious complication of MG is a myasthenic crisis. But people with the disease may also have an increased risk of developing other conditions, particularly other autoimmune diseases.

Myasthenic crisis

Respiratory muscle weakness in MG can place patients at risk for myasthenic crises, or severe breathing problems that require hospitalization. It’s estimated that about 15%-20% of MG patients will experience a myasthenic crisis at least once in their lifetime.

In such cases, patients may need temporary breathing support in the form of an oxygen mask or ventilator. Airway suction and intensive chest physical therapy also may be used to clear secretions from the airways and make breathing easier.

In-hospital treatments, such as plasma exchange or plasmapheresis, and intravenous immunoglobulin, a preparation of pooled antibodies that’s given into the vein, may be used in conjunction with standard MG therapies to ease symptoms.

In addition to shortness of breath, signs that a myasthenic crisis may be developing include:

• fast and shallow breathing
• slurred speech
• weak cough or trouble clearing mucus from the throat
• inability to lie down or speak more than a few words at a time
• more weakness than normal in any muscle group
• muscles between the ribs, neck, and stomach pulling in during breathing.

For up to half of patients, the underlying cause of a myasthenic crisis cannot be identified. However, there are some known triggers that can cause a crisis or MG flares, which are episodes in which muscle weakness in some or all muscle groups acutely worsens, but breathing assistance is not required.

These triggers may include:

• fatigue, overexertion, or lack of sleep
• infections, illness, or pain
• extreme heat or excessive sunlight exposure
• surgery and anesthesia
• pregnancy and menstruation
• stress and anxiety
• certain medications, such as antibiotics, muscle relaxants, magnesium, and heart and blood pressure medications.

Proper adherence to regular MG medications and avoiding known disease triggers is the best way to avoid myasthenic crises and prevent an MG exacerbation. Still, patients should always seek emergency care if they experience trouble breathing.

Other MG complications

In rare cases, high doses of acetylcholinesterase inhibitors (e.g., Mestinon) used to treat MG can lead to a cholinergic crisis, where too much acetylcholine at the neuromuscular junction overstimulates certain receptors and causes toxicity. Symptoms may include cramps, excessive salivation, muscle weakness and twitching, paralysis, diarrhea, and blurry vision.

Patients are advised to monitor their symptoms carefully to identify which factors make their MG symptoms worse, and to talk with their doctors when starting any new medication.

Other disorders

People with MG may be at a higher risk of developing other conditions, particularly autoimmune disorders. It’s estimated that 5%-10% of MG patients also have another autoimmune disease, but the mechanisms underlying that association aren’t completely known.

The most common autoimmune conditions linked to MG include:

• autoimmune thyroid disease, called thyroiditis
• systemic lupus erythematosus, or SLE
• rheumatoid arthritis, known as RA.

The treatment for these secondary conditions varies, but most autoimmune diseases, including MG, involve the use of steroids to keep symptoms under control. These are associated with a series of side effects, including a higher risk of developing diabetes, high blood pressure, and other cardiovascular problems.

In some cases, the autoimmune attack that drives MG also causes damage to the heart muscle and leads to cardiac problems. These can include heart failure, abnormal heart rhythms, or inflammation of the heart, known as myocarditis. Heart-related problems are more common in patients who have a thymoma, or thymus tumor.

Psychiatric disorders, including depression and anxiety, commonly coexist with MG, especially among patients with greater limitations engaging in daily activities. Because certain medications used to treat depression or anxiety may worsen MG symptoms, lifestyle changes, such as exercise and good sleep habits, are critical components of a comprehensive MG treatment plan.

Progression over time

MG symptoms tend to progressively worsen over time, especially in the first few years. Many patients start out with symptoms that are limited to the muscles of the eyes and eyelids. Except for the small proportion of patients with pure ocular MG, muscle weakness then tends to spread to other muscle groups, becoming gMG. That transition typically happens within the first three years following symptom onset.

Muscle weakness caused by MG usually worsens acutely when a muscle is intensively used and gets better with rest, leading to symptoms that fluctuate. Certain disease triggers also might cause MG symptoms to temporarily worsen.

In most cases, symptoms reach their most severe within a few years after the onset of MG. Some patients may achieve temporary or permanent symptom remission with MG treatments or removal of the thymus gland through a surgical procedure called thymectomy.

Myasthenia Gravis News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.