Myasthenia gravis (MG) is a chronic autoimmune neuromuscular disorder in which the body’s immune system produces antibodies that block or destroy the communication between nerves and muscles at the neuromuscular junction. This interruption causes muscles to become weak and more easily fatigued. MG most commonly affects muscles that control eye movement, facial expressions, chewing, swallowing, speech, breathing, as well as neck, arm, and leg movement.
Although there is no known cure, many effective treatments are available to help people manage their symptoms and lead active, fulfilling lives. Some patients even experience remission.
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What Is Myasthenia Gravis?
Myasthenia gravis is an autoimmune disorder that disrupts normal muscle function. In MG, antibodies attack or interfere with certain proteins at the neuromuscular junction needed for muscle contraction. As a result, muscles typically get weaker with repeated use and can fatigue more quickly.
How does MG affect the body?
Myasthenia gravis can cause a number of issues:
- Muscle weakness that often worsens with activity and improves with rest.
- Problems with muscles that control eye movement, facial expression, chewing, swallowing, speaking, and breathing.
- Symptom fluctuations with periods of exacerbations (worsening).
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What Are the Symptoms of Myasthenia Gravis?
Because MG can affect any voluntary muscle group, symptoms vary from person to person and diagnosis can be challenging.
Common symptoms include:
- Changes in facial expressions.
- Difficulty chewing or swallowing.
- Difficulty smiling.
- Diplopia — blurred or double vision.
- Extreme fatigue, especially later in the day.
- Impeded mobility.
- Ptosis — drooping eyelids.
- Shortness of breath or difficulty breathing.
- Slurred speech or hoarseness.
- Weakness in the limbs.
Ocular vs. Generalized Myasthenia Gravis
Ocular myasthenia gravis
Ocular MG primarily affects the muscles that control the eyelids and eye movements.
- Typical symptoms include ptosis (drooping eyelids) and/or diplopia (double vision).
- If MG symptoms remain limited to the eye muscles for a period — often around two years — it is considered ocular MG.
- In some cases, disease progression in ocular MG can advance to generalized MG over time.
Generalized myasthenia gravis
- Involves not only the eye muscles but also other muscle groups, such as those for facial expression, chewing, swallowing, speaking, breathing, and limb movement.
- Symptoms can be more widespread, potentially leading to difficulties with everyday tasks, mobility, and — in severe cases — breathing.
Knowing whether MG is ocular or generalized helps guide treatment choices and long-term management strategies.
What is a myasthenic crisis?
A myasthenic crisis is a severe exacerbation of MG symptoms, particularly those related to breathing. It can be life-threatening and requires immediate medical attention. Seek emergency care if you experience sudden or severe breathing difficulties.
Risk Factors and Complications
Who gets MG?
- Younger adult women (under 40) and older adult men (over 60) are more frequently affected, but MG can occur at any age.
- MG is not contagious and usually is not inherited; however, there can be a genetic predisposition for autoimmune disorders in some families.
Neonatal vs. congenital myasthenia
- Neonatal myasthenia gravis – occurs when babies temporarily receive MG antibodies from their mother. Symptoms typically resolve within a few weeks or months after birth.
- Congenital myasthenic syndromes – are not autoimmune; rather, they result from genetic defects at the neuromuscular junction. Their symptoms can resemble MG symptoms but are often treated differently.
Potential complications
Without appropriate treatment, MG can lead to:
- Life-threatening respiratory compromise (myasthenic crisis).
- Reduced quality of life due to weakness and mobility issues.
- Severe weakness in muscles needed for breathing, swallowing, and speaking.
How common is myasthenia gravis?
Myasthenia gravis is considered rare, with estimates varying from about 32 to 37 individuals per 100,000 people in the United States. However, many cases may be undiagnosed, and current estimates suggest more than 80,000 Americans are living with MG.
When should I see a doctor?
If you notice persistent muscle weakness — especially involving the eyes, face, swallowing, or breathing — or if you experience episodes of extreme fatigue that worsen with activity, contact your doctor or a neuromuscular specialist. Early diagnosis and treatment can help prevent serious complications.
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How Do You Diagnose Myasthenia Gravis?
Diagnosing MG can be complex.
Your doctor may use:
Physical examination
- Review of your medical history.
- Assessment of muscle strength, tone, and coordination.
- Eye function and movement tests.
Electrodiagnostic tests
- Repetitive nerve stimulation (RNS): Uses small electrical pulses to measure muscle response.
- Single-fiber EMG: Often the most sensitive test for diagnosing MG if others are inconclusive.
Blood tests
- Detect antibodies such as acetylcholine receptor (AChR) or MuSK antibodies.
- Some people are seronegative, meaning they have no detectable antibodies, but still have MG.
Imaging
- A CT scan or MRI of the chest to look for an enlarged thymus or thymoma.
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How Do You Treat Myasthenia Gravis?
Although MG is not yet curable, treatments can greatly improve muscle strength and quality of life. Your care plan may include one or more of the following options, often tailored to your specific needs.
Medications
- Anticholinesterase drugs (e.g., pyridostigmine) — Helps prevent the breakdown of acetylcholine, improving nerve-to-muscle communication.
- Immunosuppressants — This includes corticosteroids (e.g., prednisone) and other immunosuppressants such as mycophenolate mofetil and azathioprine. These medications suppress the abnormal immune response contributing to MG.
- FcRn inhibitors — Blocks the neonatal Fc receptor, thereby reducing the level of harmful antibodies circulating in the blood.
- Complement inhibitors — Blocks part of the immune system’s cascade that leads to further damage of muscle receptors.
- B-cell-directed therapies — Targets B cells (the immune cells that produce antibodies) to reduce the production of harmful antibodies.
Important: Never stop taking MG medications without consulting your doctor. Abrupt changes can worsen symptoms.
IVIG and plasma exchange (PLEX)
- Intravenous immunoglobulin (IVIG) — Provides concentrated antibodies that can alter your immune response.
- Plasma exchange (plasmapheresis) — Filters harmful antibodies from the blood.
These approaches often offer short-term relief — particularly during severe exacerbations or crises.
Thymectomy (surgical removal of the thymus)
The thymus gland is located in the middle of the upper chest. It plays a key role in T-cell development and is involved in the production of the abnormal autoantibodies responsible for MG. Patients with MG may have thymic hyperplasia (enlarged thymus), and in some cases a thymoma (tumor of the thymus) is found.
- The thymus often contributes to the development of MG by supporting harmful immune processes.
- Thymectomy — surgical removal of thymus tissue — is frequently considered to improve symptoms over the long term and reduce the need for chronic medications.
- In rare cases where a thymoma is present, removing it as early as possible is strongly recommended to prevent further complications.
Lifestyle modifications
You may be able to improve MG symptoms by making some changes to your lifestyle, including:
- Balanced diet — Emphasize fruits, vegetables, whole grains, and lean proteins.
- Moderate exercise — Low-impact activities such as gentle walking, stretching, and yoga can help maintain muscle strength and cardiovascular health. Always listen to your body and rest when muscle weakness increases. Avoid overexertion.
- Pacing and rest — Plan activities with breaks to avoid pushing muscles to the point of exhaustion.
- Stress management — High stress can worsen symptoms.
Moving forward with myasthenia gravis
Thanks to modern diagnostic tools, research, and a range of treatments — including immunotherapies, surgical options, and lifestyle modifications — most people with MG can manage their symptoms effectively. Regular follow-ups with a neuromuscular specialist and adherence to your treatment plan will help you maintain the best possible quality of life. New therapies and research continue to offer hope for improved management in the future.
Myasthenia gravis and pregnancy
Many women with MG have successful pregnancies; however, careful planning and close coordination with a multidisciplinary health care team are essential. Your team may include your neuromuscular specialist, a maternal-fetal medicine (MFM) specialist who deals with high-risk pregnancies, and potentially other specialists depending on your individual needs.
Effects of pregnancy on MG may include:
- Symptom fluctuations — MG symptoms can improve, worsen, or remain stable during pregnancy. Every individual's MG is different. Some women notice increased weakness or fatigue, especially during late pregnancy or the postpartum period.
- Medication adjustments — Certain MG medications are safer in pregnancy than others. Your care team may adjust or substitute specific drugs to minimize risks to you and your baby.
Medications during pregnancy
Some medications used to treat MG may be safer than others during pregnancy:
Anticholinesterase drugs (e.g., pyridostigmine)
Often considered relatively safe in pregnancy, but dosages may need fine-tuning.
Immunosuppressants
- Corticosteroids (e.g., prednisone) — Frequently used and generally regarded as relatively safe in pregnancy, although side effects and dosing should be closely monitored.
- Mycophenolate mofetil and methotrexate — Typically avoided in pregnancy due to potential risks to the fetus. Your doctor may switch you to alternative therapies before conception.
- Azathioprine — May be used in certain cases but requires close monitoring.
- IVIG (intravenous immunoglobulin) and PLEX (plasma exchange) — Can be used during pregnancy if needed to control MG exacerbations. These treatments are generally considered safe when carefully supervised.
- FcRn inhibitors and complement inhibitors — Data on newer therapies in pregnancy are more limited. Decisions regarding their use require individualized discussion with your neuromuscular specialist.
Planning for delivery
- Birth planning — A delivery plan is typically made with a high-risk obstetrician. In many cases, a vaginal delivery is safe, but each situation is unique. Discuss anesthesia options (e.g., epidural vs. general anesthesia) with your care team.
- Myasthenic crisis management — It is crucial to have a plan in place for managing potential respiratory compromise or severe muscle weakness during labor and delivery.
Postpartum considerations
- Symptom changes — Some women experience a worsening of MG symptoms in the postpartum period. Close follow-up during the first weeks to months after delivery is essential.
- Breastfeeding — Most MG medications (including pyridostigmine and many immunosuppressants) are considered compatible with breastfeeding. However, always confirm with your doctor, as medication safety can vary.
- Neonatal myasthenia — Babies born to mothers with MG may show temporary muscle weakness (neonatal myasthenia) due to the transfer of maternal antibodies across the placenta. Symptoms typically appear within a few days after birth and often resolve on their own or with short-term medical support.
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By UPMC Editorial Staff.
Last reviewed on 2025-02-05 by Fang Sung, MD.
