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Disease Profile

Myasthenia gravis

Prevalence
Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.
1-9 / 100 000

3,310 - 29,790

US Estimated

1-9 / 100 000

5,135 - 46,215

Europe Estimated

Age of onset

All ages

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ICD-10

G70.0

Inheritance

Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease

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Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype

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X-linked
dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.

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X-linked
recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder

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Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

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Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.

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Not applicable

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Categories

Nervous System Diseases

Summary

Myasthenia gravis (MG) is a chronic autoimmune neuromuscular disease characterized by weakness of the skeletal muscles. Common symptoms include weakness of the muscles that control the eye and eyelid, facial expressions, chewing, talking, and swallowing. Weakness tends to increase during periods of activity and improve after periods of rest. The condition results from a defect in the transmission of nerve impulses to muscles, which is due to the presence of antibodies against acetylcholine.[1] The exact reason this occurs is not known. Some cases have been linked to tumors in the thymus gland.[2] Researchers believe that variations in certain genes may increase a person's risk to develop MG, but other factors likely also play a role.[3] There is no cure for MG at this time, but treatment can significantly improve muscle weakness. Some cases may go into remission temporarily, and muscle weakness may disappear so that medications can be discontinued.[1][2]

Symptoms

Myasthenia gravis (MG) causes muscle weakness and can affect any voluntary muscle. Voluntary muscles are the muscles that we directly control to make our body do things like walk, run, write, throw, lift, smile, and chew. In MG, the most commonly affected muscles are the muscles that control eye and eyelid movement, facial expressions, and swallowing. The degree of muscle weakness varies from person to person. People with more severe disease may have many muscles affected, including the muscles that control breathing. People with mild disease may have only one muscle group involved, such as the eye muscles.[1]

In general, signs and symptoms of MG may include:[1]

  • Drooping of one or both eyelids (ptosis)
  • Blurred or double vision (diplopia)
  • Unstable or waddling gait (manner of walking)
  • Weakness in the arms, hands, fingers, legs, and neck
  • Change in facial expression
  • Difficulty swallowing and shortness of breath
  • Impaired speech (dysarthria)

People can develop MG at any age. For unknown reasons, it is most commonly diagnosed in women younger than age 40 and men older than age 60. It is uncommon in children, but some infants born to women with MG have signs and symptoms of the condition for the first few days or weeks of life. This temporary occurrence of symptoms is called transient neonatal myasthenia gravis.[3]

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
HPO ID
30%-79% of people have these symptoms
Abnormality of the thymus
0000777
Acetylcholine receptor antibody positivity
0030208
Bulbar palsy
0001283
Diplopia
Double vision
0000651
Dysarthria
Difficulty articulating speech
0001260
Dysphagia
Poor swallowing
Swallowing difficulties
Swallowing difficulty

[ more ]

0002015
Dyspnea
Trouble breathing
0002094
Muscle specific kinase antibody positivity
0030210
Myositis
Muscle inflammation
0100614
Ophthalmoparesis
Weakness of muscles controlling eye movement
0000597
Ptosis
Drooping upper eyelid
0000508
Single fiber EMG abnormality
0030006
5%-29% of people have these symptoms
Glycosuria
Glucose in urine
0003076
Hashimoto thyroiditis
0000872
Hearing impairment
Deafness
Hearing defect

[ more ]

0000365
Hyperacusis
0010780
Hyperthyroidism
Overactive thyroid
0000836
Paresthesia
Pins and needles feeling
Tingling

[ more ]

0003401
Primary adrenal insufficiency
0008207
Raynaud phenomenon
0030880
Rheumatoid arthritis
0001370
Systemic lupus erythematosus
0002725
1%-4% of people have these symptoms
Acrocyanosis
Persistent blue color of hands, feet, or parts of face
0001063
Hemolytic anemia
0001878
Hepatitis
Liver inflammation
0012115
Psychosis
0000709
Pure red cell aplasia
0012410
Seizure
0001250
Percent of people who have these symptoms is not available through HPO
Abnormality of the endocrine system
0000818
Abnormality of the immune system
Immunological abnormality
0002715
Autoimmunity
Autoimmune disease
Autoimmune disorder

[ more ]

0002960
Facial palsy
Bell's palsy
0010628
Fatigable weakness
0003473
Impaired mastication
Chewing difficulties
Chewing difficulty
Difficulty chewing

[ more ]

0005216
Limb muscle weakness
Limb weakness
0003690
Multifactorial inheritance
0001426
Nasal speech
Nasal voice
0001611
Proximal muscle weakness
Weakness in muscles of upper arms and upper legs
0003701
Thymoma
0100522

Cause

The exact cause of myasthenia gravis (MG) is unknown, but it is likely that a number of factors contribute to the risk of developing this disorder.[3]

MG is a type of autoimmune disorder. Autoimmune disorders occur when the immune system mistakenly attacks healthy tissue.[2] In MG, the body produces antibodies that block the muscle cells that receive messages (neurotransmitters) from the nerve cells.[2][1][3]

Normally when impulses travel down a nerve, the nerve endings release a neurotransmitter substance called acetylcholine. Acetylcholine travels from the neuromuscular junction - the place where nerve cells connect with the muscles they control and binds to acetylcholine receptors which are activated and generate a muscle contraction. In myasthenia gravis, antibodies block, alter, or destroy the receptors for acetylcholine at the neuromuscular junction, which prevents a muscle contraction from occurring. These antibodies are produced by the body's own immune system.[1] 

In some cases, MG is linked to tumors or other abnormalities of the thymus (a gland the plays an important role in the immune system).[2][1][3] Researchers also believe that variations in certain unidentified genes may increase the risk to develop MG.[3]

Treatment

The resources below provide information about treatment options for this condition. If you have questions about which treatment is right for you, talk to your healthcare professional.

Management Guidelines

  • Orphanet Emergency Guidelines is an article which is expert-authored and peer-reviewed that is intended to guide health care professionals in emergency situations involving this condition.
  • Project OrphanAnesthesia is a project whose aim is to create peer-reviewed, readily accessible guidelines for patients with rare diseases and for the anesthesiologists caring for them. The project is a collaborative effort of the German Society of Anesthesiology and Intensive Care, Orphanet, the European Society of Pediatric Anesthesia, anesthetists and rare disease experts with the aim to contribute to patient safety.

    FDA-Approved Treatments

    The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition. Learn more orphan products.

    Organizations

    Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

    Organizations Supporting this Disease

      Social Networking Websites

      • RareConnect has an online community for patients and families with this condition so they can connect with others and share their experiences living with a rare disease. The project is a joint collaboration between EURORDIS (European Rare Disease Organisation) and NORD (National Organization for Rare Disorders).

        Organizations Providing General Support

          Learn more

          These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

          Where to Start

          • The Muscular Dystrophy Association provides additional information on myasthenia gravis. Click on the link to view this information page.
          • MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.
          • Genetics Home Reference (GHR) contains information on Myasthenia gravis. This website is maintained by the National Library of Medicine.
          • The National Institute of Neurological Disorders and Stroke (NINDS) collects and disseminates research information related to neurological disorders. Click on the link to view information on this topic.
          • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

            In-Depth Information

            • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
            • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
            • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
            • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
            • PubMed is a searchable database of medical literature and lists journal articles that discuss Myasthenia gravis. Click on the link to view a sample search on this topic.

              Selected Full-Text Journal Articles

              • The Orphanet Journal of Rare Diseases has published an article with information on this condition. This journal is affiliated with the Orphanet reference portal for information on rare diseases and orphan drugs.

                References

                1. Myasthenia Gravis Fact Sheet. National Institute of Neurological Disorders and Stroke (NINDS). July 27, 2015; https://www.ninds.nih.gov/disorders/myasthenia_gravis/detail_myasthenia_gravis.htm.
                2. Kantor D. Myasthenia gravis. MedlinePlus. June 1, 2015; https://www.nlm.nih.gov/medlineplus/ency/article/000712.htm.
                3. Myasthenia gravis. Genetics Home Reference (GHR). July 2012; https://ghr.nlm.nih.gov/condition/myasthenia-gravis.
                4. Myasthenia Gravis Fact Sheet. National Institute of Neurological Disorders and Stroke (NINDS). 2016; https://www.ninds.nih.gov/disorders/myasthenia_gravis/detail_myasthenia_gravis.htm.
                5. Myasthenia Gravis: Frequently Asked Questions. Myasthenia Gravis Foundation of America. 2010; https://www.myasthenia.org/WhatisMG/FAQs.aspx.
                6. Shah AK. Myasthenia Gravis. Medscape Reference. March 23 2016; https://emedicine.medscape.com/article/1171206-overview.
                7. Myasthenia Gravis. NORD. 2014; https://rarediseases.org/rare-diseases/myasthenia-gravis/.
                8. James F. Howard, Jr. Clinical Overview of MG. Myasthenia Gravis Foundation of America. 2015; https://www.myasthenia.org/HealthProfessionals/ClinicalOverviewofMG.aspx.

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