Myasthenia gravis overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Keanu Ngo[2]
Overview
Myasthenia gravis (MG) is a chronic autoimmune disorder of the postsynaptic neuromuscular junction (NMJ) in which pathogenic autoantibodies impair acetylcholine-mediated neuromuscular transmission, resulting in fluctuating, fatigable skeletal muscle weakness that typically worsens with activity and improves with rest. MG is the most common acquired disorder of the NMJ and ranges in severity from isolated ocular manifestations to life-threatening myasthenic crisis with respiratory failure.[1][2]
Clinical Features
The cardinal clinical feature of MG is painless, fluctuating, fatigable muscle weakness, often with diurnal variation and worsening later in the day. Ocular manifestations, particularly ptosis and diplopia, are common initial presentations. Approximately 80–85% of patients develop generalized disease, which may involve bulbar, facial, axial, respiratory, and proximal limb muscles. Disease severity varies from isolated ocular weakness to generalized weakness with potentially life-threatening respiratory compromise. (See Myasthenia gravis history and symptoms and Myasthenia gravis natural history, complications, and prognosis.)[3][4]
Epidemiology
MG has an estimated incidence of approximately 4–30 cases per million person-years and a prevalence of approximately 150–200 cases per million, with higher estimates reported in some populations. Incidence and prevalence have increased over time, particularly among older adults. Age at onset demonstrates a broadly bimodal distribution, with early-onset disease more frequently affecting women and late-onset disease increasingly represented among older men. (See Myasthenia gravis epidemiology and demographics.)[2][5][6]
Immunologic Subtypes
MG is classified according to the autoantibodies associated with impaired neuromuscular transmission. The principal subtypes are acetylcholine receptor antibody-positive (AChR-MG), muscle-specific kinase antibody-positive (MuSK-MG), and lipoprotein receptor-related protein 4 antibody-positive (LRP4-MG). A proportion of patients remain seronegative on standard antibody assays despite a compatible clinical presentation.
| Antibody subtype | Approximate proportion | Clinical relevance |
|---|---|---|
| AChR antibody-positive | 80–85% | The most common subtype; associated with complement-mediated injury and targeted complement-inhibitor therapies. |
| MuSK antibody-positive | 5–8% | Frequently associated with prominent bulbar or respiratory involvement and may respond differently to conventional symptomatic and immunosuppressive therapies. |
| LRP4 antibody-positive | 1–4% | Less common subtype; associated with autoimmune impairment of neuromuscular transmission. |
| Seronegative | 5–15% | No detectable antibodies on standard assays; additional antibody testing may identify cases missed by conventional methods. |
Antibody subtype has diagnostic, prognostic, and therapeutic implications. AChR and LRP4 antibodies are predominantly IgG1–3 subclasses capable of activating complement, whereas MuSK antibodies are predominantly IgG4 and generally do not activate complement through the classical pathway. (See Myasthenia gravis classification, Myasthenia gravis pathophysiology, and Myasthenia gravis laboratory findings.)[7][8]
Diagnosis
The diagnosis of MG is based on a compatible clinical presentation supported by serologic testing and electrodiagnostic studies. Initial evaluation typically includes testing for AChR antibodies, with additional antibody testing and electrodiagnostic assessment when clinically indicated. Repetitive nerve stimulation and single-fiber electromyography are important diagnostic studies, particularly when initial serologic testing is negative or inconclusive.
Chest imaging, generally with computed tomography (CT), is indicated in patients with confirmed MG to evaluate for thymoma. Diagnostic interpretation must account for the clinical phenotype, test sensitivity, and limitations of individual investigations. (See Myasthenia gravis diagnosis, Myasthenia gravis laboratory findings, Myasthenia gravis other diagnostic studies, and Myasthenia gravis CT findings.)[9][7][2]
Management
The management of MG is individualized according to disease severity, antibody subtype, clinical manifestations, treatment response, and the presence of thymoma. The principal treatment objectives are to achieve remission or minimal manifestation status, preserve functional independence, prevent exacerbations, and minimize treatment-related adverse effects.
Major treatment approaches include:
- Symptomatic therapy: Pyridostigmine improves neuromuscular transmission and is commonly used for symptomatic relief, although its effectiveness and tolerability vary by antibody subtype.
- Immunotherapy: Corticosteroids and steroid-sparing immunosuppressive agents, including azathioprine and mycophenolate mofetil, are used to control autoimmune disease. Rituximab is an important treatment option, particularly in selected patients with MuSK-MG.
- Thymectomy: Surgical removal of the thymus is indicated for thymoma and is an established treatment option in selected patients with nonthymomatous, generalized AChR-MG.
- Rapid immunomodulatory therapy: Intravenous immunoglobulin (IVIg) and plasma exchange are used for severe exacerbations, myasthenic crisis, and selected situations requiring a rapid therapeutic response.
- Targeted biologic therapies: Complement inhibitors, including Eculizumab, Ravulizumab, and Zilucoplan, and neonatal Fc receptor (FcRn) antagonists, including Efgartigimod, Rozanolixizumab, and Nipocalimab, have expanded treatment options for selected patients with generalized MG.
Treatment selection and sequencing depend on antibody subtype, disease activity, prior treatment response, comorbidities, and access to therapy. The optimal placement of newer targeted biologics relative to conventional immunosuppressive therapies remains an evolving area of clinical guidance. (See Myasthenia gravis medical therapy and Myasthenia gravis surgical therapy.)[10][11][7][8]
Clinical Considerations
- Recognize fatigability: Fluctuating weakness that worsens with sustained activity and improves with rest is a key clinical clue to MG.
- Evaluate for thymoma: Chest imaging is required as part of the evaluation of confirmed MG because of the clinically important association with thymoma.
- Interpret serology in context: Negative standard antibody testing does not exclude MG. Additional serologic and electrodiagnostic investigations may be warranted when clinical suspicion remains high.
- Consider antibody subtype: AChR-MG and MuSK-MG may differ in clinical presentation and treatment response; antibody status should inform therapeutic decisions.
- Recognize respiratory deterioration: Rapidly progressive bulbar or respiratory weakness may indicate impending myasthenic crisis and requires urgent assessment.
- Monitor clinical burden: Validated instruments such as the Myasthenia Gravis Activities of Daily Living (MG-ADL) scale can help quantify symptoms and monitor treatment response.
(See Myasthenia gravis history and symptoms, Myasthenia gravis physical examination, Myasthenia gravis laboratory findings, and Myasthenia gravis natural history, complications, and prognosis.)[3][9][12]
References
- ↑ White LM, Clay FJ, Forbes AM; et al. (2025). "Complement Inhibitors for Myasthenia Gravis in Adults". Cochrane Database of Systematic Reviews. 7: CD016098. doi:10.1002/14651858.CD016098.
- ↑ 2.0 2.1 2.2 Dresser L, Wlodarski R, Rezania K, Soliven B (2021). "Myasthenia Gravis: Epidemiology, Pathophysiology and Clinical Manifestations". Journal of Clinical Medicine. 10 (11): 2235. doi:10.3390/jcm10112235.
- ↑ 3.0 3.1 Sansone G, Bonifati DM (2022). "Vaccines and myasthenia gravis: a comprehensive review and retrospective study of SARS-CoV-2 vaccination in a large cohort of myasthenic patients". Journal of Neurology. 269 (8): 3965–3981. doi:10.1007/s00415-022-11140-9.
- ↑ Manolopoulos A, Alzuabi M, Elmashala A; et al. (2025). "Immunoglobulin for Myasthenia Gravis". Cochrane Database of Systematic Reviews. 10: CD013801. doi:10.1002/14651858.CD013801.pub2.
- ↑ Pasnoor M, Miller-Wilson LA, Edwards Y; et al. (2026). "Burden of Disease in Myasthenia Gravis: A Targeted Literature Review". Journal of Neurology. 273 (5): 288. doi:10.1007/s00415-026-13662-y.
- ↑ Falso S, Spagni G, Monte G; et al. (2026). "Half a Century of Change: Demographic Trends and Their Clinical Impact in Acetylcholine Receptor Antibody-Positive Myasthenia Gravis". Journal of Neurology. 273 (4): 227. doi:10.1007/s00415-026-13670-y.
- ↑ 7.0 7.1 7.2 Gerischer L, Doksani P, Hoffmann S, Meisel A (2025). "New and Emerging Biological Therapies for Myasthenia Gravis: A Focussed Review for Clinical Decision-Making". BioDrugs. 39 (2): 185–213. doi:10.1007/s40259-024-00701-1.
- ↑ 8.0 8.1 Iorio R (2024). "Myasthenia gravis: the changing treatment landscape in the era of molecular therapies". Nature Reviews Neurology. 20 (2): 84–98. doi:10.1038/s41582-023-00916-w.
- ↑ 9.0 9.1 Shelly S, Paul P, Bi H; et al. (2020). "Improving Accuracy of Myasthenia Gravis Autoantibody Testing by Reflex Algorithm". Neurology. 95 (22): e3002–e3011. doi:10.1212/WNL.0000000000010910.
- ↑ Gilhus NE, Andersen H, Andersen LK; et al. (2024). "Generalized myasthenia gravis with acetylcholine receptor antibodies: A guidance for treatment". European Journal of Neurology. 31 (5): e16229. doi:10.1111/ene.16229.
- ↑ Sanders DB, Wolfe GI, Benatar M; et al. (2016). "International Consensus Guidance for Management of Myasthenia Gravis: Executive Summary". Neurology. 87 (4): 419–425. doi:10.1212/WNL.0000000000002790.
- ↑ Akamine H, Uzawa A, Kuwabara S; et al. (2025). "Predicting achievement of clinical goals using machine learning in myasthenia gravis". PLOS ONE. 20 (8): e0330044. doi:10.1371/journal.pone.0330044.