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What is gMG?

It exists as an autoimmune disease state, or as a paraneoplastic syndrome associated with tumours of the thymus but only rarely with other malignacies.3

The main autoantibodies associated with the development of MG target key molecules functioning at the NMJ, including the nicotinic acetylcholine receptor (AChR), muscle-specific kinase (MuSK) and low-density lipoprotein receptor-related protein 4 (LRP4).1
Anti-LRP4 autoantibodies may be less specific to MG than anti-AChR and anti-MuSK antibodies.1,5,6
 
Some patients with MG appear seronegative for autoantibodies against AChR, MuSK and LRP4, though this may be the result of low assay sensitivity during diagnostic assessment or it may mean that these patients have autoantibodies against yet unidentified target proteins.1,5 Seronegative patients have been reported to otherwise be clinically indistinguishable from seropositive patients with MG.7

The exact cause of the autoimmunity seen in MG is not yet fully understood, but many patients have abnormalities in their thymus gland (hyperplasia and neoplasia) which is thought to contribute to the presence of anti–AChR antibodies.7
In 15% of patients who develop myasthenia gravis (MG), the ocular muscles are the only muscle groups affected (ocular MG).1
In the other 85% of patients, the muscle weakness progresses and impacts other parts of their body, at which point the condition is referred to as gMG.1

The disease can be divided into more subgroups that take into account the patient’s age at disease onset, autoantibody profile and thymus pathology1:

Identifying a patient’s MG subgroup may help guide a personalised treatment regimen.1

The Myasthenia Gravis Foundation of America (MGFA) developed a 5-point classification system to further stratify patient groups with distinct clinical features, which can help indicate prognosis and response to treatment.8 Patients may be classified from Class I (ocular weakness only) to Class V (requiring hospitalisation), with subclasses (for example, Class IIIa, IIIb etc.) depending on their spectrum of clinical manifestations:8
The image shows common symptoms in MG, but is not an exhaustive list. For a thorough description of symptoms of MG, please visit our dedicated Symptoms page.
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ACh, acetylcholine; AChR, acetylcholine receptor; gMG, generalised myasthenia gravis; LRP4, low-density lipoprotein receptor-related protein 4; MG, myasthenia gravis; MGFA, Myasthenia Gravis Foundation of America; MuSK, muscle-specific kinase; NMJ, neuromuscular junction.

 Gilhus NE, et al. Myasthenia gravis. Nat Rev Dis Primers. 2019;5(1):30.  Koneczny I, Herbst R. Myasthenia gravis: Pathogenic effects of autoantibodies on neuromuscular architecture. Cells. 2019;8(7):671. Melzer N, et al. Clinical features, pathogenesis, and treatment of myasthenia gravis: A supplement to the Guidelines of the German Neurological Society. J Neurol. 2016;263(8):1473–1494.  Fagerlund MJ, Eriksson LI. Current concepts in neuromuscular transmission. Br J Anaesth. 2009;103(1):108–114.  Lazaridis K, Tzartos SJ. Autoantibody specificities in myasthenia gravis; implications for improved diagnostics and therapeutics. Front Immunol. 2020;11:212. Rousseff RT. Diagnosis of myasthenia gravis. J Clin Med. 2021;10(8):1736. Meriggioli MN, Sanders DB. Autoimmune myasthenia gravis: Emerging clinical and biological heterogeneity. Lancet Neurol. 2009;8(5):475–490. Jaretzki A, 3rd, et al. Myasthenia gravis: Recommendations for clinical research standards. Task Force of the Medical Scientific Advisory Board of the Myasthenia Gravis Foundation of America. Ann Thorac Surg. 2000;70(1):327–334. Li Y, Arora Y, Levin K. Myasthenia gravis: Newer therapies offer sustained improvement. Cleve Clin J Med. 2013:80(11):711–721. advance I am a healthcare professional registered in the EU I am not a
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