Although a number of autoantibodies have been implicated in myasthenia gravis (MG), there are many whose roles are still uncertain, according to a review recently published in the Journal of Neuroimmunology.
MG is caused when an individual produces antibodies, called autoantibodies, that attack the connection between nerves and muscles. When this connection (known as the neuromuscular junction) is broken, muscle weakness occurs.
Currently, antibodies against the acetylcholine receptor (AChR), muscle-specific kinase (MuSK) and low-density lipoprotein receptor-related protein 4 (LRP4) are the three best-characterized autoantibodies in MG.
AChR antibodies can be found in 50% of those with ocular MG and 85% of those with generalized MG, the authors said. MuSK antibodies are present in up to 10% of individuals with MG and LRP4 antibodies are found in about 2% of patients.
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Individuals who do not have antibodies against AChR, MuSK or LRP4 are considered seronegative, accounting for around 10% of all people with MG. It is possible that some of these patients have autoantibodies against other targets, though.
Antibodies against COLQ, cortactin, rapsyn, AChE and Kv1.4 are present in some patients with MG, but their roles, if any, in contributing to the disease are not yet known. Patients are not regularly tested for any of these antibodies today.
Additionally, autoantibodies against titin and the ryanodine receptor, two other proteins, don’t directly contribute to disease but may be a marker of disease severity. Some studies have found that patients with AChR antibodies who also have titin or ryanodine receptor antibodies tend to have more severe disease.
The presence of certain antibodies can be used to predict prognosis, guide treatment and monitor patients long-term, the authors wrote. More work is needed to better understand how different antibodies can predict patient outcomes, both on their own and in combination with one another.
“Ongoing research relating to autoantibodies in MG will lead to continued improvements in diagnostic accuracy and the tailoring of more effective and personalised therapies for patients with MG,” the researchers concluded.
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