Myasthenia gravis-associated ryanodine receptor antibodies inhibit binding of ryanodine to sarcoplasmic reticulum

The auto-antigen repertoire in myasthenia gravis

Myasthenia Gravis (MG) is an antibody-mediated autoimmune disorder affecting the postsynaptic membrane of the neuromuscular junction (NMJ). MG is characterized by an impaired signal transmission between the motor neuron and the skeletal muscle cell, caused by auto-antibodies directed against NMJ proteins. The auto-antibodies target the nicotinic acetylcholine receptor (nAChR) in about 90% of MG patients. In approximately 5% of MG patients, the muscle specific kinase (MuSK) is the auto-antigen. In the remaining 5% of MG patients, however, antibodies against the nAChR or MuSK are not detectable (idiopathic MG, iMG). Although only the anti-nAChR and anti-MuSK auto-antibodies have been demonstrated to be pathogenic, several other antibodies recognizing self-antigens can also be found in MG patients. Various auto-antibodies associated with thymic abnormalities have been reported, as well as many non-MG-specific auto-antibodies. However, their contribution to the cause, pathology and severity of the disease is still poorly understood. Here, we comprehensively review the reported auto-antibodies in MG patients and discuss their role in the pathology of this autoimmune disease.

Myasthenia Gravis

The treatment of patients with myasthenia gravis should be individualized according to the extent (ocular versus generalized) and severity (mild to severe) of disease, the presence or absence of concomitant disease (including but not limited to other autoimmune diseases and thymoma), and, to a lesser degree, the age of the patient. Thymectomy should be performed in patients with generalized disease, especially those who have detectable levels of circulating antibodies to acetylcholine receptor (anti-AChR), as it should be in all patients thought to have an operable thymoma (observed on imaging studies of the chest). Symptomatic therapy consists of anticholinesterase drugs (usually pyridostigmine); occasionally, other drugs are required to reduce the muscarinic side effects. At times, patients need immunosuppressive or immunomodulatory therapy with glucocorticoids, azathioprine, cyclospor-ine or cyclophosphamide, plasma exchange, and intravenous immunoglobulin. Remission, whether spontaneous or pharmacologically induced, or significant improvement can be achieved in most patients, but some treatments entail significant side effects and considerable cost.