Myasthenia Gravis

Abstract

Myasthenia gravis (MG) is an autoimmune disease, caused by IgG antibodies to postsynaptic proteins at the neuromuscular junction, including the acetylcholine receptor (AChR), the muscle-specific tyrosine kinase receptor (MuSK), and the low-density lipoprotein receptor-related protein 4 (Lrp4). With different mechanisms, these antibodies induce morphological and functional changes responsible for neuromuscular transmission failure. Thymus alterations and defects in immune tolerance play a role in the pathogenesis of MG with anti-AChR antibodies. The clinical hallmark of MG is fatigable weakness of striated muscles, with marked variability in symptom extension and severity. The diagnosis is based on antibody detection, electrophysiological findings of a postsynaptic defect of neuromuscular transmission, and clinical response to acetylcholinesterase inhibitors. MG heterogeneity should be taken into account in patients’ management. Treatment varies according to weakness pattern and severity, age of onset, thymus pathology, and antibody profile. Therapeutic options include symptomatic agents, thymectomy, plasma exchange, intravenous immunoglobulin, steroids, and immunosuppressants. Monoclonal antibodies, as rituximab and eculizumab are promising, and other biological agents are currently under study.