Myasthenia gravis (MG) is an autoimmune neuromuscular disorder that leads to fluctuating fatigability and weakness, which is mediated by circulating antibodies against postsynaptic membrane proteins, such as antibodies against acetylcholine receptor (AChR), muscle-specific kinase (MuSK), and low-density lipoprotein receptor (LRP4) (1). The gene discussed is MUSK; the disease is myasthenia gravis.