MUSK and myasthenia gravis: In myasthenia gravis (MG) mainly caused by the nAChR antibodies, a proportion of the patients harbor antibodies recognizing MuSK and Lrp4 which are responsible for pre- and postsynaptic impairments and contributive, at least in part, to a defect in ACh-release upregulation to compensate for postsynaptic dysfunction [3,4,5,6,7,8,9,10].