MUSK and myasthenia gravis: Even so, there are MG cases without autoantibodies against AChR, MuSK, or LRP4, that are called triple-seronegative (triple-SN) MG.8It can be speculated that the lack of autoantibody reactivity in these patients is due to the low sensitivity of the available tests or the presence of antigens not yet identified.8, 9