MUSK and myasthenia gravis: In terms of MG-related Abs, AChR-Ab was positive in 110 cases (89.4%) and negative in 13 cases (10.6%); MuSK-Ab was positive in 4 cases (3.3%) and negative in 119 cases (96.7%); 26 (21.1%) patients were positive for titin-Ab and 15 (12.2%) patients were positive for RyR-Ab; No LRP4-Ab positive patients were found.