MUSK and myasthenia gravis: Depending on the type of serum autoantibodies, MG can generally be classified into acetylcholine receptor antibody positive MG (AChR+ MG), muscle-specific tyrosine kinase antibody positive MG (MuSK+ MG), or lipoprotein receptor-related protein 4 antibody positive MG (LRP4+ MG) (Huang et al., 2023).