Autoantibodies (complement-activating IgG1 and IgG2; Y4 in Figure 1) are detected in a proportion of MG with or without antibodies to AChR and MuSK (Higuchi et al., 2011; Pevzner et al., 2011; Cossins et al., 2012; Zhang et al., 2012b; Shen et al., 2013; Zouvelou et al., 2013; Zisimopoulou et al., 2014; Marino et al., 2015; Li et al., 2017; Rivner et al., 2018; Yan et al., 2018b; Aoki et al., 2020). Here, MUSK is linked to myasthenia gravis.