While anti-AChR antibodies, the most common autoantibodies in MG patients, are predominantly IgG1 and IgG3, anti-MuSK antibodies are predominantly IgG4 (Rivner et al. 2018), which seems to be associated with poor response to IVIg both in MG and CIDP (Wright et al. 2015). The gene discussed is IGHG3; the disease is myasthenia gravis.