We can also not completely rule out the possibility that our study actually underestimates the frequency of MOG-IgG3 in MOG-EM/MOGAD: IgG is generally considered to be highly stable and serum samples are thus tested (or stored) for MOG-IgG and other autoantibodies without further pre-treatment as the standard procedure at most laboratories, including for this study. Here, MOG is linked to erythema multiforme.