In addition, the fact that FcRn binds IgG3 with lower affinity than IgG1, IgG2, IgG3, IgM, and IgA does not support the low IgG1 and IgG3 found in DM1 and relative preservation of other immunoglobulins [10]. The gene discussed is CD40LG; the disease is myotonic dystrophy type 1.