Since high doses of IgG result in saturation of the FcRn pathway, careful co-administration of IgG replacement therapy in PNH patients with co-existing medical conditions (e.g. immune thrombocytopenic purpura (ITP), clinically relevant hypogammaglobulinemia, multiple sclerosis) is recommended as this might further result in enhanced clearance of ravulizumab, as intravenous IgG preparations compete with endogenous IgG to bind the FcRn by their Fc regions. This evidence concerns the gene FCGRT and paroxysmal nocturnal hemoglobinuria.