Poor response to Eculizumab in Caucasian Patients with Treatment Refractory Generalized Myasthenia Gravis: A case series

Background Eculizumab, a C5 complement inhibitor, has been approved for management of patients with treatment refractory Acetylcholine receptor positive (AChR+) Generalized Myasthenia Gravis (gMG). Though majority of patients receiving eculizumab experience clinical improvement, a small number of patients may have poor response.   Objective To report three cases of poor response to eculizumab in young caucasian patients with treatment refractory gMG.   Methods Case Series   Results All three patients were young, caucasian, thymectomized, females with MGFA class III, treatment refractory MG on multiple immunosuppressant medications. All three patients had initial worsening of MG- ADL score, 1 month post eculizumab, followed by an unchanged MG ADL and MGC score, 3 months after eculizumab therapy.  No changes were noted in the number of acute exacerbations of MG, pre and post eculizumab therapy. All patients were eventually started on maintenance Plasma-exchange (PLEX) therapy, post eculizumab failure and had clinical improvement in MG-ADL and MGC scores and reduction in the number of acute exacerbations of disease.   Conclusion The exact mechanism contributing to poor clinical response to eculizumab in gMG patients remains unclear. Further studies are warranted to undermine the underlying pathogenesis.