Efficacy of FcRn antagonist efgartigimod in the treatment of Miller-Fisher/Guillain-Barré overlap syndrome: Two case reports.

Introduction: Guillain-Barré Syndrome (GBS) remains one of the most prevalent acute immune-mediated polyneuropathies. Miller Fisher Syndrome (MFS), a clinically distinct variant of GBS, is characterized by the classic triad of ataxia, areflexia, and ophthalmoplegia. The Miller-Fisher/Guillain-Barré (MFS/GBS) overlap syndrome represents an uncommon clinical entity with limited therapeutic options. Current management primarily relies on high-dose corticosteroid pulse therapy, intravenous immunoglobulin (IVIg), and plasma exchange; however, these interventions often demonstrate suboptimal clinical efficacy, particularly in resolving persistent ophthalmoplegia and bulbar symptoms. Efgartigimod, a humanized FcRn receptor antagonist, promotes lysosomal degradation of IgG antibodies, leading to rapid reduction of pathogenic autoantibodies. This mechanism positions efgartigimod as a promising treatment for antibody-mediated autoimmune disorders.

Case presentation: We describe two cases of severe MFS/GBS overlap syndrome. Both patients had preceding infectious prodromes and presented with profound symptoms, including complete external ophthalmoplegia, truncal ataxia, areflexia, dysphagia, and limb paresthesia. Upon admission, standard therapy was initiated with IVIg (0.4 g/kg/day for 5 days) followed by methylprednisolone (0.5 g/day for 5 days). While minimal improvement in eye fixation was observed, dysphagia and limb numbness remained unchanged. Subsequently, both patients received two doses of efgartigimod (10 mg/kg) over two weeks. At 30-day post-discharge follow-up, both patients exhibited sustained improvement in ocular motility and regained independent ambulation.

Conclusion: This report highlights two cases of treatment-refractory MFS/GBS overlap syndrome demonstrating suboptimal response to conventional immunomodulatory therapies. Efgartigimod emerges as a valuable treatment, offering clinical benefit in managing severe MFS/GBS overlap syndrome.