Efgartigimod combined with steroids as a fast-acting therapy for myasthenic crisis: a case report

Abstract

Background: Generalized myasthenia gravis (gMG) can be managed with acetylcholinesterase inhibitors (AChEis; e.g., pyridostigmine), corticosteroids, other immunosuppressive drugs (e.g., tacrolimus), and their combinations. Intravenous immunoglobulin (IVIg) or plasmapheresis (PLEX) may be administered if symptoms persist. PLEX and IVIg are also mainstays of treatment for myasthenic crisis. Recently, efgartigimod was approved in Japan for treating adults with gMG (irrespective of the antibody status) who do not have a sufficient response to corticosteroids and nonsteroidal immunosuppressive therapies. Efgartigimod is generally safe and well tolerated. However, since phase III trials of efgartigimod excluded those with myasthenic crisis, the efficacy of efgartigimod in treating myasthenic crisis is still unclear. Moreover, there are no reports that efgartigimod therapy can reduce the dose of corticosteroids needed to achieve a minimal manifestation status.

Case presentation: We report the case of a 70-yeat-old woman with gMG who developed a myasthenic crisis. After she was diagnosed with gMG, the patient had been treated with oral corticosteroids and tacrolimus for 1 year. However, she refused to continue taking the medication, and two weeks later, she developed ptosis, dysphagia and dyspnea. The patient was intubated and treated with efgartigimod in combination with steroid therapy, and she recovered without PLEX or IVIg. Afterward, when she experienced worsening of fatigue and increased levels of anti-acetylcholine receptor antibodies, efgartigimod therapy was effective. The patient achieved minimal manifestation status even after the reduction of corticosteroids and showed improvements in the Myasthenia Gravis Activities of Daily Living scales after 4 cycles of efgartigimod infusion.

Conclusions: Our case suggests that efgartigimod can be an alternative drug for achieving minimal manifestation status in patients with myasthenic crisis. Considering its strong efficacy and safety, efgartigimod could be expanded to use as bridging therapy in the acute and chronic phases of gMG.

Keywords: Corticosteroid; Efgartigimod; FcRn inhibitor; Myasthenia gravis; Myasthenic crisis; Neonatal Fc receptor inhibitor.

Fig. 1

Clinical course from onset to infusion of efgartigimod. The patient developed a myasthenic crisis due to refusal to take medication and was treated with efgartigimod from Day 414 (yellow arrows). In total, four cycles of efgartigimod were administered. AChR-Abs: Anti-acetylcholine receptor antibodies; MG-ADL: Myasthenia Gravis Activities of Daily Living; IVMP: Intravenous methylprednisolone pulse therapy; PSL: prednisolone

Fig. 2

Precise clinical course of the myasthenic crisis. The patient’s dyspnea and fatigue worsened despite intravenous steroid therapy (500 mg/day for 3 days); she was intubated and treated with a high dose of oral prednisolone (50 mg/day), intravenous efgartigimod (500 mg/day, weekly, 4 times), and intravenous methylprednisolone pulse therapy (1000 mg/day for 3 days, 2 cycles). The patient was extubated on the 15th day. AChR-Abs: Anti-acetylcholine receptor antibodies; MG-ADL: Myasthenia Gravis Activities of Daily Living; IVMP: Intravenous methylprednisolone pulse therapy; PSL: prednisolone

Fig. 3

Changes in the IgG level and its ratio in the first (blue), second (red), third (orange), and fourth (green) cycles of efgartigimod. In all cycles, more than 50% IgG reduction was observed, which lasted for 6 weeks