Perioperative Efgartigimod treatment for acute myasthenia gravis exacerbation with retroperitoneal mass: a case report

This case demonstrates the efficacy and safety of efgartigimod in managing an acute exacerbation of myasthenia gravis (MG) with comorbid Castleman disease, particularly during the perioperative care of retroperitoneal mass resection. A 23-year-old female was admitted with the discovery of a retroperitoneal Mass, confirmed via abdominal enhanced CT and MRI. The patient had generalized MG since 2017, with controlled but fluctuating symptoms. Preoperative assessment showed albumin levels were slightly reduced and respiratory function demonstrated severe restrictive ventilation impairment. There was acute exacerbation of muscle weakness (MG Foundation of America (MGFA) class IVb, MG-activities of daily living (ADL) score 8, and quantitative MG (QMG) score 20) with respiratory and medullary symptoms. Treatment with efgartigimod (10 mg/kg/week), prednisone 15 mg/day and pyridostigmine 270 mg/day was initiated. The symptoms improved substantially after four infusions (MG-ADL score 0, QMG score 6), and the lung function recovered. The patient continued efgartigimod treatment and underwent retroperitoneal mass resection. The mass showed massive lymph node hyperplasia (Castleman's disease, mixed type). Postoperatively, the patient experienced no infection, MG exacerbation, or other complications. Efgartigimod had a rapid onset of action, swiftly improved symptoms during acute MG exacerbation, and maintained symptom stability during the perioperative care.