A 32-year-old male patient began experiencing right eyelid ptosis in 1995, without diplopia, with symptoms worsening in the evening and improving in the morning. The fatigue test was positive, with no limb weakness or bulbar palsy symptoms. The patient improved with pyridostigmine treatment and maintained long-term pyridostigmine therapy. Between 2019 to 2021, the patient experienced recurrent eyelid ptosis and restricted extraocular muscle movement. The symptoms were partially relieved after prednisone treatment combined with sufficient doses and courses of tacrolimus and mycophenolate mofetil successively. Then, the patient maintained long-term corticosteroid therapy at a minimum dose of 30mg daily because of decreased creatinine clearance. On July 28, 2024, the patient again experienced left eyelid ptosis and poor upward movement of the right eye, with ADL: 6 and QMG: 10. Increasing the corticosteroid dose to 40mg/d did not significantly improve symptoms. Acetylcholine receptor antibody was 0.648nmol/l, indicating refractory OMG. On August 23, 2023, the patient began treatment with efgartigimod. After the first dose, left eyelid ptosis improved, with ADL: 3 and QMG: 8. After the second dose, ADL: 1 and QMG: 5, with prednisone at 35mg. After the third dose, ADL: 1 and QMG: 5, with prednisone at 35mg. After the fourth dose, ADL: 1 and QMG: 3, with prednisone at 30mg. Currently, symptoms are mostly alleviated, with efgartigimod maintenance at once every two weeks and corticosteroid reduction to 25mg. No infusion reactions or infections occurred during the treatment.