Inclusion Criteria:
1. Age ≥18 years, male or female.
2. Diagnosis of myasthenia gravis (MG) based on the following:
1. Typical clinical features of MG.
2. At least one of the following:
Seropositive for anti-AChR antibodies (confirmed by reliable assay). Abnormal neuromuscular transmission on electrophysiological testing (e.g., RNS or SFEMG).
Positive neostigmine test or documented response to cholinesterase inhibitors.
3. MGFA classification II-IV at consolidation baseline.
4. Seropositive for anti-AChR antibodies (required for enrollment).
5. Hospitalized for myasthenic crisis (MC) in the acute exacerbation and completed one treatment cycle of efgartigimod: acute exacerbation definition: Presence of MC warning signs (new or worsening within 2 weeks): Bulbar symptoms: Dysphagia, choking, weak cough, dysarthria. Respiratory symptoms: Dyspnea, respiratory muscle weakness. Generalized weakness: Head drop, jaw weakness, facial weakness. One treatment cycle of efgartigimod: 10 mg/kg IV, once weekly for 4 doses.
6. ≥2-point improvement in MG-ADL score from acute exacerbation baseline by Day 4 of efgartigimod treatment.
7. Willing and able to provide written informed consent before study participation.
Exclusion Criteria:
1. Treatment with IVIg, plasma exchange (PE), IV methylprednisolone (IVMP), or immunoadsorption (IA) within 1 month before consolidation baseline.
2. Thymectomy within 6 months before exacerbation baseline.
3. Use of immunomodulatory monoclonal antibodies or investigational drugs (not listed above) within 3 months before baseline or 5 half-lives (whichever is longer).
4. Pregnancy or lactation (women of childbearing potential must have negative pregnancy test and use contraception).
5. Known hypersensitivity to efgartigimod or any FcRn-targeting therapy.
6. Clinically significant comorbidities, including severe cardiovascular, hepatic, renal, pulmonary, or hematologic disorders, active malignancy and uncontrolled systemic infections.
7. Other autoimmune diseases that may interfere with efficacy assessment (e.g., uncontrolled thyroid disease, severe rheumatoid arthritis).
8. Any other condition deemed unsuitable by the investigator.
