It is evidenced that efgartigimod can rapidly and significantly improve the symptoms of myasthenia gravis. The global multicenter clinical trials hace confirmed that efgartigimod is safe and well tolerated. Few case reports showed that perioperative efgartigimod combined with thymectomy was safe and feasible. However, there was no sufficient data on safety and efficacy of this regimen in the treatment for patients with myasthenia gravis and thymomas. Therefore, this trial aims to evaluate the efficacy and safety of perioperative efgartigimod and thymectomy for patients with myasthenia gravis and thymomas.

Inclusion Criteria:

1. Adult patients aged ≥ 18 years and ≤ 75 years with expected survival time > 12 months;
2. Patients with systemic Myasthenia gravis;
3. AChR Antibody positive;
4. MGFA Type II- IV;
5. Clinical diagnosis of Neoplasm of thymus by enhanced chest CT (clinical stage: Masaoka-Koga Stage I-IVa);
6. Patients with American Society of Anesthesiologists (ASA) classification of 1-2;
7. Subjects have no dysfunction of major organs; blood routine, lung, liver, kidney function and cardiac function are basically normal; laboratory test indicators must meet the following requirements: Blood: White cells > 4.0 x 109/L, absolute count of neutrophils (ANC) ≥ 2.0 x 109/L, Thrombocyte count > 100 x 109/L, Hemoglobin > 90 g/L; Lung function: FEV1 ≥ 1.2 L, FEV1% ≥ 50% and DLCO ≥ 50%. Note: FEV1: Forced vital capacity measured value (liter). FEV1%:% of Forced vital capacity observed/predicted. DLCO%: measured/predicted value% of diffusion capacity of the CO in one breath; Liver function: Serum bilirubin less than 1.5 times the maximum normal value; ALT and AST less than 1.5 times the maximum normal value; Renal function: blood creatinine (SCr) ≤ 120 µmol/L, creatinine clearance (CCr) ≥ 60 ml/min;
8. Understand the study and sign the informed consent form.

Exclusion Criteria:

1. Patients whose imaging investigation suggests that the tumor has already had hematogenous metastasis (clinical stage: Masaoka-Koga IVb);
2. Patients with ocular muscular myasthenia gravis (OMG);
3. Patients who have received median sternotomy ;
4. Documented history of congestive cardiac failure; poorly controlled drug therapy on Anginal pain; electrocardiogram (ECG) documented transmural myocardial infarction; poorly controlled hypertensive; clinically significant heart valve disorders; or high-risk uncontrolled arrhythmia;
5. Patients with a loss of more than 5 Kg within the past month; severe uncontrolled systemic intercurrent illness such as active Infection or poorly controlled Diabetes mellitus; patients with combined Hemorrhagic disorder and Haemorrhagic diathesis; patients with abnormal coagulation function, having haemorrhagic diathesis or receiving thrombolysis or anticoagulant therapy; and patients with grade II-IV myelosuppression.
6. Serum pregnancy test positive or lactating females, as well as males and females of childbearing potential who are unwilling to take adequate contraception measures during treatment;
7. History of organ transplant (including autologous bone marrow Transplant and peripheral Stem cell transplant);
8. Patients with peripheral nervous system disorders or significant history of Mental disorder and central nervous system disorders;
9. Concurrent participation in other clinical investigators.
10. Patients who cannot tolerate one-lung ventilation in the Surgery; patients with severe cardiac complications, cardiovascular compensatory dysfunction, cardiac pacemaker implantation;
11. Patients with acute Inflammation due to bacterial, viral or other pathogenic microorganism Infection; known Immunodeficiency virus (HIV), Hepatitis B virus (HBV) or Hepatitis C virus (HCV) active Infection or known HIV seropositivity;
12. Patients who previously underwent Thoracic operation for Tuberculous pleurisy, Mesothelioma, Pulmonary disorder, diaphragmatic disease, ipsilateral Atelectasis involving one lobe or more than one lobe;
13. Serum IgG level < 6 g/L;
14. Received biologic agents such as rituximab or eculizumab within 6 months; IV Immunoglobulins or Plasma exchange within 1 month;