Patient description: The patient is a 35-year-old woman with myasthenia gravis, class IIa. She complains of diplopia and fatigue and weakness that affects mainly her upper limbs. She had a positive anti-AChR antibody test, and her single fiber electromyography (SFEMG) was positive. She takes pyridostigmine 60 mg three times a day. But she still has some symptoms that interfere with her job. She is a research coordinator and has 3 children. Her 70-year-old father has hypertension. She does not smoke or use illicit drugs. She drinks alcohol occasionally at social events. Her physical exam and lab studies were not remarkable for any other abnormalities. BP: 110/75 Hgb: 11 g/dl WBC: 8000 /mm3 Plt: 300000 /ml Creatinine: 0.5 mg/dl BUN: 10 mg/dl Beta hcg: negative for pregnancy

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Myasthenia Gravis Patients 18 and older Patients must have prior or current documentation of MGFA MG grades 2, 3, or 4 generalized MG, according to the MGFA classification system.48 These grades correspond to mild (2), moderate (3), and severe (4) Elevated AChR or MuSK Ab. These tests will have been performed at some time prior to entry into the study. Double seronegative MG patients with prior documentation of an abnormal decrement (>10%) on slow repetitive nerve stimulation or an abnormal single fiber EMG will also be allowed to participate Patient's signs and symptoms should not be better explained by another disease process IVIg maintenance dose of 0.2 to 2 gm/kg/4 weeks or equivalent dose administered Q 2-4 weeks±3days Stable IVIg for at least 3 cycles (definition of stability: no change in prescribed dosage or frequency by the treating physician) Patient must be receiving no more than 200g/4weeks of IVIg Patients must be willing to complete the study and return for follow-up visits Patients must be willing to give written informed consent before participating in this study. A copy of the signed consent must be kept in the patient's medical record Patients can be on the following drugs as long as there has been no dose change for 60 days: azathioprine, cyclosporine, cyclophosphamide, mycophenolate mofetil, tacrolimus, methotrexate or other immunosuppressive drugs  MGFA grade V within 6 months of screening A history of chronic degenerative, psychiatric, or neurologic disorder other than MG that can produce weakness or fatigue Other major chronic or debilitating illnesses within six months prior to study entry Female patients who are premenopausal and are: (a) pregnant on the basis of a serum pregnancy test, (b) breast-feeding, or (c) not using an effective method of double barrier (1 hormonal plus 1 barrier method or 2 simultaneous barrier methods) birth control (birth control pills, male condom, female condom, intrauterine device, Norplant, tubal ligation, or other sterilization procedures) Altered levels of consciousness, dementia, or abnormal mental status Thymectomy in the previous three months Evidence of renal insufficiency (Cr>1.5 x elevated) or liver disease (transaminases > 2.5 x elevation) at screening Skin disease that would interfere with assessment of injection site reaction History of severe reactions to IVIg or SCIg Participation in a research study within the last 3 months