Thymectomy Trial in Non-Thymomatous Myasthenia Gravis Patients Receiving Prednisone Therapy

Inclusion Criteria: * Male and female MG patients age greater than 18 and less than 65 years * Onset of generalized MG within the last 5 years * Positive serum anti-acetylcholine receptor binding antibodies (muscle acetylcholine receptors, AchRAb =/\> 1.00 nmol/L. AchRAb levels of 0.50-0.99 nmol/L will be acceptable if there is another confirmatory test for MG, including single-fiber electromyography (EMG), repetitive nerve stimulation, or unequivocal edrophonium testing.) * MGFA class II-IV at entry, using the MG Foundation of America (MGFA) classification, while receiving optimal anti-cholinesterase treatment with or without oral prednisone Exclusion Criteria: * Ocular MG without generalized weakness (MGFA Class I) or minimal weakness that would not require the use of corticosteroids * Myasthenic weakness requiring intubation (MGFA Class IV) in the prior month * Immunosuppressive therapy other than corticosteroids in the preceding year * Medically unfit for thymectomy * Chest CT evidence of thymoma. * Pregnancy or lactation; contraindications to the use of corticosteroids, unless postmenopausal or surgically sterile. Women considering becoming pregnant during the period of the study are to be excluded. * A serious concurrent medical, neurological or psychiatric condition that would interfere with thymectomy or subsequent clinical assessments * Current alternate day dose of prednisone \> than 1.5 mg/kg or 100 mg or the equivalent daily doses (\> 0.75 mg/kg or 50 mg). * Pa…