Rationale - Additionally to thymectomy, which indication of is still debated in absence of thymoma, the long-term treatment of generalized myasthenia gravis includes usually prednisone and azathioprine. However, the most used scheme for prescribing and tapering corticosteroid in MG resulted in a very important cumulative dose of prednisone. Indeed, at twelve month, more than 50 percent of patients are still daily treated with at least 18 mg of prednisone and the proportion of patients who are in remission and no longer taking prednisone is very low (Palace and NEWSOM Davis, Neurology 1998). Prolonged corticosteroid therapy is accompanied with various and major side effects, hypertension, osteoporosis, weight gain, glaucoma. Therefore, tapering, eventually discontinuing, prednisone earlier is a relevant therapeutic goal.