This research study is a multicentre prospective pharmacokinetic study. The clinical and biological data will be collected in the framework of a prospective study. The drug to be evaluated is a glucocorticoid routinely used to treat Systemic lupus erythematosus (SLE) patient. Initial dose of prednisone must be oral and at least 0.5mg/Kg/day, but the precise dosage and the tapering regimen will be determined according to the clinical judgment of the investigator. The duration of the research period for each patient will be 3 months. Three visits (which are all usual care visits) will be needed within the 3 months of the study for collecting data and/or blood sampling