Maintenance of Remission With Rituximab Versus Azathioprine for Newly-diagnosed or Relapsing Eosinophilic Granulomatosis With Polyangiitis.

Inclusion Criteria: * patients with a diagnosis of EGPA according to Lanham and/or ACR 1990 criteria and/or Revised Chapel Hill Nomenclature and/or MIRRA study inclusion criteria * 18 years of age or more * with newly-diagnosed EGPA or after a vasculitis flare and remission achieved within the past year * independently of ANCA status * within 30-360 days following achievement of vasculitis remission (corresponding to a Birmingham Vasculitis Activity Score (BVAS)=0) achieved with an induction regimen including the one used in the REOVAS trial: either CS alone or in association with CYC (total dose ranging from 4.5-10 g for patients \<65 years old and from 3-10g for patients ≥65 years old) or RTX (2 x 1g (D1, D15) or 4 weekly 375 mg/m2). * with a stable prednisone dose for 30 days or no more prednisone * after oral immunosuppressive drug cessation if started at remission. * Patients included in the REOVAS trial and achieving remission can be included at month 12 visit if they fulfil the other criteria * Patients able to give written informed consent prior to participation in the study. * Affiliation with a mode of social security (profit or being entitled). Exclusion Criteria: * patients with GPA, MPA or other vasculitides * patients with vasculitis not in remission defined as a BVAS \>0 * acute or chronic active infections (including HIV, HBV or HCV) * active or recent cancer ( \<5 years), except basocellular carcinoma and low activity prostatic cancer controlled by hormona…