Smart dosing of rituximab may keep rare blood vessel disease at bay

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Granulomatosis with Polyangiitis Or microscopic polyangiitis complying Or kidney-limited disease With or without detectable ANCA (anti-neutrophil cytoplasmic antibodies) at the time of diagnosis or relapse, and at remission. * Who have achieved remission using a treatment combining corticosteroids and an immunosuppressive agent, including corticosteroids, cyclophosphamide IV or oral (the use of another immunosuppressant is allowed, according to the current French guidelines, as well as plasma exchanges and/or IV immunoglobulins, or rituximab). * Interval of 1 month between the end of the immunosuppressant treatment and the randomization time if cyclophosphamide or methotrexate were used, interval between 4 and 6 months if rituximab was used * Age \> 18 years without age limit higher when the diagnosis is confirmed. * Informed and having signed the consent form to take part in the study. Exclusion Criteria: * Other systemic vasculitis * Secondary vasculitis (following neoplastic disease or an infection in particular) * Induction treatment with a regimen not corresponding to that recommended in France. * Patient who has not achieved remission. * Incapacity or refusal to understand or sign the informed consent form. * Incapacity or refusal to adhere to treatment or perform the follow-up examinations required by the study. Non-compliance * Allergy, documented hypersensitivity or contraindication to the study medication (cyclophosphamide, corticosteroids, azathioprine, rituximab) * History of severe allergic or anaphylactic reactions to humanized or murine monoclonal antibodies. * Pregnancy, breastfeeding. Women of childbearing age must use a reliable method of contraception throughout the duration of immunosuppressive treatment up to 1 year after the last infusion of rituximab * Infection by HIV, HCV or HBV * Progressive, uncontrolled infection requiring a prolonged treatment (tuberculosis, HIV infection, etc.). * Severe infection declared during the 3 months before randomization (CMV, HBV, HHV8, HCV, HIV, tuberculosis). * Progressive cancer or malignant blood disease diagnosed during the 5 years before the diagnosis of vasculitis. Patients suffering from non-metastatic prostate cancer or those cured of a cancer or a malignant blood disorder for more than 5 years and not taking any antineoplastic agents for more than 5 years may be included. * Participation in another clinical research protocol during the 4 weeks before inclusion. * Any medical or psychiatric disorder which, in the investigator's opinion, may prevent the administration of treatment and patient follow-up according to the protocol, and/or which may expose the patient to a too greater risk of an adverse effect. * No social security * Churg and Strauss syndrome * Viral, bacterial or fungic or mycobacterial infection uncontrolled in the 4 weeks before the inclusion * History of deep tissue infection (fasciitis, osteomyelitis, septic arthritis)in the first year before the inclusion * History of chronic and severe or recurrent infection or history of preexisting disease predisposing to severe infection * Severe immunodepression * Administration of live vaccine in the four weeks before inclusion * Severe chronic obstructive pulmonary diseases (VEMS \< 50 % or dyspnea grade III) * Chronic heart failure stade III and IV (NYHA) * History of recent acute coronary syndrome, unrelated to vasculitis