The primary, ANCA-associated systemic vasculitides (AASV), including Wegener’s granulomatosis and microscopic polyangiitis, are progressive, multisystem, autoimmune diseases which respond to immunosuppressive therapy. Their treatment with corticosteroids and cytotoxic drugs has been standardised in a first wave of studies (ECSYSVASTRIAL project), but limitations of such regimens include only partial efficacy and appreciable treatment-related toxicity.