Rituximab or azathioprine maintenance in ANCA-associated vasculitis.

report that rituximab prevented relapse of antineutrophil cytoplasm antibody (ANCA)–associated vasculitis better than azathioprine. However, the study de -sign tilted the playing field in favor of rituximab. Figure 2 of their article indicates that a 500-mg infusion of rituximab was administered every 6 months for 18 months. In addition, an extra dose of rituximab was administered at baseline. In contrast, in the azathioprine cohort, azathio-prine therapy was progressively decreased during follow-up. This design begs two questions.First, what would the study outcome have been if the dose of azathioprine had been kept constant and the dose of rituximab had been tapered?Second, why was it deemed necessary to taper the dose of azathioprine? Decades of experience indicate that azathioprine is a relatively safe long-term therapy. That cannot be said for rituximab.