Pharmacokinetic Study of Rituximab Induction Regimen in ANCA-associated Vasculitis

The aim of the investigators' study is to evaluate whether monitoring serum rituximab levels could be an interesting tool in the follow-up of ANCA-associated vasculitis patients. All consecutive patients, hospitalized for a new diagnosis of ANCA-associated vasculitis or the relapse of a known ANCA-associated vasculitis, in which the decision to start an induction regimen with rituximab has been taken, will be included. Serum rituximab levels (along with serum anti-rituximab antibodies levels) will be determined (at M+1 and M+3) and the correlation with clinical outcome at M+6 will be analyzed.