Antineutrophil cytoplasmic antibody associated vasculitis (AAV) is a group of necrotizing pauci-immune multi systemic diseases characterised by glomerulonephritis with absence or paucity of immunoglobulin deposits. The most common forms of AAV are granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (EGPA) [
1‐
4]. In most cases, AAV is associated with the presence of anti-neutrophil cytoplasmic antibodies (ANCAs). Many studies have documented that the most important factors associated with a bad prognosis of AAV are age at onset, markedly decreased glomerular filtration rate (eGFR< 15 ml/min), a high Birmingham Vasculitis Activity Score (BVAS), pulmonary involvement at presentation and high levels of PR3 ANCA [
5]. Renal involvement at onset is a major predictor for the outcome in AAV; patients with PR3-AAV have a greater risk of relapse while MPO ANCA patients are characterised by a worse renal function and higher levels of proteinuria at the onset of the disease [
6]. Treatment of AAV is considerably improved since the introduction of immunosuppressive therapy that consist of an induction of the remission phase (3–6 months), followed by a remission maintenance (for at least 18 months), associated with plasma exchange in patients with a severe or life-threatening form of the disease. The introduction of corticosteroids and cyclophosphamide (CYC) as an induction therapy in AAV improved patients’ survival from 20% to over 80% at 2 years [
7‐
9]; therefore CYC is the treatment of choice for the induction of remission in AAV. However treatment with CYC is associated with a high risk of infectious complications, cardiovascular disease, myelosuppression and malignancy [
10,
11]. Infertility is another major problem, however there are anecdotic cases of successful conceptions and pregnancies in p-ANCA associated vasculitis during CYC treatment [
12]. Taking into consideration the importance of a prolonged therapy with CYC and the high relapse rate of the disease, many therapeutic trials showed less severe adverse events and no less efficacy using less toxic induction treatment or reduced dose of intravenous pulse CYC versus standard dose [
5]; however CYC sparing strategies seem to show a higher risk of relapse. Many other studies have been performed to show less toxicity with alternative treatments for remission induction; most of them are limited by a small cohort of patients with severe renal involvement [
13]. Rituximab (RTX) has been used in ANCA associated vasculitis since 2003. The RAVE [
14] and RITUXVAS trials [
15] showed no difference between the anti-CD20 antibody RTX versus CYC for remission induction in patients with GPA and MPA. Unfortunately the RAVE trial evaluated new or relapsing GPA or MPA in patients without severe renal involvement and in the RITUXVAS trial all patients with severe renal disease also received CYC in the induction phase. Thus, there are very few data about the outcome in patients with severe renal involvement treated only with RTX and steroids for remission induction. In a recent multi-centre retrospective study [
16], Shah S et al. reported a favourable outcome in terms of remission and dialysis independence in patients with severe renal involvement treated with RTX. In many clinical trials both MPA and GPA are included; however it is debatable if they represent distinct diseases or a continuum, and current classification systems sometimes confuse the distinction of these two clinical entities. Moreover some authors suggest a distinction in the ANCA type, not just based on clinical features, for the characterisation of the disease. In this single centre retrospective study, we report the clinical outcomes in 8 patients with de novo or recurrent MPO-ANCA associated vasculitis and severe renal involvement treated with RTX with no CYC association. We treated this group of patients with RTX without CYC taking into account the presence of comorbidities and the high risk of toxicity and infectious complications in this specific population. Furthermore, there is growing evidence about the efficacy of RTX in patients with severe renal involvement [
16,
17,
18]. We have focused this study on the subgroup of MPO vasculitis because MPO are more often associated with crescentic glomerulonephritis, renal involvement [
17], failure to obtain complete remission and poorer renal outcome. In addition, post-hoc analysis in the RAVE trial showed that RTX was more effective in remission induction in the PR3 ANCA group than in the MPO group.