PO:35:227 | Long-term renal and survival outcomes in microscopic polyangiitis: data from an observational monocentric cohort

Roberta Prevedello¹, Federica Davanzo¹, Luca Iorio¹, Eleonora Fiorin¹, Marta Codirenzi¹, Roberto Padoan¹, Andrea Doria¹. | ¹Unità di Reumatologia, Dipartimento di Medicina DIMED, Università degli Studi di Padova, Padova, Italy.

Background. Microscopic polyangiitis (MPA) is an ANCA-associated small-vessel vasculitis, often causing severe renal involvement that may lead to dialysis or transplantation. While ANCA-associated vasculitides have been extensively studied, data focusing specifically on MPA remain limited.

Materials and Methods. MPA patients fulfilling the 2022 ACR/EULAR criteria, who were followed at our centre between May 2004 and May 2025, were analysed retrospectively. Clinical and laboratory data as well as information regarding induction and maintenance therapy, were collected at diagnosis, during relapses, and at last follow-up. Furthermore, variables potentially associated with death, renal outcomes and relapse were investigated.

Results. Of the 71 MPA patients included (median age 66 years; 54.5% female), 98.6% were ANCA-positive, mostly MPO-ANCA (91.5%). At diagnosis 94.4% had renal involvement. Induction therapy consisted of glucocorticoids alone (16.9%) or with immunosuppressants (83.1%), mainly cyclophosphamide (31%) and rituximab (19.7%), while mycophenolate mofetil (21.4%) was the most used for maintenance. Over a median follow-up of 55 months, 90% achieved remission, 18.3% died, 26.8% experienced at least one relapse and 26.8% progressed to end-stage kidney disease (ESKD). Among those, 18.3% required dialysis and 7% underwent kidney transplantation. Baseline characteristics are summarized in Table 1. Survival, based on Kaplan-Meier curves, was significantly lower in patients aged >65 years (p=0.0019), with rapidly progressive nephritis (p=0.0263), arterial hypertension (p=0.0251), or dialysis at onset (p=0.0445). No significant differences in survival were observed based on induction with rituximab (p=0.5597), cyclophosphamide (p=0.227), or maintenance immunosuppressants (p=0.058). Neither VDI >5 nor ANCA Renal Risk Score (ARRS) >8 were associated with increased mortality. In multivariate analysis, faster ANCA negativity was independently associated with better survival (HR 0.76, 95% CI 0.59–0.96, p=0.022), indicating a protective effect while hypertension was independently associated with lower risk of relapse (HR 0.18, 95% CI 0.04–0.72, p=0.016). Other univariate predictors of relapse included lower baseline prednisone (p=0.038) and disease progression before remission (p=0.046). Progression to ESKD was significantly associated with higher BVAS (p=0.002), higher FFS (p=0.003), nephrotic-range proteinuria (p=0.007), elevated serum creatinine and lower eGFR at diagnosis (both p<0.001). However, no variables retained significance in multivariate analysis for ESKD due to excessive covariate interaction.

Conclusions. In this MPA cohort, renal involvement was common and often severe, frequently progressing to ESKD. Advanced age, rapidly progressive nephritis, and need for dialysis at onset were associated with reduced survival, while faster ANCA negativity emerged as a protective factor. Although remission was achieved in most patients, relapse and long-term renal damage were frequent. No specific induction or maintenance regimen showed significant prognostic impact, whereas baseline hypertension was independently associated with a lower risk of relapse.