Objective: There are limited data on the long-term prognosis of microscopic polyangiitis (MPA). A systematic review was performed to estimate the survival, renal survival and relapse rates in patients with MPA.
Methods: Articles included in MEDLINE and EMBASE databases were reviewed. Randomized or non-randomized trials, cohort, case-control and cases-series studies of patients with MPA diagnosed according to Chapel Hill Consensus Conference definitions, a high rate of biopsy-confirmed diagnosis, follow-up >1 year and follow-up losses <10%. Two independent authors using a predefined questionnaire for evaluating the quality and risk of bias for each study extracted data.
Results: Eighteen studies for MPA prognosis (n = 940) and six for MPA outcomes after transplantation (n = 65) were included. Survival rates were 77-100% at 1 year, 46-80% at 5 years and 60-80% at 10 years. Higher mortality density occurred within the first months after diagnosis. Vasculitis was the cause of death in 32-50% of patients. Relapses were detected in 19-39% of cases (median time to relapse 15-43 months). Renal graft survival was 85-94% at 1 year and 51-87% at 5 years. Age, renal involvement and immunosuppressive treatment were related to mortality. Lower relapse rate was achieved with 12 vs 6 CYC pulses.
Conclusion: Evidence regarding MPA prognosis is weak. MPA mortality is mainly concentrated in the first months after diagnosis. Fewer than 50% of deaths are related to MPA activity. MPA long-term prognosis is less severe, although relapses are frequent. End-stage renal failure is a frequent complication of MPA, and renal transplantation could be an effective therapy in these patients. Early diagnosis, early initiation of a tailored therapy according to risk factors and a longer follow-up of the patients are needed.